Paleoclimate Cycles are Key Analogs for Present Day (Holocene) Warm Period

Guest Post By Renee Hannon


Detailed pattern correlation of Earth’s temperature changes during the past 450 kyrs reveals observations about several cyclic climate patterns. The past four glacial cycles are increasing in duration from 89 kyrs to 119 kyrs. Within these glacial cycles, two warm periods occur about 200 kyrs apart and have strikingly similar temperature characteristics. These two warm patterns suggest processes modifying Earth’s temperature could be repeatable and predictable. In contrast, two other warm periods have different and distinct characteristics. These two warm periods occur during a predominantly elliptical orbit and a predominantly circular orbit, respectively, and on approximately 400 kyr cycles.

Preliminary simplified models of astronomical and oceanic controls on temperature variations for the past four warm periods have been developed. Although process interactions are very complex, separating out predominate causes and effects on global temperature should help improve future climate mathematical simulation models. Climate models need to include astronomical as well as oceanic and atmospheric forcing to reliably predict the duration and temperature changes of the future Holocene interglacial Warm period.


The Holocene Warm Period was compared to four interglacial warm periods and their glacial cycles during the past 450,000 years using EPICA Dome C isotope ratios and temperature estimates to identify pattern similarities and trends.  Interestingly, a hierarchy of correlative events and common patterns occur amongst the glacial cycles and warm periods.

Warm periods are anomalous events referred to as interglacial periods within a glacial cycle. Glacial cycles last for approximately 100 kyrs and warm periods range from 10 to 30 kyrs. For simplicity, these glacial cycles and warm periods are referred to as I through V, with I being present day and V being the oldest as defined in Figure 1. Glacial/interglacial transitions known as Terminations (I-V) and common usage names from literature, marine isotope stages(“MIS”), and approximate age are also noted in Figure 1.

Figure 1: EPICA Dome C isotope temperature estimates over the past 450 kyrs show four warm periods prior to the present-day Holocene warm. Warm periods last approximately 10-30 kyrs.

Calculated temperatures from the Antarctica Dome C data are multiplied by 0.5 to correct to approximate global temperatures rather than polar temperatures. Uncorrected, the magnitude of the delta degree C would be double than what is shown in the figure.

Correlation of Glacial Cycles

Figure 2 is a traverse which displays the four past glacial cycles. The temperature curves for each cycle are turned sideways with time plotted on the vertical axis. This technique is similar to creating a geologic cross section and enables correlation of events between the past glacial cycles. The key repeating event for each cycle is the rapid onset of warming following abrupt terminations of glacial periods. This significant event was used as a datum for each glacial cycle. Datuming is a useful tool that allows recognition of relative changes between cycles. Very cold is highlighted in blue and warm periods in red. The blue, yellow and green lines are an interpretation of internal correlations within each cycle bounded by bold red lines.

Figure 2: A traverse of the past five interglacial-glacial cycles. Cycles are datumed on the Terminations/Onsets. EPICA Dome C isotope temperature estimates are plotted as curves in 1 degree C increments on the horizontal scale (cold to left and warm to right). The vertical scale is time in 20 ka increments. Actual age is plotted on each cycle. Interglacial warm periods are highlighted in red and the coldest portion of the glacial period in blue. Dark red is calculated ratios of warm:cycle.

These glacial cycle patterns are what geologists call bottom-loaded sequences. They are well-behaved cycles with the warmest interglacial period, shaded in red, always following the termination of the previous glacial period. The green line within the warm period highlights a brief cooling event that approximately correlates to the 8.2 kyr event in the present-day Holocene. The blue correlation line is the base of the coldest full glacial period shaded in blue which occurs at the end of each cycle. The full glacial period ranges in duration from 35 to 60 kyrs in Cycle V to Cycle II, respectively. In the middle of each cycle there is a mild glacial period consisting of smaller cold stadials and warm interstadials (Dansgaard-Oeschger cycles). The yellow lines attempt to correlate these minor stadial events.

While there is uncertainty of +/- 3 kyrs in picking the exact timing of events this is not enough to change the main trends and observations. Although these curves are not stretched, stretching would likely improve correlation of the higher frequency events such as the stadials and interstadials. Several observations are evident from the glacial cycle traverse:

  • Duration of glacial cycles are progressively increasing from 89 kyrs in Cycle V to 119 kyrs in Cycle II. Cycle II is 34% longer in duration than Cycle V. The cycles are not spaced equally at 100 kyrs apart. Javier previously challenged the 100 ky cycle (see his Table 1 and Figure 5) over the past 800 kyrs using interglacial peak to peak duration.
  • The full glacial period at the top of each cycle is also increasing in duration from past to present but not necessarily getting much colder between cycles (+/- 1 degree C).
  • Cycle V has the longest warm period and Cycle III the shortest initial warm period. Maximum average warm temperatures are not that different (+/- 1 degree C).
  • Cycle III stands out as having an abbreviated initial interglacial warm followed by a second warm period (MIS 7c). This has been recognized in the literature and is frequently debated as to whether the second warm period is a true interglacial or an interstadial. A similar suppressed interstadial can be correlated to Cycle II (yellow lines). Regardless, MIS 7c is considered to be part of the larger Cycle II and its onset is not as significant as the Termination event.
  • There appears to be an internal event within the interglacial warm periods that correlates to the 8.2 kyr Holocene event. Stadials, or cooling events, also appear correlative within the glacial periods (yellow lines) that have similar patterns suggesting a similar natural process was repeated.

Interglacial Warm Periods Comparison

Patterns in historical temperature changes were also evaluated for the past four interglacial periods and compared to the present-day Holocene. On the largest scale as seen in Figures 1 and 2; Warm II, III, and IV have asymmetric patterns with rapid initial warming and slower cooling. Warm V has more of a symmetrical pattern, with the climate optimum occurring towards the end of its warm period. Onset of present day warm appears similar to the beginning of a symmetrical pattern and perhaps analogous to Warm V.

In the following sections, warm patterns are compared in more detail for the duration of the warm interglacial period, the warming onset and cooling period.

Warm Period Duration Patterns

The warm interglacial periods over the past 450 kyrs range from 9 kyrs to 32 kyrs in duration using a delta oC temperature cut-off of minus 1 (Figure 2, Table 1). All past warm periods have been approximately 2 degrees C warmer than the Holocene. Most interglacial durations have bimodal patterns and tend to be asymmetrical. Warm V is an exception with a more symmetrical pattern (Figure 2).

Table 1: Warm Period Durations over the past 450 kyrs (dark red on Figure 2 which corresponds to a minus 1oC delta cut-off).

Interglacial Period Duration (kyr)
Warm I 12+
Warm II (MIS 5) 17
Warm III (MIS 7e) 9
Warm IV (MIS 9) 14
Warm V (MIS 11) 32

Warm periods II and IV are discussed together due to their similar patterns and Warm periods III and V are discussed separately due to their different patterns. Javier (his Figures 13 and 14) and others have also recognized that Warm periods III (MIS 7E) and V (MIS 11) have different interglacial characteristics.

Warm Periods II and IV: The Holocene warm pattern is generally bimodal and similar to Warm II (MIS 5) and IV (MIS 9) with the exception of the onset warming and a lower initial climate optimum (Figure 3). These three warm periods have an initial brief climate optimum of 2 to 3 kyrs like the early Holocene. This is followed by a brief cooling with a V-shape pattern like the Holocene 8.2 kyr event and then a longer more stable warm period lasting about 7 to 8 kyrs like the Middle Holocene warming.

Figure 3: Holocene temperatures in red overlain on Warm II and IV periods. Bottom horizontal axis corresponds to the Holocene time and top horizontal axis is the past warm time in thousands of years. Colored bar at top refers to the older warm phases. The red text corresponds to the Holocene events.

There is only one key stadial cooling event during Warm II and IV periods. This key stadial event drops temperatures by about 2 degrees C and lasts for a couple thousand years. It also appears similar in timing to the Holocene 8.2 kyr stadial (Figure 3). This intervening stadial may represent a recurring event that happens after the initial climate optimum and will be discussed later.

There are numerous oscillating events during the warm periods with minor temperature variations (<1.5 deg C) that are short duration (tens to hundreds of years). These events would be like the Holocene events that include the Roman Climate, and the Medieval warm followed by the Little Ice Age which are discussed extensively in the literature. They are difficult to see on the graphs in Figure 3 and appear more as background noise during the Holocene warm period due to the compressed scales used here.

These minor events are probably unique to each warm period and have been attributed to long term ocean cycles, Pacific and N. Atlantic multi-decadal and decadal climate cycles, orbital obliquity, solar variability, and greenhouse effects.

Additionally, the bimodal patterns for Warm Periods II and IV are strikingly similar as previously discussed by Hannon. The main difference is Warm IV is compressed by about 6 kyrs. This is demonstrated by stretching the Warm IV curve to match Warm II as shown in Figure 4. These warm periods are approximately 200 kyrs apart. The striking similarity of these two warm periods suggests that the sequence and interaction of natural causes (solar and oceanic) are comparable and repeatable.

Figure 4: Graphs with Warm II (blue) and IV (green) overlain. Horizontal axis for Warm II is in kyr and plotted at top of each graph. Warm IV horizontal axis is plotted on bottom of each graph. Vertical axis is in 1 deg C units and same for all datasets. In the second graph, Warm IV was stretched by ~6 ka.

Warm III and V Anomalous Periods:
Warm III (MIS 7e) and V (MIS 11) exhibit less well-behaved patterns during their warm period (Figure 5). Warm III has a very brief initial climate optimum lasting 2 kyrs and then begins to enter a significant cooling period with nearly coincidental timing as seen in the Holocene 8.2 kyr event (Figures 2 and 5). Then temperatures stabilize for about 4 kyrs before resuming a rapid cooling descent.

Warm V has a similar initial temperature as the Holocene. However, it quickly enters a brief cooling (Figure 5). It is not certain whether this brief stadial at 423 kyrs is equivalent to the Holocene Younger Dryas stadial or the 8.2 kyr cooling (Figure 2). Warm V is unique because it has an extended warming period that is even warmer than the initial climate optimum. Warm V’s second extended warm is almost 2 degrees C warmer than present-day (Figure 5). EPICA discusses Warm V compared to the present-day in more detail here.

Figure 5: Holocene temperatures in red overlain on Warm III and V periods. Bottom horizontal axis corresponds to the Holocene time and top horizontal axis is the past warm time in thousands of years. Colored bar at top refers to the past warm phases. The red text corresponds to the Holocene events.

Warming Onset Patterns

Warm II, IV, and V warm periods display a rapid linear warming to their climate optimum (Figure 6). Warm II and IV have a similar steep slope of m=0.89 and 0.85 respectively. Whereas Warm V has a flatter slope of m=0.67, giving it more of a symmetrical pattern (Figures 1 and 2).

The initial Holocene warming is characterized by two events; the Boiling/Alleröd (B/A) interstadial and the Younger Dryas stadial, referred to as a stair-step pattern (Figures 3 and 5). The only interglacial warm period during the past 450 kyrs that exhibits a similar behavior is Warm III. Warm III has a B/A interstadial equivalent at 248 kyr, but it is not as warm as the B/A. An onset slope calculated for Warm III immediately following this interstadial is quite steep (m=1.1). A slope was not calculated for the Holocene due to the stair-step pattern.

As previously mentioned, the climate optimums of both Warm II and IV are approximately 2 degrees C higher than the Holocene present-day. Perhaps the Younger Dryas cooling during the Holocene warming onset intervened and prevented the Holocene from reaching the initial climate optimums seen in Warm II and IV. This was also observed by Javier, his Figure 14.

Figure 6: Comparison of the onset patterns and slopes. Past warm periods have a linear increase with an excellent regression. The linear equation and R2 are presented on each chart.

Cooling Patterns

Final cooling slopes for the warm periods are more gradational than the onset warming and are similar with slopes ranging from 0.38 to 0.31 (Figure 7; Table 2). Warm II, IV, and V have a gradual cooling over 5 -10 kyr and then continue into a series of stadial and interstadial periods during the next mild glacial phase. Warm III has an initial rapid cooling, stabilizes and then a final cooling (Figure 5). Different slopes were calculated for Warm III (Figure 7). The initial rapid cooling slope is very steep (m=0.8), however the overall cooling is like the other warm periods.

If the Holocene Warm I behaves similarly to Warm IV, the cooling onset should begin very soon and within hundreds of years (Figure 3). If the Holocene Warm I behaves like Warm II, the cooling onset should begin within a few thousand years (Figure 3). If the Holocene Warm behaves more like Warm V, cooling onset is probably 10 thousand years away (Figure 5).

Figure 7: Comparison of cooling patterns and slopes. Cooling of past interglacial periods have a linear decrease with an excellent regression. The linear equation and R2 are presented on each chart and slopes range from 0.40 to 0.31.

Table 2: Comparison of Onset and Cooling slopes for Warm Periods

Warm Period Onset Slope Cooling Slope
Warm II (MIS 5) 0.89 0.36
Warm III (MIS 7e) 1.10 0.80/0.34
Warm IV (MIS 9) 0.86 0.38
Warm V (MIS 11) 0.68 0.31

Hierarchy of Events and Accuracy Observations

Scientists have attributed interglacial warming and pacing to the Milankovitch cycles. The Milankovitch cycles consist of eccentricity (elliptical orbit), obliquity (axial tilt), and precession (wobble) of Earth’s orbit resulting in cyclical variation in summer insolation in the northern hemisphere. A strong case for obliquity dominance has been made by Javier and Tzedakis, and precession is favored by Ellis and Palmer. These papers provide excellent overviews of the Milankovitch processes.

It is interesting to note that scientists compare astronomical data with precise accuracy to geologic timescales with uncertainties on the order of +/- 5 kyr. Picking the exact onset age of an interglacial period, the precise peak of a climate optimum, and their durations can vary +/- 3 kyr depending on the criteria used. Precession cycles occur on an approximately a 20 kyr scale and obliquity on a 41 kyr scale. The geologic timescale and interpretation error is approximately 25% of a precession cycle and 12.5% of an obliquity cycle.

In the following analyses, Milankovitch processes (eccentricity, obliquity, and summer insolation) are correlated to different events based on degree of temperature variation and duration. These events are the longer term glacial cycle, rapid onset of interglacial warm periods, and interglacial warm duration and cooling. All references to insolation/summer insolation in this post are “Northern Hemisphere Summer Insolation at 60 degrees North” (Berger, 1992).

Glacial Cycle Control Observations

In general, the cycle of eccentricity from circular to more elliptical and back to circular takes approximately 100 kyrs. Additionally, each 100 kyr cycle can be predominately more circular or predominantly more elliptical (Figure 8).

There are five intervals of Glacial Cycles I-V over the past 450 kyrs that increased in duration from past to present (89 kyr long to 119 kyr long). They are not precisely 100 kyr events. Closer evaluation of the eccentricity cycles demonstrates that each cycle also varies in duration and are not precisely 100 kyr events.

Figure 8: Glacial cycles I – V plotted with Eccentricity (orange) and summer insolation (blue). Duration (kyr) between eccentricity cycles in orange, between summer insolation in blue, and between termination/onset cycles in gray. See Figure 2 for detailed glacial cycle correlations.

Eccentricity and precession/summer insolation appear to correlate with the duration of the glacial cycles (Figure 8). Each eccentricity cycle has become increasingly longer in duration over the past 450 kyrs. The eccentricity cycles generally correlate with the progressively longer glacial cycles. However, the duration of summer insolation cycles, which are strongly influenced by eccentricity, coincides nicely with the glacial cycle duration (Figure 8).

An interesting observation is Glacial Cycle V occurs when eccentricity cycles are predominately circular (Ecc 5). Glacial Cycle V is the shortest glacial cycle over the past 450 kyrs and lasted only 89 kyrs. Because Earth is currently in a circular orbit, the Holocene Glacial Cycle appears more likely to be analogous to Glacial Cycle V with a shorter glacial cycle.

Glacial Cycles II and IV occur when the eccentricity cycles are between circular and elliptical (Ecc 2 and Ecc 4). These cycles are 200 kyrs apart. Ecc 2 has an asymmetrical pattern because it is more elliptical initially and then continues to decrease to an almost circular orbit. Glacial Cycle II occurs during Ecc 2 and has the longest mild and full glacial period.

Glacial Cycle III occurs when the eccentricity cycle is the most elliptical (Ecc 3). Glacial Cycle III also is an exceptional cycle which has two warm periods; Warm period III (MIS 7e) and a second warm period (MIS 7c). During elliptical cycles, both obliquity and summer insolation are amplified.

Warm periods occur at the beginning of each eccentricity cycle as Earth is going from a circular orbit to elliptical. In the middle of each eccentricity cycle, as Earth’s orbit is going from elliptical back to circular, mild glacial to full glacial periods exist, except for Glacial Cycle III which has a second stunted warm period.

Warm Onset Controls

The most significant event of the interglacial/glacial cycle is the termination of the glacial period and rapid onset of the interglacial period. This has happened five times over the past 450 kyrs.

In geologic terms, the warm onset event would be described as an unconformity representing a significant geologic episode such as continental uplift or massive erosional periods. Therefore, the observed rapid onset of warm interglacial periods should be caused by powerful events such as an alignment of external astronomical forces (eccentricity, obliquity, and precession/insolation). Warm onsets only occur when three external forces are increasing: 1) eccentricity, 2) obliquity, and 3) summer insolation as shown in Figures 8 and 9. All major warm onsets have commonality of these three increasing astronomical forces escalating in combination. All three play a role although not always equally.

Figure 9: Obliquity (red) plotted with Dome C isotope/temperature data (gray). Each obliquity cycle is 41 kyrs apart. As discovered by Javier, ~a 6.5 kyrs shift demonstrates a good correlation with interglacial warm period duration.

Warm III (MIS 7e) is a good example. As Javier points out in his Figure 10, MIS 7e onset did not initiate when the obliquity cycle was increasing because insolation was decreasing. As soon as summer insolation began to increase combined with increased obliquity and increased eccentricity, then warming onset began.

Warm V (MIS 11) was also initiated by increasing summer insolation and eccentricity. However, the increase in obliquity was not far behind. Warm V has a lower onset slope possibly due to the predominance of insolation and a more circular orbit. This slower onset results in a more symmetrical pattern for the warm period. Warm periods tend have a slower onset such as Warm I and V during the time when the eccentricity cycle is predominantly circular (Table 2).

There are an additional five occurrences when obliquity increases without initiating a subsequent warm interglacial. These occur when eccentricity is changing from elliptical to circular and insolation is below 550 W/m2 (Javier, Table 5). Obliquity is only successful in initiating an interglacial warm when eccentricity transitions from circular to elliptical and summer insolation is increased. The only exception is a second stunted warm period (MIS 7c) that occurred during the most elliptical cycle. During elliptical cycles, both obliquity and summer insolation are amplified and enhanced obliquity could explain a stunted warm period.

There are approximately ten occurrences when precession/insolation increases without initiating a subsequent interglacial. During this time eccentricity was changing from elliptical to circular orbit and/or obliquity tilt was decreasing.

Steeper and stronger onsets occur when Earth’s orbit is more elliptical and more gradual onsets when the orbit is more circular (Table 2, Figure 8). Obliquity and precession/insolation are more amplified during an elliptical orbit and less pronounced during a circular orbit.

Warm Duration Controls

The past five warm periods last from approximately 10 kyr to 30 kyr (Table 1). The duration of the interglacial warm period correlates well to obliquity which appears to be a dominate control as proposed by Javier (Figure 9 and his Figures 9 and 12). Obliquity cycles are 41 kyr in duration and most of the warm cycles are less than the obliquity cycle. Obliquity increases precede the warm periods by about 6 kyrs due to Earth’s thermal inertia (Javier). Summer insolation cycles have a higher frequency of about 21 kyrs (11 kyrs for ½ cycle) and do not correlate as well as obliquity does with warm periods (compare Figures 8 and Figure 9).

Obliquity is the greatest control on duration and cooling of the warm periods. Most of the warm periods ended due to decreasing obliquity. Although it appears summer insolation frequently decreases during this time.

Warm Periods II and IV have very similar patterns as discussed in the previous section and Figure 5. These two interglacial warm periods occur during a semi-elliptical eccentricity cycle with a similar insolation and obliquity cycle (Figures 8 and 9).

Warm periods III and V are extremely different end members. Glacial Cycle III and Warm III occurs when eccentricity is the most elliptical. Glacial Cycle V and Warm V occurs when eccentricity is predominantly circular.

During the most elliptical orbit, obliquity has the greatest tilt ranging from 22.1 to 24.5 degrees and insolation is the greatest ranging from approximately 430 to 550 W/m2. When [insolation] is greater than 550 W/m2, it can result in an interglacial period (Javier, his Figure 12). Warm III has two warm periods during this elliptical orbit with amplified obliquity tilt and summer insolation cycles. This initial warm period (MIS 7e) was short lived because obliquity began to decrease and ended the Warm period prematurely (Javier). A second stunted interglacial occurs during this cycle, MIS 7c, and was initiated by amplified obliquity.

Interestingly, Warm V is the longest warm period in duration but has the shortest glacial cycle. The short Glacial Cycle V is consistent with the shortest eccentricity/insolation cycle as previously discussed in the eccentricity control. Javier has attributed the extended duration of Warm V (MIS 11) to an additional increasing insolation cycle in the middle of its period as shown in Figure 8.

2nd Order Control Observations

Several smaller warm events (interstadials) and abridged coolings (stadials) which last only thousands of years occur within each warm period. They are easily recognized in Figures 3 and 5. Many of the Holocene intermediate events have been extensively studied and named including; Boiling/Allerod warming interstadial followed by the Younger Dryas Cooling Stadial, and the intervening 8.2 kyr Stadial or cooling during Holocene optimum. Key stadial and interstadial events occur less frequently during warm periods than the Dansgaard-Oeschger cycles which occur primarily during mild glacial periods.

A cooling stadial that is equivalent to the 8.2 kyr event is present in both Warm II and IV shortly after the climate optimum causing the bimodal warming pattern. It is interesting that this event occurs 2 to 3 kyrs after the warm onset. Perhaps a decrease in precession triggered the Holocene 8.2 kyr cooling event as well as in Warm II and IV. The result was a meltwater pulse where glacial lake melting modifies the AMOC (Atlantic Meridional Overturning Circulation) resulting in a cool period.

Cycles of precession/ summer insolation which occur more frequently than obliquity cycles may explain the occurrence of smaller stadials and interstadials within the warm periods. Insolation and obliquity have different frequency cycles. Obliquity full cycles occur every 41 kyrs and insolation varies from 18 to 23 kyrs. Insolation could be a second order modifier on obliquity and initiate an overprint creating a stadial or interstadial during or between obliquity cycles.

Conceptual Models for Warm Periods

A generalized model for Warm II and IV is proposed in Figure 10 to demonstrate the hierarchy and timing of astronomical processes and oceanic processes on these similar Interglacial Warm periods. It is simplified from the detailed science describing these processes and serves as a guide for whether astronomical or oceanic processes dominate. The model assimilates the processes discussed in the previous section for the Holocene and by Javier.


Figure 10: Summary of processes for Warm II (blue) and IV (green) warm periods. Horizontal axis is relative time for kyr. Onset occurs during increasing Eccentricity, Obliquity, and precession/insolation. Obliquity is dominant control over cooling and thus, warm duration. Higher frequency precession/insolation creates stadials and interstadials.

Warm II and Warm IV occur during a semi-elliptical eccentric cycle (Ecc 2 and 4) and are approximately 200 kyrs apart as show in Figure 8. The rapid warming onset require the Milankovitch cycles (eccentricity, obliquity, and precession/Insolation) to be increasing simultaneously or within close timing of each other. These combined cycles terminate the previous glacial period and initiate the onset of the warm interglacial period. Most warm duration culminations coincide with obliquity which subsequently controls the duration. Warm durations can be interrupted by higher frequency insolation creating either a stadial (8.2 kyr event) as in the case of Warm I, II and IV or an extended warm period as in the case of Warm V. The minor temperature fluctuations of +/- 1.5 degrees C during the flatter portion of the warm durations are dominated by oceanic processes (Javier).

A conceptual model is also proposed for the anomalous Warm III and V periods in Figure 11. Eccentricity is very small or circular for Warm V and very elliptical for Warm III. As discussed in the onset section, increasing insolation may have initiated both warming periods with obliquity increasing shortly thereafter.

Figure 11: Proposed processes for anomalous Warm III and V periods. Horizontal axis is time in Kyr. Onset occurs during increasing Eccentricity, Obliquity, and precession/insolation. Vertical axis is relative global temperatures. Curves are Dome C isotope/temperature data.

Warm III had the steepest onset and cooling slopes. The first initial warm period was short-lived. A second stunted warm period occurred approximately 40 kyrs later. The glacial cycle was also one of the longest at 113 kyrs. During the most elliptical cycle, both precession and obliquity are amplified and can initiate a stunted “interglacial” period like MIS 7c.

Interglacial warm periods and glacial cycles show the following characteristics during Elliptical orbits:

  • Astronomical forces dominate during the elliptical orbits. Both Earth’s axial tilt is more extreme and Earth’s wobble is more dramatic.
  • Glacial cycles tend to be longer (>100 kyrs).
  • Temperature changes are dramatic and abrupt with rapid warm onsets and faster cooling slopes.
  • Obliquity increases can result in a couple of interglacial periods.
  • Predominantly elliptical orbits repeat approximately every 400 krys.

When Earth is in a circular orbit like Warm V and present day Warm I, Earth’s tilt and wobble are less. Subsequently, astronomical forces play a lesser role in the interglacial warm periods. Obliquity tilt and summer insolation still control the warm initiation and closure. However, onset and cooling are more gradual.

Warm V onset was primarily driven by an early increase in insolation and a second increase by obliquity. The warm period was extended by a second summer insolation pulse resulting in its optimum. The warm duration finally ended by decreasing obliquity. The quiet or more stable portions of the long warm period were probably dominated by oceanic processes.

Circular orbits show the following characteristics:

  • Circular orbits have less obliquity tilt, lower precision wobble and less summer insolation.
  • Glacial Cycles tend to be shorter (<90 kyrs).
  • Warm onsets and cooling are more gradual resulting in more symmetrical patterns.
  • Oceanic processes dominate during the warm duration creating minor temperature changes (+/- 1.5 degrees C).
  • Predominately circular orbits repeat approximately every 400 kys.

These models were an attempt to compile astronomical and oceanic processes discussed by previous authors (Javier and Ellis and Palmer) and to explain the various repeatable patterns seen in the Dome C isotope/temperature data. Although process interactions are very complex, separating out predominate causes and effects on global temperature should help improve future climate simulation models. Climate models need to include astronomical as well as oceanic and atmospheric forcing to reliably predict future temperature changes and the duration of the Holocene interglacial warm period.

Astronomical processes appear to be the key control for significant temperature changes. Oceanic and atmospheric processes create minor temperature fluctuations during warm periods. However, the culmination and eventual cooling is astronomically controlled. It is impossible for humans to control Earth’s orbit, tilt, or wobble. Since astronomical processes affecting significant climate changes are out of our control, a focus on adaptation instead of climate manipulation is a much better use of resources.

Summary and Conclusions

A Glacial Cycle traverse illustrates that the duration of interglacial/glacial cycles progressively increases from past to present over the past 450 kyrs and are not a simple 100 kyr cycle. Eccentricity and its influence on summer insolation appears to play a dominate role in the duration of glacial cycles. Circular orbits tend to have shorter cycles (<100 kyrs) and more elliptical orbits tend to be longer (>100 kyrs).

Conceptual models are proposed using astronomical and oceanic processes described in the literature to explain repeatable patterns observed in past interglacial warm periods. Prioritizing dominate processes operating in different warm periods may provide general guidelines for future climate models.

Past Warm II and IV periods are well behaved and exhibit strikingly similar warming/cooling patterns suggesting a repeatable interplay of astronomical, oceanic, and atmospheric processes. These repeatable patterns occur every 200 kyrs during semi-elliptical eccentric cycles.

On the other hand, anomalous Warm III and V periods tend to have less predictable patterns and are unique. Warm III occurred during the most elliptical orbit and Warm V during the most circular orbit. Glacial cycles during elliptical orbits tend to have rapid onset and several warm/cool periods because obliquity is amplified and summer insolation dominates. Warm periods during circular orbits tend to have slower warm onsets and are more symmetrical. Oceanic processes may play a greater role during the warm periods but play a minor role in controlling the onsets or eventual cool periods.

During the last 450 kyrs, the five major warm onsets with rapidly increasing temperatures are triggered by increases in the eccentricity, obliquity, and precession of Earth’s orbit. The nearly concurrent increase in these three astronomical forces appears a necessary component for a major warm onset. Obliquity is the dominate control for ending these major warm periods and entering a cooling phase.  Higher frequency procession/summer insolation appears to play a secondary role in overprinting the duration pattern with a stadial event such as the Holocene 8.2 kyr or extending a warm period like in Warm V. Oceanic processes dominate during periods of minor temperature changes (+/- 1.5 degrees C).

Dome C isotope ratios and their associated temperature estimates in combination with astronomical data provide ample evidence that astronomical forces control warming and cooling cycles. Because the astronomical processes affecting significant climate changes are beyond human control our focus should be on adaptation rather than climate manipulation. It is not a question if cooling will occur but simply a question of when.

Special thanks to Andy May and Donald Ince for reviewing and editing the article.


161 thoughts on “Paleoclimate Cycles are Key Analogs for Present Day (Holocene) Warm Period

  1. This needs to be published. I’ve read some of your articles on LinkedIn, which are also excellent.

      • Superb! A really, really interesting article and a tremendous amount of work! It should definitely be published in my humble opinion. Thanks for submitting it and thanks to WUWT for providing so much interesting stuff to read. Science isn’t dead after all.

      • Honestly… Am I the only geo who sees cycles in just about everything I look at?

        Figure 2 is really cool… A stratigraphic cross-section of glacial stages.

      • David, no you are not the only one. Almost all natural phenomena is cyclic. As long as there are oscillatory cyclic forcing functions the outcomes will be cyclic as well.
        It’s only now with our better astronomical observations that we are beginning to determine the correlations between orbital cycling and energy flux on earth.
        The issue may be in humanities inability to comprehend timescales or dimensions beyond our limited comprehension. Most cannot see the wobbling top that is earth as it orbits and precesses because it occurs over too long a time scale.

      • Some ten years ago I was described by Dr. S as a ‘cyclomaniac of supreme ignorance’, surely must qualify for a free life long membership.

      • Andy May, thank you from the humblest of layman for all your work of late editing and proofing all these wonderful posts. And your 4 part series was fascinating, particularly (for me) part 4. My big take away there was that as the northern hemisphere has cooled, the southern hemisphere has warmed. BUT, it hasn’t warmed to the same degree as the northern hemispheric cooling. That one fact, to me, is telling (and may well be the death knell for agw theory). Oddly strange, as your part 4 was perhaps one of the very best posts that i’ve yet to see here at wuwt, it only received fewer than 100 comments! (i mean, WUWT?!)…

      • Good work, but I would add a Figure 2B, restarting each series at the beginning of each cycle, when each inter-glacial begins. I’d like to see how closely the red, green, and blue lines match up. (I’m not sure why you started at the end of each book and read backwards in time.)

      • Figure 2 is consistent with how geologic cross sections are constructed which enable viewing the Earth as if it were cut open from the side. Therefore, youngest is at the top and oldest at the bottom. Thanks for your comments.

    • Eccentricity appears to be a control on the duration of the glacial cycle not necessarily the duration of the interglacial warm period. Since both Glacial Cylce V and I occur during a predominately circular orbit, their glacial cycle may be similar and shorter than 100 kyrs. This does not necessarily suggest that the interglacial warm periods (MIS 1 and 11) will be similar. MIS 11 warm period was extended due to an secondary summer insolation pulse. Obliquity is currently decreasing which may end MIS 1 warm period on time, consistent with other past Warm periods.

  2. How much time before the end of the current Holocene inter-glacial? It seems that temperatures in the past fell quite abruptly leading into the next glacial period. And the trigger…Milankovich forcings only partially explain.

    • I put a range in the article for the cooling of the current Holocene interglacial when compared to the past interglacial. The end of the Holocene warm ranges from hundreds of years to ten thousand years. However if decreasing obliquity is the key control on cooling, a more precise forecast can be made.

  3. Excellent. Apparent that research such as Javier’s and Renee’s are getting close to the true explanations of the ice-ages. Yet research of this important type seems to be ignored compared to the fake scare-mongering stuff.

    • Beng135:
      Dont forget, none of these factors actually explain WHY we are presently in an ice age. It just addresses some of the details about the odd cyclicity imbedded into it. These M cycles have been presumably occuring for 100’s of millions of years without pushing the planet into an ice age. So the other question remains, what started the downward slide in temperatures between Miocene and now, and what will need to happen for overall downward trend to reverse itself?

      • Maybe we were hit with something? Or had a gravitational nudge. The solar system does move around a spiral arm of our galaxy. I would look for the big picture to explain it too. Certainly the earthly climate-ocean stuff had nothing to do with it.

      • Steve are you serious? You can pick up any geology text and many other books that have detailed explanations of what triggered the onset of glaciation. I refer u to Canada Rocks, chapter 9 – The Ice Sheets Arrive & page 332 but I encourage u to read the entire chapter.

      • I suggest we look at the changes in ocean currents with separation of the continents due to tectonic plate movement.

      • Steve R. – Tectonic movements – sliding around to present position with land-locked north pole and sea-locked south.

      • Steve,

        No mystery there. The posited cosmoclimatological glaciation cycle might be in play, but what clearly is important is plate tectonics and oceanic circulation derived therefrom.

        The key event in triggering a cooler and drier earth was the separation of Antarctica by deep oceanic channels from South America and Australia at the Eocene-Oligocene boundary. This set up the Southern Ocean and caused rapid ice sheet formation on Antarctica. When the Southern Ocean briefly shoaled between South America and West Antarctica during the Miocene, the ice sheets waned.

        The next important event was the closure of the Inter-American Seaway by the Isthmus of Panama at the Pliocene-Pleistocene boundary. The impact on oceanic circulation led to the initiation of Northern Hemisphere ice sheets. A narrower, shallower version of the Seaway briefly reopened around 1.8 Ma (the old start date for the Pleistocene), but the gap was too negligible to have much effect on oceanic circulation.

      • Plate tectonics has an effect, if the land masses prevent oceanic currents from mixing the polar and equatorial regions, the poles can get below freezing. If they don’t the poles will be kept warm enough to prevent ice from forming.

  4. Very good. This is where climate science should have been focused for these past few decades. Until we can explain the big details about the current interglacial, it seems we have little chance of filling in the small details (like CO2) correctly.

  5. Before blindly accepting that Milankovitch cycles are the cause of glaciations and interglaciations, the author ought to investigate evidence contrary to M cycles and the assumptions built into the correlation of climate with M cycles. Once you accept the M dogma, it’s easy to assign percentages of orbital parameters, but as a geologist pointed out years ago, you can find patterns in a keg of nails if you try hard enough.

    • I don’t think anyone is blindly accepting M-cycles. Its not like we are going to take a consensus vote so relax.

      • Don is right, its always wise to look in the mirror. Confirmation bias is insidious. The consensus never finds the keys to unlock the secrets to anything. Look for information that exists that you may not even be aware of as a matter of practice.

        I have been crushed and blessed many times using this practice. I learned this lesson from my father to hunt deer. He said “The deer are not where you think they are. The minute you enter the woods their job is to keep track of you. Walk for a bit and then stop, be very still and the deer will walk right into you. He was right but I couldn’t shoot such a beautiful creature. I could eat them but not shoot them.

    • There’s a reason that an incoherent dipmeter is called “a bag of nails”… Not even geologists can find a pattern in it… LOL!

    • @Don- Is there some particular contrary evidence that you think bears on this concepyual framework?

      • Yes, there is a lot (which I’ve commented on them many times on WWUT). Some of the most significant are:
        1. The N Hemisphere should be out of phase with the S Hemisphere but glacials and interglacials are almost exactly synchronous between hemisphere.
        2. M cycles are far to slow to explain the rapidity with which major climate changes occur.
        3. Younger Dryas climate changes from full glacial to full interglacial, back to full glacial, and back to full interglacial occurred in less than a century, far to quickly to have been caused by M cycles.
        4. The basis for correlation of orbital changes to climate were originally made by ‘stretching’ and ‘compressing’ curves until they fit, then claiming that the correlation ‘proves’ M cycles as the cause of glaciations and interglaciations.
        5. And a bunch more.

      • The point 1 above about n/s hemisphere being out of synch is not entirely correct. Eccentricity drives total annual insolation, globally, unlike the other two orbital parameters.

    • Don, I was not trying to imply that M cycles are the only cause of glacial and interglacial cycles. I am proposing a conceptual model to highlight when astronomical forces were more dominant influences versus oceanic influences. And I do appreciate the fact that dust and other factors play a partial role in the onset of interglacial periods. I would appreciate your thoughts on other key forces to evaluate for glacial cycle duration, interglacial onset and eventual cooling.

      • Exiting new data now show excellent correlation between sun spots, total solar irradiance, influx of cosmic radiation, cloud production from ionization by incoming radiation, and global temperatures. These correlations are summarized in a paper I wrote for the Elsevier volume, “Evidence-based climate science.”

      • Don, how is it that insolation variations can explain a cooling northern hemisphere, and a warming southern hemisphere over the past 7k years of the holocene? (thank you in advance)…

    • Yes, but if we are in a cycle similar to V, then it’s quite a while off, if I read this correctly

      • The duration of glacial cycle may be similar during circular orbits, not necessarily the duration of the interglacial warm period. The cooling and ending of the warm period corresponds more to decreasing tilt, obliquity.

      • It would be hilarious if it wasn’t completely tragic. Humanity bands together to fight Global warming when in fact it is actually cooling on just a slightly longer time frame. The trillions spent on reducing meaningless CO2 could buy us a massive orbiting reflector or moon based reflectors to increase insolation and save us all from being buried in ice.
        Perhaps such a device could also be used to fry grasping, self indulgent politicians and actors.

      • Every time I hear some proposal for geo-engineering using reflective mirrors in space or sticking stuff into orbit to “control the weather”‘ I get really worried. We don’t have enough knowledge to risk messing about in this kind of way and could create a real catastrophe. At the very least we risk damaging astronomical research and satellite communication systems.
        Ironically there is some Hollywood scare fest about to hit cinemas in which some satellite climate control system goes haywire and starts frying up the Earth’s surface, presumably because some bad guys hack the controls. Vaguely plausible, the most scary part is that the part of the President of the USA is played by an Al Gore lookalike (good casting I suppose).
        I don’t think I could sit through another climageddon film starring Al Gore without starting to either laugh or scream hysterically so I guess I won’t be going to watch this.
        But life often follows fiction so please discourage the grossly irresponsible ideas to use orbital debris as a means of experimenting with climate.
        Perhaps it really is Al Gore in the film !

  6. Good, if dense, review of ice age cycling. Looks a lot more like astronomy than Fred Flintstone’s SUV.

  7. Thank you very much for the citations, Renée. Without trying to be an interested party, it is a very good article that goes quite in depth into the main issues that play a role in the glacial-interglacial cycle, and very well written and educative for the non initiated.

    I’d like to abound just on a couple of points.

    Regarding the duration of the present interglacial, the astronomical disposition of precession, and more importantly obliquity, clearly classifies the Holocene as a standard interglacial. This means that it won’t last more than 4k years, but it could be less. My personal bet is 2k years, but I don’t expect to be around to collect. That is unless the CO2-maniacs turn out to be correct and both climate sensitivity is really high and CO2 is really stable in the atmosphere. I consider each very unlikely and the probability of both being correct exceedingly small.

    Already the Little Ice Age was a time when the world was very close to glacial inception, and glaciers grew to their maximum extent. But the rebound at the end that still continues probably bought us several millennia. Instead of freaking out over the warming we should be celebrating.

    Once this interglacial ends it will be ~ 70,000 years until the next, unless we learn to control the orbit of the planet or the climate, also very unlikely. During this time temperatures will not suffer a collapse but will be decreasing at a rate that is slower on average than the rate we have seen during global warming. The problem is that agriculture will become progressively handicapped. We should have more success dealing with that problem. We can move to greenhouse, high yield hydroponics on a CO2 rich atmosphere. We could also try to ameliorate the glaciation by playing with albedo, or a number of solutions that we cannot even imagine. It should be the end of the world.

    The Younger Dryas appears to have been a freakish event that affected greatly the Northern Hemisphere, not so much the Southern Hemisphere, and almost nothing the oceans (barely noticeable in LR04 benthic core). It coincided with a time of low solar activity, but that doesn’t seem sufficient. There is some evidence (not enough) that a meteorite could have also hit at the time. Other unknown factors might have contributed, perhaps an abrupt change in the Atlantic Meridional Overturning Circulation, or a Heinrich event producing huge amounts of icebergs. There is evidence for all of them. Perhaps a cosmic coincidence.

    • It shouldn’t be the end of the world.

      A comment editor is sorely missed by those of us that hit the button without reviewing.

    • Thanks Javier. I very much enjoyed reading your articles. And I agree that the Holocene interglacial warm will be similar to Warm II and IV (MIS 5 and 9), but with a shorter overall glacial cycle.

    • Think you mean “expound” rather than “abound”.

      There is nothing the least bit unusual about the Younger Dryas or the Dryas events that preceded it during the last termination. Every termination is marked by such cooling events, as major meltwater pulses enter the oceans.

      The odds against a celestial impact are literally astronomical. There is no physical evidence of such a highly improbably event, and no reason to suppose such a thing. The latest stag in the dark du jour is an alleged platinum anomaly in Greenland ice and at some sites in North America.

      I’m with Mark Boslough, an impact physicist at Sandia National Laboratories in Albuquerque, NM, quoted by Earth Magazine, who (with the vast majority of geologists) remains unconvinced that a large impact occurred at the beginning of the Younger Dryas. “The working hypothesis [for the impact theory] is always changing. Sometimes it’s an airburst, sometimes it’s an exploding comet that struck many different places, sometimes it’s a single impact that hit ice or water,” Boslough says. “I am all for having multiple working hypotheses but you need to limit them to those that are physically possible and consistent with the evidence,” he says. In short, he says it’s unlikely that an impact that left no crater could have had climate consequences globally, but if something big did hit ice or water — explaining why there is no crater — it would have produced copious steam, but not the shocked minerals or nanodiamonds that previous studies have claimed as evidence for an impact. Regarding the newly described platinum anomalies across the US, Boslough says he’s awaiting independent confirmation of the results by other researchers.

      It should be obvious that whatever slightly elevated platinum might actually exist, it can’t be of ET origin, since none of the other element markers or other indicators of an impact have been found. Just more of the same from the same crew who have tried to eke out a career from this evidence-free, ludicrous, false on its face assertion.

      • Gloateus, that is why I said that the impact evidence is not enough. Without a crater and/or a proper signature the impact hypothesis will remain not sufficiently supported by evidence.

        I disagree that every glacial termination is marked by a YD type of event, or at least I have not seen that evidence myself. Renée has been so kind as to provide a figure 6 above with terminations II, III, IV, and V, and none of them shows a YD event. If termination I was there you would see a clear difference with the rest. YD in the middle of the warming shoot, that probably sabotaged the interglacial maximum temperature, remains a unique event as far as we know.

        Regarding the Pt spike, its magnitude is very rare in the ice core, and its temporal coincidence absolute. And the chance for that is small. It is clear to me that this spike has to be related to the YD. The Pt origin can be due to terrestrial or extraterrestrial causes, and in my opinion finding a terrestrial cause might prove more difficult. Pt mining was not well developed in the Paleolithic.

        Regarding the absence of a crater, absence of evidence does not constitute evidence of absence.

        While I remain skeptical of the impact theory because of, as I said in the above message, insufficient evidence, I also think that the hypothesis cannot be dismissed summarily as Mark Boslough does.

      • Javier,

        Please see Renee Hannon August 4, 2017 at 1:23 pm

        She mentions the YD event for Termination V.

      • Javier
        I’m a great fan of your writings but here I agree with Gloateus that the YD is normal glacial period instability and does not require special explanation. You yourself have shown how the greater equator-pole temperature gradient during glaciation gives more climatic “potential energy” and ultimately instability. In fact for me it is the Bolling-Allerod that is a real phenomenon rather than the YD which is just the interval between the BA and the Holocene. Is not the BA just the last of the many D-O events or “micro-interglacials” that occurred during the last glacial interval. Probably brief self-terminating excursions of the AMOC.

  8. I don’t believe 4 cycles is enough to tell you anything about something as chaotic as glacial cycles.

    • Except that they are not chaotic but deterministic. Milankovitch predicted that their spacing should be according to orbital cycles. It was found later that it is.

    • MarkW,

      Javier is absolutely correct. The ebb and flow of ice ages is completely deterministic from orbital variability (see the plot I posted on a previous comment). The next ice age is inevitable and no amount of atmospheric CO2 will prevent it from happening again. If alarmists want something to worry about that we know with absolute certainty will occur, they should worry about a km thick glacier bearing down on the East Coast of the US, much of Europe and most of Russia. This will displace 100’s of millions of people, cause trillions in economic harm, precipitate global famine and result in widespread disease, just as it has in the past. During the last ice age, rather than displacing 100’s of millions, the regions impacted were largely unpopulated by man. This inevitable consequences will be a whole lot more inconvenient than a few cm of ocean level rise or a phantom temperature trend.

    • I think this is real science, with a derived hypothesis put forth for consideration and supporting evidence or refutation. Completely unlike the AGW hypothesis which uses contrived and/or utterly false narratives and appeals to emotion. Anyone is free to pose challenges or data which provide a superior explanation. There is probably a lot of room for questions regarding the exact mechanisms or triggers as well as a great deal more detail on shorter time frames. This is honest to G correlation with actual events which can be verified. If instances can be found where the correlation doesn’t exist, that would be fair criticism and require satisfactory explanation. Likewise, one would hope that the detailed mechanisms within the broad cycles can be identified to flesh out exactly how these events transpire. That information would be potentially very valuable to the human race. Hopefully before the polar bears become the dominant species.

    • Mark,

      The cyclic record goes all the way back to the start of the Pleistocene, at least. The difference is that from ~2.6 Ma to ~1.0 Ma, the cycles are 41,000 years.

  9. Examining ice cores was one of the first steps of due diligence I applied to climate science and there’s absolutely no doubt that the primary influence is orbital and axial variability.

    The precession of perihelion has a large effect owing to the asymmetries between hemispheres, where the S is mostly water and the N is mostly land, moreover; the snow belt in the S is mostly over water, thus snow doesn’t have as much of a chance to accumulate. As the orbit gets more elliptical this effect is amplified. One thing that the consensus fails to recognize is the importance of hemispheric asymmetry relative to how orbital and axial variability drives climate change.

    The axial tilt affects the relative strength of the seasons. At low tilt angles, cold is concentrated towards the poles and heat is concentrated in the tropics and polar seasonal variability increases. As the tilt increases, the isotherm of 0C migrates towards the tropics as tropical conditions migrate towards the poles and polar seasonal variability is reduced.

    I’ve also noticed that the 3 orbital and axial variabilities act independently and when the peaks align, we hit the min and max temperature extremes with changes in axial tilt driving transitions. If they don’t align exactly, interglacial and glacial periods will be longer, but less intense, as has been the case for the current interglacial period which has been both longer and cooler than the last one.

    Here’s an interesting plot of ice core data (DomeC and Vostok) smoothed to 22K years in order to cancel out the effects of the precession or perihelion. The effects of axial tilt and ellipticity are clearly evident. It also looks like the temporal alignment of the two cores is quite different as we go further back into the past.

  10. While we may not be able to control earth’s orbit, it is not actually the position of the earth and sun that is the forcing (god I hate that word). It is the variation in strength and uniformity of solar energy (insolation?) that results from those cycles.

    Instead of bemoaning something we cannot control like orbits, seems to me we should be looking into methods for increasing (cause I like warmer) the solar energy to compensate and make more comfortable the planet on which we live.

    Although I realize the stress on lack of control is to combat alarmist taxation fantasies. And of course unexpected consequences may be worse than the cycles we have hehe.

  11. I skimmed a lot and will go back to this very interesting post. Thank you Renee. It has been my view (and that of many others) that a bottom up approach favored by the proponents of CAGW IS simply, totally unworkable. Proponents have kindly falsified the approach themselves for us by their preoccupation with jiggering the data to try to fit model performances to observations and missing the mark by 200-300%. I’ve argued that top down from the big geological changes are the only way to frame modelling.

    I don’t subscribe to the chaos view of climate change that most sceptics do when they pooh pooh the CAGW folks’ “It’s physics, don’t you know”. The path of an air molecule has no self will or mysteriousness. It does go where it is ordered to go by the physics. However, it is metaphysics to think you can corral and bin all this into a predictive model of any use, and, attractive as it may seem with it’s pretty patterns and things, chaos and it’s “strange attractors” is really a metaphor for too tough a problem to solve.

    An engineer has no problem with PV=nRT without being concerned about the details of what’s happening inside the package. The large view of climate is a similar integration. The biggest warming occurs in the big picture and the short term ocean based effects will have brackets on variability imposed by the ocean. Net feedbacks will be negative, period, as long as we have an ocean.

    • JV,
      Try Science magazine back in the mid to late-’70s, which is where I first saw a Fourier analysis of the cycles, giving credence to the Milankovitch claims.

  12. Warmists hate paleoclimate data as there is very little evidence of the co2 control knob. Very good post!

    • Yeah too bad in all of eternity, the earth hasn’t had the opportunity to reveal how it would respond to this much CO2 increase in this short of time. We just have to assume there would have been no effect on top of the existing cycles, and go with that then.

  13. My link, , shows how the interglacial cycles can be explained by paramagnetic oxygen and wandering magnetic poles. This is not nutcase stuff, no pyramids etc. The paper takes a long time to study, but it is a promising theory. Let’s discuss the possibilities.

  14. Just another nail in the coffin of AGW, good science hopefully will prevail. Can anybody (Geos) suggest an explanation for what started the cycles such as the closing off of the central american isthmus and the Pacific/Atlanta currents?

  15. OK so we’re on a Tilt-a-Whirl ride around the Solar System. What’s all this CO2 crap about?

  16. What is a bit concerning is that the LIA (Little Ice Age) began 300 years before the long term solar minimums. Perhaps volcanoes had something to do with the onset of Global Cooling. But, that raises more questions. Did ENSO become less of a climate driver? Orbital mechanics cannot account for the onslaught of cooling, which began in the NH sometime before 1315.

    • I think the orbital mechanics are presented as the driver of the major modal shifts while events like the LIA may be a big deal for humans but don’t really register as important events in the larger scheme of things. If the overall pattern can withstand scrutiny then the next task will be to look for evidence of what smaller phenomena cause or contribute to these smaller events. Until we get rid of the notion that CO2 is responsible for every frosty morning or ruined picnic, no real science can or will be done. The fact that it takes real courage for someone to publish such obvious information is pretty telling as to the intellectual environment Renee is to be applauded for this work.

  17. Excellent. There’s always a sense the warmists are looking through the telescope at the wrong end. Big, long-term forces: geology, astronomy.

  18. Excellent, thorough and informative analysis. I plan to re-read a few times. Two points: (1) the article sadly omits to mention a fine Younger Dryas type event in Warming V, clearly seen on the chart, (2) Outside of the scope of this article, it would be interesting to analyze the start of the ice age cycles — that is, prior to the start there were no ice ages and the climate was more stable, right? So what happened to change that into the current ice age cycles. I know this is cutting edge stuff, but if climate science can’t explain the ice ages (which at this point they can’t, although they can correlate them with orbitals but no heat budget is known) then they can hardly pretend to tell us what’s going on now (ok, they can pretend).

    • NZ Willy, I did briefly mention the Warm V “Younger Dryas” equivalent in 2nd paragraph under Warm III and IV Anomalous Warm Periods and in shown in Figure 5. See below.

      “Warm V has a similar initial temperature as the Holocene. However, it quickly enters a brief cooling (Figure 5). It is not certain whether this brief stadial at 423 kyrs is equivalent to the Holocene Younger Dryas stadial or the 8.2 kyr cooling (Figure 2). Warm V is unique because it has an extended warming period that is even warmer than the initial climate optimum. Warm V’s second extended warm is almost 2 degrees C warmer than present-day (Figure 5).”

  19. @author
    Interesting and informative. Minor quibble – your figure 10 labels for the x axis (relative time) are mislabeled relative to the tick marks. Confusing, that’s all.
    I have read Javier’s posts over at Judith Curry’s blog – perhaps you should consider cross posting this article there too for greater exposure.

    • Good catch on figure 10. Labels must have shifted during reformatting. I’ll definitely get that corrected.

  20. Renee – fascinating article. Is it available some place where your charts can be viewed full-size and printed?

    The very first chart, I believe, is all one needs to debunk CAGW. Ask anyone who has drunk the cool-aid how it is possible to prove that the very last tick on the chart is due to anthropogenic CO2, and every other point on the chart is natural.

    The second point to make is that the +2 mark is nothing to worry about when compared to the -2 mark which will signal a real existential threat to mankind. We are worrying about the wrong problem.

  21. AND YET, we keep hearing from the agw crowd that ECS is 3C because that’s what the paleo data tells us. And, pray tell, HOW is the paleo data telling us this? If anything, one would think, the paleo data is telling us that CO2’s role is very small. Think of all the massive earth changes that we see from glacial to interglacial. Changes in orbital shifting, albedo, water vapor (which dwarfs that of trace CO2) to name a few. And the resultant change in global temperature from all of these major earth changes is only 4-5C. How is it that tiny CO2 plays anything but a minor role in what we see in the glacial cycle?

    • Afonzarelli: “Think of all the massive earth changes that we see from glacial to interglacial. Changes in orbital shifting, albedo, water vapor (which dwarfs that of trace CO2) to name a few. And the resultant change in global temperature from all of these major earth changes is only 4-5C.”

      WR: Great observation. Blames all IPCC forecasts.

      • Yes Robert, I agree. However if we can separate out key controls and on what part of the cycle they are operating on, then we can make some intelligent forecasts.

      • I agree, Renee — we CAN, I believe, make some intelligent forecasts, as opposed to the sort of … “forecasts” that we encounter today, seemingly based on intervals of observation that are way too short for the patterns we wish to forecast.

        We have to look at data outside of human-lifespan intervals, together with data within human-lifespan intervals to do this. The current … “forecasts” seem myopically focused on the latter, unless I totally don’t get it.

  22. I think this is a marvelous explanation of the macro factors in controlling earth’s climate. I do think there is room to look at the micro factors, like solar variability and the behavior of the oceans, to get to a comprehensive description to the mechanisms of climate.

    • Dave, a better understanding of the micro factors will surely help predict the minor temperature fluctuations that occur during the Warm durations. I also believe micro factors assist the macro factors and create the unique characteristics of each interglacial cycle. First we need scientists to accept which factors are really key so we can focus time, energy and funding on them.

      • “First we need scientists to accept which factors are really key so we can focus time, energy and funding on them.”

        Dr. Spencer says that all the time. We can’t figure what portion of warming is anthropogenic until we figure out what portion of warming is natural…

  23. A great article. Thank you for an excellent analysis of complex data. Good stuff for the science folks that inhabit this WEB site.
    But. Far too complex to sell to the public. Eye glaze will defeat the best analysis.
    Can anyone write a 3 page summary targeted at high school graduates?
    Lots of pictures.
    Something the denizens of the WEB will understand. And our politicians.

    • The process I typically follow is to run the detailed data by my scientific peers to determine the strengths and weaknesses of my hypothesis. This will help refine the existing model or result in multiple scenarios. Then I will eventually pull together a simplified presentation for management.

  24. Can anyone write a 3 page summary targeted at high school graduates?

    … interspersed multiple times with entertaining diversions, like maybe the latest pop song sensation, or the next fashion craze, or the next generation iphone ad, … or, heck, maybe even ads for car insurance?

    Can’t keep the old attention span too bottled up on one line of thought, you know. Focused concentration is old school, … an antique, … a thing for independent thinkers — weirdos! Tell ’em what you’re gonna tell ’em, … tell ’em, … tell ’em what you told ’em, … and entertain ’em every step of the way. Throw in some jokes. Don’t be too serious. End sentences in question marks, in order to visualize that strange questioning tone of intonation that young people employ today when they speak, … just to keep it real.

    Nah, I’m not being sarcastic.

    • I am only a high school graduate. The article says that climate changes cyclically, mostly due to the earth wobbling about its axis. The rest of the article uses data to provide evidence for that assertion. Didn’t take 3 pages.

  25. 1. The Onset of the Holocene and its forcing is well explained in Part 1 of Holocene Pattern
    Recognition in

    2. The figure 9 of Javier is incorrect: The true obliquity of Warm One Max is (wiki) at 8700 BC
    (10650 BP) at the
    height of 24.5 degrees… and Javier put it lower at 24.25 and at least 2000 yrs later. Then
    there is the attempt of 6 kyr shifting below it without astronomic reasoning….

    3. The obliquity curves in figure 9 differ in amplitudes and periods, compare the narrow bottom
    width of MIS 9 to the wide bottom width of the next wave…. curfe fitting…..

    4. The article, unfortunately does not understand the concept of orbital eccentricity and
    circularity. The following: The interglacials occur, when the Sun (on its way from one
    focus via the center to the opposite focus) reached one focus position and carries out,
    within this focus interglacial, its RETURN movement, because the Sun cannot stop on
    its way, brake and
    go backward. The Sun does its turnaround WITHIN the interglacial in the FOCUS position.
    The long glacial is the way back after a completed turnaround. Therefore, there cannot
    be a interglacial with a CIRCULAR orbit. The elliptical orbit is reserved for interglacial focus

    We clearly have a crude obliquity 41 kyr curve produced by curve fitting intent, therefore the
    true curve top and bottom dates were shifted to gusto and the amplitudes do not match the
    real values.
    Sorry for going into details, messing up the obliquity party. .

    • J. Seifert. Thank you for the reference articles about the Holocene onset and detailed climate pattern studies.

      I agree there is a higher order 100 kyr cycle and your Milankovitch sun motion cycle explains it well. You state the orbital process related to the sun’s motion much clearer than I was able to. Is your M line similar to the eccentricity cycle and if not, what is the difference?

      I concur that obliquity is second order to the Milankovitch line which initiates interglacial onset. However, there appears to be a shorter term astronomical effect which initiates cooling of the interglacial periods. Perhaps obliquity?

      I do have a several questions on your analyses of Holocene interglacial temperature controls. You calculate a sinuous EOO-wave which is a control on temperature during the Holocene interglacial period. If I read your study correctly, it is masked almost 70% of the time by cosmic meteor impact and volcanic eruptions creating short cooling events such as the 8.2 kyr event. This makes predictability of temperature variations during interglacial more challenging.

      Warm Periods II and IV in my post have very similar bimodal patterns and show a cooling event similar to the 8.2 kyr Holocene event (Figures 2, 4). Of course, my analyses compare larger events and not the details you reference in the Holocene. However, the timing and similar temperature duration of the key 8.2 kyr equivalent in the Warm II and IV interglacials makes me believe it’s not a random cosmic impact, but a well behaved astronomical event.

      Thank you for your comments and I appreciate any further discussion.

  26. Great article. What I would like to see – following several of the other comments – is for the analysis to be extended to incorporate other inputs. Orbital cycles are one element, now correlate in the Sun’s galactic motion, the Sun’s various cycles and known behavior, continental drift, and magnetic pole movement. As was discussed in previous articles, the climate is a chaotic system and cannot be reduced to only one element.

  27. “Yep. I’ll be curious to see how this is received by the cycle-skeptics.”

    Before you start partying too hearty at this brilliant salvation of Milankovitch by superimposition of his cycles, I want to point out that we still lack a physical basis.

    The only M cycle in and of itself changes net energy input to the planet is eccentricity. The other two M cycles, and the hybrid summer 60 north merely redistribute energy in time and space.

    Before the Pleistocene, benthic cores show a weak 41kyr signal, but no apparent eccentricity signal at 1 or 400kyrs. To make physical sense of the obliquity signal we must invoke the asymmetrical distribution of land and ocean between the hemispheres as an amplifier or wave guide. This is easy to do at the arm waving level, but not yet so easily in the physical specifics.

    There also remains the problem, which Wim promises to solve, of why these weak orbital changes lie dormant for hundreds of millions of years between the macro glacial periods where they show their stuff.

    • gymnosperm August 5, 2017 at 9:55 am

      There also remains the problem, which Wim promises to solve, of why these weak orbital changes lie dormant for hundreds of millions of years between the macro glacial periods where they show their stuff.

      To me the answer is simply that the deep oceans have to be cold enough for an ice age to develop.
      After the warm peak around 85 mya the deep ocean have on average been cooling down again.
      When cold enough, ice began to develop in the polar regions, and our current ice age started.
      Whether the Antarctic circumpolar current is running or not doesn’t matter much if the deep ocean temperatures are 15C or even higher as they were 85 mya.

      • Veizer and Prokoph (2015) have done some work that casts some doubt on the extremely high paleo ocean temperatures indicated by 18O.

        Regardless, a lot of energy must be lost from a large warm ocean before you will get frosty poles; as you say.

        Another contradiction to the focus on 60 north insolation is that Antarctica froze first.

        It boils down to energy in and energy out, and we have been on a long downhill slide in net energy.

        I am eagerly awaiting Wim’s upcoming post.

      • Gymnosperm: “I am eagerly awaiting Wim’s upcoming post”

        WR: The answer you want to get is in the second (and third post) to come. But I think you will like the next one too.

      • gymnosperm August 8, 2017 at 10:00 am

        Veizer and Prokoph (2015) have done some work that casts some doubt on the extremely high paleo ocean temperatures indicated by 18O.

        Does this have much influence on eg this reconstruction, going back ~108 my.?

        I do assume the temperature peak around 85 mya will be there anyway. It doesn’t matter much whether the peak was 10, 15 or 20K above present temperatures. The energy required to heat the oceans to this peak was abundantly available. At least 100 million km^3 magma from various LIP’s prior to the peak temperatures, enough to warm all ocean water some 100K.

        A question: are numbers available for the time it takes for the geothermal flux through oceanic crust to re-establish after a sudden warming of deep ocean water of eg. 1K?

  28. One thing which has always amazed me about warmists is how simple math which does not work out. Please let me elaborate. I welcome input if I am not doing something correct here.

    The global temperature of the Earth is 15°C (288°K). The background temperature of the Universe is 3°K -270°C). This means the Sun-Earth-Atmosphere interaction raises the temperature of the Earth 285°K. This 285°K temperature rise is what we have to account for in all discussions.

    If the Earth had no atmosphere, the temperature of the Earth would be -18C (255°K) ( The Sun-Earth interaction (well described in this article) accounts for 252°K of the total 285°K temperature rise or 88.4% of the temperature of the Earth. The Sun-Earth interaction accounts for most of the temperature rise on Earth. This leaves only 11.6% (or 33°C) of temperature for the atmosphere to effect.

    If one looks at the major greenhouse gases (GHG) and their contribution to the other 33°C of temperature rise, we have, in order, Water Vapor (95%), Carbon Dioxide (3.618%), Methane (0.36%), Nitrous Oxide (0.95%), and CFC/Misc Gases (0.72%) (

    Man does not contribute to Water Vapor, that I am can see, so the entire 95% of water vapor’s influence on atmospheric warming is a result of natural processes. Therefore, 31.35°C of the 33°C temperature rise is a result of things outside man’s control leaving only 1.65°C for man to affect. We must now go down to next most important GHG, namely Carbon Dioxide (CO2).

    A simplified Carbon Cycle is available on from NASA ( which shows Plant respiration at 60 GtC/y, Microbial respiration/decomposition at 60 GtC/y, Ocean respiration/decomposition at 90 GtC/y, and man’s contribution of 9 GtC/y. This all add up to 219 GtC/y. Nature’s contribution is 210 of 219 GtC/y or 96%. After Water Vapor’s effect, we are only left with 1.65°C which CO2 can effect and natural processes account for 96% of that effect or 1.58°C of the remaining 1.65°C leaving man to only influence 0.068°C.

    I can keep doing these calculations with the remaining GHGs, like Methane (since 81.7% is natural and only 18.3% is man-made), and man’s effect becomes even smaller, but let’s stop here and review the bidding. Of the 285°K/C temperature rise, man is responsible for 0.068°C (at most) of that rise or 0.0238% (at most) of the total temperature rise percentage. Stopping at CO2, man’s contribution is a rounding error and completely irrelevant to any increase in temperature in the Sun-Earth-Atmosphere interaction.

    I welcome input.

    • UndercoverInAK August 5, 2017 at 11:27 am

      If the Earth had no atmosphere, the temperature of the Earth would be -18C (255°K)

      Our moon tells something different. Even with a much lower albedo (~0,11 vs ~0,30) its average surface temperature is just 197K.
      On earth the temperature of the crust is completely caused by internal heat. The sun influences only the temperature of the upper 15m or so of the soil.

      Going deeper the temperature increase ~25K for every kilometer (geothermal gradient)
      To me it is clear that the sun provides enough energy to explain the temperature changes of the shallow top layer of the soil.
      Removing the sun and the atmosphere and allowing the crust to cool down, the surface temperature would stabilize around 50K, the temperature required to radiate away to space the small geothermal flux.
      (~65 mW/m^2 for continental crust, ~100 mW/m^2 for oceanic crust).

      With an average surface temperature of 288K and no atmosphere earth would radiate ~390 W/m^2 (emissivity = 1.0) directly to space (and cool down rapidly). The atmosphere reduces the loss to ~240 W/m^2, which the sun resupplies. So no warming of the surface by the atmosphere required.

      More interesting and relevant is the mechanism for the oceans

      • Ben,

        Thanks, and great input/data which I concur with. I am not sure it changes the math however. The Earth’s internal radiogenic/primordial heat is part of the Sun-Earth system/dynamic which causes the Earth (without an atmosphere) to be 255°K/-18°C leaving only a 33°K/C temperature rise to reach the Earth’s endstate (with an atmosphere) of 288°K/15°C. The 50-60°K/C difference between the Moon’s and Earth’s mean temperature is the result of the internal radiogenic/primordial heat, albedo differences, liquid water thermal properties, planetary size difference, background temperature, etc since they both occupy relatively the same distance from the Sun, the galaxy, and space in general. These are all factors humans have no effect on.

        The point of my statement/argument; however, was to focus on what human’s contribute. The Sun-Earth system/dynamic is responsible for the overwhelming majority of the Earth’s temperature leaving only 11.6% (33°C) for humans to effect. Of that 11.6% (33°C), water vapor is responsible for 95% (31.35°C) of the retained temperature at the surface of the Earth leaving only 1.65°C for the rest of the GHGs to act on/effect. Humans do not have any effect on water vapor in the atmosphere that I am aware.

        CO2, the next most abundant GHG, is responsible for 3.6% of the remaining 5% coming out to about 72% of 1.65°C or 1.19°C. Nature is responsible for 96% of the CO2 in the atmosphere meaning nature brings the surface temperature of the Earth up another 1.14°C with humans responsible for 4% (~0.047°C) of CO2.

        Methane, the next most abundant GHG, has a ~7.2% effect on the surface temperature. Of the resultant temperature (1.65°C) for GHGs to effect, that means Methane rises the surface temperature of the Earth 0.119°C. Nature is responsible for 81.6% of Methane produced (or 0.097°C) leaving human’s effect at 0.022°C. Adding 0.022°C to human’s CO2 contribution (of 0.047°C), we are at 0.069°C (Understand number is different from first reply. It is due to rounding errors).

        We can continue the math for Nitrous Oxide, CFC’s, and Misc gases, but we will keep adding progressively smaller and smaller numbers, and we are left with nature being responsible for 99.72% of surface temperature (or about 32.9°C) and humans being responsible for ~0.1°C. Of the total temperature change from -270°C/3°K to 288°K/15°C (total of 285°C/K), humans are responsible for ~0.1°C or 0.035%.

        The math simply does not allow humans to have any significant effect on global surface temperatures. Even if we doubled, tripled, or quadrupled CO2, Methane, Nitrous Oxide, CFCs, and Misc gases, our effect on global surface temperatures would be at most 1/10th of 1%. The Sun-Earth interaction, radiogenic/primordial heat, liquid water thermal mass/heat transfer abilities, ocean convection currents, CO2 emitted by land/ocean plant respiration/decomposition, natural Methane production, average cloud cover, etc) has an overwhelming effect (99.965%) on global surface temperatures. The human effect on global surface temperatures is, quite frankly, a rounding error currently at 0.035%.

        I think we are in agreement other than your last statement. Without an atmosphere, we would be at -18°C and would not have liquid oceans except near ocean floors due to radiogenic/primordial heating which would stop/significantly reduce any oceanic currents/effects on the atmosphere.

        I appreciate the discussion and welcome other inputs.

      • UndercoverInAK,

        You said, “Humans do not have any effect on water vapor in the atmosphere that I am aware.” Actually, we do have a small, but probably negligible effect. The extraction of ground water to irrigate cultivars in arid and semiarid climates contributes water vapor during the growing season(s). The burning of fossil fuels releases water vapor as a by-product of combustion. Hot, arid regions like Phoenix use evaporative cooling and misters that puts water vapor into the air. Lastly, the numerous industrial activities that need cooling (like steel mills), usually rely on things like river water. Because the water is elevated in temperature, it evaporates at a higher rate than it would if left in the river.

        Because water bodies cover more than 71% of the surface of Earth, the contribution from anthropogenic water vapor, above what would be the case for natural evaporation and transpiration, probably only contributes to changes in local microclimates on land. However, I think that it would be wrong to assume that humans have no effect.

      • UndercoverInAK August 6, 2017 at 7:12 am

        Thanks, and great input/data which I concur with. I am not sure it changes the math however. The Earth’s internal radiogenic/primordial heat is part of the Sun-Earth system/dynamic which causes the Earth (without an atmosphere) to be 255°K/-18°C leaving only a 33°K/C temperature rise to reach the Earth’s endstate (with an atmosphere) of 288°K/15°C.

        Seems you miss my point.
        The calculation that results in 255K for planet earth results in ~270K for our moon. Actual average temperature ~197K. This means the whole calculation makes no sense. Better would be to calculate the radiative balance temperature for only the sunlit side, and average with the ~3K dark side temperature.
        Results in ~162K for the moon. Adding some geothermal heat plus some heat transfer from day to night side and the actual 197K for the moon is simply to explain.
        To me the moon is a good indicator of what the temperatures on earth would be without atmosphere and oceans (difference in rotational speed makes no big difference).
        Leaves the problem of explaining why earth is over 90K warmer than the moon ;-)

    • WR: UndercoverInAK, an interesting comment.

      I would like to add one thing. “If the Earth had no atmosphere” I would like to change in “If the Earth had no atmosphere and no oceans”.

      In posts to follow I will explain why. Oceans have an autonomous effect. An effect, made by salt (!) water. The effect is huge.

      • Clyde,

        Concur with all. Everything I have seen is our effect is in the 0.001% range. As you state, oceans predominate. Even if we are in the 5% range of water vapor, our overall effect does not change the calculations that much. We become 5% of the first effect (water vapor), 4% of the next effect (CO2), and 18% of the next effect (CH4), 5% of the next effect (N20), and finally 65% of the remaining effect (CFC’s and Misc Gases). We start off too small to become a factor in the overall temperature of the Earth. And a lot of the 65% of CFC’s and Misc Gases have a cooling effect.

        WR: I would like to read with regard to salt water. Sounds interesting. Willing to learn. Will search for reply.


        I am using Wikipedia data for moon. I can research more (and have), but their numbers are generally acceptable for many calculations (not all, but many, as Climate Alarmists, I have found, are not good at simple math and put stuff on Wikipedia which disproves their own argument, in my opinion).

        Mean at equator = 220°K (-53°C) Mean at 85° = 150°K (-123°C) and doing simple math of taking the average = 185°K (-88°C) which comes close to your 197°K and close to your 162°K (-111°C) . I only see the minimum getting down to 100°K (-173°C) nowhere near ~3°K your write about above. I assumed radiogenic/primordial heat, rotational differences, albedo, etc accounted for the delta, but to be honest, haven’t got into the weeds to discover the difference. The Earth’s average heat flux is 91.9 W/m2 which is significant by itself, but not compared to the sun (~1000 W/m2, if memory serves me correct). The Moon rotates much slower (27+ days) than the Earth (1 day) resulting in the cold becoming colder on the dark side, but also the hot becoming hotter on the light side. Rotational speed may be a wash especially given your graph above showing heat only goes down to 15m. If it was deeper, we may have a heat conduction issue to resolve. I would have to research this data set more. It is intriguing, but got to believe that heat is lost pretty rapidly if only down to 15m when that side of the moon is not facing the sun.

        I would argue, but haven’t done the math, even if Earth’s temperature without atmosphere (and frozen oceans) was colder than 255°K (-18°), the math would not change much. Let’s assume the atmosphere had 66°C to play with vice 33°C which I cite. End result is 0.1% human contribution would become around 0.2% human contribution. Still insignificant. One can double, triple, or quadruple a very minute quantity and one is left with still a very minute quantity. Let’s make atmosphere’s contribution 99°C. We are now at 0.3% max. Again, haven’t done the math to actually get real numbers. If we go the other way, human contributions only get smaller.

        End result, from a mathematical perspective, the human effect on overall surface temperature of the Earth is minute, insignificant, a rounding error. We are comparable to a single flee on a Mastodon’s head thinking we are somehow in control of this great beast. We live vicariously through the Mastodon, but we are in no way, shape, or form, in control of the Mastodon. But occasionally, we get the Mastodon to itch an itty bitty spot on top of his head. We think we are important, but we are not. That is our contribution to Earth’s surface temperature, sorry to say.

        My take. As always, I welcome input and constructive comments.

      • UndercoverInAK August 7, 2017 at 8:41 pm

        Mean at equator = 220°K (-53°C) Mean at 85° = 150°K (-123°C) and doing simple math of taking the average = 185°K (-88°C) which comes close to your 197°K and close to your 162°K (-111°C) . I only see the minimum getting down to 100°K (-173°C) nowhere near ~3°K your write about above.

        ~3K is the theoretical black body temperature in radiative balance with the Cosmic background radiation.
        Just as the 255K is a theoretical black body temperature, reached by distributing incoming solar evenly around the entire planet. Physically impossible.
        On the actual moon the night side temperatures are a bit higher than 3K causing the lunar average to reach ~197K. For the day side temperatures are at radiative maximum. Lunar surface is a lousy conductor, Equatorial temperatures change only for the upper 40 cm or so.
        But this is beside the point.
        To me the whole idea of the atmosphere INCREASING the surface temperatures is nonsense, whether the difference is 33K or the more realistic ~90K. Surface temperatures can be easily explained by realizing that geothermal HEAT is the reason for the temperature just 15 meter below our feet. The flux is very small (~65 mW/m^2 not W/m^2), but the simple fact that we HAVE a flux means that the temperature of the entire crust is caused by geothermal heat.

        The atmosphere merely reduces the energy loss to space, so yes, without atmosphere it would be colder, but no the atmosphere does not INCREASE the surface temperature.
        Compare to a well insulated house. Inside temperature equal to outside, let’s say 0C.
        Switch on the heating system, and the temperature will stabilize at a (much) higher value when the energy loss through the walls equals energy input of the heating system.
        What did cause the much higher temperatures, the heating system or the wall insulation?

        Just realize that with a given surface temperature, going up in the atmosphere the temperatures decreases ~6,5K/km, going down into the crust the temperature increases 25K/km.

    • Oh, sounds hunky dory when one leaves out atmospheric dynamics, mainly positive feedback loops. The double edge sword of CO2 is well documented. CO2 can persist in air for centuries, while water vapor comes and goes quite frequently by way of evaporation and rain and snow. Since the rate of evaporation increases with temperature, the amount of water vapor in the air, and the warming it causes, is amplified by the amount of other greenhouse gasses in the air. So calculate till you are blue in the face, but simplistic scenarios that ignore radiative contributions and interactions, which is really what the “greenhouse effect” boils down to, don’t further anyone’s understanding and just distort reality. Your concluding remark that you just proved CO2 is completely irrelevant, is a real winner.

  29. From the second paragraph under the article’s “Abstract” section:
    “Although process interactions are very complex, separating out predominate causes and effects on global temperature should help improve future climate mathematical simulation models.”

    Well, there you go . . . who’d have thunk it!

    Make sure the IPCC gets copied on this, OK?

  30. I liked this part: “the culmination and eventual cooling is astronomically controlled. It is impossible for humans to control Earth’s orbit, tilt, or wobble. Since astronomical processes affecting significant climate changes are out of our control, a focus on adaptation instead of climate manipulation is a much better use of resources.”

    It’s already been demonstrated that Jupiter has a small but definite gravitational effect on Earth’s orbit, (among others, including those of Mercury and Venus), so what’s the issue? That accounts for orbital eccentricity, that and the Sun’s tidal pull.

    There is that idiotic notion that we should try to do things that will alter the climate to make it cooler, still prevailing among the control freak climate people, whose livelihood in the form of grants depends on their kowtowing to political bodies. All this does is pave the way for more disastrous events. For instance, if you cut down most of the trees in an area that receives a lot of rain, you will start having floods because there is nothing to soak up the rainwater. Tree roots do that job, and very nicely, too, as do water-seeking plants like grasses. Disturb this and you get severe erosion, flooding, and loss of arable soil.

    Good article. I found that the cold periods and warm periods both have a wave form in their length of time, One lags the other. So when will the next glacial period start? Oh, I think that was the winter of 1985, when the temperature in Chicago dropped to -25F w/wind chilll of -80F. Just a head’s up: the Farmers Almanac is forecasting cold (not just cool) weather in September in my kingdom, and snow in some places, including Montana. Keep an eye on it.

    • Good comment.
      Your point about trees is important.
      It would come as a surprise to many to learn that there are more trees in the USA today than there were 100 years ago:

      This article gets lost in AGW BS but it’s an important fact nonetheless. They also ignore an important contributory cause – CO2 fertilisation.

      Mat Ridley has shown that not only the USA but the whole earth 🌏 is greener now than 40 years ago. I don’t have the numbers, but I would guess that global tree numbers are also up over that period. These facts are the exact opposite of what most people, brainwashed by dystopian green agitprop, believe. What will it take to re-aquaint people with the simple truth that the end is not nigh, and CO2 is making the earth greener and more habitable?

  31. This paper shows the importance of the Millennial Cycle and supports my earlier forecasts of a coming long term cooling. The paper states “……G7, and likewise the sine representations have maxima of comparable size at AD 0, 1000, and 2000. We note that the temperature increase of the late 19th and 20th century is represented by the harmonic temperature representation, and thus is of pure multiperiodic nature. It can be expected that the periodicity of G7, lasting 2000 years so far, will persist also for the foreseeable future. It predicts a temperature drop from present to AD 2050, a slight rise from 2050 to 2130, and a further drop from AD 2130 to 2200 (see Fig. 3), upper panel, green and red curves.”
    Climate is controlled by natural cycles. Earth is just past the 2003+/- peak of a millennial cycle and the current cooling trend will likely continue until the next Little Ice Age minimum at about 2650.See the Energy and Environment paper at
    and an earlier accessible blog version at
    Here is the abstract:
    This paper argues that the methods used by the establishment climate science community are not fit for purpose and that a new forecasting paradigm should be adopted. Earth’s climate is the result of resonances and beats between various quasi-cyclic processes of varying wavelengths. It is not possible to forecast the future unless we have a good understanding of where the earth is in time in relation to the current phases of those different interacting natural quasi periodicities. Evidence is presented specifying the timing and amplitude of the natural 60+/- year and, more importantly, 1,000 year periodicities (observed emergent behaviors) that are so obvious in the temperature record. Data related to the solar climate driver is discussed and the solar cycle 22 low in the neutron count (high solar activity) in 1991 is identified as a solar activity millennial peak and correlated with the millennial peak -inversion point – in the UAH6 temperature trend in about 2003. The cyclic trends are projected forward and predict a probable general temperature decline in the coming decades and centuries. Estimates of the timing and amplitude of the coming cooling are made. If the real climate outcomes follow a trend which approaches the near term forecasts of this working hypothesis, the divergence between the IPCC forecasts and those projected by this paper will be so large by 2021 as to make the current, supposedly actionable, level of confidence in the IPCC forecasts untenable.”
    The forecasts in Fig 12 of my paper are similar to those in this Ludecke et al.paper.

    It is well past time for a paradigm shift in the forecasting methods used by establishment climate science. The whole dangerous global warming delusion is approaching collapse.

    • Correction. The comment should begin with Another recent paper emphasizes the importance of the Millennial Cycle and also supports forecasts of a coming long term cooling .
      “Harmonic Analysis of Worldwide Temperature Proxies for 2000 Years
      Horst-Joachim Lüdecke1, *, Carl-Otto Weiss2 DOI: 10.2174/1874282301711010044
      This paper states…….

      • Dr. Norman. Thanks for the link to your article. The +/-60 yr and 1000 yr cycles in the Holocene warm period are very intriguing. And I certainly concur with your article recommendations.

      • Dr Norman Page,
        But the key question remains: What is the (small, but unknown) influence of the recent CO2 releases on that long-cycle (1000 years) + short cycle (60,66, or 70 years) theoretical sum in the real-world temperature record?
        Can the two cycles be “subtracted out” adequately to yield the 0.5 to 0.1 possible CO2-factor in the recent record? That is, I agree that we are at a recent high (2000-2010) from the 1940’s high, and that short-term high was above the 1880-1890’s previous short term peak. But the 2010-2017 “peak has drawn longer than the previous short-term peaks – possibly due to the influence of CO2 not found before.

        We are still rising from the LIA minimum, but the MWP was no “single, clear, explicit maximum” that can be found in the proxy records. It was a long, drawn-out high period lasting a few hundred years. And, during that long high period, the 60-70 year short cycle continued its confusing influence on the peaks.

        If this latest paper extrapolates short term peaks in 2000-2010, 2070-2080, 2140-2150 (which are reasonable), is not the Modern Warming Period only now near its peak (not actually at the highest point), and will not the global average temperatures stutter and stammer around today’s high points for another two-three short cycles before sliding down towards the next ice age?

      • Renee .Good to hear from an exploration geologist. The world energy industry and economic power relationships have been completely transformed by the seismic data processing and geological interpretative methods ( eg seismic stratigraphy) of the fossil fuel industry – they work. The fact that ones interpretations may be tested in short order at a cost of many millions of dollars concentrates the mind on getting them right rather than adhering to a fashionable consensus which is only tested long after one has retired.
        RA Cook
        As I said above “Earth’s climate is the result of resonances and beats between various quasi-cyclic processes of varying wavelengths. It is not possible to forecast the future unless we have a good understanding of where the earth is in time in relation to the current phases of those different interacting natural quasi periodicities.” Any particular instrumental or proxy temperature time series is an “emergent property” which simple cannot be calculated from the convolution of its component parts. We just cherry pick the orbital , solar activity and earths magnetic field data inputs and algorithms( i e use one’s best scientific judgement ) in order to illustrate a coherent working hypothesis and narrative which best fits the majority of the climate driver and temperature data.
        In the real world other things are never equal – everything only happens once, but the principal components eg the ephemerides are stable over millions of years and solar activity obviously has at certain periods obvious millennial, centennial and decadal quasi cycles. My paper, shows the basis for my working hypothesis and the resulting forecasts. No millennial peak can be expected to repeat exactly either in shape or amplitude .Fig 12 above shows the simplest case based on a peak and inversion point in the temperature trend at about 2003/4 and the corresponding driver solar activity peak at 1991 The effect of CO2 must be small and even the sign of the climate CO2 sensitivity is unknown at this the AR5 IPCC report itself says in Footnote 16 page 16 (5):
        “No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies.”
        Paradoxically the claim is still made that the UNFCCC Agenda 21 actions can dial up a desired temperature by controlling CO2 levels. This is cognitive dissonance so extreme as to be irrational. There is no empirical evidence which requires that anthropogenic CO2 has any significant effect on global temperatures.

  32. Renee
    Thanks for the excellent and well-researched article.
    In my view the correlation shown in fig 9 between the obliquity cycle and temperature lagged by 6,500 years, which you correctly attribute to Javier, is surely of central importance to the whole question of glacial-interglacial timing and causation. I would have expected you to focus more attention on it.

    It is clear from fig 9 that obliquity is the primary forcer of the glacial cycle. Every 2 or 3 obliquity peaks – lagged by 6,500 years by the ocean’s thermal inertia, induces an interglacial.

    Which obliquity peaks induce interglacials and which do not is straightforwardly predictable from precession and eccentricity. Regarding precession, it is not precession per se but the modulation of precession that is the critical factor, that is, the oscillation in the amplitude of the precession peaks. This modulation follows eccentricity – the maximal peaks of precession modulation occur at the peaks of eccentricity.

    It is obvious from orbital considerations why precession modulation should follow eccentricity. In fact it simplifies analysis of Milankovich forcing to consider precession modulation and eccentricity as one and the same phenomenon.

    And that’s all it is. An obliquity peak – thermally lagged by 6,500 years, coinciding with a peak of precession modulation/eccentricity, causes an interglacial. Due to different timings, sometimes an eccentricity peaks will fall exactly half way between two lagged obliquity peaks. In this case you get a double-headed interglacial, as occured 200k and 600k years ago and will happen again 200k years in the future.

    • Ptolemy2, nice summary. Javier’s article went into detail on obliquity which is why I didn’t repeat it here and just referenced his research.

  33. Typo in 2nd sentence of paragraph beginnning: “During the most elliptical orbit, . . “. The word in this 2nd sentence should be ‘insolation’ not ‘isolation.’ When isolation is greater than 550 W/m2,

  34. Renee,
    You said, “…and precession (wobble) of Earth’s orbit resulting in…” Shouldn’t you say “…precession (wobble) of Earth’s rotational axis resulting in…”?

  35. Renee,
    One thing troubles me about your narration. That is, you talk about the astronomical influences and treat Summer insolation as an astronomical influence when it is actually a result of the orbital conditions. Ultimately, it is the total and/or NH Summer insolation that will force the climate into glacial or interglacial conditions. However, the total insolation is primarily a function of the ellipticity, and the NH insolation is a function of ellipticity, obliquity, and axial precession. Wobble in the ecliptic or apsidal precession should not have any influence on insolation.

    • Clyde,

      I correlated three key factors in my article…eccentricity, obliquity, and summer insolation at 60 degrees N. I mention precession because it is a direct calculation and strongly influenced by eccentricity. Eccentricity and obliquity are also individual, precise measurements.

      I agree insolation is a secondary calculation that is based on all three components; precession, tilt and orbit (ellipticity?). That’s makes insolation more of an indirect and uncertain calculation. I’m not suggesting one is better than another. It’s just another piece of the puzzle. I did lump it with astronomical data, because in the larger scheme of forces (oceanic, atmospheric, geologic) that’s where it belongs.

      I do understand that insolation varies significantly by latitude. I have not included total insolation but may look at that parameter in future evaluations. Can you give reference of what is a better parameter to use, total insolation or summer insolation?

  36. Andy May – But how do you explain that the roughly 100,000 year cycle is basically absent prior to about 700 kbp? Have you looked at the ice and ocean sediment core isotopes of C-14 and Be-10, which are thought to be proxies for variations in solar output, which likely swamp the orbital variations? I agree that there are cycles within cycles, but this includes solar activity too!

    • Ken,

      As IMO Javier has shown, the previous ~41,000 year obliquity cycle persists within the apparent longer cycles after the mid-Pleistocene transition. The seemingly ~100,000 year cycle after that switch is an artifact from averaging ~82,000 year and ~123,000 year cycles, consisting of two or three tilt cycles. As the Pleistocene wore on, average temperature got colder, such that some of what previously would have been interglacials at 41,000 year intervals became stillborn.

  37. This great post and other recent ones by Wim Rost and Javier have given me the thought that perhaps WUWT participants could collaborate in a project to create a definitive model based simulation to allow hindcasting and forecasting of all the Milankovich parameters into both past and future:

    Summer insolation at 65N
    Ecliptic and aspidal angle

    With past reconstructions of global temperature, sea level (for north and south hemispheres respectively), glacial extent, ice rafting events, AMOC status and any others considered relevant.

    With the establishment sanctioned AGW obeisant scientists and institutes only pretending interest in palaeoclimatic reconstructions while in fact trying to ignore (or worse – sabotage) palaeo climate data (e.g. the lynching of Law Dome C) it is probable that the most serious research community in palaeo climate is right here at WUWT.

    Could a combined database with computer model be created by a consortium of WUWT contributors with the appropriate skills? One objective could be prediction of future glacial inception and cooling toward the next glacial maximum.

    This could also allow an accurate test for any real effect of CO2 on climate, resolved as a departure of the climate system from its predicted Milankovich trajectory. (This might take a while however – but everything in climate is slow since it originates in the ocean.)

    • We should pay special attention to ‘zonal effects’ and ‘length of season’ effects. Orbital changes effect both.

      We know yearly seasonal variations, ruled by orbit. Orbital changes like obliquity enhance or diminish the seasonal effect. This has at least zonal consequences and besides that specific regional consequences that affect weather and ‘systems’.

      Zonal / regional effects are enhanced by ‘length of season’. I don’t see many attention for the effects of length of season.

      Zonal and regional effects can induce specific processes that influence / change the climate system. After which it acts in a different way. Therefore we need to know the regional / zonal effects.

  38. This post has some excellent figures which offer some insight from a different point of view. That of a system response, thus:
    A. fig1 shows a saw tooth. Oscillate between two points, a fast trip point at tooth bottom to peak, and a slow down drift after trip. Time between trip points is irregular. The down drift is a ratcheting/friction movement, a chaotic thing as the four cycles show, with cycle III showing that wild/very chaotic swings in the ratcheting movement is possible.

    B fig4 highlights the similarity between cycles II and IV. Indirectly it highlights how different they could be when compared to cycle III. That is the drift is chaotic in both amplitude and time.

    C fig3 is interesting as it compares cycles II and IV to early V. Here other factors weigh in in providing additional information. The 8.2ky event is highlighted. But one can also see the 5.2ky event (3.2ky bce) as a spike. That is a well known period from archaeology as well. Another similar event occurs earlier at 7.2ky and can also be made out. The span of years from ~7.2ky to ~4ky have left much in archaeology. Fig3 in fact highlights the irrepeatability of the ratcheting on small timespan. Note that the 5.2ky spike was a time of major destruction.

    D… Now make out what you will of this part. The span 7.2k to 4ky in archaeology (in support also of Dodwell) show Earth tilt swings beyond what is assumed (JN Stockwell in 1872 gave only half the story). Milankovitch based part (?) of his theory on that assumption.

  39. Thank you. Valuable article and data series. This is what is needed, in a more concise form, for school science curriculums to create discussion and debate, versus the single anthropologic doctrine that is promoted.

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