By Andy May
We hear a lot about the AMO, or the Atlantic Multidecadal Oscillation. How much does it influence the global mean surface temperature or GMST? Exactly what is the AMO? These are the issues we will discuss. First let’s look at various definitions of the AMO.
Enfield, et al.: “The AMO index [is a] ten-year running mean of detrended Atlantic SSTA [sea surface temperature anomaly] north of the equator.”
Gray, et al.: Uses detrended raw tree-ring measurements to demonstrate a strong and regular 60-100 year variability in basin-wide (0-70°N) North Atlantic sea surface temperatures (SSTs) that has been persistent for the past five centuries.
Trenberth & Shea: “To deal with purely Atlantic variability, it is highly desirable to remove the larger-scale global signal that is associated with global [anthropogenic] processes, and is thus related to global warming in recent decades … Accordingly, the global mean SST has been subtracted to derive a revised AMO index.”
NCAR uses the Trenberth & Shea method, but NOAA uses the original methodology and detrends the North Atlantic temperatures using a least squares linear trend. We will also use the original Enfield and Gray method in this post.
The reason for the AMO SST 60-70-year pattern is unknown, but according to Gray et al. it extends back to 1567AD, so it is a natural oscillation of some kind. Some have speculated that it is a result of the thermohaline circulation in the North Atlantic or a “combination of natural and anthropogenic forcing during the historical era.” (Mann, Steinman, & Miller, 2020). But while interesting these ideas are speculative. Further if the oscillation has existed since 1567, it seems unlikely that it is caused by human CO2 and aerosol emissions.
It is clear that “global” warming is mostly an extra-tropical Northern Hemisphere phenomenon. This is discussed here in figures 1A & 1B and here in the discussion around figure 1, which is also shown as figure 1 below. Regions outside the extratropical Northern Hemisphere don’t change temperature as quickly or as drastically.
A similar pattern can also be seen for the modern era in figure 2.11 in Chapter 2 of AR6 (page 316), part of which is shown as figure 2 below.
Trenberth and Shea’s method of detrending the AMO by first subtracting the global average surface temperature from it is an attempt to remove “global anthropogenic changes” from the AMO signal so it can be viewed as a natural phenomenon. This assumes that global warming has no natural component and is all anthropogenic. However, there is no evidence to support this assumption outside of global climate models. Thus, the Trenberth and Shea version of the AMO index can be discarded if our intent is to show the correlation between GMST and the AMO.
We clearly have a chicken-and-egg problem here. The cause of the AMO pattern is unknown, but does the AMO influence global temperature patterns? Or does some sort of global 60-70-year pattern of warming and cooling affect or cause the AMO?
Figure 3 shows the AMO pattern using HadSST and ERSST sea surface temperatures detrended with linear least-squares best-fit lines. Yearly averages are plotted and the curves are not smoothed.
In figure 3 we see that both the HadSST and the ERSST sea surface temperature records produce the same pattern and closely match each other. This is not surprising since they mostly use the same raw data from ICOADS v. 3 and similar processing methods. Both the 1900-1910 and the early 1970s were colder across the Northern Hemisphere. The spike at the end of both records is probably due to the Hunga-Tonga volcanic eruption in January of 2022.
In figure 4 we plot the detrended HadSST 4.1 record shown in figure 3 with the HadCRUT 5 global surface temperature anomaly detrended in the same way.
Figure 4 is very similar to figure 2 in May & Crok, 2024, but it is extended through 2024 and HadCRUT 4 is replaced by the newer HadCRUT 5. In addition, the detrended HadSST 4.1 AMO region record replaces the NOAA unsmoothed record used in May & Crok.
Figure 4 opens some possibilities. The AMO pattern may influence the global mean temperature anomaly, or the reverse may be true. The former idea is more attractive given the apparent influence that the Northern Hemisphere has on global climate as shown in figures 1 and 2. There is a very close correspondence between the two temperature anomalies and there is very little, if any, time lag between the two, at least in these plots of yearly averages. We can’t be sure which record is driving the other, but they clearly correlate very well.
Figure 2 in May & Crok was criticized because the AMO index plotted did not conform to the Trenberth & Shea definition of the index, that is, the global mean temperature anomaly was not used to detrend the North Atlantic SSTs. But, if we are trying to show the correlation between the AMO and GMST, why would we do that? Even so, figure 3 in Trenberth and Shea shows that the AMO pattern can still be seen after subtracting the GMST, a testament to its strength. Removing the least squares linear trend has “no physical meaning” as Trenberth and Shea write in their paper, but detrending imposes no bias and does not attempt to hide the correlation.
In conclusion, I think it is very clear from the data presented in this post that Northern Hemispheric climatic changes drive global changes as shown in figures 1 and 2. It is also clear that the AMO and global average surface temperature patterns are closely related, with the AMO being the stronger pattern of the two. Gray, et al. show that the AMO 60-70-year AMO pattern extends into the past at least to 1567AD, which argues against any anthropogenic cause for the AMO or GMST patterns.
Works Cited
Enfield, D., Mestas-Nunez, A. M., & Trimble, P. (2001). The Atlantic multidecadal oscillation and its relation to rainfall and river flows in the continental U.S. Geophysical Research Letters, 28(10). Retrieved from https://agupubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1029/2000GL012745
Gray, S. T., Graumlich, L. J., Betancourt, J. L., & Pederson, G. T. (2004). A tree-ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 A.D. Geophys. Res. Lett., 31. doi:10.1029/2004GL019932
Mann, M., Steinman, B., & Miller, S. (2020). Absence of internal multidecadal and interdecadal oscillations in climate model simulations. Nat Commun, 11. doi:10.1038/s41467-019-13823-w
May, A., & Crok, M. (2024, May 29). Carbon dioxide and a warming climate are not problems. American Journal of Economics and Sociology, 1-15. doi:10.1111/ajes.12579
Trenberth, K., & Shea, D. (2006). Atlantic hurricanes and natural variability in 2005. Geophysical Research Letters, 33. Retrieved from https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006GL026894
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Interesting. And it’s not surprising that trough-to-trough temperature moves little, while trough-to-crest looks material. Some other supporting data from far away from the Atlantic:
I’m in Calgary AB and our main weather station is at our airport. Records go back to 1883. Google Earth history and air photos available online show that the site was class 1 or 2 until the late 1980s (when Calgary expanded to be adjacent, then completely surrounding the airport). Data from “extreme weather watch” lists the daily high and low temperature records for every day of the year (because of ties, approximately 400 data points in each set).
Most high temperature records set: 1920s, 1980s. Most low temperature records set: 1890s, 1950s. There appears to be a 60 year cycle.
But not for low records in the 2010s. UHI removed the minima, the current City of Calgary heat map (to help save people from dangerously high summer temperatures because climate change is now scary) shows a daytime temperature 10 degrees C hotter than the now-more-distant farming fields that still surround the city.
For comparison’s sake I looked at Boulder, CO. Highest temperatures 1950’s and 2010s. Lowest temperatures 1930s and 1990s. Almost completely out of phase from 1400 miles north along the Rocky Mountains. And also roughly in phase with a consistent portion of the AMO curve as displayed.
Interesting, but areas in or on either side of the Rocky Mountains are not good places to try to get a climate signal. The Rockies form a climatic barrier, with different trends on either side.
Don Easterbrook looked at glaciers on Mt Baker.. Seems linked to inverse AMO
It is interesting that the surface weather tie to changes in the solar cycle are opposite on either side of the Rocky Mountains. See Robert Currie, 1993, Luni-Solar 18.6 and Solar cycle 10-11 year…
Currie’s figure 4 is attached. It shows how climatic cycles in the US vary over a solar cycle. Those west of the Rockies go one way and east the opposite. In the Rockies it is mixed. See Currie’s paper for the details. The tie of weather patterns to the solar cycle is strongest east of the Rockies.
I found it interesting that Currie notes one should not average climate data prior to looking for signals, he believes it is better to analyse individual records. Hmmm, I agree:
https://andymaypetrophysicist.com/2021/06/23/how-to-compare-today-to-the-past/
Averages can be misleading, someone tell the IPCC please!
Thanks, Andy.
A cross-correlation analysis shows no lag or lead between the two datasets.
Next, a Granger-causation analysis has three possible results for two datasets A and B:
1) A Granger-causes B
2) B Granger-causes A
3) A Granger-causes B, AND B Granger-causes A
Of course, the AMO and HadCRUT5 fall into category 3) … which often means that both are caused by a third variable C …
Best to you and yours,
w.
Thanks Willis, you may very well be correct. I like Wyatt and Curry’s idea that changes in Arctic ice cover might drive these oscillations, these changes might be driven by solar changes, but who knows?
I find it annoying that the IPCC dismisses the AMO and other oscillations, to the point where they renamed the AMO the AMV, which is absurd. It is an oscillation and not natural variability.
It should be noted that there is a similar long-term oscillation in ENSO. This is readily seen with a long term moving average of ENSO (i.e. greater than 10 years), especially if the short term variations are removed.
There is a good correlation between such a long-term moving average of ENSO, lagged by several years, and the AMO. In all likelihood it is ENSO that is the driver of this correlation.
As for the 60 – 70 year periodicity, I would posit that it is related to the path length divided by the velocity of the ‘Global Conveyor Belt’. Anthony Watts showed in his post, a couple of days ago, that the AMO is an integral part of the ‘Global Conveyor Belt.
There is no doubt that major long-term weather oscillations can be related to one another, this includes the NAO, AO, ENSO, AMO, PDO, etc. But, as Willis notes above this may just mean that all are caused by the same thing and the most likely ultimate cause is the Sun. The problem is the whole thing has not been properly described, so all we can do is speculate. Speculation is good, it helps us figure out ways to investigate these mysteries, but we don’t understand it all yet.
“…the most likely ultimate cause is the Sun.” Or clouds or both.
Yes. I like to think of the oceans as the intermediary between the sun and the atmosphere.
The effect of the AMO on Icelandic sea ice is also identifiable, the red dots on this chart representing the minimums
AMO matches well with unadjusted Ireland temperatures..
And inversely with Arctic sea ice extent.
And unadjusted Reykjavik temperatures
You mentioned Gray.. I found this chart showing Gray’s AMO reconstruction.
Thanks, great graph.
A warm AMO during the Maunder Minimum makes sense, negative NAO drives a warm AMO, but colder during the Dalton Minimum is a big problem, especially as British naval ships observed a great loss of sea ice 1815-1817.
Annually-averaged variations in areal cloud coverage over the NH Atlantic Ocean, within a plausible range of +/- 2%, might be the fundamental “driver” of the AMO, while still not explaining the cycle period, which appears to be more variable than the stated “60-70 years” based on the article’s plots of de-trended AMO SST anomalies over the last 50 years (not even a half-cycle is obvious).
Unfortunately, we don’t have good data (satellite-based or otherwise) for accurately establishing such cloud coverage variations earlier than about the early 1960s, when the first imaging weather satellites were launched.
One possibility: some as-yet-unrecognized cycle of solar activity coupled with Henrik Svensmark-theorized coupling of solar activity to resulting variations in cloud coverage on Earth.
The 80-100 year Gleissberg period of solar activity appears now to be just too short to be considered. Also, this recent trending seems to “disassociate” the 50–70 year PDO secondary frequency from the AMO frequency over the last 50 years.
Interestingly, when I put a question to Google about any 200-year cycle being revealed by ice cores, I got the very surprising answer shown in the attached screen-grab!
Of course, this then further requires an explanation for what drives the oscillations (“shifts”) in the “bipolar seesaw”. Yikes!
I’ve explained previously how cyclic variations in sea ice may occur naturally due only to the geography of the Arctic Ocean and the insulating properties of sea ice.
There is a small amount of energy input into the Arctic Ocean which can build up over time and eventually lead to sea ice melt and more energy venting from open water.
The energy loss from the venting then cools the Arctic ocean and the sea ice eventually returns.
When the Arctic has more sea ice it allows the air above to it cool significantly more. This difference drives changes in atmospheric currents which results in the cloud changes you mentioned.
There may also be other long term ocean cycles leading to variations which are harder to see given the long cycle time.
Well, the problem with your explanation is that the seasonal variations in Arctic sea ice coverage significantly exceed the year-after-year variations in such coverage. See the attached graph showing the relevant statistics (in grey, derived from 1978–2024 data, or about a 46-year continuous interval).
IOW, why doesn’t the minimal Arctic sea ice extent around every September allow “venting” of any asserted buildup of excess energy in the ocean water?
It is the central core of sea ice that limits the venting during the key time period of Sept – Dec when the ice is still low and solar energy is also low.
Well, the Arctic sea ice extent graph that I posted shows that for the month of September (the historic minimas) that max/min variability has been a ratio of 8:4 = 2:1 over the period of 1978–2024, with a near-term minimum historic low in 2025. In comparison, the plot of AMO given in the above article’s Figure 3 indicates 2024-2025 has the recent maximum of AMO SST temperature anomaly for the North Atlantic occurring in 20024-2025. This would be consistent with your hypothesis of “venting” of built-up thermal energy.
However, the fly-in-the-ointment is your underlying assumption that ocean currents bring in “small amount of energy input into the Arctic Ocean which can build up over time” underneath the “central core of sea ice” without considering that ocean currents can also remove heat transported to the Arctic oceans (see Bob Weber’s graphic of water circulation exiting the Arctic, including that “central coe of sea ice” given below, ref: https://wattsupwiththat.com/2025/05/26/musings-on-the-amo/#comment-4076936).
It’s complicated. IMHO, we don’t have sufficient scientific data over a full AMO cycle to reach any reasonable conclusion of cause-versus-effect.
No argument with you observations. However, this view is one that nicely fits the data collected over many years. We’ve seen a flat bottom to the sea ice extent since 2007. This would occur if just enough ice loss allows venting of the built up energy.
If I am right I would expect to see an ice build up starting again very soon. The AMO warm phase is already about 30 years long. If sea ice is the driver, then it should start increasing in the next few years.
There are a number of solar-related cycles that affect climate. The 61-year Jupiter-Saturn cycle includes adjacent cycles of 57 and 65 years. The AMO may be a partially resonant response.
Here, temperature predicted from filtered sunspot data is compared to sea-surface temperature. This result suggests the AMO cycle likely peaked in 2016. We’ll know after the current spike fades.
When ever l see a warm blob of water on the North Atlantic or any ocean, l instinctively think of a persistent area of high pressure blocking as the cause. As the current example of this weather patterning warming the waters to the west of the British Isles clearly shows its effects.
So my instincts for looking for a cause of the AMO, would be to look for links between it and the increase/decrease in high pressure blocking in the North Atlantic over the years.
The AMO warms in response to negative North Atlantic Oscillation episodes and regimes, as in 2023, and though 1995-1999.
Well that would make sense and suggests am thinking along the right lines.
As during negative NAO the Bermuda and/or Azores high pressure systems are strong and aid to the warming of the waters in the mid and southern North Atlantic. While also driving this warmer water northwards along their western flanks.
Negative NAO is lower pressure by the Azores, and higher pressure by Iceland.
All this discussion about a temperature variation of 1deg C or so over 180 years, without consideration of measurement uncertainty?
Geoff S
Yep, there’s that PROBITY gremlin again.
Come on, readers. It is childishly inadequate to simply read about measurement uncertainty, understand it to some level, then ignore it by giving a free pass to articles that omit it, partly because they look plausible in pictures.
All of us remember bits from our education. Two bits that I remember from math/stats in the 1960s are: First, understand your distribution. Second, give similar weight to both the magnitude and the uncertainty of a number, treating them as an ever-present pair.
So, readers, what are your estimates of the uncertainty of these temperature values? What does this estimate do to the credibility of the papers using these parameters?
Geoff S
I’m uncertain about what you’re saying here Geoff.
What I’m highlighting about temps records is their lack of –
probity /prō′bĭ-tē/
nounComplete and confirmed integrity; uprightness.
Lacking in probity – and utility.
The degree of hotness of a thermometer tells you nothing about the source of heat, does it? You might just as well furiously record wind speed and direction. But why?
Neither will improve the accuracy of your crystal ball one jot!
A good polishing with a microfibre cloth will be much more efficacious.
I’m not sure where you’re going with that comment. Are you saying an observed phenomena (AMO) may not exist because we can’t quantify the uncertainty of observations and measurements that reveal its presence?
I am questioning how much of the data remains credible as one imposes more and more estimates of temperature measurement uncertainty on it.
For a simple example, if you include Pat Frank’s measurements of drift in old LIG thermometers, the first 50 years on these graphs might be in a different place. For another example, the pictorial detail in the wriggle matching would be less clear in this first 50 years than in the last 50. Third example, effects of instrument/ shelter change might explain the gross pattern better than actual T change.
Basically, worst case, the whole pattern becomes a straight line flopping about inside a sea of uncertainty between brackets that enclose it all with 95% statistical likelihood.
We have devised ways to quantify uncertainty. They should be used routinely to clarify the nature of the above examples. That is the purpose of uncertainty analysis.
Breaking news – US President Trump, by executive order signed (manually, with witnesses) yesterday, has made formal uncertainty analysis to be a lawful requirement.
Geoff S
Thank you for the excellent reply!
I guess the issue resolves to the philosophical question of “If you can’t objectively measure a physical parameter (regardless of the degree of uncertainty associated with such measurement) does it really exist?”
Here I’m thinking about the current challenge in physics of “dark matter” and “dark energy”.
As for President Trump’s EO, pffthtptt!. . . one cannot mandate human behavior!
“Patterns” influence nothing at all.
The atmosphere is chaotic. Unpredictable. “Patterns” are just people trying to impose their will on temperature observations. All well and good, but completely useless.
Experts detect “patterns” in the stock market, and some claim that these “patterns” can be used to predict future stock movements. The experts then make a living by selling their predictions to the ignorant and gullible, possibly because the experts know that the future cannot be predicted by peering into the past, and they cannot make money by following their own predictions. Would that make them frauds?
And so it is with “climate scientists” who make a living from writing “scientific” papers which are completely worthless. Is
a useful or useless scientific paper published in Nature? Unless someone can demonstrate otherwise, 100% of papers published by “climate scientists” have no utility at all – of no benefit to humanity.
OMG, studying past patterns is useless?? There goes the whole field of geology! /sarc/
Andy, maybe you could try being sarcastic about something I said, not something I didn’t say. Are you trying to say that geologists can predict when the marine fossils found at over 6000 m altitude will once again be beneath the sea?
When you say
what did you mean? Sounds a bit silly to me.
Such a ridiculous statement!
As but one example, Nicolaus Copernicus is known for studying the patterns of planetary “epicycles” which directly led him to propose a heliocentric model of the solar system, which challenged and subsequently overthrew the prevailing geocentric model that had placed Earth at the center.
Another ridiculous statement.
Richard Lindzen and William Happer can both be considered as eminent climate scientists, well-published in the field, offering great insights into factors that affect climate. In particular, they have independently and jointly published on the idea that atmospheric CO2 has an asymptotic limit as to its impact on climate. In a recent publication (https://apps.legislature.ky.gov/CommitteeDocuments/262/30750/Jul%2018%202024%20Happer%20%26%20Lindzen%20Summary.pdf ), they argue that at current atmospheric CO2 concentrations, CO2’s ability to absorb LWIR radiation from Earth’s surface (aka a “greenhouse gas” effect) is limited (i.e., nearly saturated). This implies that increasing CO2 concentrations beyond a certain point will have diminishing returns in terms of warming, leading to the very significant conclusion (potentially saving $trillions of taxpayer dollars) that future “net-zero” efforts will have a trivial effect on global temperature variations. That knowledge is a benefit to all of humanity.
Patterns influence nothing at all. Maybe I should have included “in and of themselves”, but I assumed rational people would know this from the context. I apologise. Copernicus, as you pointed out, performed observations, noticed that they didn’t support consensus thinking, and formed a testable hypothesis to explain these observations. His subsequent testing by observation confirmed his speculations.
Climate is the statistics of weather observations, but if you think that “eminent climate scientists” are required to perform basic arithmetical calculations, then so be it.
Which is complete nonsense, as adding CO2 to air does not make it hotter. However, you then assert
What knowledge would that be? Sorry, but “implications” based on magical thinking are not “knowledge”.
Lol.
But the AMO doesn’t exist in simulations, therefore it doesn’t exist. /sarc/
Just so. Remember, the science (of computer simulations) was settled long ago,
Oceans transport heat to the poles. The atmosphere is terrible at it. More heat to the poles means a warmer planet. Simple as. It’s why we are in the interglacial and also why we are in an ice age.
During the Holocene Climate Optimum the waters at least 6 degrees warmer than today according to temperature sensitive molluscs near Svalbard Island.
https://journals.sagepub.com/doi/abs/10.1177/0959683617715701
Actually, they don’t. They are water on the surface of an oblate spheroid, and the deeper bits just sit where they are. Gravity holds the water in place, just like a puddle on a flat surface. All the Sun’s surface warming dissipates at night, and the only thing that stops oceans and deep lakes from freezing right through, is gentle but continuous heat from beneath.
Climate scientists might say otherwise, but they believe in fables like the GHE!
Adding CO2 or H2O to air does not make it hotter, and water at the Equator doesn’t magically move North or South to cool down.
“…the only thing that stops oceans and deep lakes from freezing right through, is gentle but continuous heat from beneath.”
Actually, it’s because ice, being less dense than liquid water, floats. If it sank to the bottom, the oceans themselves would have frozen solid by now.
Are you trying to disagree with something I wrote, but can’t quite figure what?
Seawater freezes at around -1.8 C. No deep water on Earth gets this cold – gently warmed from beneath – causing convection, and all that entails.
Yes, and if a bicycle had three wheels, it would be a tricycle. I’m sorry, but I can’t see the point of your comment.
It is a logical fallacy to go from the “axiom” of
“***I*** do not understand your point …”
to the “conclusion” of
“… and therefore it is completely impossible that you might have a ‘valid’ point to make”.
.
Yes, “johnesm” was disagreeing with you.
No, “johnesm” is perfectly well aware of the physical properties of ice and water that result in even relatively “shallow” lakes at high latitudes, let alone “deep” ones, traversing winters cold enough to freeze their surfaces with intact lifeforms.
Doing an Internet search for more up-to-date references than I possessed when I woke up this morning led me to the following URL :
https://teacherscollegesj.org/what-would-happen-to-life-on-earth-if-ice-sank/
An extract :
Clearly the entire Earth “freezing overnight” is a “thought experiment” that has no parallel in the real world … but what about, say, the Arctic ocean in the 3 to 5 months of “night” around the northern hemisphere winter solstice ?
The “Daily mean temperatures for the Arctic area north of the 80th northern parallel” DMI webpage indicates that January and February for the “80°N polar cap” has average temperatures of around -30°C, a lot lower than the -2°C needed to form sea-ice.
Davies (2013), “Global map of solid Earth surface heat flow”, showed that “geothermal heat” mainly rises through the Earth’s crust along undersea dorsals …
… and Paul Lowman’s “Global Tectonic and Volcanic Activity of the Last One Million Years” webpage at NASA shows that the only dorsal that could provide large quantities of “geothermal heat” in the Arctic is the Gakkel ridge (see image attached to the end of this post).
.
If (sea) ice sank into (sea) water, what physical mechanism would stop the “indentations” around both Alaska / Northern Canada and the Russian coast from “filling up from the bottom” with ice each and every NH winter ?
You don’t seem to know what you are complaining about.
You pose silly questions like
What about it? Are you agreeing with me that deep water doesn’t freeze? You’re being a bit obscure.
Maybe you should quote something I said, and then provide some facts to support any assertion that I am wrong. Or you can just burn strawmen you have laboriously constructed.
I don’t care much either way.
?
Are you so ignorant that you don’t know there is ocean circulation to the poles? What did you think causes most of the polar ice to melt?
Arctic air temperature is related to NH SST, NH sea ice inversely correlates with NH SST.
The ocean floor is near freezing and the surface is not except at the poles. If you were right the ocean bottom layer would be warmer on average than the surface.
Thank you Michael Flynn for your outstanding display of stupidity.
I accept flattery from anybody.
There is certainly ocean at the North Pole, and certainly none at the South Pole. There is no “polar ice” melting at the South Pole, as far as I know, and if there is ice at the North Pole, it obviously hasn’t melted yet – otherwise it would be water.
Deep water does not freeze because it is gently heated from below. Deep ocean currents are due to convection, not magic. Just basic physics.
I may be stupid, but not stupid enough to believe that adding CO2 or H2O to air makes it hotter, or that the Earth’s surface has not cooled.
Is that what smart people like yourself believe?
“Is that what smart people like yourself believe?”
No actually. CO2 responds to sensible heat changes. The climate keys off of the equatorial Pacific ocean heat content anomaly, with CO2 changing last.
mydrrin,
Actually it is the opposite, the atmosphere transports more heat to the poles except very close to the equator. See attached plot. It is from Schmitt, Oceanography, 2018.
https://www.jstor.org/stable/26542649
Good to see the rapid warming of the world isn’t being denied in this blog post. Denial ends with baby steps
“The spike at the end of both records is probably due to the Hunga-Tonga volcanic eruption in January of 2022.”
Gone off the deep end like the rest of the HT fanatics. Why bastardize an otherwise decent article with this specious and speculative nonsense?
As there were other similar large SST increases without such an eruption, it was unnecessary and inconsistent to invoke this special pleading regarding HT-HH as a cause of the latest warming spike.
If you’re going to promote this special pleading for the 2023-25 spike then please also hand-wave away all the other short-term SST spikes, as they all will need to be attributed to something as well.
Was there an HT-HH equivalent for the ’97/98 ENSO? Or for the 1970’s SST spikes? NO.
Now you’re trapped into having to explain other spikes as a series of singular special events.
You’ve really trapped Andy this time, Bob. No statistical difference with previous temperature spikes relative to ENSO. /sarc/
Robert I think you didn’t get something here. Andy May et al have claimed HT-HH caused the recent temperature spike, not ENSO. The recent ENSO activity change of about 1°C was barely different in magnitude than the ’97/98 ENSO, as my previous plot showed.
What you should understand is the UAH LT tracks SST at r=.92 w/ 3 month lag, using 12ma∆. The most recent UAH spike is just following the SST spike, as it did before.
If people are going to assume a single event like the 2022 HT-HH eruption caused the recent spike then these same people are then going to need to assign a separate cause to prior spikes, one that doesn’t involve ENSO, in order to be intellectually consistent.
That is the trap the HT-HH advocates have fallen into.
Further, UAH anomaly versus ONI isn’t the best direct comparison, and when you make such a graph in the future please endeavor to align the zeroes of both axes.
“Some have speculated that it is a result of the thermohaline circulation in the North Atlantic or a “combination of natural and anthropogenic forcing during the historical era.” (Mann, Steinman, & Miller, 2020).” How is it that “anthropogenic forcing,” i.e. increasing downwelling infrared radiation from increasing CO2 in the atmosphere, can increase “sea surface temperature” as it is defined – the temperature of the top few feet of the sea. Seawater is opaque to IR and therefore the most more IR can do is to increase the temperature of the very few water molecules at the immediate surface and force more evaporation at this surface. The amount of increased evaporation from CO2 caused IR (~2 watts/m^2 or so) is tiny compared to that caused by solar radiation (hundreds of watts/m^2) and cannot therefore be measured. Perhaps my understanding is errant or incomplete but it seems to me that IR cannot be involved in the AMO variations.
I have mentioned several times how Arctic sea ice variations are the most likely driver of the 60-70 year cycle and the AMO. The insulating characteristics of sea ice along with the geography of the Arctic Ocean come into play.
This leads to cyclic changes affecting global atmospheric circulations and resulting cloudiness. Since the bulk of the changes occur in the NH, this is where the biggest changes are seem.
“Arctic sea ice variations are the most likely driver of the 60-70 year cycle and the AMO”
That is the leading theory today, and the most likely. The sea ice variations might be related to changes in the Sun.
That’s the tail wagging the dog, the warm AMO melts the sea ice. The AMO and Arctic are colder when the solar wind is stronger, because of positive North Atlantic Oscillation conditions which drive the colder AMO and reduce atmospheric humidity events and cyclones into the Arctic.
Or to the chaotic motions of the atmosphere, aquasphere and lithosphere, connected to everything in the universe.
If Sir Isaac Newton was right about every particle in the universe having an effect on every other particle in the universe, then Lorenz’ question “does the flap of a butterfly’s wings in Brazil set off a tornado in Texas?” (and its converse) is a serious overstatement of the change required to set off a tornado anywhere.
The IPCC grudgingly acknowledges that it is not possible to predict future states of the atmosphere, but goes on to imply that “climate scientists” can safely ignore the laws of the universe.
Ja. Ja. I told you. The global warming is coming from the north and slowly moving south. https://breadonthewater.co.za/2025/05/10/an-evaluation-of-the-greenhouse-effect-by-carbon-dioxide-2/
First graph
Who did it? Various factors. Urbanization is a factor. But the warming of oceans is coming mostly from earth itself: increasing volcanic action, especially NH.
Think not out of the box but put yourself in a box. We are living in a big boiler with heaters from the bottom and the top.
Sorry I forgot. Great article, Andy!
Henry, and the top one only gets turned on in the morning, and starts getting turned off for the night around midday. In the polar regions, it stays on for six months, but is turned very low.
Every other warm AMO phase is during each centennial solar minimum, which means that the long term average AMO frequency has to be 55 years. The reason for the last two AMO envelopes being 60 and then 70 years long, is that the late 1800’s centennial minimum began 130 years before the current centennial minimum began. The 1800’s had 40 year AMO cycles, because the Dalton minimum started 80 years before the Gleissberg minimum started.
The cause of a warmer AMO is weaker solar wind states causing negative North Atlantic Oscillation regimes. It is a wind driven negative feedback to changes in indirect solar forcing, and with a considerable overshoot. Ten year smoothing of the AMO series obscures the annual scale solar forcing of the AMO. Stronger solar wind states correlate to the coldest AMO periods, in the mid 1970s, mid 1980’s, and early 1990’s, and the cold blobs in 2013-15 and 2018, all during positive NAO regimes.
Anything that changed sharply from 1995 is warm AMO driven, increasing specific humidity, decreasing low cloud cover, increasing upper ocean heat content, retreating continental glaciers, less drought in the Sahel, and lots more.
AMO anomalies are locked to solar cycles, in a curious manner. AMO anomalies are always colder around sunspot cycle minimums during a cold AMO phase, and never the coldest around sunspot minimum during a warm AMO phase. Which can only be explained by the shifts in the major lows and highs in the solar wind relative to the sunspot cycles. Major lows in the solar wind were at sunspot maximum in 1969 and 1979, and they shifted to just after sunspot minimum from the 1990’s.
https://www.woodfortrees.org/graph/esrl-amo/from:1880/mean:13/plot/sidc-ssn/from:1880/normalise
The coldest AMO anomalies in the early 1900’s are the same pattern as the 1970-80’s, colder near sunspot minimum, suggesting stronger solar wind states, positive NAO/AO conditions, and land heatwaves.
https://www.woodfortrees.org/graph/esrl-amo/from:1903/to:1926
Solar wind temperature and pressure:
Something Joe Bastardi said got me studying the AMO and ENSO data sets.
During a centennial low in solar activity the AMO will be warmer due to an increase in negative North Atlantic Oscillation states. Negative NAO also means increased El Nino conditions, which have a lagged negative influence on the NAO and hence the AMO, which is in total lagged about 8 months.
During the warm phase of the AMO only, major warm pulses to the AMO peak in August following an El Nino episode, e.g. Augusts 1998, 2005, 2010, 2016:
https://psl.noaa.gov/data/correlation/amon.us.data
The negative NAO influence of El Nino episodes is not apparent during a cold AMO phase. Ron Clutz later linked me a paper with the same warm AMO-ENSO findings, and that La Nina episodes have a positive influence on the NAO, only during cold AMO phases.
Great work Andy!
I stumbled across this AMO correlation…
When writing this post:
https://wattsupwiththat.com/2025/04/08/evidence-of-catastrophic-glacier-melt-in-new-york-city/
The alleged acceleration in sea level rise in The Battery tide gauge record appears to correlate to the most recent shift in the AMO phase from cold to warm.
Thanks David,
It is amazing that so many climate indicators correlate to the AMO so well. But we remember that the Great Mann has proclaimed the AMO doesn’t exist and is simply the function of anthropogenic warming and “regular” volcanic eruptions! /sarc/
Just like the PDO and pH…
This isn’t the correlation they’re looking for…