Guest post by David Middleton
(Featured image borrowed from http://www.hockeyministries.org/rwt-blog-52316)
Unfortunately this article is behind a pay wall. While some of the points in the abstract are reasonable, these two seem to be totally unsupported in any literature of which I am aware…
An average global temperature increase of 0.6o to 0.9oC from 1900 to the present, occurring predominantly in the past 50 years, is now rising beyond the Holocene variation of the past 14,000 years, accompanied by a modest enrichment of δ18O in Greenland ice starting at ~1900. Global sea levels increased at 3.2 ± 0.4 mm/year from 1993 to 2010 and are now rising above Late Holocene rates.
“An average global temperature increase of 0.6o to 0.9oC from 1900 to the present, occurring predominantly in the past 50 years, is now rising beyond the Holocene variation of the past 14,000 years…”
It appears that they are relying on Marcott et al., 2013 for the temperature claim.
Here is an enlarged version of the temperature curve…
The problem is that the authors of Marcott et al., 2013 unequivocally stated that their reconstruction was not amenable to such claims
One author, Jeremy Shakun (currently at Harvard) weighed in via Skype for Dot Earth. When more questions came in, the group of authors wrote that they would respond more completely to questions about the work and now they have done so, on the RealClimate blog. Here’s a short excerpt and link to the rest:Q.
What do paleotemperature reconstructions show about the temperature of the last 100 years?A.
Our global paleotemperature reconstruction includes a so-called “uptick” in temperatures during the 20th-century. However, in the paper we make the point that this particular feature is of shorter duration than the inherent smoothing in our statistical averaging procedure, and that it is based on only a few available paleo-reconstructions of the type we used. Thus, the 20th century portion of our paleotemperature stack is not statistically robust, cannot be considered representative of global temperature changes, and therefore is not the basis of any of our conclusions. Our primary conclusions are based on a comparison of the longer term paleotemperature changes from our reconstruction with the well-documented temperature changes that have occurred over the last century, as documented by the instrumental record. Although not part of our study, high-resolution paleoclimate data from the past ~130 years have been compiled from various geological archives, and confirm the general features of warming trend over this time interval (Anderson, D.M. et al., 2013, Geophysical Research Letters, v. 40, p. 189-193).Q.
Is the rate of global temperature rise over the last 100 years faster than at any time during the past 11,300 years?A.
Our study did not directly address this question because the paleotemperature records used in our study have a temporal resolution of ~120 years on average, which precludes us from examining variations in rates of change occurring within a century. Other factors also contribute to smoothing the proxy temperature signals contained in many of the records we used, such as organisms burrowing through deep-sea mud, and chronological uncertainties in the proxy records that tend to smooth the signals when compositing them into a globally averaged reconstruction. We showed that no temperature variability is preserved in our reconstruction at cycles shorter than 300 years, 50% is preserved at 1000-year time scales, and nearly all is preserved at 2000-year periods and longer. Our Monte-Carlo analysis accounts for these sources of uncertainty to yield a robust (albeit smoothed) global record. Any small “upticks” or “downticks” in temperature that last less than several hundred years in our compilation of paleoclimate data are probably not robust, as stated in the paper.
The most complete Holocene “thermometers” are Greenland ice cores. They do not indicate that the warm up from the Little Ice Age is anomalous…
I performed a GISS station search centered on 71.4 N latitude, 23.5 W longitude and downloaded the 12 GISS/GHCN instrumental records with at least 60 years of continuous data up to 2011.
Next I calculated a temperature anomaly relative to 1961-1990 for each of the 12 stations and then averaged them together to create a temperature reconstruction. The climate in the Warming Island area is statistically indistinguishable from that of the 1930’s.
Then I took that reconstruction back to 1000 AD with the GISP2 ice core d18O data (Kobashi et al., 2010)…
The Modern Warming is also statistically indistinguishable from the Medieval Warm Period in the Warming Island / Greenland Sea region.
“Global sea levels increased at 3.2 ± 0.4 mm/year from 1993 to 2010 and are now rising above Late Holocene rates.”
The sea level claim is preposterous…
A Geological Perspective of Recent Sea Level RiseAll of the estimated sea level rise since 1700 is represented by the light blue blob and dark blue line inside the black oval. Sea level isn’t doing anything now that it wasn’t already doing before All Gore invented global warming. And Holocene sea level changes have been insignificant relative to the Holocene transgression…Figure 1. Sea 1evel rise since the late Pleistocene from Tahitian corals, tide gauges and satellite altimetry.
Figure 2. Northern Hemisphere temperature, atmospheric CO2 and sea level since 1700 AD.
We can adapt to this without breaking a sweat…
Figure 3. Projected sea level rise through 2100 AD.
Particularly since sea level rose just as fast from 1931-1960 as it has risen since 1985…
Figure 4. Paracyclical sea level rise since 1931.
Anyone threatened by 6-12 inches of sea level rise over the next 85 years is already being flooded by high tides and/or storm surges. The red areas on this EPA map would be threatened by 1.5 meters of sea level rise.
Figure 5. Coastal areas threatened by 1.5 meters of sea level rise along US Gulf Coast (US EPA).
Bear in mind the fact that it would take an average rate of sea level rise nearly twice that of the Holocene Transgression for sea level to rise more than 1.5 meters (~5 feet) over the remainder of this century. This caused sea level.to rise by ~10 mm/yr for about10,000 years…
Figure 6. Animatiion of Late Pleistocene to Early Holocene deglaciation (Illinois State Museum).
Approximately 52 million cubic kilometers of ice melted during that 10,000 year period.
The Holocene Highstand
There are at least two schools of thought regarding Holocene sea level changes. The view favored by the IPCC and the so-called scientific consensus is that of a rapid rise in sea level during the early Holocene followed by a static quiescence from about 6,000 years ago up until the dawn of the “Anthropocene” (generally the Industrial Revolution). The second school of thought, favored by many (if not most) sedimentary geologists, is that of a dynamic Holocene sea level and a pronounced Holocene Highstand.
Figure 8. Sea level was 1-2 meters higher than it currently is during the Holocene Highstand.
Evidence for a Holocene Highstand is global in nature, consisting of stranded beaches and other facies associated with shorelines 1-2 meters higher than present day from 4-7 kya.
Another point of contention is their claim about extinction rates. Extinctions in the geologic record are measured at the genus and family level, not the species level. Comparing modern species extinction rates to extinctions in the fossil record are nothing more than Hockey Stick factories.
While at some distant point in the future, an “Anthropocene” may be identified as stratigraphically distinct from the Holocene, Walters et al., 2016 does not make much of a case for it. This appears to be another exercise in splicing modern high resolution data onto lower resolution proxy data (AKA Hockey sticking).
I contacted Dr. Colin Waters via email to inquire about the source of their temperature reconstruction. He replied very promptly and cordially. Dr. Colin Summerhayes and Dr. Alexander Wolfe also joined the conversation. I found our discussions to be very enjoyable and informative. Dr. Waters authorized me to post this passage from our email discussion…
“The temperature curve in Figures 1B and 6B of the Science paper on the
Anthropocene was derived from Marcott et al., Science 339, 2013.
In the abridged version of the article the figure 14,000 should be
amended to 1,400 to be consistent with what we say in the main body of the paper”.