Climate Audit

Can we agree that the discovery of Distachia at Quelccaya dated to about 5000 year ago and located about 400-500 m above its present level is evidence that it was warmer at that time than at present at Quelccaya, Peru? Yeah, yeah, I know the argument that maybe Distachia is 400-500 m out of equilibrium with temperature in 2006, but maybe it’s only 100 m out of equilibrium. If the point is going to be argued, I’d like to see it argued in a more substantive way than a mere possibility and there’s a large population of climate scientistis capable of arguing the point if it could be argued.

Regardless of this point, finding Distachia 400-500 meters above present limits is hardly problematic for pre-Hockey Team paleoclimatology – who postulated a Neoglacial period succeeding the Holocene Optimum about 5000-6000 radiocarbon years ago – both terms used many years ago in the prominent text Porter and Denton (1967; 1976). Wood and Smith 2004 stated of this :

The Neoglacial was initially described as a world-wide glacial event that followed a period during which glaciers were at their Holocene minimum (Porter and Denton 1967).

So how does the information about 5000 year old Distachia (alpaca moss) from high altitudes at Quelccaya tie in with Hockey Team views on the Holocene Optimum? How does one reconcile this with the idea of "unprecedented" modern warmth?

Mann was asked about the Holocene Optimum in 2003 by Inhofe’s Senate committee, who were told that the Holocene Optimum was "restricted to high latitudes" and the JJA season (northern summer/southern winter), that "decades ago some scientists believed that this was a time of globally warmer conditions. It is now well known that this is not the case. More abundant evidence now demonstrates, for example, that the tropical regions were cooler over much of the year". With his typical congeniality, Mann decried Legates’ supposed "lack of familiarity" with the literature.

46. How did the temperatures of the mid-Holocene Optimum Period (6000 to 9000 BP) compare with those observed today? Was it a global or a local phenomenon? What was or were the cause or causes of any temperature anomalies in that period? What is the cause of the 104 to 105 year timescale changes in deuterium, oxygen isotope, etc., concentrations in ice core records? Are such changes global or local?

Paleoclimate experts have established that mid-Holocene warmth centered roughly 5000 years ago was restricted to high latitudes and certain seasons (summer in the Northern Hemisphere and winter in the southern hemisphere). Because much of the early paleoclimate evidence that was available (for example, fossil pollen assemblages) came from the Northern Hemisphere extratropics, and is largely reflective of summer conditions, decades ago some scientists believed that this was a time of globally warmer conditions. It is now well known that this is not the case. More abundant evidence now demonstrates, for example, that the tropical regions were cooler over much of the year. All of these changes are consistent with the expected response of surface temperatures to the known changes in the Earth’s orbital geometry relative to the Sun during that time period and associated climate feedbacks, as detailed in peer-reviewed scientific publications [e.g., Hewitt, C.D., A Fully Coupled GCM Simulation of the Climate of the Mid-Holocene, Geophysical Research Letters, 25 (3), 361-364, 1998; Ganopolski, A., C. Kubatzki, M. Claussen, V. Brovkin, and V. Petoukhov, The Influence of Vegetation-Atmosphere-Ocean Interaction on Climate During the Mid-Holocene, Science, 280, 1916-1919, 1998].

Climate model simulations indicate quite good agreement with paleoclimate evidence now available. These models calculate that global annual average temperatures were probably about the same or a few tenths of a degree C cooler than today (the late 20th century) during this time period [Ganopolski, A., C. Kubatzki, M Claussen, V. Brovkin, and V. Petoukhov, The Influence of Vegetation-Atmosphere-Ocean Interaction on Climate During the Mid-Holocene, Science, 280, 1916-1919, 1998; Kitoh, A., and S. Murakami, Tropical Pacific Climate at the mid-Holocene and the Last Glacial Maximum simulated by a coupled ocean atmosphere general circulation model, Paleooceanography, 17 (3), (19)1-13, 2002.]. That’s a far cry from the very out-of-date claim made by Dr. Legates in his testimony. Dr. Legates’ comments regarding climate changes over the past 1000 years reflect a similar lack of familiarity with a whole body of paleoclimate research, especially with the new insights gained through the augmented research program, during the past decade.

Mann re-iterated this position at realclimate in December 2004 in one of their very first posts:

This [Holocene Climatic Optimum] is a somewhat outdated term used to refer to a sub-interval of the Holocene period from 5000-7000 years ago during which it was once thought that the earth was warmer than today. We now know that conditions at this time were probably warmer than today, but only in summer and only in the extratropics of the Northern Hemisphere. This summer warming appears to have been due to astronomical factors that favoured warmer Northern summers, but colder Northern winters and colder tropics, than today (see Hewitt and Mitchell, 1998; Ganopolski et al, 1998). The best available evidence from recent peer-reviewed studies suggests that annual, global mean warmth was probably similar to pre-20th century warmth, but less than late 20th century warmth, at this time (see Kitoh and Murakami, 2002).Ganopolski, A., C. Kubatzki, M. Claussen, V. Brovkin, and V. Petoukhov, The Influence of Vegetation-Atmosphere-Ocean Interaction on Climate During the Mid-Holocene, Science, 280, 1916-1919, 1998.

Hewitt, C.D. and J.F.B. Mitchell, A Fully Coupled GCM Simulation of the Climate of the Mid-Holocene, Geophys. Res. Lett., 25, 361-364, 1998.

Kitoh, A., and S. Murakami, Tropical Pacific Climate at the mid-Holocene and the Last Glacial Maximum simulated by a coupled ocean-atmosphere general circulation model, Paleoceanography, 17, 1-13, 2002.

realclimate linked to the following NOAA website about the Holocene Optimum:

We also now know from both data and "astronomical" (or "Milankovitch") theory that the period of above modern summer temperatures did not occur at the same time around the northern hemisphere, or in the southern hemisphere at all.

Whatever else one may think of Distachia 400-500 meters above present limits, it is evidence that warmth in the Holocene Optimum was not "restricted to high latitudes" and appears to refute the claim it has been "demonstrate[d]" that "tropical regions were cooler over much of the year" in the Holocene Optimum. Maybe Lee or Steve Bloom could ask realclimate whether they’ve sent a corrigendum to Inhofe about their prior evidence – after all the Distachia was reported in December 2002 and Mann, who proclaimed hs "familiarity with the literature" was presumably aware of it.