I hope this isn’t too confusing and I don’t want to repeat all the details here as you can read the articles and comments yourselves and ask questions on the comments section. In the comments section to my last article on April 25 , “Klem” commented: “there is NO WAY to conclude from the BEST study that it is caused, or isn’t caused, by human emissions.” And a few lines later he or she wrote this; “Good question, perhaps 800 years I would guess. Since that is roughly how long it takes for CO2 to respond to earlier temperature changes.” There is an embedded (and amusing) contradiction between these two statements. If you reread the entire exchange from my April 17th article  and my April 25th article plus the comments it should be easy to spot. In my reply, I offered a growler of Loudoun County’s own Corcoran Beer to the first person to discover Klem’s self-contradiction. I hasten to add that I am not trying to embarrass Klem, whom I really don’t know and who’s comments I enjoy receiving. But I thought this would be an excellent learning tool to get people to think critically and skeptically about our climate or indeed about anything. Skeptical thinking is in short supply in America, sadly and I was kind of hoping Klem would see his/her error and go for the win him/herself. In retrospect announcing the contest in the comments section was probably not a good idea.
In summary, The BEST study was conducted by a group of deniers out to prove climate science wrong. Instead they proved science has been right all along and that the deniers had been wrong. No surprise there. The deniers confirmed that the current rate of increase of global land temperature is 2.76 degrees Celsius (5 degrees Fahrenheit) per century. This rate far exceeds any rate from natural causes outside of a collision with a giant meteorite and therefore also proves indirectly that the cause is human emissions of greenhouse gases. Atmospheric levels of these gases are increasing at a rate two orders of magnitude faster than the rate of increase during the recovery from the last ice age. This is Klem’s second point that it took nature 800 years to do what we are doing in less than 8 years.
Clearly Klem’s first statement is wrong but the second is a marvel of cognitive dissonance. He is right that the increase in Antarctic temperature began about 800 years +/-600 years before the rise in atmospheric CO2 as shown in Figure 3 below. The termination of the ice age was extremely fast and violent in geological time scale but slow compared to what humans have been doing. So his second statement contradicts the first. The rate of increase reported by the BEST group confirms a human cause which is why the deniers have been denying the BEST results as best they can. The second statement as used by deniers to aver that CO2 is not a greenhouse gas is also wrong. Global warming deniers are living a great lie and the more they argue with reality the more they contradict themselves. They are digging a deeper hole of deceit. It is inevitable.
As to the contest, we have a winner. Several people emailed me their explanations but Candice Guillaudeu emailed this: “Is it that the graph line for CO2 is rising very fast over a very short period of time, way less than the 800 years as Klem writes?” And I think this is good enough to win the growler since I was looking for somebody to recognize the importance of the rate of change. It is all about the first derivative.
I have been planning to write about the denier canard that “the atmospheric CO2 level follows the global temperature rise by 800 years and therefore was an effect not a cause of global warming” as some new results have been published in Nature, Science, Climate Dynamics and PNAS describing the Last Glacial Maximum (LGM) to Holocene transition and I had been putting it off. Klem pushed me to tackle this. So let’s take a look.
The ice ages were discovered by Louis Agassiz in 1837 . This discovery was at first not very well received and he had many detractors until other naturalists, notably Charles Darwin, began to point out the evidence of extensive glaciation such as terminal moraines and gouged valleys all over Europe and subsequently North America. This is a fascinating story and one well documented by Doug Macdougall in his recommended book Frozen Earth .
Discovering the causes of the ice ages became a focus of many scientists. Two lines of argument emerged. Joseph Adhemar pioneered the idea that Earth’s orbital variations drove the climate changes and suggested a role for Earth’s precession in 1842  and Svante Arrhenius implicated changes in atmospheric carbon dioxide in 1896  building on the experimental verification of carbon dioxide as a green house gas by John Tyndall in 1861 . Tyndall also identified methane, water vapor, ozone and nitrous oxide as greenhouse gases. Carbon dioxide is the principle green house gas  both because of the larger quantity than methane, ozone or nitrous oxide and because it obeys different physical laws than water vapor. Carbon Dioxide is the Earth’s thermostat. Briefly, at earth surface temperatures, carbon dioxide wants to be a gas and water wants to be a liquid. Water vapor within the range of Earth surface temperatures can only ever be a feedback and cannot be a forcing function. It has a residency of about 8 days in the atmosphere. This is why nobody worries about cars running on hydrogen exhausting water vapor and causing global warming.
In both arguments, changing albedo plays a critical amplifying role. Albedo is the reflectivity of the Earth surface. Ice and snow being white have high albedo as they reflect most of the incoming solar radiation. If it gets reflected rather than absorbed then it cannot warm the planet. The water, soil and vegetation exposed when the ice and snow melt are darker and absorb most of the incoming solar radiation.
Earth’s orbit varies in three ways which I’ve described previously: obliquity, precession and eccentricity. James Croll, 1875  and Milutin Milankovitch, between 1920 and 1941  amended Adhemar’s analysis to include obliquity and eccentricity. Every day the Earth spins on an axis which is currently pointing towards the North Star, Polaris. This axis is not perpendicular to the orbital plane about the sun but is tilted at an angle of 23.5 degrees. This angle called obliquity varies between 22.5 degrees and 24.5 degrees. When the obliquity is 24.5 degrees, the earth at 65 degrees north latitude (Alaska, Northern Canada, Greenland, Scandinavia, Siberia…) receives an increase of about 30 Watts/meter squared of incoming solar radiation. The change in total received radiation from the sun integrated over a year doesn’t change much at all. Lorius et al report that this averaged value hasn’t changed over the last 160,000 years by more than 0.7 W/m2. The received solar energy is simply moved around in time and space over the Earth’s surface. In addition to obliquity changes, the Earth’s spin wobbles or precesses (It is not always pointed towards Polaris) and the eccentricity of the Earth’s orbit around the sun gradually changes from a circular orbit to a slightly elliptical one. These variations and their implications for Earth climate are described by John Imbrie and Katherine Palmer Imbrie in their 1979 book Ice Ages . Precession causes opposite insolation changes between the northern and southern hemispheres, while obliquity causes synchronous insolation changes in the two hemispheres.
Another important consideration is the circulation of water in the oceans. See my article from September 16, 2012 . The ocean currents, of which the Gulf Stream is a part, form the Great Ocean Conveyor discovered by Wally Broecker and shown in Figure 1 . Observe the blue current flowing south in the deep Atlantic. This is called the Atlantic Meridional Overturning Circulation (AMOC) and it can slow down as we will discuss.
This background information will be used to help us understand what happened during the transition from the LGM to the Holocene. Study of palaeoclimate and earth systems science has led to understanding of how the Earth operates as a system.
Figure 1. “Schematic of the ocean circulation (from Kuhlbrodt et al. ) associated with the global Meridional Overturning Circulation (MOC), with special focus on the Atlantic section of the flow (AMOC). The red curves in the Atlantic indicate the northward flow of water in the upper layers. The filled orange circles in the Nordic and Labrador Seas indicate regions where near-surface water cools and becomes denser, causing the water to sink to deeper layers of the Atlantic. This process is referred to as “water mass transformation,” or “deep water formation.” In this process heat is released to the atmosphere. The light blue curve denotes the southward flow of cold water at depth. At the southern end of the Atlantic, the AMOC connects with the Antarctic Circumpolar Current (ACC). Deep water formation sites in the high latitudes of the Southern Ocean are also indicated with filled orange circles. These contribute to the production of Antarctic Bottom Water (AABW), which flows northward near the bottom of the Atlantic (indicated by dark blue lines in the Atlantic). The circles with interior dots indicate regions where water upwells from deeper layers to the upper ocean.” (text from )
The birth of a denier myth
Figure 2 shows data from the Vostok ice core from Antarctica. This figure shows the remarkable correlation between high atmospheric carbon dioxide concentrations and temperature. This figure was shown by Al Gore in his movie An Inconvenient Truth with dramatic effect in 2006. Five years earlier in 2001, Eric Monnin  showed that during the transition from the LGM the temperature in Antarctica preceded the rise in carbon dioxide by about 800 +/- 600 years. Monnin wrote that “The estimated time lag is small in comparison with the 6000-year duration of the closely tied temperature and CO2 concentration increases and does not cast doubt on the importance of CO2 as an amplifying factor of the temperature increase.”
The temperature captured by the ice core which Monnin studied was in fact the temperature in Antarctica and not the global temperature something scientists knew as did Gore and the reality-based community. In fact that CO2 lags and amplifies Antarctic temperature was predicted by Lorius et al in 1990 . “Changes in the CO2 and CH4 content have played a significant part in the glacial-interglacial climate changes by amplifying, together with the growth and decay of the Northern Hemisphere ice sheets, the relatively weak orbital forcing.”
Figure 2: Vostok ice core records for carbon dioxide concentration and temperature change. 
By conveniently ignoring Monnin’s own conclusion and the fact that the core represented only Antarctic temperature, deniers made up the myth that global temperature preceded carbon dioxide by 800 years. There are several striking differences between deniers and the rest of us. Skeptical scientists ask questions. Several come to mind. What was the temperature of the rest of the world and how quickly did that rise? Where did the carbon dioxide and methane come from? Deniers, not being skeptical, do not ask questions and ignore relevant information. Congressman Joe “We are soooo sorry BP” Barton (R-OIL) said what he was paid to say at the time, “An article in Science magazine illustrated that a rise in carbon dioxide did not precede a rise in temperatures, but actually lagged behind temperature rises by 200 to 1000 years. A rise in carbon dioxide levels could not have caused a rise in temperature if it followed the temperature.” You can bet that Barton had never read a Science article in his life. And this is where Klem gets the 800 year number not from the actual science but from some denier blog. In reality, nature increases atmospheric carbon dioxide by volcanism, melting permafrost, defrosting methane clathrate, and carbon cycle feedbacks  all of which pale in comparison to the rate of human emissions.
So what really did happen between 20,000 years ago at the peak of the glacial extent and 10,000 years ago at the start of the Holocene and the beginning of human civilization, the discovery of agriculture and the creation of cities? My next article will address all of the fascinating science which has recently been published. This is a great story. Stay tuned.
Figure 3: The global proxy temperature stack (blue) as deviations from the early Holocene (11.5–6.5 kyr ago) mean, an Antarctic ice-core composite temperature record (red), and atmospheric CO2 concentration (yellow dots). The Holocene, Younger Dryas (YD), Bølling–Allerød (B–A), Oldest Dryas (OD) and Last Glacial Maximum (LGM) intervals are indicated. Error bars, 1-sigma; p.p.m.v. = parts per million by volume. From Shakun et al. Figure 2a .
 Tony Noerpel, http://brleader.com/?p=8136
 Tony Noerpel, http://brleader.com/?p=8276
 Louis Agassiz, Etudes sur les glaciers, privately published, Neuchatel, 1840; described in  and .
 Doug Macdougall, Frozen Earth, University of California Press, 2006.
 Joseph Adhemar, Revolutions de la mer, privately published, Paris, 1842. Described in  and .
 Svante Arrhenius, “On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground”, Philosophical Magazine and Journal of Science, Series 5, Volume 41, April 1896, pages 237-276. http://www.rsc.org/images/Arrhenius1896_tcm18-173546.pdf
 John Tyndall, On the Absorption and Radiation of Heat by Gases and Vapour, and on the Physical Connexion of Radiation, Absorption an Conduction, Philosophical Magazine Series 4, vol. 22: 169-94, 273-85, 1861. Available in Archer and Pierrehumbert, The Warming Papers, Wiley-Blackwell, 2011.
 Robert Berner, The Phanerozic Carbon Cycle, 2004.
 James Croll, Climate and time, Appleton & Co., 1875. Described in  and .
 Milutin Milankovich, several papers discussed in  and .
 John Imbrie and Katherine Palmer Imbrie, Ice Ages, Harvard, 1979.
 Tony Noerpel http://brleader.com/?p=2103
 Wally Broecker, The Great Ocean Converor, Princeton, 2010.
 Kuhlbrodt, T., A. Griesel, M. Montoya, A. Levermann, M. Hofmann, and S. Rahmstorf, 2007: On the driving processes of the Atlantic meridional overturning circulation. Rev. Geophys., 45, RG2001, doi:10.1029/2004RG000166.
 Eric Monnin et al., Atmospheric CO2 Concentrations over the Last Glacial Termination, Science 291, 112 (2001); DOI: 10.1126/science.291.5501.112.
 Lorius, C. Et al., The ice-core record: climate sensitivity and future greenhouse warming,” Nature, Vol. 347, 13 September, 1990.
 J.D. Shakun, P.U. Clark, F. He, S.A. Marcott, A.C. Mix, Z. Liu, B. Otto-Bliesner, A. Schmittner, and E. Bard, “Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation”, Nature, vol. 484, 2012, pp. 49-54. DOI.
 Tony Noerpel, http://brleader.com/?p=1414