Duet on Ice: More denier silliness at WUWT

This will be short-ish - by HotWhopper standards :). It's about a duo of articles at WUWT. About ice at opposite ends of the earth - Greenland and Antarctica.

Jim Steele's Bold Greenland Prediction

Jim Steele wrote an article (without mentioning Camille Parmesan once!) predicting that Greenland will start accumulating ice next year. He pulled something out of thin (Arctic) air and wrote:

And based on historical analyses, Greenland will likely begin gaining mass in the coming years.

As Jan Kjetil Andersen said, that is a very bold prediction. And Greenland will have a lot of catching up to do:

Fig. 3.3. Monthly mass anomalies (in Gigatonnes, Gt) for the Greenland ice sheet since April 2002 estimated from GRACE measurements. The anomalies are expressed as departures from the 2002-2014 mean value for each month. For reference, orange asterisks denote June values (or May for those years when June is missing). Source: NOAA Arctic Report Card Dec 14

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 Euan Mearns opts for the outdated laggy denier meme

The second article I'll comment on is about CO2 and temperature. Euan Mearns wrote a very long article (archived here) repeating the worn out, dated denier meme that CO2 lags temperature therefore climate science is a hoax. Well, not quite, but almost. Problem for Euan is that he doesn't keep up with the science. He's relying on a very highly-cited 1999 paper in Nature, by Jean-Robert Petit and colleagues, reporting analysis of the Vostok ice core. The paper showed that:

Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years.

The actual "lag" had long been questioned by scientists, including the authors of the paper, who themselves wrote:

However, considering the large gas-age/iceage uncertainty (1,000 years, or even more if we consider the accumulation-rate uncertainty), we feel that it is premature to infer the sign of the phase relationship between CO2 and temperature at the start of terminations. 

This is explained more, in this realclimate.org article from 2007.

...it is very challenging to put CO2 records from ice cores on the same timescale as temperature records from those same ice cores, due to the time delay in trapping the atmosphere as the snow is compressed into ice (the ice at any time will always be older than the gas bubbles it encloses, and the age difference is inherently uncertain). 

Last year there were two papers that came out around the same time, which markedly reduced the "lag" in the Antarctic ice cores. One was by Parrenin and co, published in Science and the other by  Joel Pedro and colleagues, published in Climate of the Past. Both are discussed in an article by Edward J. Brook in Science mag. He wrote:

One reason that the answer to the above question [which came first - CO2 or temperature change] is more complicated than it may seem is a peculiarity of air preservation in ice. Over the top 50 or 100 m of an ice sheet, the snowpack (firn) gradually becomes denser before it becomes solid ice containing air bubbles. Air diffuses rapidly through the firn, and the trapped air is therefore younger than the surrounding ice. In places with little snowfall, the age difference can be several thousand years. The age difference cannot be reconstructed perfectly, leading to uncertainty in the age of the air (containing the CO2 record) relative to that of the ice (containing the climate record).

A second problem is related to the question itself. The global carbon cycle is an interlinked set of processes that both impact, and are impacted by, climate. For example, warming of the sea surface releases CO2, and that increase contributes to further warming. Ocean circulation changes driven by changes in climate affect the amount of CO2 sequestered in the deep ocean, in turn influencing surface temperature. It seems unlikely that a change in global climate would not influence CO2 concentrations and vice versa. Seeking simple cause and effect is thus difficult.

If you don't have time to read the papers themselves but want to find out more, I strongly suggest reading Edward J. Brook's article. It not only reports the findings of the papers, it discusses what is still not known plus the inherent uncertainties in analysis of ice cores.

It's just a shame that Euan Mearns doesn't read more science.

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Parrenin, Frédéric, Valérie Masson-Delmotte, Peter Köhler, Dominique Raynaud, Didier Paillard, Jakob Schwander, Carlo Barbante, Amaëlle Landais, Anna Wegner, and Jean Jouzel. "Synchronous change of atmospheric CO2 and Antarctic temperature during the last deglacial warming." Science 339, no. 6123 (2013): 1060-1063. DOI: 10.1126/science.1226368 (pdf here)

Brook, Edward J. "Leads and Lags at the End of the Last Ice Age." Science 339, no. 6123 (2013): 1042-1043. DOI: 10.1126/science.1234239 (pdf here)

Pedro, Joel B., Sune Olander Rasmussen, and Tas D. van Ommen. "Tightened constraints on the time-lag between Antarctic temperature and CO 2 during the last deglaciation." Climate of the Past 8, no. 4 (2012): 1213-1221. doi:10.5194/cp-8-1213-2012

Petit, Jean-Robert, Jean Jouzel, Dominique Raynaud, Narcisse I. Barkov, J-M. Barnola, Isabelle Basile, Michael Bender et al. "Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica." Nature 399, no. 6735 (1999): 429-436. doi:10.1038/20859 (pdf here)