Paper Reviewed
Comiso, J.C., Gersten, R.A., Stock, L.V., Turner, J., Perez, G.J. and Cho, K. 2017. Positive trend in the Antarctic sea ice cover and associated changes in surface temperature. Journal of Climate 30: 2251-2267.

Multi-trillion dollar government policies are constantly being pursued by those who believe rising atmospheric CO2 concentrations are causing dangerous global warming, which warming they contend will trigger untold harm on the biosphere by melting large portions of the polar ice sheets, raising global sea levels, inducing more frequent and severe extreme weather events and causing a host of other climate-related catastrophes. Surprisingly, key support for enacting such policies typically does not come from observational data, but from complex computer model simulations of how bad the future climate might get.

For those who utilize and trust in the scientific method, forming policy (especially multi-trillion dollar policies!) on the basis of what could or might happen in the future would seem to be a clear act of imprudence. Sound policy, in contrast, is best formulated when it is based upon repeatable and verifiable observations. Consequently, it is of great importance in the debate over what to do (or not do) about rising atmospheric CO2 emissions to evaluate model-based projections of future climate against real-world observations, when they become available, to learn whether or not they are in agreement. And when they are not in agreement, scientists and politicians should always defer to the data and have the courage to abandon or shun policies (or attempts to formulate such) that are based upon disproven model projections.

So, one might ask, how good are the computer model projections of future climate? Do they match well with observations?

Thanks to a recent paper published in the Journal of Climate by Comiso et al. (2017), we can definitively answer this question as it relates to sea ice in the Antarctic.

According to the most recent report by the Intergovernmental Panel on Climate Change (IPCC), CO2-induced global warming will result in a considerable reduction in sea ice extent in the Southern Hemisphere. Specifically, the report predicts a multi-model average decrease of between 16 and 67 percent in the summer and 8 to 30 percent in the winter by the end of the century (IPCC, 2013). Given the fact that atmospheric CO2 concentrations have already increased by 20 percent over the past four decades, evidence of sea ice decline should already be evident in the observational data if such model predictions are correct. But are they?

Turning to the work of Comiso et al., this team of six researchers set out to produce an updated and enhanced dataset of sea ice extent and area for the Southern Hemisphere for the period 1978 to 2015. The key enhancement over prior datasets included an improved cloud masking technique that eliminated abnormally high or low sea ice values, assuring their study to be the most definitive study of Antarctic sea ice trends to date.

In describing their findings, the six scientists report the existence of a long-term increasing trend in both sea ice extent and area over the period of study (see figure below), with the former measure increasing by 1.7 percent per decade and the latter by 2.5 percent per decade.

Figure 1. Monthly anomalies of Southern Hemisphere sea ice extent (left panel) and area (right panel) derived using the newly enhanced SB2 data (black) of Comiso et al. and the older SBA data (red) prior to the enhancements made by Comiso et al. Trend lines for each data set are also shown and the trend values with statistical errors are provided. Source: Comiso et al. (2017).

With regard to these observed increases, Comiso et al. write they confirm "that the trend in Antarctic sea ice cover is positive," adding that "the trend is even more positive than previously reported because prior to 2015 the sea ice extent was anomalously high for a few years, with the record high recorded in 2014 when the ice extent was more than 20 x 10⁶ km² for the first time during the satellite era."

Consequently, it is clear that despite a 20 percent increase in atmospheric CO2, and model predictions to the contrary, sea ice in the Antarctic is expanding and to record levels. These observations are in direct opposition to the model-based predictions of the IPCC. And given this incredibly bad (opposite) prediction on such a key "fingerprint" of global warming theory (retraction of sea ice), it would seem the height of folly to not pull back and disengage from trillion dollar policies (e.g., Paris Climate Accord or the Rio Climate Treaty) designed to restructure global economies.

Reference
IPCC. 2013. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.