Global Temperature Change

The NAS just published a free-access paper by James Hansen and collaborators, ”Global temperature change”, PNAS, September 26, 2006, vol. 103, no. 39, pp. 14288-14293.  Here is the abstract text:

Global surface temperature has increased {approx}0.2°C per decade in the past 30 years, similar to the warming rate predicted in the 1980s in initial global climate model simulations with transient greenhouse gas changes. Warming is larger in the Western Equatorial Pacific than in the Eastern Equatorial Pacific over the past century, and we suggest that the increased West–East temperature gradient may have increased the likelihood of strong El Niños, such as those of 1983 and 1998. Comparison of measured sea surface temperatures in the Western Pacific with paleoclimate data suggests that this critical ocean region, and probably the planet as a whole, is approximately as warm now as at the Holocene maximum and within {approx}1°C of the maximum temperature of the past million years. We conclude that global warming of more than {approx}1°C, relative to 2000, will constitute “dangerous” climate change as judged from likely effects on sea level and extermination of species.

From the paper (SST = sea surface temperature):

Fig. 3. SST in 2001–2005 relative to 1870–1900, from concatenation of two data sets, as described in the text.

Fig. 5. Modern sea surface temperatures in the WEP compared with paleoclimate proxy data.  Fig. 5 shows that recent warming of the WEP has brought its temperature within <1°C of its maximum in the past million years.