It's mid-February 2012 and the various groups reporting global surface temperature data have all posted numbers that are on the low side compared to thus far in the 21st century, though still several tenths of a degree above the 20th century average. NASA's Goddard Institute for Space Studies (GISS) in particular, which I've been following and posting guesses/predictions on for several years now, has just posted a January 2012 number of 0.36 as the global land + sea temperature anomaly, 0.15 degrees C below the 2011 annual average of 0.51 and 0.27 degrees below the 2010 (and 2005) record of 0.63 degrees.
So naturally, those who deny the scientific evidence for human-caused warming have been going on about cooling, how warming has stopped for many years, and so forth. Though not as adamantly as they were back in 2008 - that cooling proved very brief; perhaps they have learned to be more cautious. If I was in mind to go with simple linear trends and didn't believe the science on warming myself, the January 2012 number of 0.36 sounds like a pretty good bet for the whole of 2012 at this point, maybe it should be even lower.
But I understand the science and know quite clearly warming will continue (with some minor ups and downs) until we stop with the fossil carbon burning - and it may take a while after that to actually stop. I've plugged some numbers in and come up with a science-based prediction for 2012: 0.65 C (plus or minus about 0.07). That middle value would break all previous records. Even on the low end it would put 2012 at the 5th or 6th warmest year on record (just slightly cooler than the remarkable early warm year of 1998 in the GISS index). Why am I so sure 2012 will be so warm?
A few months ago Tamino at Open Mind posted a fascinating analysis of warming obtained by fitting the various observational temperature series to a linear combination of El Nino, volcano, and solar cycle variations (using sun spots as a proxy for the latter), plus an underlying trend, allowing for some offsets in time between the causative series and the temperature. Year to year global average temperatures fluctuate significantly, by several tenths of a degree. Taking into account these "exogenous" factors, however, greatly reduced the level of variation. Not only does this more clearly show the underlying trend, once the "exogenous" components are removed, but it occurred to me this also allows prediction of future temperatures with considerably more confidence than the usual guessing (though I've done well with that in the past), at least for a short period into the future.
See below for a detailed discussion of what I've done with Tamino's model, for the GISS global surface temperature series. In brief, however, I present the results of two slightly different models of the future, first with no El Nino contribution beyond mid-2011, and second with a pure 5-year-cycle El Nino (starting from zero in positive phase) from mid-2011 on.
|Year||Model 1 prediction for GISS Jan-Dec
global average temperature anomaly
|Model 2 prediction|
While there's some variation in future years, the final average temperature for 2011 should be close to 0.58 (similar to the temperatures in 2009). Temperatures in 2012 are likely to be much warmer - at least breaking the record of 0.63 set in 2005 and 2010, possibly (model 2) by as much as 0.15 degrees. With the continued waxing of the solar cycle and continued increases from CO2 effects, however warm 2012 is, 2013 should be even warmer (unless we get a big volcano or another strong La Nina then).
The final 2010 Goddard Institute for Space Studies (GISS) global land+ocean temperature numbers are out and just as I predicted, this year was the hottest in their record. Once again my prediction (really mostly a guess) was within just a few hundredths of a degree of the final number for the year:
|Year||Arthur's Feb 2008 prediction||GISS - January 2011||Difference|
As I noted back in December last year, way back in February 2008 when the whole world (at least of climate "skeptics") seemed to be touting a new global cooling trend, I had made some slightly educated guesses about the global average temperature through the end of that year, and for good measure for 2009, 2010, 2011 and 2012 too. My numbers were calibrated to the Goddard Institute global land and ocean temperature index as were the others on the thread - here are mine:
Ok, this time I'm going to start with the graph, and explain what's going on after. Seems to work for other folks... :