On February 8, 2007, climatologists at the NASA Goddard Institute for Space Studies (GISS) announced that 2006 was the fifth-warmest year in the past century. GISS scientists estimated that the five warmest years on record were, in descending order, 2005, 1998, 2002, 2003, and 2006. Other climatology groups ordered the years somewhat differently due to different measuring techniques, especially in areas with sparse measurements, but they also considered these years to be the warmest. According to NASA GISS director James Hansen, 2007 is likely to see warmer temperatures than 2006 and could prove to be the warmest on record, thanks to an El Niño and continued emissions of greenhouse gases.
The top image is a global map showing temperature anomalies during 2006, blue being the coolest and red being the warmest. Areas with cooler-than-average temperatures appear primarily in the northern Pacific Ocean and Southern Ocean, as well as the interior of Antarctica. The very warmest regions appear in the Arctic and the Antarctic Peninsula, which is consistent with climate predictions that global warming will occur more quickly and dramatically in high latitudes. The red colors that dominate the image reveal the overall warmth of 2006 compared to the long-term average.
The graph below the image tracks mean global temperatures compared to the 1951 to 1980 mean. This graph shows two lines, the 5-year mean, indicated in red, and the annual mean, indicated in pink. Temperatures peaked around 1940 then fell in the 1950s. By the early 1980s, temperatures surpassed those of the 1940s and, despite ups and downs from year to year, they continued rising beyond the year 2000.
Days before NASA GISS announced 2006’s warm temperatures, the Intergovernmental Panel on Climate Change (IPCC) released a new assessment of climate change. A consensus document complied by more than 1,200 authors and reviewers representing 113 nations, predicts continued warming of 0.2 degrees Celsius per decade for the next few decades. Like the previous report, published in 2001, this assessment estimated how likely it was that “most of the warming” that occurred in the latter half of the 20th century resulted from increases in greenhouse gases from human activities. The 2001 report gave a probability of greater than 66 percent. The 2006 report gave a probability of greater than 90 percent. A special report in Nature described the current report as a turning point “not because of the figures themselves, which are largely in line with previous IPCC forecasts, but because the science behind them is now certain enough to make a serious response from policymakers almost inevitable.”
NASA graph adapted from the Goddard Institute for Space Studies Surface Temperature Analysis by Robert Simmon.