The planet’s average temperature rose by a degree, compared to the mid-20th century baseline, to 58.3 degrees Fahrenheit. Although weather patterns cause yearly fluctuations, the trend is markedly toward rising temperatures, with each decade warmer, on average, than the one preceding it. The temperature increase parallels the increase in concentrations of atmospheric greenhouse gases.
The analysis of the year’s global temperature records was released by NASA’s Goddard Institute for Space Studies (GISS). Focusing on U.S. records, NOAA announced that 2012 was the warmest year documented in the continental U.S., a full degree Fahrenheit warmer than the previous warmest year, in 1998, and 3.2 degrees Fahrenheit above the 20th century average. Widespread drought accompanied the heat, with overall precipitation 2.57 inches below the 20th century average, earning the year a ranking as the 15th driest on record.
As startling as comparing averages is, local weather on any given day is what we experience. Every state among the lower 48 had above-average annual temperatures in 2012; 19 states experienced record high temperatures, and in 47 out of the 48 states there was some place that was hotter than ever before. GISS director James E. Hansen observes that “…the frequency of unusually warm extremes is increasing. It is the extremes that have the most impact on people and other life on the planet.”