Hottest Year in U.S. of the Past 34 Years; Ninth Hottest Globally

Every month University of Alabama in Huntsville climatologists John Christy and Roy Spencer report the latest global temperature trends from satellite data. In their year-end roundup, Christy notes that 2012…

…was the warmest year on record for both the contiguous 48 U.S. states and for the continental U.S., including Alaska. For the U.S., 2012 started with one of the three warmest Januaries in the 34-year record, saw a record-setting March heat wave, and stayed warm enough for the rest of the year to set a record.

Compared to seasonal norms, March 2012 was the warmest month on record in the 48 contiguous U.S. states. Temperatures over the U.S. averaged 2.82 C (almost 5.1° Fahrenheit) warmer than normal in March; the warmest spot on the globe that month was in northern Iowa. The annual average temperature over the conterminous 48 states in 2012 was 0.555 C (about 0.99 degrees F) warmer than seasonal norms.

With regard to global average temperatures, 2012 was only the ninth warmest year amongst the last 34 years….

…with an annual global average temperature that was 0.161 C (about 0.29 degrees Fahrenheit) warmer than the 30-year baseline average, according to Dr. John Christy, a professor of atmospheric science and director of the Earth System Science Center at The University of Alabama in Huntsville. 2012 was about three one-hundredths of a degree C warmer than 2011, but was 0.23 C cooler than 2010.

Eleven of the 12 warmest years in the satellite temperature record have been been since 2001. From 2001 to the present only 2008 was cooler than the long-term norm for the globe. Despite that string of warmer-than-normal years, there has been no measurable warming trend since about 1998. The long-term warming trend reported in the satellite data is calculated using data beginning on Nov. 16, 1978.

Although the warmest years have occurred in recent years, Christy pointed out last month that global average temperatures have been essentially flat since 1998: 

Since 2002, there has been a plateau of relatively warmer temperatures with only 12 months when the global average temperature was cooler than the long-term seasonal norm. In fact, compared to the 30-year temperature baseline, the most recent five years (12/07-11/12) averaged only 0.003 C (0.173 to 0.176 above seasonal norms) warmer than the preceding five years (12/02-11/07). …

The long term 0.14 C per decade warming trend measured by microwave sounding units on a series of satellites is consistent with the low-end of global climate change predictions made by some climate models; it is also within the potential range of natural climate variability, especially since most of the warming happened over such a short period of time.

Below are the newest data updated through December, 2012:

Go here to see the monthly satellite data.