Every month University of Alabama in Huntsville climatologists John Christy and Roy Spencer publish the latest global temperature trend data obtained from NOAA satellites. This month Christy reports that the 2014 was third warmest year in the satellite record. However, the folks who run the surface thermometer networks claim that 2014 is the warmest year on record (see below).
First, from Christy: 2014 was third warmest, but barely
2014 was the third warmest year in the 36-year global satellite temperature record, but by such a small margin (0.01 C) as to be statistically similar to other recent years, 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. "2014 was warm, but not special. The 0.01 C difference between 2014 and 2005, or the 0.02 difference with 2013 are not statistically different from zero. That might not be a very satisfying conclusion, but it is at least accurate."
The 2014 average temperature anomaly also is in keeping with temperatures since late 2001, when the global average temperature rose to a level that is generally warmer than the 30-year baseline average. The most recent 13 complete calendar years, from 2002 through 2014, have averaged 0.18 C (about 0.33 degrees Fahrenheit) warmer than the 30-year baseline average, while the global temperature trend during that span was a warming trend at the rate of +0.05 C per decade — which is also statistically insignificant.
Global Temperature Trend Update: December, 2014
December temperatures (preliminary)
Global composite temp.: +0.32 C (about 0.58 degrees Fahrenheit) above 30-year average for December.
Northern Hemisphere: +0.46 C (about 0.83 degrees Fahrenheit) above 30-year average for December.
Southern Hemisphere: +0.18 C (about 0.32 degrees Fahrenheit) above 30-year average for December.
Tropics: +0.30 C (about 0.54 degrees Fahrenheit) above 30-year average for December.
With a global average temperature that was 0.32 C (about 0.58 degrees Fahrenheit) warmer than seasonal norms, December 2014 trailed only December 2003, which averaged 0.37 C (about 0.67 degrees Fahrenheit) warmer than seasonal norms, among the warmest Decembers in the satellite temperature record. While December 2014 ranked second warmest for both the globe and the Northern Hemisphere, it was only the sixth warmest December in the tropics despite an El Niño Pacific Ocean warming event that seems to be forming there.
On the other hand, Scientific American is reporting that according to the temperature data compiled by the researchers at the Japan Meteorological Agency 2014 is the warmest year since 1891. From SciAm:
The upward march of the world's average temperature since 1891 is a trademark of human-influenced global warming with 2014 being the latest stop on the climb. All 10 of the hottest years have come since 1998.
The average temperature was 1.1°F above the 20th century average according to JMA's data. That edges 1998, the previous warmest year, by about 0.1°F.
One big difference between 2014 and 1998 is that the latter was on the tail end of a super El Niño, which has the tendency to spike temperatures. In comparison, 2014 was the year of the almost El Niño.
Instead, record warmth in other parts of the Pacific as well as the hottest year on record in Europe were some of the main drivers in fueling the heat.
Climatologists basically agree that last few years have been warmer than the 20th century average, but the temperature trend since 1998 has been essentially flat.