On the Capital Weather Gang blog, Andy Freedman says NASA’s declaration that 2010 has been the hottest year on record isn’t the definitive last word:
The two other groups that maintain official global surface temperature data – the U.S. National Oceanic and Atmospheric Administration (NOAA) and the UK Met Office Hadley Centre, which works in conjunction with the University of East Anglia Climatic Research Unit – will soon release data that may conflict with NASA somewhat, by ranking 2010 differently. NOAA, for example, currently ranks 1998 as the warmest year on record, rather than 2005, which is in NASA’s top spot.
The discrepancies, as Freedman explains, are due to differences in the methods each group of researchers use to gather and analyze temperature data. But Freedman says whether 2010 officially tops the charts is beside the point. What matters – and what NASA, NOAA, and the UK’s Met Office all agree on – is the trend (my emphasis):
NASA, NOAA, and the UK’s records are all consistent in showing a sharp uptick in global temperatures beginning during the latter half of the 20th century, and continuing on through the present day. Furthermore, NASA, NOAA, and the UK data all show the 2000s were the warmest decade since instrumental records began.
In fact, the NASA analysis released last week rebuts the argument that warming has slowed or ceased in the past decade. “Contrary to frequent assertions that global warming slowed in the past decade… global warming has proceeded in the current decade just as fast as in the prior two decades,” [NASA's James] Hansen and his colleagues wrote.
It’s that long-term trend that is most important, given the numerous factors that can influence year-to-year weather and climate. So when you hear conflicting stories about whether this year was really the warmest, remember the overall context in which this first, second, or perhaps third-ranking warmth is occurring.