Global Temperature in 2015

by James Hansen[a], Makiko Sato^a, Reto Ruedy[b],[c] Gavin A. Schmidt^c, Ken Lo^b,c

Source: Earth Sciences Institute, Columbia University

Abstract. Global surface temperature in 2015 was +0.87°C (~1.6°F) warmer than the 1951-1980 base period in the GISTEMP analysis, making 2015 the warmest year in the period of instrumental data. The 2015 temperature was boosted by a strong El Niño, nearly of the same strength as the 1998 “El Niño of the century”. The updated global temperature record makes it clear that there was no global warming “hiatus”. Global temperature in 2015 was +1.13 (~2.03°F) relative to the 1880-1920 mean. Accounting for interannual variability, it is fair to say that global warming has now reached ~1°C, almost ~2°F.

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How Warm Was This Summer?

Dr. James Hansen

Let's look at the surface temperatures in the summer of 2010, which justifiably received a lot of attention. Figure 1 shows maps of the June-July-August temperature anomaly (relative to 1951-1980) in the GISS temperature analysis (described in paper in press at Rev. Geophys., available at this link) for 2009 and 2010, as well as maps for December-January-February (Northern Hemisphere winter, Southern Hemisphere summer) for the past two years.

June-July-August 2010 was the 4th warmest in the 131 year GISS analysis, while 2009 was the 2nd warmest¹.  2010 was a bit cooler than 2009 mainly because a moderate El Nino in the equatorial Pacific Ocean during late 2009 and early 2010 has been replaced by a moderate La Nina. Also most of Antarctica was cool in winter 2010, while it was warm in 2009. Antarctic winter temperature anomalies are very noisy, fluctuating chaotically from year to year.

The maps make clear that perceptions of how hot it was depend on where you live. The two warmest anomalies on the planet this past summer were Eastern Europe and the Antarctic Peninsula. Not many people live on the Antarctic Peninsula and an anomaly of even several degrees in winter there is not a big deal. But the warm anomaly centered in Eastern Europe, which covered most of Europe and the Middle East, was noticed, to say the least. It was also quite warm in Japan, where the prior summer had been cooler than the 1951-1980 mean. The United States, which had been unusually cool in the summer of 2009, was warm this past summer, except the Pacific Northwest, which was cooler than the 1951-1980 climatology. Continued...

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Global Temperature Trends: 2008 Annual Summation

by James Hansen, Makiko Sato, Reto Ruedy, Ken Lo

The Goddard Institute for Space Studies has analyzed the global temperature trends based on 2008 surface air temperature leading to the conclusion that, despite the cold brought on by the strong La Nina event last year, 2008 was the ninth warmest year since measurements began in 1880.

Calendar year 2008 was the coolest year since 2000, according to the Goddard Institute for Space Studies analysis [Reference 1] of surface air temperature measurements (Figure 1, below). In our analysis 2008 is the ninth warmest year in the period of instrumental measurements, which extends back to 1880. The ten warmest years all occur within the 12-year period 1997-2008. The two standard deviation (95 percent confidence) uncertainty in comparing recent years is estimated as 0.05°C [Reference 2], so we can only conclude with confidence that 2008 was somewhere within the range from 7th to 10th warmest year in the record.

The map of global temperature anomalies in 2008, Figure 1 (right), shows that most of the world was either near normal or warmer than in the base period (1951-1980). Eurasia, the Arctic and the Antarctic Peninsula were exceptionally warm, while much of the Pacific Ocean was cooler than the long-term average. The relatively low temperature in the tropical Pacific was due to a strong La Nina that existed in the first half of the year. La Nina and El Nino are opposite phases of a natural oscillation of tropical temperatures, La Nina being the cool phase

Continued...

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