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Tuesday, August 31, 2010
Has 2009-2010 been the warmest period ever?

Posted by Kooten

Recently, Canada’s Global National News (Friday, July 16, 2010) carried a story indicating that 2010 was the hottest year on record. A follow-up article in Victoria’s Times-Colonist newspaper (July 18, 2010, p.A12) made a similar claim. The claims remind me of the children’s story “The Emperor has no Clothes,” about a tailor who managed to convince the emperor and his entourage that they were incapable of seeing the wonderful tunic he was sewing. When the emperor paraded in his new suit, a child exposed the scam by asking why the emperor had no clothes on.

Thus it is with climate. Although Victorians experienced a mild winter and spring, the last few months have been colder than usual. The Canadian prairies experienced a miserable winter and things were not much better elsewhere in North America and Europe. However, a few weeks of warm weather in Europe and eastern Canada, and it becomes easy to sell the idea that temperatures are the highest they have ever been and that 2010 is on course for become the warmest year ever! Is this so?

NASA temperature data underlie these stories. Consider the ten warmest years as reported in Table 1. The data in the table are here , but viewed on three different dates as indicated. Since data collected in August 2007 are available only through 2006, 2007 is not included in the earliest ranking given in Table 1.

Table 1: Ten Warmest Years based on Average Contiguous 48 U.S. Surface Air Temperature Anomalies, 1880 through 2006

Date when data was retrieved from NASA website
8/20/2007 5/27/2009 4/26/2010
1934 1934 1998
1998 1998 2006
1921 1921 1934
2006 2006 1921
1931 1931 1999
1999 1999 1931
1953 1953 1990
1990 1990 2001
1938 1938 2005
1939 1954 2007

NASA scientists have adjusted the data in ways that make more recent years appear warmer - scientists have dropped weather stations and/or used a different method for ‘adjusting’ the data. Thus, the number of years from the past two decades that appear in the top twenty warm years (only the top ten are shown in Table 1) has increased from 7 to 8 and finally to 11. In the May 2009 listing, 2007 is the 14th warmest year in the historical record, but it has moved up to tenth by the April 2010 listing. While it may be true that the latest adjustments are scientifically better than earlier adjustments, it seems odd that the most recent years now show up as among the warmest in the temperature record, contrary to evidence from satellite data and reconstructions by the Climate Research Unit at East Anglia University in the UK - reconstructions that use the same underlying data as NASA.

Other evidence fails to support the NASA story. Using the unadjusted U.S. weather station data, 22 out of 50 states recorded their highest temperature during the 1930s. Likewise, a 2006 study in the Journal of Geophysical Research found that 1941 was the warmest year experienced in Greenland between 1784 and 2005, while the 1930s and 1940s were the warmest decades; 1863 was the coldest year while the coldest decade was the 1810s (although it corresponded to two volcanic eruptions in 1809 and 1815). A 2010 study in Climatic Change reconstructs winter and spring temperatures for Stockholm going back 500 years. The warmest and coldest years are reported in Table 2. Notice that 1863 was the warmest winter/spring, while 1569 was the coldest.

Table 2: Ten coldest/warmest January-April Seasons in the Past 500 Years, Stockholm, Sweden, Temperature Anomalies in oC from 1961-90 Average

Rank Year Rank Year
Ten coldest Ten warmest
1 1569 1 1863
2 1573 2 1990
3 1557 3 1743
4 1595 4 1525
5 1572 5 1989
6 1942 6 1605
7 1614 7 1822
8 1600 8 1790
9 1574 9 1762
10 1940 10 2008

ICECAP NOTE: See (below, enlarged here) how NASA temperatures have been significantly manipulated since 1980. The changes produced a cooling of the warm blip in the 1930s and 1940s and a warming post 1980 for numerous reasons.


Posted on 08/31 at 05:00 PM
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