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Saturday, January 16, 2010

James Hansen, Reto Ruedy, Makiko Sato, Ken Lo: If It’s That Warm, How Come It’s So Damned Cold?

If it’s that warm, how come it’s so damned cold?

James Hansen, Reto Ruedy, Makiko Sato, Ken Lo

The past year, 2009, tied as the second warmest year in the 130 years of global instrumental temperature records, in the surface temperature analysis of the NASA Goddard Institute for Space Studies (GISS). The Southern Hemisphere set a record as the warmest year for that half of the world.

Global mean temperature, as shown in Figure 1a, was 0.57 °C (1.0 °F) warmer than climatology (the 1951‐1980 base period). Southern Hemisphere mean temperature, as shown in Figure 1b, was 0.49 °C (0.88 °F) warmer than in the period of climatology.

See link for figures -- sorry I cannot copy them from the pdf file -- drat!!!
Figure 1. (a) GISS analysis of global surface temperature change. Green vertical bar is estimated 95% confidence range (two standard deviations) for annual temperature change. (b) Hemispheric
temperature change in GISS analysis. (Base period is 1951–1980. This base period is fixed consistently
in GISS temperature analysis papers – see References. Base period 1961–1990 is used for comparison
with published HadCRUT analyses in Figures 3 and 4.)

The global record warm year, in the period of near‐global instrumental measurements (since the late 1800s), was 2005. Sometimes it is asserted that 1998 was the warmest year.

The origin of this confusion is discussed below.

There is a high degree of interannual (year‐to‐year) and decadal variability in both global and hemispheric temperatures. Underlying this variability, however, is a long‐term warming trend that has become strong and persistent over the past three decades.

The long‐term trends are more apparent when temperature is averaged over several years. The 60‐month (5‐year) and 132 month (11‐year) running mean temperatures are shown in Figure 2 for the globe and the hemispheres. The 5‐year mean is sufficient to reduce the effect of the El Nino–La Nina cycles of tropical climate. The 11‐year mean minimizes the effect of solar variability – the brightness of the sun varies by a measurable amount over the sunspot cycle, which is typically of 10–12 years' duration.

Complete paper at this link:

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