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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Archived Rebuttal

This is the archived Intermediate rebuttal to the climate myth "1934 - hottest year on record". Click here to view the latest rebuttal.

What the science says...

1934 is the hottest year on record in the USA which only comprises 2% of the globe. According to NASA temperature records, the hottest year on record globally is 2005.

Steve McIntyre's discovery of a glitch in the GISS temperature data is an impressive achievement. Make no mistake, it's an embarrassing error on the part of NASA. But what is the significance?

NASA's "Y2K" glitch

Contrary to many reports, the error wasn't a Y2K bug but a mixup over data corrections with the NOAA. NASA GISS obtain much of their temperature data from the NOAA who adjust the data to filter out primarily time-of-observation bias (although their corrections also include inhomogeneities and urban warming - more on NOAA adjustments). From January 2000, NASA were mistakenly using unadjusted data.

USA temperature versus global temperature trends

What is often overlooked is the temperature adjustments only applied to temperatures in 48 U.S. states. The U.S.'s land area accounts for only 2% of the earth's total surface area. Thus this has had infinitesimal effect on global trends.

The graph below (courtesy of Open Mind) compares the global temperature trend from before and after adjustments. Before the error was discovered, the trend was 0.185°C/decade. After corrections were made, the trend was still 0.185°C/decade. The change to the global mean was less than one thousandth of a degree.

GISS temperature before and after Y2K adjustment
Figure 1: Global temperature anomaly before (red squares) and after (black diamonds) NASA's "Y2K" corrections (Open Mind).

Updated on 2010-06-26 by John Cook.



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