McIntyre and NASA data

2007-08-16

in Daily updates, Politics, Science, The environment

SAW Gallery, Ottawa

There is a lot of talk in the media about how Steve McIntyre – an amateur scrutineer of climate statistics – found an error in data released by NASA. Specificically, it was mistankingly believed that data that had not been corrected for urban heat effects had been. This data pertains only to the United States and the correction implies that about 0.15 ºC of the observed warming there was just a statistical error. In itself, this would not get much attention. What does get attention is that this changes the rankings of the hottest recorded years in the United States. Rather than 1998 being the hottest recorded year in the United States, 1934 now wins. Many news sources are treating this data revision as though it demonstates a serious flaw in the overall quality of our climate understanding.

The Fourth Assessment Report of the Intergovernmenal Panel on climate change is based on a far broader collection of data than just NASA data pertaining to just the United States. As such, their overall conclusion that is barely affected by this change. Likewise, the worldwide figures for hottest years still cluster in the last decade. The report’s Summary for Policy Makers explains:

Eleven of the last twelve years (1995–2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850). The updated 100-year linear trend (1906 to 2005) of 0.74°C [0.56°C to 0.92°C] is therefore larger than the corresponding trend for 1901 to 2000 given in the TAR of 0.6°C [0.4°C to 0.8°C]. The linear warming trend over the last 50 years (0.13°C [0.10°C to 0.16°C] per decade) is nearly twice that for the last 100 years. The total temperature increase from 1850–1899 to 2001–2005 is 0.76°C [0.57°C to 0.95°C]. Urban heat island effects are real but local, and have a negligible influence (less than 0.006°C per decade over land and zero over the oceans) on these values.

This information is based on a broad collection of sources including satellites and ground stations around the world. It also incorporates evidence from ice cores and other historical indicators of temperature and greenhouse gas concentrations. What the McIntyre situation demonstrates is the degree to which perceived anomalies are seized on by people with pre-determined agendas to either support or refute the overall climate change consensus. While the data is not a statistical threat to that consensus, it does have the ability to foster doubt in the general public and among policy-makers, especially when presented out of context.

Having people out there scrutinizing the data is excellent, and a good check against the proliferation of misleading information. At the same time, it is necessary to be rigorous in our thinking about how one new piece of information affects the overall picture. Likewise, it is important to remain aware of the degree to which individual agendas influence how information is processed, and what responses it evokes.

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{ 6 comments… read them below or add one }

. August 17, 2007 at 9:18 am

Yesterday, Google News had 22 stories on this. Now, there are forty.

. August 17, 2007 at 10:07 am

“In response to earlier reports, Dr. James Hansen, top climate scientist with NASA, has issued a statement on the recent global warming data correction. He points out ‘the effect on global temperature was of order one-thousandth of a degree, so the corrected and uncorrected curves are indistinguishable.’ In a second email he shows maps of U.S. temperatures relative to the world in 1934 and 1998, explains why the error occurred (it was not, as reported, a ‘Y2K bug’) and, in response to errors by ‘Fox, Washington Times, and their like,’ attacks the ‘deceit’ of those who ‘are not stupid [but] seek to create a brouhaha and muddy the waters in the climate change story.'”

Via Slashdot

B August 18, 2007 at 1:16 am

It is 61 Google News stories now.

Anon August 27, 2007 at 9:35 am

Looking over our shoulder
Thoughts on the GISS temperature adjustment
Posted by Andrew Dessler at 2:01 PM on 26 Aug 2007

. August 27, 2007 at 4:25 pm

What is often overlooked is the temperature adjustments only applied to temperatures in 48 U.S. states. As the USA comprises only 2% of the globe, 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.

Source

. August 31, 2007 at 11:21 am

Global Warming Debate Overheats With Bad Numbers
(The following is a guest post by The Wall Street Journal’s Keith Winstein. Carl Bialik will be back tomorrow.)

Did a blogger fix a calculation error in NASA’s global-warming records, making 1934, and not 1998, the hottest year on record?

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