McIntyre and NASA data

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.

Author: Milan

In the spring of 2005, I graduated from the University of British Columbia with a degree in International Relations and a general focus in the area of environmental politics. In the fall of 2005, I began reading for an M.Phil in IR at Wadham College, Oxford. Outside school, I am very interested in photography, writing, and the outdoors. I am writing this blog to keep in touch with friends and family around the world, provide a more personal view of graduate student life in Oxford, and pass on some lessons I've learned here. View all posts by Milan