New study shoots down another climate denier myth

This article was written by my colleague and top science writer, Mitchell Anderson, who gave me permission to reprint it here.

Another climate change denier myth - this one a favorite of Anthony Watts and his "Watts Up With That" blog - has just bit the dust.

Many skeptics for years have sought to explain away decades of climate research by showing slides of weather station thermometers sited next to heating vents or surrounded by asphalt.

This much-touted "urban heat island effect" was supposed to trump all those fancy graphs and equations that egghead scientists were fixated on. Except it's not true.

A recent peer-reviewed paper [pdf] in the Journal of Geophysical Research looked at data from 114 weather stations from across the US over the last twenty years and compared measurements from locations that were well sited and those that weren't.

They did find an overall bias, but it was towards cooling rather warming.

According to the authors,

"the bias is counter intuitive to photographic documentation of poor exposure because associated instrument changes have led to an artificial negative ("cool") bias in maximum temperatures and only a slight positive ("warm") bias in minimum temperatures."

Oops.

This is latest in an expanding body of science that has looked at the urban heat island effect in excruciating detail and found nothing to undermine the observed and disturbing warming in the US over the last several decades.

The IPCC found that:

Over the Northern Hemisphere land areas where urban heat islands are most apparent, both the trends of lower-tropospheric temperature and surface air temperature show no significant differences. In fact, the lower-tropospheric temperatures warm at a slightly greater rate over North America (about 0.28°C/decade using satellite data) than do the surface temperatures (0.27°C/decade), although again the difference is not statistically significant.

Another paper in Climate Change in 2007 stated:

Studies that have looked at hemispheric and global scales conclude that any urban-related trend is an order of magnitude smaller than decadal and longer time-scale trends evident in the series (e.g., Jones et al., 1990; Peterson et al., 1999)...Thus, the global land warming trend discussed is very unlikely to be influenced significantly by increasing urbanization (Parker, 2006).

While such dense scientific prose is not as photogenic as a picture of a weather station in a parking lot, the fact is that science has thoroughly picked over this red herring.

This myth is now officially busted.

 

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Comments

[jsgaetano]

03:12 AM on 01/22/2010

Another hilarious denier myth is the "sun is warmer" myth. Pretty interesting how they make sure not to talk to researchers who study the sun, in the same way they avoid researchers who study the climate.

[realpolitic]

03:33 PM on 01/22/2010

The funniest myth must be that the climate has always been changing, as if climate scientists were clueless to that fact.

[realpolitic]

01:00 AM on 01/22/2010

I like the "myth officially busted" language from "Mythbusters" on television. The myth of the heat island effect always rested on a shaky argument. First of all, North American temperatures have risen more at night than have daytime temperatures. So nights have gotten warmer moreso than have days, which does not coincide with some heat island effect. Secondly, most of the warming has taken place in polar regions where presumably there is no heat island effect. Thirdly, it is not so much the temperatures at any one time, but the temperatures over time there are important. So the argument would have to be the heat island effect is increasing over time. Finally, NASA has always controlled for this effect by comparing urban temperatures reading sites with rural and adjusting the long-term trend of urban stations to be consistent with the nearest rural stations. However, really we can knock down all the denier myths we please and it will not change their position an iota because the denier position is not based on reason, but ideology.

http://www.giss.nasa.gov/research/news/20011105/

http://www.skepticalscience.com/urban-heat-island-effect.htm