杏吧原创

A group of scientists known for their scepticism about climate change has reanalysed two centuries鈥� worth of global temperature records. Their study largely confirms previous ones: it finds strong evidence that Earth is getting hotter.

鈥淭he valid issues raised by [climate] sceptics, when addressed fully and in detail, do not significantly change the answer,鈥� says lead author of the University of California, Berkeley. In , Muller questioned whether global temperature records showed a significant warming during the 20th century.

His project, the (BEST), has now pulled together global temperature data going back to 1800 from 15 sources, including datasets held by the World Meteorological Organization and US and UK government agencies.

BEST concludes that land temperatures have risen by 1聽掳C since the 1950s. This is largely in line with the three existing global temperature records: , maintained by NASA, the US National Oceanic and Atmospheric Administration鈥檚 and , kept by the UK Met Office. The 1聽掳C of warming reflects warming above land masses only, so is not yet a truly global estimate.

In a series of papers that have not yet been peer-reviewed but are available on the BEST website, the researchers examine how reliable the temperature data is.

Contrary to , the BEST researchers find that including data from weather stations in cities 鈥� which are warmer than rural areas 鈥� makes little difference to the overall trend. 鈥淯rban warming does not unduly bias estimates of recent global temperature change,鈥� they say.

Blogger Anthony Watts of has repeatedly claimed that because weather stations are poorly placed 鈥� for instance, or other heat sources. However, BEST found no statistically significant difference in the trends seen at well-placed and poorly placed stations.

No surprise

鈥淭hese initial findings are very encouraging and echo our own results, and our conclusion that the impact of urban heat islands on the overall global temperature is minimal,鈥� says of the University of East Anglia in Norwich, UK, the climatologist at the heart of the 鈥渃limategate鈥� scandal. Jones helped to compile the HadCRU dataset.

鈥淭hey get the same result that everyone else has gotten,鈥� says of Penn State University in University Park. 鈥淭hat said, I think it鈥檚 at least useful to see that even a critic like Muller, when he takes an honest look, finds that climate science is robust.鈥�

The refused to comment on the studies because they have not been through peer review. Other climate scientists expressed similar reservations.

Muller defended the decision to circulate the results before publication, saying he was going through peer review 鈥渋n the traditional way: by circulating preprints and giving seminars and talks鈥�.

The blogosphere responds

Prominent critics of climate science contacted by New 杏吧原创 say the temperature record is not at issue.

鈥淚 haven鈥檛 ever suggested that temperatures haven鈥檛 risen since the 19th century. Quite the contrary,鈥� says blogger and mathematician Steve McIntyre of . Nevertheless, McIntyre questions BEST鈥檚 analyses of urban heating and weather station quality.

鈥淭hey鈥檙e concentrating on the wrong question,鈥� says , science adviser to , a London-based think tank that has former British finance minister Nigel Lawson for chairman. 鈥淓verybody agrees that the temperature has warmed. The people who disagree about temperatures are the barking mad end of the spectrum.鈥�

He claims the uncertainty lies in the size of the human effect on the climate, as compared to natural effects (see 鈥�Climate myths: Human CO₂ emissions are too tiny to matter鈥�).

Science writer , who was editor of New 杏吧原创 from 1962 to 1966, says: 鈥淭he graph of global land temperature changes associated with BEST鈥檚 announcement neatly confirms that the warming stopped about 15 years ago. The sun鈥檚 recent laziness has apparently cancelled any effect of ever-increasing manmade greenhouse gases.鈥�

In contrast, an analysis published this summer found a significant warming trend between 1995 and 2010. Studies of solar activity have found no correlation with global temperature trends.