Climate scepticism

The BBC has put together a couple of interesting points and counterpoints regarding global warming. Ever in a conversation with a sceptic and at a lack of argument? Read on my dear!

What are some of the reasons why “climate sceptics” dispute the evidence that human activities such as industrial emissions of greenhouse gases and deforestation are bringing potentially dangerous changes to the Earth’s climate?

1. EVIDENCE THAT THE EARTH’S TEMPERATURE IS GETTING WARMER IS UNCLEAR

Sceptic:

Instruments show there has been some warming of the Earth’s surface since 1979, but the actual value is subject to large errors. Most long-term data comes from surface weather stations. Many of these are in urban centres which have expanded in both size and energy use. When these stations observe a temperature rise, they are simply measuring the “urban heat island effect”. In addition, coverage is patchy, with some regions of the world almost devoid of instruments. Data going back further than a century or two is derived from “proxy” indicators such as tree-rings and stalactites which, again, are subject to large errors.

Counter:

Warming is unequivocal. Weather stations, ocean measurements, decreases in snow cover, reductions in Arctic sea ice, longer growing seasons, balloon measurements, boreholes and satellites all show results consistent with the surface record of warming. The urban heat island effect is real but small; and it has been studied and corrected for. Analyses by Nasa for example use only rural stations to calculate trends. Recently, work has shown that if you analyse long-term global temperature rise for windy days and calm days separately, there is no difference. If the urban heat island effect were large, you would expect to see a bigger trend for calm days when more of the heat stays in the city. Furthermore, the pattern of warming globally doesn’t resemble the pattern of urbanisation, with the greatest warming seen in the Arctic and northern high latitudes. Globally, there is a warming trend of about 0.8C since 1900, more than half of which has occurred since 1979.

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