Greenhouse Gas Emissions (Aircraft) - 7th January 2010

Mr. Graham Allen (Nottingham, North) (Lab)

1. Whether his Department has made an assessment of the effects on greenhouse gas emissions of the temporary grounding of aircraft following the terrorist attacks in New York and Washington DC on 11 September 2001.

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The Minister of State, Department of Energy and Climate Change (Joan Ruddock)

The Department has not made an assessment of the effects on greenhouse gas emissions of the temporary grounding of aircraft following the terrorist attacks in New York and Washington DC on 11 September 2001.

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Joan Ruddock

I am grateful to my hon. Friend—and it has not taken me five years to dream up an answer. First, this is not a question of greenhouse gases. The scientific interest that followed the grounding of the aircraft was do with the issue of contrails, which are the evaporation and condensation trails emitted by aircraft. We do not know the science of contrails very clearly, but there are two possible effects: first, that they reflect radiation back beyond the earth, and therefore have a cooling effect—or, secondly, that they become cirrus clouds and trap radiation, and therefore have a warming effect. The phenomenon that was observed was thought possibly to be due to the absence of contrails leading to a heating effect. However, the Department has followed subsequent studies, and we now believe that there is no evidence that contrails, or the lack of them, were responsible for the temperature rise observed at the time, and that it was a natural fluctuation.

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