Sweltering summers will become the norm, according to Walker Institute scientists
Release Date 17 January 2007
Scientists from the Walker Institute at the University of Reading have shown how the temperature of continents could increase up to 80 per cent faster than oceans as greenhouse gases increase – meaning extreme temperatures will be more likely in the future.
London summer temperatures could reach the 40s by 2050 according to climate models, meaning possible heat exhaustion for those struggling to work and serious health risks for the very young and the very old – could this mean a mass exodus from the capital during the summer months?
Scientists already know greenhouse gases are causing continents to warm up faster than oceans. For the first time, the Walker Institute study published this week, quantifies this effect and shows that 20 climate models all give similar results. The study predicts that future warming over land could be 40 to 80 per cent faster than over the oceans. The results show we can expect more extreme temperatures – such as the European heatwave of summer 2003, which caused 35,000 deaths
"The fact that warming over land is more rapid than over sea is clearly important for climate impacts, since people live on land. Excessively high temperatures can cause a range of problems such as disruptions to train services due to rails buckling in the heat. In very hot weather people's health can also suffer," said Dr Rowan Sutton, from the Walker Institute at the University of Reading and lead author of the study.
The Walker Institute study compares the different speed of warming over land and sea for 20 climate models used in the IPCC (Intergovernmental Panel on Climate Change) 4th Assessment Report, which is due out next month.
The fact that 20 models all show similar results increases confidence in the predictions. The model results are also similar to what has been observed over the last 50 years and this provides more evidence that global warming is already happening.
During the last 50 years, the continents have warmed twice as much as the oceans, so the study finds from observations. Warming has been greatest in winter over Europe, North America and Russia. In the tropics, the land and sea have warmed at a similar rate.
The faster warming over land is often assumed to be a simple consequence of the different capacity to take up heat between the ocean and the land, but this explanation is incomplete. The Walker Institute study explains that it is because the oceans are wet and the land is much drier.
Dr Sutton added: "Over the sea, a warming increases the amount of evaporation and this removes heat from the surface. Hence, for a given average warming, the temperature will be lower than over land where there is much less water available for evaporation."
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