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Dr Chris Huntingford, Climate Modeller, Centre for Ecology and Hydrology, said:
“It has now been confirmed that the burning of fossil fuels has altered rainfall patterns at the global scale. Next we need to understand how these observed large-scale adjustments translate to local changes in extreme rainfall events. Following that, we must project in to the future to see how continued emissions of carbon dioxide may lead to further local rainfall changes. These highly regionalised estimates of rainfall will be essential in aiding governments to prepare for what might, in some circumstances, represent dangerous climate change.”
Dr Peter Stott, Climate Scientist, University Of Reading and co-author of the paper, said:
“The paper is saying there is a significant human influence on global rainfall patterns and this includes an increase of precipitation north of 50 degrees northern latitude, an area that includes the UK. We looked at annual rainfall trends rather than any particular season.
“In the UK wetter winters are expected which will lead to more extreme rainfall, whereas summers are expected to get drier. However, it is possible under climate change that there could be an increase of extreme rainfall even under general drying.
“Recent events are associated with unusual weather patterns that could be linked to the tropical oceans; such patterns have been seen before. The problem for the UK is that there is a lot of uncertainty about what will happen in future regarding extreme rainfall. We need more research to understand the links better between extreme weather events and climate change. As part of this we need to develop an “operational attribution capability” to determine to what extent recent the risk of weather events can be linked to climate change by working out whether the risk of such events has increased or not.”
Dr Myles Allen, Climate Dynamics Group/climateprediction.net, University of Oxford, said:
“This is a very important paper. We already knew that external drivers like volcanic eruptions affect large-scale precipitation, but for the first time this paper identifies the fingerprint of human influence. This means that the precipitation trends they identify may be harbingers of more to come.
“They are looking at trends in yearly-average precipitation, which doesn’t necessarily relate directly to trends in the risk of extreme precipitation events, such as those we are suffering from in Oxford. Different physical factors drive trends in annual mean precipitation to those which control the risk of precipitation extremes.”
Dr Nathan Gillett, Lecturer in Climate, Climatic Research Unit, School of Environmental Sciences, University of East Anglia, and co-author of the paper, said:
“This study shows that there has been a significant human effect on global rainfall patterns, with human influence causing a decrease in rainfall in some regions, and in increase in rainfall in others, such as the region north of 50N, which includes the UK. It concentrates on annual rainfall totals averaged over large regions.
“Climate models generally predict that the UK will become wetter in winter and drier in summer in response to human influence. However, climate models also predict increases in extreme rainfall in most regions of the globe, as a warmer atmosphere can hold more water. In the UK we have a seen a trend towards more extreme rainfall in the winter, but no clear trend in summer extreme rainfall.
“Therefore while our study shows a human influence on rainfall at the global scale, the role of human influence in the recent UK flooding remains uncertain. I’m involved in a study, based in Climatic Research Unit, which seeks to identify the role of human influence in UK extreme precipitation trends.”