Forecasts for the 2009 hurricane season were wide ranging earlier this year, from an active season to a near-normal or below average one. In reality, 2009 remained much quieter than in a number of recent years, getting off to the slowest start for 17 . This has been down to a number of factors, but is most likely due to El Niño, which warms surface waters and slows the wind shear required to generate tropical storms.
This quiet season has caused many people to question the link between hurricane intensity and climate change. However, events of one particular year, or even a number of years, may not be representative of a more long term trend and therefore cannot be used as evidence for global warming or cooling.
Marshall Shepherd and Thomas Knutson discuss the debate on the linkage between global warming and hurricane activity in an article in Geography Compass. Research has focussed on the roles of anthropogenic forcing and natural variability in the recent increasing trend in hurricane intensity. The article highlights the need for significantly more observations, such as sea surface temperatures and vertical wind shear, alongside more modelling of the role of these factors, before the links between global warming and hurricanes can be fully understood.