Dec 7, 2012
Eastern US set for stormy ride
As hurricane Sandy recently demonstrated, big cities are not invincible when extreme weather arrives. In late October Sandy roared along the heavily populated eastern seaboard of the US, leaving millions of people without power for days, bringing transportation to a standstill and causing the New York Stock Exchange to close for the first time since 11 September 2001. The location of this storm and its timing – the start of the peak holiday-shopping season – made it an extremely costly storm, with damages estimated to be in the region of $50 bn – the second most expensive storm in the US, after hurricane Katrina in 2005.
Until recently, extreme weather has been infrequent in this part of the US, but a new study shows that residents might have to brace themselves for a wilder future, as climate change sets our weather onto a roller-coaster path.
Joshua Fu, from the University of Tennessee, US, and colleagues created a high-resolution climate model (4 km by 4 km grid squares) to simulate extreme weather patterns in the eastern US. Assuming we follow a fossil-fuel-intensive future, their findings indicate that both heatwaves and extreme precipitation are likely to become more frequent and severe for this region by the middle of the 21st century.
Most of our information about future climate comes from global climate models, which tend to have a resolution of hundreds of kilometres. In highly populated regions more local detail is essential in order to plan appropriately for the future. Fu and his colleagues used dynamical downscaling (using global climate-model output to provide the initial and boundary conditions) to model regional climate in the eastern US.
"This is a computationally demanding method, requiring more than six million CPU hours," Fu told environmentalresearchweb. "We cannot afford to do this for the entire US, but we modelled this area because there are very few extreme event studies and a large population."
Their findings suggest that heatwaves are likely to become over 10% more intense by 2057, with average temperatures increasing by around 3 °C and New York being one of the hardest-hit places. Meanwhile, deluges of rain are also going to be more intense and frequent, with annual extreme precipitation increasing by over 100 mm per year by 2057 – an increase of more than one third on current levels. The number of extreme precipitation days could double in some regions, with eastern coastal regions experiencing some of the greatest increases. Whether we will see more hurricanes like Sandy is not yet clear. "Our model predicts long-term climate trends, but does not yet predict short-term events, like hurricanes, well," said Fu. The study is published in Environmental Research Letters.
Global climate models have long predicted that climate change will bring more intense and frequent heatwaves and extreme precipitation events, but downscaled models like the one produced by Fu and his colleagues are the only way of pinpointing the locations most at risk.
"These results can be used by policymakers to develop adaptation and mitigation plans for the future," said Fu. "For example, several nuclear plants on the US east coast had to shut down during July 2012 because of a heatwave. If heatwaves continue to increase, large buffers will be needed to provide enough power". Similarly the results can be used to plan where to prioritise spending on storm and flood defences, and how to deal with heatwave-induced disease outbreaks such as Lyme disease and West Nile Virus.
Now Fu and his colleagues are turning their attention to other parts of the States, using 12 km by 12 km grid resolution downscaled models to get a feel for how extreme it could become elsewhere.
About the author
Kate Ravilious is a contributing editor for environmentalresearchweb.