New Report Outlines Our Future: Climate Change Set to Make America Hotter, Drier and More Disaster-prone
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Those extreme temperatures would also exact a toll on public health, with worsening air pollution, and on infrastructure increasing the load for ageing power plants.
This 8 November 2011 image shows a storm bearing down on Alaska. Photograph: Ho/AFP/Getty Images
But nowhere will see changes as extreme as Alaska, the report said.
"The most dramatic evidence is in Alaska, where average temperatures have increased more than twice as fast as the rest of the country," the draft report said. "Of all the climate-related changes in the US, the rapid decline of Arctic sea ice cover in the last decade may be the most striking of all."
Other regions will face different extreme weather scenarios. The north-east, in particular, is at risk of coastal flooding because of sea-level rise and storm surges, as well as river flooding, because of an increase in heavy downpours.
A flooded farm along the Mississippi River is seen in Cairo, Illinois. Photograph: Stephen Lance Dennee/AP
"The north-east has experienced a greater increase in extreme precipitation over the past few decades than any other region in the US," the report said. Between 1958 and 2010, the north-east saw a 74% increase in heavy downpours.
The midwest was projected to enjoy a longer growing season – but also an increased risk of extreme events like last year's drought. By mid-century, the combination of temperature increases and heavy rainfall or drought were expected to pull down yields of major US food crops, the report warned, threatening both American and global food security.
The report is the most ambitious scientific exercise ever undertaken to catalogue the real-time effects of climate change, and predict possible outcomes in the future.
It involved more than 300 government scientists and outside experts, compared to around 30 during the last such effort when George W Bush was president. Its findings were also much broader in scope, Jacobs said.
There were still unknowns though, the report conceded, especially about how the loss of sea ice in Greenland and Antarctica will affect future sea-level rise.
Campaign groups said they hoped the report would spur Obama to act on climate change in his second term. "The draft assessment offers a perfect opportunity for President Obama at the outset of his second term," said Lou Leonard, director of the climate change programme for the World Wildlife Fund. "When a similar report was released in 2009, the Administration largely swept it under the rug. This time, the President should use it to kick-start a national conversation on climate change. "
However, the White House was exceedingly cautious on the draft release, noting in a blogpost: "The draft NCA is a scientific document—not a policy document—and does not make recommendations regarding actions that might be taken in response to climate change."