Climate change is not a distant threat but has “moved firmly into the present”, according to a US government report released today.
Rising greenhouse gas emissions have made US summers longer and winters shorter, increased the risk of some extreme weather events and raised sea levels, finds the 1,300-page analysis, compiled by 300 scientists. It is the United States’ third national assessment of climate change impacts, following similar reports in 2000 and 2009.
“This national climate assessment is the loudest and clearest alarm bell to date signalling the need to take urgent action to combat the threats to Americans from climate change,” says John Holdren, President Barack Obama’s science advisor and director of the White House Office of Science and Technology Policy.
Overall, the average US temperature has increased by 0.7-1.0 degrees Celsius since 1895, with the pace of warming quickening after 1970. The mercury is poised to rise another 1.1-2.2 degrees Celsius within the next few decades. And by the end of the century, it could reach sizzling temperatures 2.8-5.6 degrees Celsius hotter than today’s conditions, unless the world commits to major reductions in greenhouse gas emissions.
Such changes are already affecting how Americans live and work, warns the report, which examines climate change impacts at the regional and state levels. In the Pacific Northwest, spring is starting earlier, changing the timing of snowmelt and in turn reducing water supplies in summer. In Alaska, receding sea ice is exposing large swathes of the state’s coast to erosion, prompting some coastal villages to plan costly relocations. And the Northeast has seen a 70% increase in the amount of rain falling as heavy downpours, increasing the region’s risk of flooding.