To Your Health

Future generations of Americans can expect to spend 25 days a year sweltering in temperatures above 100F (38C), with  climate change on course to turn the country into a hotter, drier, and more disaster-prone place.

The National Climate Assessment,  released in draft form on Friday , provided the fullest picture to date of the real-time effects of climate change on US life, and the most likely consequences for the future.

The 1,000-page report, the work of the more than 300 government scientists and outside experts, was unequivocal on the human causes of climate change, and on the links between climate change and extreme weather.

“Climate change is already affecting the American people,” the draft report said. “Certain types of weather events have become more frequent and/or intense including heat waves, heavy downpours and in some regions floods and  drought. Sea level is rising, oceans are becoming more acidic, and glaciers and Arctic sea ice are melting.”

The report, which is not due for adoption until 2014, was produced to guide federal, state and city governments in America in making long-term plans.

By the end of the 21st century, climate change is expected to result in increased risk of asthma and other public health emergencies, widespread power blackouts, and mass transit shutdowns, and possibly shortages of food.

“Proactively preparing for climate change can reduce impacts, while also facilitating a more rapid and efficient response to changes as they happen,” said Katharine Jacobs, the director of the National Climate Assessment.

The report will be open for public comment on Monday.

Environmental groups said they hoped the report would provide Barack Obama with the scientific evidence to push for measures that would slow or halt the rate of climate change – sparing the country some of the worst effects.

The report states clearly that the steps taken by Obama so far to reduce emissions are “not close to sufficient” to prevent the most severe consequences of climate change.

“As climate change and its impacts are becoming more prevalent, Americans face choices,” the report said. “Beyond the next few decades, the amount of climate change will still largely be determined by the choices society makes about emissions. Lower emissions mean less future warming and less severe impacts. Higher emissions would mean more warming and more severe impacts.”

As the report made clear: no place in America had gone untouched by climate change. Nowhere would be entirely immune from the effects of future climate change.

A heatwave swept across the US in 2011, with temperatures reaching over 110F (43C). Photograph: Timothy A Clary/AFP

Some of those changes are already evident: 2012 was by far the hottest year on record, fully a degree hotter than the last such record – an off-the-charts rate of increase.

Those high temperatures were on course to continue for the rest of the century, the draft report said. It noted that average US temperatures had increased by about 1.5F since 1895, with more than 80% of this increase since 1980.

The rise will be even steeper in future, with the next few decades projected for temperatures 2 to 4 degrees warmer in most areas. By 2100, if climate change continues on its present course, the country can expect to see 25 days a year with temperatures above 100F.

Night-time temperatures will also stay high, providing little respite from the heat.

Certain regions are projected to heat up even sooner. West Virginia, Maryland and Delaware can expect a doubling of days hotter than 95 degrees by the 2050s. In Texas and Oklahoma, the draft report doubled the probability of extreme heat events.