WASHINGTON, D.C.: A government report warned on Friday (Saturday in Manila) that the United States could face more frequent severe weather including heat waves and storms for decades to come as temperatures rise far beyond levels being planned for.

The draft Third National Climate Assessment, a scientific study legally mandated to advise US policymakers, made few bones that carbon emissions have been causing climate change—a source of controversy among some lawmakers.

The study, which was submitted for public and expert review and could be revised, said that there was “strong evidence” that human activity had already roughly doubled the probability of extreme heat of the kind seen in Texas and Oklahoma in the summer of 2011.

The assessment expected temperatures to keep rising and offered different scenarios for the future, including temperatures rising between 2.8 and 5.6 degrees Celsius after 2050 if emissions climb further. Such a rise would be far beyond the level anticipated by world leaders in United Nations-backed climate change negotiations, which have committed to holding warming to no more than two degrees Celsius above pre-industrial levels.

The report warned that climate change “threatens human health and well-being in many ways,” including through more frequent storms, wildfires, diseases and worse air quality.

Rising sea levels have already damaged infrastructure and climate change could increasingly reduce the reliability of water supplies, particularly in the southern half of the United States and Great Plains, the report said.

While US agriculture will likely remain resilient in the next 25 years, yields of major crops could start declining by mid-century and warming oceans could threaten fish, the study said.

Environmental advocates hoped that the release of the draft report would bring fresh momentum to efforts to tackle climate change.

“Climate change is taking its toll on people and their economies, and will only become more intense without a strong and rapid response here in the United States and around the globe,” said Andrew Steer, president of the World Resources Institute.

President Barack Obama has hinted that he will make a new effort on climate change in the wake of his November 6 reelection and massive Storm Sandy. Efforts by Obama’s Democratic Party to mandate cuts in carbon emissions failed in 2010 in the Senate. Lawmakers of the rival Republican Party said that legislation would be too costly and voiced doubt over climate science. Since then, the Obama administration has ordered higher standards for power plants. US emissions dropped in 2011, largely because of increased use of natural gas instead of coal.