WASHINGTON – Harmful effects from global warming are already here and worsening, the first climate report from Barack Obama's presidency warns.

The language on climate change is the strongest ever to come out of the White House.

Global warming has already caused more heavy downpours, the rise of temperatures and sea levels, rapidly retreating glaciers and changes in river flows, according to the document released Tuesday by the White House science adviser and other top officials.

"There are in some cases already serious consequences," said report co-author Anthony Janetos of the University of Maryland. "This is not a theoretical thing that will happen 50 years from now. Things are happening now."

The White House document – a climate status report required periodically by Congress – contains no new research. But it paints a fuller, more cohesive and darker picture of global warming in the U.S. than studies during the George W. Bush years.

One administration official, Jane Lubchenco, called the new report a game-changer that would inform policy but not dictate a solution.

The "major disruptions" already taking place will only increase as warming continues, the authors wrote. They project the average U.S. temperature could rise by as much as 11 degrees by the end of the century.

"Thresholds will be crossed, leading to large changes in climate and ecosystems," the study said in one of its key findings, adding that the survival of some species could be affected.

For example, in the last few decades, winters in parts of the Midwest have warmed by several degrees, and the time without frost has grown by a week, the report said.

Shorter winters have some benefits, such as longer growing seasons, but those are changes that require adjustments just the same, the authors note.

Water – too much or too little – is a dominant theme through much of the report, which says that resource will continue to be a major problem in every region of the country. The U.S. Southwest is expected to get drier and hotter, for instance.

White House science adviser John Holdren said the global warming report "tells us why remedial action is needed sooner rather than later."