20-Year Intense Downpours to Occur Every 6 Years

Wildfires in the American West are "strongly associated with increased spring and summer temperatures and correspondingly earlier spring snowmelt in the mountains," the report said.

There is less clarity in the report when it comes to how much influence humans are having when it comes to hurricanes, reflecting the ongoing discussions taking place among scientists in peer-reviewed science journals.

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"Over the past 50 years there has been a strong statistical connection between tropical Atlantic sea surface temperatures and Atlantic hurricane activity," the report reads. "This evidence suggests a human contribution to recent hurricane activity. However, a confident assessment of human influence on hurricanes will require further studies using models and observations, with emphasis on distinguishing natural from human-induced changes."

Computer climate models, however, project that for every 1.8 degrees Fahrenheit increase in ocean temperatures due to human-induced warming, rainfall from hurricanes will go up 6 to 8 percent. Hurricane wind speeds could increase by 1 to 8 percent.

"These are fairly significant numbers," Karl said.

Democratic lawmakers in Congress say the report highlights the need to curb greenhouse gasses.

"There is no safe haven. There is no place you can live that won't suffer the consequences of global warming," said Rep. Ed Markey, D-Mass., chairman of the House Select Committee on Energy Independence and Global Warming. "People have been watching huge floods, droughts, storms that are otherwise unaccountable and historic in their nature. And now people, I think, will have the dots connected."

Some scientists, such as NASA climatologist James Hansen, believe the dots have been connected for a long time. Next week, Hansen will mark the 20th anniversary of a 1988 appearance before a Senate hearing in which he made the case that humans, not natural causes, were responsible for the warming of the planet. He has largely been proven right by an enormous body of subsequent scientific research.