The Environmental Protection Agency report says climate change is unequivocally causing hurricanes and heat waves.
In a new report, it says: "There is indisputable evidence that human activities such as electricity production and transportation are adding to the concentrations of greenhouse gases that are already naturally present in the atmosphere."
Seven of the 10 warmest years on record for the continental United States have occurred since 1990, it says, and six of the 10 most active hurricane seasons since the mid-1990s.
Even the birds show evidence of climate change, says the report, with species moving their wintering grounds an average of 35 miles northwards since 1966. Some, it says has shifted as much as 100 miles north.
And while those who shivered their way through last winter might find it difficult to believe, snow apparently covered an average of 3.18 million square miles of North America during the years 2000 to 2008, compared with 3.43 million square miles during the 1970s.
Meanwhile, a coalition of environmental groups and environmental scientists has sent a letter to Congress urging it to take strong action on climate change.
"This must be the year that the United States passes comprehensive climate and energy legislation into law in order to create jobs, strengthen our national security, and reduce carbon pollution," the letter says.
"Special interests have fought energy reform for decades. They’ve kept America dependent on foreign oil and protected corporations that pollute the air our children breathe and the water they drink. It is long past time to end our reliance on old technology and dirty energy sources and put America back in control of its energy future."