From the EPA Report:
"Greenhouse gases are accumulating in the Earth's atmosphere as a result of human activities, causing global mean surface air temperatures and subsurface ocean temperatures to rise," the administration said in its report.
"The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability," the report says.
"Human-induced warming and associated sea level rises are expected to continue through the 21st century," it says. "Secondary effects...include increases in rainfall rates and increased susceptibility of semi-arid regions to drought."