September marks the end of winter when the sea ice that surrounds Antarctica swells to its maximum extent.
Pacific hurricanes form off Mexico and head northwest into wide open ocean, so they don't usually do much damage to the continental U.S.
As temperatures go up, ground-level ozone goes up, making for poorer air quality. Check out the trend in various cities across the U.S.
Cities tend to be warmer than the surrounding countryside, a phenomenon known as an urban heat island. See details for 60 U.S. cities.
The relentless heat that has plagued the western half of the country this summer has ratcheted up California’s terrible drought once again.
On the decadal scale, the gap between highs and lows has been growing since the 1970s.
Record lows are outpacing record highs since last year. This is becoming rarer in a warming world.
Scientists say increased CO2 emissions are making poison ivy worse.