How much sunlight Earth reflects naturally varies a lot. The bigger the range of natural variability, the greater the odds that any evidence of a manmade effort to brighten up the planet would be lost in the “background noise.”
Most of the Arctic boundary waters were warmer than average in summer 2013, but a few cool pockets appeared in the western Arctic and the Greenland Sea. Warmer waters are drawing new species from lower latitudes into the Arctic.
Averaged over September 2013, sea ice extent was 2.07 million square miles—larger than last year's record low, but still more than 17 percent below average and the sixth smallest September extent on record.
To be consistent with NOAA's use of 30-year periods for the official "climate normals," the National Snow and Ice Data Center switched its baseline period for sea ice analyses from 1979-2000 to 1981-2010. Compared to the new normal, the low ice conditions of the recent past will appear less abnormal than they used to.
A heat wave struck the Midwest in late August and early September 2013. This map shows the hottest temperatures in the United States between August 1 and September 8, 2013, based on data from NOAA's Real-Time Mesoscale Analysis.