Scientific American: Global warming first emerged clearly in the 1990s and has become more evident with each passing year. The last decade was the hottest such span on record and is very likely to be surpassed as the 21st century progresses. A new report from the U.S. National Oceanic and Atmospheric Administration lists 10 indicators that global warming is happening: rising humidity; rising sea-surface temperature as well as heat stored in deeper waters; shrinking sea ice, glacier and springtime snow …