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 cover; rising temperatures over land and sea; and rising sea levels.
All point to a rapidly warming world. And all are based on actual observations, from satellites high in the sky to meteorological stations in the middle of a Kansas cornfield.
You can debate how bad global warming will be or what to do about it, but it's hard to deny it's happening anymore. The physics of greenhouse gases trapping heat are clear.
The politics are murkier. Legislative efforts to combat climate change have failed in the U.S. But the Environmental Protection Agency plans to curb greenhouse gas emissions—noting that rising temperatures and a dangerous human impact on climate are undeniable.