All of this data--and its conformance with predictions from computer-generated models--provide key evidence of climate change. "The fact that nature is confirming a posteriori the anticipation of models from 15 or 20 years ago is strong proof," Le Treut says. "It is very difficult to say that this is coincidental."
"The human signal has clearly emerged from the noise of natural variability," NCAR's Trenberth adds. "Numerous changes in climate have been observed at the scales of continents or ocean basins. These include wind patterns, precipitation, ocean salinity, sea ice, ice sheets and aspects of extreme weather."
This means that the science of climate change may partially undergo a shift of its own, moving from trying to prove it is a problem (it is now "very likely" that greenhouse gases in the atmosphere have already caused enough warming to trigger stronger droughts, heat waves, more and bigger forest fires and more extreme storms and flooding) to figuring out ways to fix it. "I would like to see a network of phenological data--such as bloom dates of particular plants--that could be tracked in real time worldwide," NOAA's Peterson says. "Temperature is a good parameter to measure. But the effects of the changes in temperature are relevant to measure directly, too."