The three take-home messages from the latest IPCC Assessment Report (Volume 2, Impacts) are the same as those listed by the much shorter summary offered by the American Association for the Advancement of Science two weeks ago (The New York Times, March 18, 2014, “Scientists Sound Alarm on Climate”):
1. Climatic change is here and now. Contrary to what some would have you believe, scientists are overwhelmingly in agreement about the gases responsible for climate change, the reasons for their increasing concentrations, and that the Earth’s surface temperature is increasing.
2. There are risks that the effects of climatic change will be severe, pervasive, and irreversible. They already are severe and pervasive.
3. The sooner we reduce emissions of heat-trapping gasses, primarily carbon dioxide, those risks become lower. The longer we wait and do nothing, both the risks and the costs grow.
I would elaborate this third point by pointing out the difference between climatic change and climatic disaster. Although climatic change has already begun, and although the effects will continue to increase for decades even if we eliminate the emissions of heat-trapping gasses today — despite the fact that it’s begun and will get worse — it will continue to worsen unless we take steps to stop it. In other words, it’s too late to prevent climate change, but it’s not too late to keep it from getting much, much worse.
Gloomy as this statement is, there are many encouraging signs that the public, industries, and even some governments are beginning to feel the effects of climate change and beginning to do something about it. Perhaps this is the long-awaited groundswell.