lightblueline

Urgency

The last two years have seen a remarkable turnaround in public perceptions of climate change, especially in the United States. Some critical threshhold seems to finally have been breached, and we see now that both the House of Representatives and Senate are at last considering meaningful legislative proposals to deal with the anthropogenic carbon dioxide emissions that are a major cause of warming. Al Gore’s movie, An Inconvenient Truth, was clearly an important catalyst for change. Another catalyst has been the release this year of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC: see www.ipcc.ch.) The IPCC was established in 1988 by the World Meteorological Association and United Nations Environment Programme, with a mission to assess the scientific basis for human-induced climate change, and to recommend policy options for what to do about the problem. The IPCC has released four comprehensive reports in its 19 year history, each sounding a successively more urgent warning about the impacts of fossil fuel burning on climate. Now, in its latest report, the IPCC states that most of the increase in temperature (about 0.7 °C or 1.3 °F since the start of the industrial revolution, with most of that increase in the last 40 years) is “very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” In IPCC terminology, very likely means with greater than 90% probability. In 2001, the Third IPCC report had put the probability of human influence on climate at 67%. The new assessment, based on decades of intensive and increasingly sophisticated experimental observations and computer modeling, is the most authoritative statement yet, and has been a clear driver for the recent legislative initiatives. This is the good news.