Friday's release of a much-anticipated report on global warming from the UN's Intergovernmental Panel on Climate Change (IPCC) in effect asks a profound question of humanity: What do you want your climate to look like over the next several centuries – and probably longer?
The report states in unequivocal terms that the climate is warming globally and that since the middle of the 20th century, human industrial activity – the burning of fossil fuels and, to a lesser extent, land-use changes – is warming's main driver. Since the last report in 2001, confidence in that statement has risen from "likely" (greater than a 66 percent chance) to "very likely" (greater than 90 percent).
But beyond detailing current and projected effects of warming – including sea-level rise, vanishing alpine glaciers, and increases in severe-weather events – the report hints at the need for a conscious control over the environment and a unity of purpose that humans have yet to achieve on such an enormous scale.
"When people think about climate impacts, they think about something very narrow: What icky things are going to happen where I live?" says Jerry Mahlman, a senior research associate at the National Center for Atmospheric Research in Boulder, Colo. "They don't say: What's going to happen to the poor Bangladeshi farmers who get hit with a triple whammy" – rising sea levels, more intense tropical cyclones, and reduced supplies of fresh water. "Everyone wants to talk about their particular piece of turf. But this is a problem that is intrinsically and fundamentally global."
The new report, which focuses on the science of climate change, is the first of three main volumes the IPCC will release this year, plus a final "synthesis report." The document the IPCC unveiled Friday (available at ipcc.ch) in Paris is the first volume's short form – the summary for policymakers.
The report already is prompting calls for more-concerted action to reduce carbon-dioxide (CO2) emissions.