Our Planet Is Like 'Overweight Smoker with a Heart Condition': An IPCC Report Q&A

[xchrom]

http://www.commondreams.org/view/2013/09/27-0

"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased."

Thus opens the landmark 2013 Intergovernmental Panel on Climate Change (IPCC) report issued today. Working without pay, hundreds of our most dedicated and talented climate experts have collaborated over a six-year period to create the most comprehensive and authoritative scientific document on climate change ever crafted. The first 31 pages of what will be a 4,000-page tome was released this morning after an all-night approval session that stretched until 6:30 this morning in Stockholm, Sweden. This "Summary For Policymakers" lays out a powerful scientific case that significant climate change with severe impacts is already occurring, humans are mostly responsible, the pace of climate change is expected to accelerate, and we can make choices to cut emission of carbon dioxide and other heat-trapping gases that will limit the damage.

Q: How much has the planet warmed, and what has caused the warming?

The report documents that Earth's surface temperature warmed by 0.85°C (1.5°F) between 1880 - 2012. Two-thirds of this warming (0.6°C, 1.1°F) came after 1950. Human-emitted heat-trapping gases likely were responsible for 0.5 - 1.3°C of this post-1950 warming, while human-emitted aerosol particles reflected away sunlight and likely caused cooling (-0.6° - 0.1°C change in temperature.) Climate change due to variations in solar energy, volcanic dust, and natural sources of heat-trapping greenhouse gases were likely responsible for a small -0.1° - 0.1°C change in temperature since 1950. The sun was in a cool phase between 1978 - 2011, and the report estimates that lower solar output cooled Earth's climate slightly during this period. The influence of cosmic rays on climate over the past century was to weak to be detected, they said. In short, the report shows little support for a significant natural component to global warming since 1950. In fact, natural effects may well have made Earth cooler than it otherwise would have been. The report says that "The best estimate of the human-induced contribution to warming is similar to the observed warming over this period." In other words, close to 100% of the observed warming is due to humans.

[Champion Jack]

1. No surprises there