UN climate report offers stark warnings, hope

Climate change is happening, it's almost entirely man's fault and limiting its impacts may require reducing greenhouse gas emissions to zero this century, the U N's panel on climate science said today.
The fourth and final volume of the Intergovernmental Panel on Climate Change's giant climate assessment offered no surprises, nor was it expected to since it combined the findings of three reports released in the past 13 months.
But it underlined the scope of the climate challenge in stark terms. Emissions, mainly from the burning of fossil fuels, may need to drop to zero by the end of this century for the world to have a decent chance of keeping the temperature rise below a level that many consider dangerous.

Failure to do so, which could require deployment of technologies that suck greenhouse gases out of the atmosphere, could lock the world on a trajectory with "irreversible" impacts on people and the environment, the report said. Some impacts already being observed included rising sea levels, a warmer and more acidic ocean, melting glaciers and Arctic sea ice and more frequent and intense heat waves.
"Science has spoken. There is no ambiguity in their message. Leaders must act. Time is not on our side," UN Secretary-General Ban Ki-moon said at the report's launch in Copenhagen.
Amid its grim projections, the report said the tools are there to set the world on a low-emissions path and break the addiction to burning oil, coal and gas which pollute the atmosphere with heat-trapping CO2, the chief greenhouse gas.

"All we need is the will to change, which we trust will be motivated by knowledge and an understanding of the science of climate change," IPCC chairman Rajendra Pachauri said. The IPCC was set up in 1988 to assess global warming and its impacts. The report released today caps its latest assessment, a mega-review of 30,000 climate change studies that establishes with 95-percent certainty that most of the warming seen since the 1950s is man-made. The IPCC's best estimate is that just about all of it is man-made, but it can't say that with the same degree of certainty.
Today only a small minority of scientists challenge the mainstream conclusion that climate change is linked to human activity.

Sleep-deprived delegates approved the final documents Saturday afternoon after a weeklong line-by-line review in Copenhagen that underscored that the IPCC process is not just about science. The reports must be approved both by scientists and governments, which means political issues from UN climate negotiations, which are nearing a 2015 deadline for a global agreement, inevitably affect the outcome.