Every year representatives from governments around the world gather to discuss the problem of global warming as part of the United Nations Framework Convention on Climate Change, a 1994 treaty which has been signed by 194 nations. In 2012, the 17th annual meeting was held in Durban, South Africa. The stated goal of these meetings has been to limit global warming to 2° Celsius – about 3.5° Fahrenheit over average pre-industrial temperature. This is the maximum level of warming that has been labeled as safe by the Intergovernmental Panel on Climate Change (IPCC) – the United Nations scientific advising body on the matter.
we need 100% cuts by 2050 to avert 2°C warming.
Warming beyond this level is not safe because it threatens to accelerate due to “tipping points” in the global climate. These tipping points refer to a specific time at which a natural system, after being stressed by global warming, “flips” into a different state and begins to release greenhouse gases in a self-sustaining reaction instead of being a carbon dioxide ‘sink’. James Hansen and other climate scientists have issued dire warnings about this possibility. In fact, Hansen and other scientists have recently revised their assertions that limiting warming to 2°C will prevent climate tipping points. They, and many other climate scientists, believe now that warming must be limited to 1°C to avoid these catastrophic feedbacks, which are already beginning to take effect.
“With the current global warming of ~0.8°C evidence of slow feedbacks is beginning to appear,” Hansen wrote in 2011.
These “slow feedbacks” include processes like ice sheet melt and the release of methane from thawing Arctic permafrost and warming shallow oceans, and threaten to rapidly increase the effects of global warming if climate tipping points are exceeded. Their effects are rarely included in climate models and policy, and are a major reason why some scientists are concerned that estimates and forecasts have been underestimating the speed and severity of climate change.
“There’s evidence that climate sensitivity [to greenhouse gases] may be quite a bit higher than what the models are suggesting,” said Ken Caldeira, senior scientist at the Carnegie Institute for Science at Stanford University.
That is why many scientists and policy analysts are calling for greater emissions cuts than what has been proposed in international negotiations. So what is necessary to avoid runaway global warming? More