http://canberra.yourguide.com.au/news/opinion/opinion/past-the-threshold-for-dangerous-warming/1076869.html

Past the threshold for dangerous warming

.................Earlier this month, Australian of the Year Professor Tim Flannery warned that a soon-to-be-issued report from the Intergovernmental Panel on Climate Change would show that the atmospheric concentration of greenhouse gases had crossed the threshold for dangerous climate change.

The news prompted renewed calls for governments to implement measures to reduce emissions. Alarmingly, the situation is more serious than suggested by Professor Flannery. His statements were made on the basis that the new report would show the concentration of greenhouse gases reached 455 parts per million in 2005, some 25ppm above previous estimates. The significance of this figure is that some people have suggested it is necessary to stabilise the atmospheric concentration of greenhouse gases at 450ppm to ensure the global average surface temperature does not increase by more than 2 degrees above pre-industrial levels. Warming of 2 degrees is viewed by many as the threshold for dangerous climate change. The weight of scientific evidence suggests that keeping temperature increases below the 2 degrees threshold will require the atmospheric concentration of greenhouse gases to be stabilised at levels below 400ppm, not 450ppm.

Put more simply, we crossed the threshold for dangerous climate change some time ago. Worse still, there is little, if any, chance of stabilising the atmospheric concentration of greenhouse gases at levels below 500ppm.

There is too much momentum in the global economy and carbon-dependent activities, and not enough political support for change domestically and abroad, to achieve these targets.............