Claimed to be the first assessment of global impacts of climate change assuming atmospheric concentrations carbon dioxide (CO2) are stabilised, the findings are intended to help policy makers to interpret what would constitute dangerous climate change. Since the UN Kyoto climate change protocol requires "dangerous" climate change to be avoided, this will have an important bearing on future negotiations to agree tougher greenhouse gas emissions limitations after the "first commitment period" of 1990 to 2008-2012.
According to climate modellers at the UK's Hadley Centre for Climate Prediction and Research, a continued unmitigated increase in world emissions of CO2 - the most important greenhouse gas - will lead by the 2080s to a three degrees centigrade increase in global temperatures and a 40cm increase in sea levels. The impacts of these and related changes, the scientists predict, will include "substantial" dieback in tropical forests, an increase in the annual number of people flooded from 13m to 94m, and an additional 290m people worldwide at risk of falciparum malaria.
The report goes on to predict that stabilising the atmospheric CO2 concentration at 750 parts per million (ppm) or 550ppm could significantly ameliorate these impacts. However, achieving either of these targets would require very large cuts in global emissions, including far larger cuts for regions such as the EU than the aggregate minus 8% it has committed to achieve by 2008-2012.
In terms of global temperatures, restraining the peak CO2 concentration to 750ppm- or double the current level - would delay the projected temperature increase by 50 years. Achieving a peak of only 550ppm - or double the pre-industrial level - would delay it by over 100 years so that global temperatures would only rise by two degrees centigrade by the 2230s.
Whereas an estimated 3bn extra people would suffer water resource stress by the 2080s with an unmitigated increase in global CO2 emissions, limiting the peak concentration to 550ppm would cut this number to 1bn. In contrast, limiting the peak to 750ppm would have little positive effect, the scientists predict.
Stabilising CO2 would also limit the number of people likely to suffer from flooding, the study shows, from 94m people without emissions restraint to 34m if CO2 is stabilised at 750ppm and 19m people with stabilisation at 550ppm.
Please enter your details
Not a subscriber?
Take a free trial now to discover the critical insights and updates our coverage offers subscribers.