, the international group of climate scientists and advisory group to the U.N. whose opinions represent the consensus of the vast majority of the world's leading climate experts, issued a stark warning: Unless the world takes quick action to curb greenhouse gases, especially carbon dioxide, the Earth's average temperature would, over the coming century, increase between 1.5 and 2.5 degrees Celsius compared to the global average temperature between 1980 and 1999.

If that happens, the IPCC said, up to 30 percent of all animal and plant life would face extinction by the end of this century. In addition, an increase in droughts, desertification, severe flooding due to typhoons, rising sea levels due to melting icebergs and disruptive weather patterns worldwide could lead to millions of people becoming "climate refugees," with countries just a few meters above sea level like the Maldives in danger of disappearing underwater completely.

The IPCC offered a number of suggestions to mitigate the most damaging effects of climate change. The scientists suggested that, in order to stabilize CO2 and other greenhouse gas concentrations at 450 parts per million by the end of this century, the highest level where it might still be possible to mitigate the worst effects, according to their climate models, developed countries need to reduce their emissions between 25 percent and 40 percent by 2020, based on their 1990 emission. If the concentration rises above 450 ppm, climate catastrophe is all but certain. Speed is also of the essence, the IPCC added, as world emissions needed to peak by 2015 in order for the concentration level to eventually settle at 450 ppm.

The IPCC did not specifically call on developing nations to announce numerical targets for reduction, though. It has always been the position of countries such as China, India and Brazil that today's climate crisis was caused by developed nations that have been burning coal and oil since the mid-1800s, and that it's their responsibility to take the lead in reducing emissions. The U.N. seemed to agree, but the IPCC did warn that developing nations could not continue "business as usual" when it came to setting reduction goals.