The Kyoto protocol and short-term reduction targets for greenhouse gas emissions are an important first step in tackling climate change. However, these need to go hand in hand with long-term commitments. Model-based estimates up to the year 3000 show that a gradual transition to an emission-free economy is possible at an acceptable price within the next 50 to 100 years. The findings were published by several members of the European Climate Forum (ECF) in the current issue of Science (Science, 12 December 2003).
To avoid dangerous climate change, global per capita greenhouse gas emissions need to be reduced to a small fraction of the present levels of developed countries within the next hundred years. In the worst case, if all available fossil fuel resources (conventional and exotic) are used and emissions are not reduced, model simulations indicate that the sea level could rise by about 8 meters and the average air surface temperature by about 9 degrees Celsius in the later part of this millennium.
Because of the long residence time of CO2 of more than 100 years in the atmosphere, climate response is governed by cumulative rather than current CO2 emissions. Important is not the detailed emissions path, but that emissions are strongly reduced over a period of 50 to 100 years. Thus the detailed reductions achieved during the Kyoto period are less critical than the start of a transition to a sustainable path of continually decreasing emissions. This requires policies extending well beyond the Kyoto horizon. Cost estimates indicate that the implementation of an effective climate policy would delay economic growth over a period of fifty years by perhaps one to two years - an acceptable price for the avoidance of dangerous climate change.