The 2007 IPCC report, compiled by several hundred climate scientists, has unclearly concluded that our climate is warming rapidly, and that we are now at least 90 per cent certain this is mostly due to human activities. The amount of carbon dioxide in our atmosphere now far exceeds the natural range of the past 650,000 years, and it is rising very quickly due to human activity.
If this trend is not halted soon, many millions of people will be at risk from extreme events such as heat waves, drought, floods and storms, our coasts and cities will be threatened by rising sea levels, and many ecosystems, plants and animal species will be in serious danger of extinction.The next round of focused negotiations for a new global climate treaty (within the 1992 United Nations Framework Convention on Climate Change process) needs to begin in December 2007 and be completed by 2009.
The prime goal of this new regime must be to limit global warming to no more than 2C [3.6F] above the preindustrial temperature, a limit that has already been formally adopted by the European Union and a number of other countries.Based on current scientific understanding, this requires that global greenhouse gas emissions need to be reduced by at least 50 per cent below their 1990 levels by the year 2050.
In the long run, greenhouse gas concentrations need to be stabilized at a level well below 450 parts per million (measured in CO2-equivalent concentration). In order to stay below 2C, global emissions must peak and decline in the next ten to fifteen years, so there is no time to lose.As scientists, we urge the negotiators to reach an agreement that takes these targets as a minimum requirement for a fair and effective global climate agreement.
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