Scientists in climate change fields have called for tougher targets which is 350 PPM but not 450 PPM in climate change negotiations to be held in Copenhagen in December 2009.
Bo Ekman, founder of the Tällberg Foundation, supported by the Stockholm Environment Institute and over 170 signatories, including a dozen of the world's leading environmental scientists, such as James Hansen, Robert Corell and James Lovelock, have made the call in the media.
Other signatories include Jacqueline McGlade, Executive Director of the European Environment Agency; José Maria Figueres, ex-president of Costa Rica; the former Swedish Prime Minister, Göran Persson; and authors Bill McKibben, Mark Lynas and Tim Flannery.
The parts per million (PPM) of Carbon Dioxide (CO2) in the atmosphere has long been a key indicator for climate change. Setting a PPM limit is one of the guiding principles behind the ongoing climate negotiations. Several proposals for an upper limit for CO2 have come forward and until recently scientists estimated that the level could reach 450 PPM without threatening life on Earth.
However, latest studies show that is not enough.
"We are concerned that the negotiations are heading in the wrong direction," said Professor Johan Rockström, Executive Director of the Stockholm Environmental Institute. "The CO2 threshold under discussion is too high. Today, the scientific community has a pretty clear picture of how much CO2 our atmosphere can sustain, and there is growing evidence that 350 PPM should be our target, rather than 450 PPM."
The latest studies show that a 450 PPM level of CO2 is expected to cause more than a one meter rise – and perhaps as much as a 3 meter rise – in the sea level during this century, and more than 20 meters over a longer period. The global mean temperature on Earth will increase by 2 degrees Celsius above pre-industrial levels, which carries enormous implications for global and regional ecosystems.
"The shocking conclusion I have reached is that the safe level of atmospheric carbon dioxide is no more than 350 parts per million and it may be less. Today, CO2 emissions are increasing by 3 percent annually. Setting an upper limit of 350 PPM doesn't just mean stopping this annual increase. It will mean taking actions that, during this century, will lower the PPM level to less than 350. Even if we do this, populations across the globe will still have to face significant adaptation to climate change." said James Hansen.
"The 350 PPM upper limit is currently a hot topic in the U.S, and according to scientists this is the figure that we have to deal with," said Bo Ekman. "We hope that the advertisement we put up in the media will help politicians and decision-makers realize that we cannot negotiate with nature, and that this is the greatest challenge of our time."
By Xuefei Chen, People's Daily Online correspondent in Stockholm.
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