Climate scientists issued a plea to politicians on Friday to set aside remaining scientific uncertainties about global warming and act now to head off potentially disastrous climate change.
The call came in a joint declaration at the end of a conference in Amsterdam on the science of global change, attended by 1800 scientists from 100 countries.
Stung by the claims of President Bush that scientific uncertainty might rule out firm action against global warming, the scientists stressed that their carefully calibrated climate models could be under-estimating, rather than over-estimating, the risks the world was running by filling the atmosphere with greenhouse gases.
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The conference declaration warns that the Earth鈥檚 life-support systems 鈥渁re characterised by critical thresholds and abrupt changes. Human activities could inadvertently trigger such changes with severe consequences for the Earth鈥檚 environment and inhabitants鈥�.
The probability of such changes 鈥渉as yet to be quantified, but is not negligible,鈥� says the declaration, adding that the changes could also be irreversible.
The plea will go to negotiations next week in Bonn, Germany, where governments will attempt to rescue the Kyoto Protocol. This first step to halt climate change is under threat because of the withdrawal of the US, the world鈥檚 largest emitter of greenhouse gases.
Dead wood
Meanwhile, the head of the international scientific panel assessing the risk of climate change warned that initiatives to persuade the US and waverers such as Japan and Australia to accept the Protocol risk undermining its scientific soundness and making it environmentally useless.
Attending the conference, Bob Watson, chairman of the Intergovernmental Panel on Climate Change, said countries could offset carbon dioxide emissions by claiming improvements in forest management, provided their actions took after 1990. 鈥淏ut some countries want to be allowed to take credit for the recovery of their forests from bad land management practices in the late 19th 肠别苍迟耻谤测.鈥�
Latest IPCC estimates are that forests in rich countries covered by Kyoto emissions targets are soaking up around 1.5 billion tonnes of carbon from the air each year, he said, much of it from natural regrowth. If they were allowed to claim all that in carbon credits, 鈥渢hey could meet all their obligations under the protocol without doing anything鈥�. he said.
The claims highlighted tensions within the scientific community over using forests as carbon 鈥渟inks鈥�. Watson remains in favour of using sinks. But his predecessor as IPCC chairman, Bert Bolin, said that at best, they could be 鈥渁 temporary measure鈥�.
鈥淔orests are not permanent sinks for carbon,鈥� they can be burned or chopped down, he said.