Opponents of ratification argue that New Zealand is a small contributor to greenhouse gas emissions (less than 1 per cent of the global total), there are big uncertainties about what effects any given level of greenhouse gases in the atmosphere would have, and there are long lags before any moves to cut emission would do any good.
They ask why New Zealand should impose costs on itself ahead of competitors and trading partners, when the environmental benefits are small, uncertain and far off.
Dr Watson acknowledges the uncertainties. The panel's reports contain many qualifications and caveats.
"But I would say that the very large majority of [climate]scientists would agree that the Earth's climate is warming and that further warming is absolutely inevitable," he said.
Most climate models suggest that so far we had felt only 50-70 per cent of the effects of the emissions that have already occurred, he said.
Though there would be beneficial effects in some parts of the world from climate change, most of the world could expect adverse effects on agriculture, water resources and human health.
The faster the build-up of greenhouse gases and the longer it continued, the more the adverse effects would dominate over beneficial effects.
"It is a policy issue for governments whether that constitutes a reason for action," he said. It was not for the panel to say.
Seventeen national academies of science, mainly European, but some from large developing countries, had endorsed the panel's processes and conclusions, and called for ratification of the Kyoto Protocol.
As for the risks of being in the first wave of countries to sign up to the protocol, Dr Watson said that sometimes setting an environmental target stimulated innovation. That was what happened with the ozone hole.
"Many industries at the time of the Montreal Protocol process objected that we didn't know how to reduce chlorofluorocarbon emissions [which deplete stratospheric ozone] and that a top-down target would impose heavy costs on the industries affected," he said. "But it stimulated a lot of innovation and in the end the economic cost of displacing CFCs was small.
"The parallel here is that Kyoto would probably stimulate significant research and development into the dietary efficiency of sheep and cattle, and there are some strong indications that that sort of work would pay off."
Methane belched by sheep and cattle is New Zealand's largest source of greenhouse gas emissions.
Dr Watson said some of the world's largest companies evidently saw a competitive advantage in moving early on emission reductions, citing BP, Shell, Dow Chemical, DuPont, Eastman Kodak, Asea Brown Boveri, Ford, IBM and RTZ.
"They believe eventually there will be regulation and that it is better to get ahead of the market, that they will look green to green consumers and that Governments will be more likely to listen to them about sensible regulation," he said.
nzherald.co.nz/climate
Intergovernmental Panel on Climate Change (IPCC)
United Nations Environment Program
World Meteorological Organisation
Framework Convention on Climate Change
Executive summary: Climate change impacts on NZ
IPCC Summary: Climate Change 2001
