The 1980s were the warmest decade on record, and in 1990 the Intergovernmental Panel on Climate Change concluded that the greenhouse effect could cause significant global warming by the middle of the 21st century. Still, there is considerable doubt among some scientists over whether such predictions amount to a "strategic threat," as Democratic vice-presidential candidate Al Gore says. The main greenhouse gas is carbon dioxide, so any plan to head off global warming could mean major changes for advanced ind ustrial countries like the United States. Is it better to take a "wait and see" attitude or prepare for the worst? BUSH
During the negotiations leading up to the Earth Summit in Rio de Janeiro in June, the administration resisted "targets and timetables" for reducing carbon dioxide emissions.
This put the United States at odds with many other countries (including its allies in Western Europe) who wanted to cut CO2 emissions to 1990 levels by the year 2000 as part of an international treaty on climate change.
Instead, US officials maneuvered a treaty at Rio that requires countries to formulate and publish plans for reducing greenhouse gases while taking into account each nation's special circumstances.
Bush says the US and the Netherlands are the only countries so far to implement such action plans.
The administration predicts its plan will reduce greenhouse gas emissions by 7 to 11 percent below projected levels in the year 2000, and it has committed $25 million to help other countries prepare their plans. CLINTON
Says there is no doubt that global climate change is an "unprecedented new threat," which he sees as an important consideration in energy and economic policy.
He says, "We need to reduce our oil consumption and increase our energy efficiency dramatically if we are to lead the fight against global warming, sharpen our competitive edge in trade, and reduce our vulnerability to cutoffs in the availabiliy of foreign oil."
Unlike Bush, Clinton favors a target (1990 levels) and timetable (the year 2000) for reducing carbon dioxide emissions.
Also unlike his opponent, he would push for more fuel-efficient autos - raising corporate average fuel economy (CAFE) standards from the current 27.5 miles per gallon to 40-45 m.p.g. - because car exhaust contributes a large portion of greenhouse gases.
This is part of his broader goal of improving the country's energy efficiency by 20 percent by the year 2000. PEROT
No formal position on global warming. However he says in his book, "United We Stand: How We Can Take Back Our Country":
"On too many environmental questions we don't even have agreement about the scientific facts. We can't operate in the dark. We certainly can't afford to create solutions to problems that may
not exist. We need to get the facts straight. We don't need to create false choices. We can't afford a debate that doesn't need to take place."
Perot proposes investing more in research to solve problems, but does not say whether the private sector or government will pay for this.