The corporate debate over global climate change is undergoing a paradigm shift of monumental proportion. Corporate boardrooms worldwide are now discussing what can be done to prevent and reverse global warming, and how to position their companies to gain a competitive edge while doing so. These discussions just gained even more impetus with this week's Supreme Court ruling that authorizes the Environmental Protection Agency to regulate carbon dioxide emissions and frees states to unleash the power of the marketplace in encouraging businesses to "green" themselves.

Just as scientific evidence of the impacts of climate change -- warming temperatures, shrinking ice caps and increasingly unstable weather patterns -- has continued to mount, so has evidence of the threat, according to a preponderance of scientific evidence, that warming temperatures pose to the global economy.

A 2006 report by Sir Nicholas Stern, head of the United Kingdom's Government's Economic Services and former chief economist of the World Bank, found that if no action is taken to control greenhouse-gas emissions "the overall costs and risks of climate change will be equivalent to losing at least 5 percent of global GDP each year, now and forever." The global economic impact of a "do-nothing" scenario would be on the level of the Great Depression of the 1930s.

Companies large and small are realizing that ignoring climate change is bad for business. While the deep emission reductions required to stop catastrophic climate change have costs associated, many businesses have found that the path to an economy that reduces carbon dioxide can create new opportunities.

Carbon is starting to have a value as governments mandate caps on carbon emissions and allow industry to buy and sell emission-reduction credits on the open market. First implemented in Europe, this concept of "cap and trade" is growing. The global carbon market was worth $21.5 billion in 2006, up from $11 billion in 2005, according to the World Bank. Venture-capital investment and business activity in clean technologies, renewable energy, energy efficiency and low carbon fuels has also grown, with the worldwide market for wind, solar, geothermal and fuel-cell energy projected to reach $200 billion by 2020.

Stern's report, released last October, offers a comprehensive analysis of the economics of climate change, calculating costs of both action and inaction. The report has two major conclusions: Action to avert the worst effects of global warming will be less costly than the costs of doing nothing, and there is considerable potential for economic growth associated with greenhouse-gas-emission reductions. These are messages with resonance to business.

Stern's conclusions are echoed by the McKinsey Global Institute, McKinsey & Company's private economics research group, which finds that the world can cut energy demand growth by half in 2020 by employing existing technologies that have an internal rate of return of 10 percent or more. These investments pay for themselves, and make good economic, as well as environmental, sense.

Similarly the Climate Group has authored a report, "Carbon Down, Profits Up," which finds that businesses have "considerable scope to cut energy use and emissions and reap significant financial benefits."

That report profiles 84 companies that have cut greenhouse-gas emissions by using energy more efficiently, increasing reliance on renewable energy and switching to lower carbon fuels. None of the companies reported a negative economic impact from their actions, and more than 20 achieved emissions reductions of 25 percent or higher while increasing profits and lowering costs.

While there is significantly more work required to reduce global greenhouse-gas emissions, a growing body of evidence indicates that for many companies this work can grow, not stifle, the bottom line.

Recently, a group of 25 senior level executives, brought together by the Climate Group, the British consulate-general, McKinsey Global Institute, the Bay Area Council and the S.F. Chamber of Commerce, met to discuss the economics of climate change. While the economic and other threats from global climate change remain daunting, meetings such as this are providing real hope that corporate leaders are prepared to do something about it. The faster others follow their lead, the faster the potentially disastrous effects of climate change can be averted.