McCarthy: The impact part is probably pretty clear. You can think of it almost as the 'So what?' question. Work Group I says the climate has changed and it's mostly due in the last 50 years to human activity...the climate will become more variable. More extreme events, more heavy precipitation events, more hot spells, more dry spells, stronger winds. Then we deal with what you could call in the vernacular 'So why should I care? What will be the effects?'

The climate changes that are going to be most devastating lie largely in the tropical and sub-tropical regions. But even in a country like the U.S., if you look at a hot spell like the one a few summers ago in Chicago, hundreds of people died. Those people were not people like you or me, they were elderly, infirm, who could not afford to buy or maybe even turn on an air-conditioner or a fan.

Even in a country like the U.S., you have an increasing proportion of the population that is vulnerable to these extremes in climate.

That's part of our message: that no nation or region can take comfort in the fact that they are prepared for this--even in the regions that are less affected, there will be a larger portion of the population than there is now vulnerable to these changes.

THC: Do you think it will be difficult to persuade developed nations to make changes to their carbon dioxide emissions or forestry practices given that the most serious impacts are probably going to be in developing nations?