It is very tempting to just answer "Yes" to this question, as it would seem to be a simple matter of fact. However, the reality is that the issue is rather complicated (and often political). For excellent coverage of climate science, I continue to recommend RealClimate.org. But to really answer the question being posed, you have to get into what I call the "sciensocioeconomic" aspects of the issue; looking at climate change in as simple a way as the question above suggests doesn't provide a lot of insight into today's Gordian policy knot. To do that, you have to add some additional questions.

1. Will increasing greenhouse gas (GHG) concentrations raise global temperatures?

We know for a fact that natural levels of GHGs in the atmosphere keep the planet about 59 degrees warmer than otherwise would be expected and thus enable life to succeed so well. All things being equal, increasing GHG concentrations in the atmosphere increases the radiative forcing of GHGs in the atmosphere and raises global temperatures.

2. Is there uncertainty as to the magnitude of the temperature change?

The earth’s climate is a hugely complicated system. How long will it take the oceans to warm under different GHG scenarios? Will increased cloud cover from more water vapor in a warmer atmosphere counter or speed up the warming? How rapidly will sea ice disappear, and how significant a positive temperature feedback will that create (currently, a significant amount of sunlight reflects off ice and bounces back into space)? And of course, how rapidly will GHG concentrations rise?

The bottom line is that the specific magnitude and timing of global climate change can be debated indefinitely. There is, however, general scientific agreement that temperatures will increase significantly over the next century.

3. Is there uncertainty as to the impacts of projected temperature change?

It should be no surprise that there’s even more uncertainty over the potential impacts of climate change than over the issue of temperature rise itself. The complexity of the planet’s hydrological, biological, and other systems guarantees such uncertainty. Scientists are in general agreement, however, as to the nature of many of these impacts, even if they continue to debate their magnitude.

4. Is there uncertainty as to whether we can prevent or substantially moderate climate change and its impacts?

Just stabilizing concentrations of CO2 in the atmosphere would require a 70% reduction in global emissions. As a practical matter, such dramatic decreases would be extremely difficult to achieve. Even the Kyoto Protocol, which took considerable political effort to bring into force (yet does not include several key industrialized countries or developing nations), barely slows increasing GHG concentrations. Looking at the question in this way, one can see that preventing or substantially moderating climate change begins to look very difficult indeed.

5. Is there uncertainty over the economic impacts of trying to prevent or substantially moderate climate change?

Predictions of what would happen to the U.S. and world economies if we seriously tackled climate change range from economic Armageddon to economic nirvana, depending on who is doing the modeling and what assumptions are made in the course of such modeling. While I do not believe material efforts to address climate change would be economically ruinous, I do believe they would not be a win-win solution in which everyone comes out ahead. Certain sectors and industries would almost certainly be disrupted.

What does this all add up to? It adds up to a policy debate that is far more complicated than the basic science might suggest. Where one comes down on climate change tends to be influenced by far more than the science, from near-term economic self-interest to one’s perspective on inter-generational equity. A real challenge with the climate change issue is that its downsides can, if desired, be portrayed as so uncertain and long-term, while the costs of addressing it are far more immediate. Our political system is simply not designed to deal with this kind of situation. That’s why there’s doubt about global warming - or, more accurately, what to do about it.

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Dr. Mark C. Trexler has more than 25 years of energy and environmental experience, and has focused on global climate change since joining the World Resources Institute in 1988. He is now president of Trexler Climate + Energy Services, which provides strategic, market, and project services to clients around the world.