Check out this compelling roundtable discussion of four expert climate change scientists: The State of the Climate — and of Climate Science.
It originally appeared in the June 2009 issue of DISCOVER Magazine. (I just "discovered" it ...) The introduction does a great job of describing the crossroads we're at today as science and public opinion meet:
"In the list of world challenges, global warming might be at once the most alarming and the most controversial. According to some predictions, climate change caused by human activity could cause mass extinction in the oceans, redraw the planet’s coastlines, and ravage world food supplies. At the same time, a significant portion of the American public questions whether global warming will really cause any major harm; many still doubt that human-driven warming is happening at all."
Here are a few highlights of the discussion:
"I spend a lot of time studying the ice sheets at the bottom of the planet—how they form and how they collapse. The poles are like the planet’s air conditioner. When things are working well, the poles keep the planet nice and cool and we don’t think about it. When things stop working, the poles can start to melt and there’s a puddle on the floor. Today both poles are getting warmer; in Greenland and Antarctica you can see the surface of the ice dropping, and you can see there’s less mass when you measure the ice from space. The process has been ongoing, but it looks like it’s happening faster than it was. We know the ice sheets have come and gone in the past. Why is this any different? One of the most compelling reasons is that in the past the ice sheets from the two poles didn’t move together—one would lead and the other would follow. This time, both the north and south are spewing ice into the global ocean, accelerating at the same time."
— Robin E. Bell, a senior research scientist at Columbia University’s Lamont-Doherty Earth Observatory
[... the Earth got warm in the past, too] "but it got warm over millions of years, and ecosystems had a chance to adapt. What we’re seeing are rates of increase in greenhouse gases and warming that exceed natural rates by a factor of 100. So what we’re doing is really unusual when seen from a geologic perspective.
[Humans are doing in centuries what natural processes do over millions of years?] "Yes, and the other timescale mismatch is that what we do over the next decades will affect life on this planet for hundreds of thousands of years, if not millions of years. We are at a critical juncture in earth history. If we don’t do the right thing and there are geologists around 50 million years from now, they’ll be able to look at cores and see the remnants of a civilization that developed advanced technology but didn’t develop the wisdom to use it wisely."
"To me the most compelling evidence [that human behavior is actually warming the planet] is the fact that the stratosphere — the upper atmosphere — is cooling while the lower atmosphere and the land surface are warming. That’s a sign that greenhouse gases are trapping energy and keeping that energy close to the surface of the earth. I mentioned that in ocean acidification, you actually see animals that should make shells unable to make shells anymore. You could demonstrate the same kind of effect in a bell jar in the lab. There is a level of certainty about it."
— Ken Caldeira, a professor at Stanford and staff member in the department of global ecology at the Carnegie Institution of Washington
"One of the most remarkable achievements of the 20th century was the way we were able to increase the global food supply in pace with unprecedented population growth. We will have to raise the food supply another two times to feed all of the people that we think will be alive by the latter third of the 21st century. We have reason to be somewhat sanguine about doing it if climate stays more or less the same, but how will we do it with the climate change? Based on our simulations and on 25 years of research, what bothers us most is that in the tropics, where the majority of poor people live today, crops are currently raised at temperatures pretty close to their photosynthetic optimums."
— Bill Easterling, Dean of the College of Earth and Mineral Sciences at Pennsylvania State University
You can read the full discussion and learn more about the credentials of the panelists at The State of the Climate — and of Climate Science.