Creation care interview with Sir John Houghton in Physics TodaySeptember 8, 2007 at 4:48 pm | Posted in Climate change, Houghton, Interviews, Physics Today | 1 Comment
PT: The US is far behind a lot of other countries in doing anything about climate change and reducing emissions.
JH: Yes it is. US carbon dioxide emissions are well over 20% greater than they were in 1990 and still rising. Your administration is extremely backward in doing anything about it. However, there are signs of change. For instance, I gave testimony to the US Senate in July 2005 along with three other scientists. There was a big audience, and we had a robust exchange. Since that time the Senate has been expressing more concern about the issue.
There are good signs too in other parts of the US—California and some of the eastern states are beginning to set targets for greenhouse gas emissions. Many cities are setting targets for reducing emissions, and much of the population is beginning to take the problem seriously. But you have an awful long way to go.
PT: What kinds of responses do you get from your audiences?
JH: On the whole, the response is very positive. One problem in climate change is that people at large are very ignorant about it. They know it will get a bit warmer, but they don’t know the influence climate change will have on sea level, or extreme events like droughts, floods, and heat waves, and what the impacts will be. But they are keen to learn and to discover there’s a lot they can do about it.
PT: What suggestions do you give people about what they can do about climate change?
JH: I tell them they can look at their own carbon dioxide emissions. In this country [the UK], anyway, I encourage people to buy green electricity, guaranteed to come from non-fossil-fuel sources. Then they can make sure their home is well insulated and not overheated in winter or overcooled in summer. They can buy appliances that are very efficient and don’t use more energy than they need. They can buy an efficient car which offers good miles per gallon and travel less than they might otherwise. They can recycle their waste. And they can get well informed so as to be able to influence government and industry to do the right things.
PT: In lectures aimed largely at nonscientists, how much science do you include?
JH: I try to explain clearly the science behind climate change. The greenhouse effect has been known for over 200 years. If carbon dioxide is added to the atmosphere, its blanketing effect increases as it absorbs more of the infrared radiation emitted by the surface, making the Earth warmer than it would otherwise be. That effect is multiplied by positive feedbacks—for instance, water vapor, another powerful greenhouse gas, increases in the atmosphere as the Earth warms, thus enhancing the blanketing effect. There are other feedbacks too, some positive, some negative. Some we know about quite well, some we are rather uncertain about, like the effects of clouds. I try to explain the uncertainties and what we are not sure about, but there is enough there that we are sure about to give great cause for concern.
I then talk about the impacts. I say the most important impact of climate change will be the rise of sea level, because as the oceans warm, the water expands and also glaciers are melting. The rate of rise will be around half a meter per century. It could be more because of a contribution from melting of the polar ice caps. Just how fast the ice caps will melt is uncertain at the moment, but there are increasing signs it could be substantial.
If you happen to live near the ocean, sea-level rise is likely to become a big problem. In Bangladesh, 10 million people live below the 1-meter contour; 25 million people in southern China and millions too in the Nile Delta; Florida and some parts of the Gulf Coast will notice it seriously too. Lots of cities are built close to the ocean and will have to take expensive actions to cope with sea-level rise.
The oceans will take centuries to warm to the bottom. Sea-level rise is not going to stop, even if we turn the carbon dioxide tap off tomorrow.
Another impact is more heat waves. A heat wave in Europe in 2003 killed over 20 000 people. It was completely unprecedented, way outside the bounds of normal natural variability. Scientists who have studied it concluded that most of the risk of that event arose from the increase in greenhouse gases. As the Earth warms further, such a summer is likely to be normal by the middle of the century and [be considered] a cool summer by 2100. That’s something to make one sit up and think.
The third impact is on the hydrological, or water, cycle. With more water vapor in the atmosphere because of more evaporation from the warmer oceans, there will be more average rainfall. That is already occurring in some parts of the world. But that extra water vapor provides more energy for the hydrological cycle through the release of latent heat as water vapor condenses to form clouds. The result is that rainfall will tend to come down in more intense storms—hence more floods. It also means there will tend to be more frequent and intense droughts.
Climate models, which include all the physical processes and all the dynamics and so on, don’t tell you exactly where all this is going to occur, because we are not clever enough yet. But the tendency to more frequent and intense floods and droughts is a robust result. Recent scientific papers estimating the likely increase in such events suggest possible increases of factors of 5 and even 10 by later this century. An increase by a factor of 5 in the number of floods in many parts of the world would be very devastating. And droughts lasting years rather than months—an expectation from the models—is a very frightening prospect, particularly in parts of the world which are prone to drought and where they don’t have the ability to cope with it.
So there are going to be lots of environmental refugees. We are talking perhaps hundreds of millions of environmental refugees in the world by 2050.
That’s the story I tell. I don’t hype it up. I believe in giving the most conservative picture I can while being faithful to the evidence. It has been generated through much lively discussion and debate within the IPCC by hundreds, even thousands, of the world’s best climate scientists.