John Christyn haastattelu Alabaman yliopistolla, kesäkuu 2008

MOT: Last year you compared observed temperature trends with modern simulations in tropical troposphere. What did you find out?

Christy: Well, one of the places where the greenhouse effect, according to climate models, is supposed to be the easiest to see – if you want to find out if the greenhouse effect is working as the climate models say –, you go to the tropical atmosphere, the troposphere, and there is the largest signal, where the warming should be very strong.

So we looked what the models showed on that in terms of their best guess – the IPCC often uses this term “best guess”. So we looked at the climate models’ best guesses, all of them, compared that with observations and found a significant difference. So what it looks like is that, the way the real climate is evolving is different than what climate models say it should be doing, if the greenhouse gases are having this large effect.

So since we did not find that effect in the real observations, our conclusion is that these climate models should be used with great caution, because they are not reproducing what we see in the world.

MOT: How crucial are these results, if we think about the credibility of climate models in general?

Christy: I think they are quite significant, because this is a hypothesis test, of where models have the largest signal. And so, if we go to where the models say something is very strong, and we can’t find it, that is a way to test the models and show that there is something wrong there.

MOT: How critical id this amplification, this positive feedback for climate models?

Christy: The reason climate models show such a large warming in the tropical atmosphere is due to the enhancement of water vapor and clouds. Carbon dioxide is a small greenhouse gas in terms of the atmosphere. Clouds and water vapor by far are the dominant greenhouse forcings, and so the way it typically works in the climate models is, if CO2 increases a small amount, then the greenhouse effect of clouds and water vapor increases even more, and that’s why this temperature in models rises so much. Now what we’ve found is that the temperature is not rising at that rate and so perhaps the greenhouse effect of clouds and water vapor is not correctly demonstrated in climate models.

MOT: This finding of yours, how much could it reduce the global warming simulations?

Christy: If what we’ve seen over the past 30 years represents what the greenhouse effect really is doing, we find that the result is about half of the best guess of climate models today, and that’s a big difference in terms of temperature, from 2,8 in the year 2100 to 1.4 in the year 2100.

MOT: Recently a paper by Allen and Sherwood came out from Yale, a study about tropospheric warming based on thermal winds, and they found no discrepancy there between model simulations and the real warming, and this finding has been used as a counter argument to your study. What would you say about that?

Christy: It’s important to know that in our study we use direct measurements of atmospheric temperature, and the two ways we use them are the thermometers that are carried by balloons, so that’s a direct measurement there, and the microwave emissions from oxygen in the atmosphere so that’s another independent direct measurement. And these two agree very well, and we have several other papers, by the way, that show this to be the case.

In the Allen and Sherwood work, which is quite clever when you think about it, they used wind from the balloon releases, and a model equation, called a thermal wind equation, to interpret what the temperature might be, given those changes in winds. There are a lot of assumptions in that process. They did a pretty good job of showing the wide ranges with those different assumptions. And it turns out in fact that when you take the wide range of their error, that in the low end, it agrees with what our particular studies have shown on this very modest warming. But the range that they show is very large, because the errors in this process are quite extensive. I probably, like many other people on the earth prefer direct measurements of something, rather than an inferred measurement of something so important as temperature.

MOT: Do you have any explanation for this disagreement between model simulations and observations in the troposphere in your paper?

Christy: I think one of the main discrepancies is likely the way clouds work. When you look specifically at the real observations of clouds, you find that they vary quite a bit in their greenhouse gas forcing, so that they are able to shrink and therefore allow heat to escape to space. It is important to remember, once that heat escapes to space, it’s gone forever. So with this waxing and waning, this up and down of the way clouds operate, the system is constantly losing heat to space at different rates, and as the temperature warms, the clouds tend to allow more heat to escape and therefore the heat does not build up continuously as it does in climate models.

MOT: If you were in charge, what would you do about climate change and the environment?

Christy: On a number of occasions I have been in congressional hearings in Washington, and the question is asked from the congressman or the senate: if you were in charge, what would you do. And I would probably say, let’s look at the environmental issues today, and find out, which ones are most important to attack. And it turns out in terms of cost and benefit that, global warming is one of the poorest investments you can make, because there’s so much CO2 involved, we can only make tiny fractions of a difference in it’s amount, which means virtually no change in whatever the climate is going to do.

But if you attack something like water pollution, where we know how to clean up water, then you’re talking about saving millions of peoples’ lives today. When you talk about providing nutrients to children, vitamins and so on, you’re talking about saving the lives of millions of people today. So I would ask the congressman and senators to look at the broad range of what can be done, and spend the money where it’s effectively used.

MOT: What would be the impacts on the poor people of the world, if we try to resist warming with very strict restrictions?

Christy: I’ve had the experience of living in Africa and one thing I learned about energy in Africa is this: without energy, life is brutal and short. And I saw the effects of having no energy in peoples’ lives. So any process that makes energy less accessible, and that generally means making energy more expensive, means you are going to degrade the quality of life of people, especially those who already are poor and have difficulty acquiring energy. For example in our country, the poorest people are the ones who spend the most on energy in proportion of their income, so they are the ones who are hurt quickly and the hardest.

I remember many times in Africa for example, looking at that energy system, it’s quite inefficient; the women would rise early in the morning, they would walk an average of three miles one way, to the edge of the forest, chop down the wood, put it on their back, haul that wood three miles back to their homes and then burn the wood inside their huts. And I’ve been in many African huts and found it very difficult to breathe because of the smoke that comes out of their fires.

The United Nations estimates today that, between 1.8 million and 5.2 million women and children die each year, because of breathing in the smoke that they have inside their huts. That’s a dramatic and horrible statistic when you think about it, and that’s because of a poor energy policy and energy availability in those countries. That’s something we can do something about too in terms of helping, if you had an environmental issue; provide good energy to folks, and they won’t have to chop down forests, destroy habitats where wildlife lives and kill themselves with the smoke that comes from burning biomass systems.

MOT: Climate activists claim that you are only a shill for the big oil companies. What would you say about that?

Christy: People who don’t like to accept facts about the observations of the climate system, tend to find other ways to comfort themselves in their beliefs. So if they believe the climate is in terrible shape and we’re all going to be living through a catastrophe, they will find ways to denigrate those who bring facts forward, and so when people say someone like me might be a shill for the carbon industry, they’re just not telling you the truth.

I do not take any money from these industries at all. My funding is from state and federal grants, I perform on those grants, my publications are published in the peer reviewed literature, anyone can read them. My data are on the web so you can analyze and check them out. So it’s just a corner that people like to run to to give themselves comfort when they can’t find an explanation that goes against their beliefs.

MOT: Thank you.

Toimittaja Martti Backman