How well do scientists understand climate change?
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Salazar: What is the most important thing for people to understand about climate change?
Moore: I think that the most important thing for us to recognize is that without any scientific doubt, no scientific doubt at all, carbon dioxide is increasing in the atmosphere at about 0.5 percent per year, and that increase is due primarily to the burning of fossil fuels. Secondary causes include land–use change and deforestation.
Right now, the amount of additional carbon being added to the atmosphere each year is about 6 billion tons of carbon as CO2. And that’s an easy number to remember. It’s roughly a ton of carbon per person per year that is being added to the atmosphere as carbon dioxide.
And the other thing that we know for sure is that carbon dioxide is a greenhouse gas, like water vapor and like other gasses, and that’s actually very important to the planet. Without that, this planet would be very cold. But the increase in greenhouse gas concentration, primarily CO2, but also methane, leads to concerns about global warming.
Then other things are a consequence of that. For instance, if you begin to melt the polar ice caps, you decrease the reflectivity of the planet, which would add to the warming. So the first concern is the build–up of gasses, and the second concern is potential feedbacks on other parts of the Earth system, like the arctic ice cap.
Salazar: What role do scientists play in observing the changes happening to Earth right now?
Moore: Scientists, of course, play a key role. That’s because this is an extremely complicated problem. The way we approach the question is, for one, we use the most advanced computers to execute the calculations that result from the physical, chemical, and biological laws that we know, that we’ve deduced over long periods of time, and then to structure those into a mathematical model. Originally we did this for weather, and then for climate, and now we’re looking at the Earth system. So we have mathematical representations of the basic processes of the planet.
The second thing is that models require data. They require huge amounts of data. A primary source of that information is from satellite observations, because you need global data. The types of things that we look at are land cover, the albedo of the planet, ice cover, its structure, sea surface temperature, ocean winds, stratospheric temperatures, cloud patterns and water vapor, which is a greenhouse gas.
All of this information is then compared with what the mathematical models are doing, and through that process we try to improve the models. For instance, how do you test a climate model out a hundred years? You really can’t. Whereas, you can test a weather model every day by predicting the weather and seeing what happens. So we use climate variability such as El Nino, or North Atlantic oscillation, other large–scale climate patterns. And these become the proof principle, the test of the porridge, how well we’re doing, how well do we understand the system.
Salazar: How much progress has been made in scientists’ understanding of climate change?
Moore: I think that we’ve really made quite remarkable progress in the last ten or fifteen years on understanding the Earth system, and in particular the climate of the Earth. Part of that has come about through increased observations and deeper understanding of the processes. But frankly, we also now have the computing power to execute a number of these known calculations. I believe that we’re narrowing in on the critical phenomenon.
There are some key issues that still remain very, very difficult. For instance, as you warm the planet, you will increase water vapor in the atmosphere. That will lead to an increase in bright clouds, which could then increase the reflectivity of the planet, which could cool the planet. This is a very tough problem, because, water is a greenhouse gas. As you put more water vapor into the atmosphere, you further warm the planet. But, perhaps there could be a feedback loop which could cool the planet.
Salazar: What are the greatest problems we’ll face in a warming world?
Moore: The greatest problem we’re facing may well be that changes in the patterns of precipitation will have a very, very profound impact. That’s a much tougher thing to predict than simply temperature, even the distribution of temperature.
And another on the minds of many is, are we going to see an increase in the severity of severe storms? There are already indications of that. So, questions of changes in the distribution of rainfall, changes in the distribution and magnitude of severe events, these are the kinds of things that really affect people’s lives. And those are the kinds of challenges that we’re going to have to step up to in the next ten years.
Berrien Moore is the director of the Institute for the Study of Earth, Oceans, and Space at the University of New Hampshire.
