The Triangle

Issue date: 8/6/04 Section: Sci-Tech

Media Credit: Sydney Morning Herald The arctic ice sheet has receded alarmingly over the past few decades. It is likely to disappear altogether over the next century, with climate repurcussions on a global scale.

Susan Kilham is a professor of environmental science in the Department of Bioscience and Biotechnology. This interview was given July 20, 2004.

The Triangle: What do we know right now about climate change? We know that carbon dioxide is a greenhouse gas, that its concentration is increasing in the atmosphere and in the past 100 years, the Earth has warmed.

Susan Kilham: We know a lot because we are now beginning to understand some of the connections between increased CO2 and a lot of other processes that are happening in the world.

For example, I just read a paper in Nature or Science, one of those two, over this past week that shows there's a lot more dissolved organic carbon being released in the tundra areas into the rivers ... in the northern areas. The polar regions are warming faster than the middle regions of the Earth.

This is very interesting and a big change in how stream ecosystems work, and there were a lot of competing hypotheses for why this is happening.

This paper studies a lot of [reasons] why things could be happening, but what is happening is increased uptake of CO2 [by plants that need it for photosynthesis] and consequently increased processing of CO2 and higher growth rates. Because of these increased growth rates, they are releasing more dissolved organic carbon into the rivers and streams.

?: But there's no net increase in CO2. It's simply being taken from the atmosphere and being put into the streams, right?

SK: Well, this DOC (dissolved organic carbon) is actually changing the rivers because, for example, DOC keeps UV radiation from penetrating very far and that changes the dynamics of these very sensitive ecosystems. It also increases bacterial metabolism, since the bacteria are heterotrophs and take up this dissolved organic carbon and use it as food. As the bacterial growth rates increase, the biogeochemistry is changing. The other thing about global warming that I'm particularly interested in is the whole current system of the ocean.

?: This is the phenomenon that was exaggerated in the movie The Day After Tomorrow, right?

SK: Yes, everything was exaggerated in that movie. That was interesting because the National Center for Atmospheric Research in Boulder, Colo. wrote a piece about that movie and they said it was interesting because really what the movie did was take a couple of plausible scenarios and take the most extreme case of those.

So each piece of that had some measure of probability to it, but it was always the most extreme case and they put it together in truncated time scales.

?: So what changes are we seeing in the ocean currents right now?

SK: They're slowing down. What's happening is that the polar ice in the arctic ocean is shrinking. The sea ice melt in the arctic does not increase the ocean levels, because that water is already displaced. But it does increase the fresh water content of the sea water, diluting it a little bit.

And that affects the world's current system, because the world's current system is driven by the cold, very salty water, and thus very dense water in the North Atlantic sinking deeply at a very rapid rate. We are talking about billions of gallons per minute here. That drives the entire ocean current system. So this sea ice melt is decreasing the density of the water that is sinking, and thus as the water becomes less dense, it isn't sinking as rapidly and it's not sinking as deeply.

?: How much change have we seen in the amount of time we are measuring this?

SK: The problem here of course is in sampling this, because sampling in the ocean is extremely difficult. But they are putting in all the buoy systems and so forth, and so they are observing this decreasing density of the North Atlantic deep water and the decreasing rate at which that water is moving. Really, they don't have a really long record, maybe 25 years or so ...

?: But enough to see a trend that is happening gradually ...

SK: Absolutely!

?: So we're seeing all these changes. We're putting more carbon dioxide into the atmosphere, we're cutting down trees that pull out carbon dioxide from the atmosphere. So is it safe to say that we are increasing the net amount of carbon dioxide in the atmosphere by a rate unprecedented before?

SK: Yes, exactly.

?: Right, so what can we reasonably anticipate now? For example, you said the polar regions are warming faster than the equatorial regions. Why is that?

SK: Well, that's because the distribution of heat on the Earth is driven by current systems and the result of that is that the warmer air tends to flow towards the poles from the equator.

As a result, the amount of warming is much greater in the polar regions than it is in the more temperate and equatorial latitudes. And this is a combination of air currents and oceans interactions; these air-ocean interactions drive our planet's climate.

And that's why things such as trying to make a connection between a change in the rate of the major ocean currents and some change in the atmosphere, how they interact, is not an easy thing to come to grips with. We don't have the long time scales of measurements.

?: I read a report awhile back about beetles and other herbivorous insects in northern Canada, Alaska and Siberia that had increased metabolic rates due to warmer temperatures, and were thus eating away at the boreal forests at increased rates. And that in turn leads to a further reduction in the carbon sinks (the forests) and increased amounts of CO2 in the atmosphere to continue the cycle. Is that what your research has focused on?

Media Credit: http://www.sucarha.com

SK: My research isn't concerned with that, although I have read about it. What I'm more concerned about is the melting of the permafrost, because that can kill whatever is perched on top of the permafrost, and the taiga and the boreal forests are usually sitting on top of this.

What happens when the permafrost melts is that the soil can become very waterlogged and it can kill the trees as a result of that. Also when the soil becomes waterlogged, it becomes anoxic and all the bacterial processes that go on in anoxic conditions increase and result in releasing large amounts of CO2.

And so the waterlogging of the soils, increased CO2 release from bacteria, and the subsequent death of the trees is a really serious problem. And this year, it's been hotter in some areas of Alaska than even here in Philadelphia. And the big problem is of course that there are a lot of animals that depend on the sea ice. Polar bears, for example, are suffering really badly. They are being killed by toxic chemicals and their habitat is being taken away from them.

And since they only feed on the sea ice, the amount of time that they have to feed and accumulate enough fat to get through the summer is becoming lesser each year. They can, of course, feed during the summer, on the permanent sea ice in the middle of the Arctic, but the vast majority of them come ashore [onto the North American continental landmass] during the summer and don't feed at all. Churchill, Canada is famous for that, and so that's a big problem we are facing right now, and we are seeing them slowly becoming extinct.

?: We're talking about the ones on the North American continent? Not the ones in the Arctic, right?

SK: Well, no, we're talking about polar bears in general. The ones that still have their sea ice are being killed by toxic chemicals. Polar bears are pretty much going to go extinct in the next couple of decades. There's no way to avoid it.

They're already having huge problems. It's a result of all the toxicants that are released into the atmosphere. Due to air currents, all these toxic chemicals get channeled towards the poles, and something known as a cold air distillation process takes place in the atmosphere that concentrates these pollutants. And so polar bears have extremely high concentrations of these toxic chemicals in their bodies.

This is because the polar bears are at the top of the food chain, and all the toxic chemicals absorbed by animals lower down on the food chain go through a process called biomagnification and accumulate in the polar bears in high concentrations.

And of course it's more severe in these animals because they have special mechanisms for concentrating all the fat for long term storage, and a large amount of these toxic chemicals are readily fat soluble. So we're finding many bears these days that have serious developmental problems.

For example, we're finding bears that have both male and female sex organs, neither of which are functional. So these bears are doomed, with zero ecological fitness. There are also many other developmental problems we are seeing because these chemicals are endocrine disrupters, and they disrupt the development of the fetus.

?: Let's suppose that we reach maximum efficiency and we emit carbon dioxide at the current rate we are emitting, without any increase. This itself is very hard to do, but let's say that we can somehow keep carbon dioxide emissions constant at year 2000 levels, what can we expect to see? We're obviously going to see some changes, but can we avoid an environmental disaster without an economic disaster?

SK: My personal opinion, I doubt it. First of all, CO2 emissions are going to increase because there are no major attempts by the major CO2 producers of this world to decrease the increase of CO2, the United States being number one and China coming along very quickly on its coattails. The rate of fossil fuel consumption and CO2 emissions have are shooting up very rapidly.

?: Right, because China recently became the second largest consumer of oil in the world after Japan.

SK: Yes, and this is also because of their size. This problem is not going to go away. Their population is still increasing. So what we've done with population is slow the rate of increase, and that's a good thing. But we're still going to have about 10 billion people by the year 2050 and that's a lot of people. They'll be cutting down more trees, they're going to be burning every last bit of fossil fuel that we have by 2050.

?: So what can we do?

SK: Well, I'm not a good person to ask because I'm a pessimist. But there are people who aren't pessimists. There are many conservation organizations and things like that through which people work to try and make things better. I think that the problem is a political one.

There is no political will for this. People in U.S. or China or other countries don't vote on environmental issues. You gather 100 people and ask them whether they voted for one candidate or the other based on environmental concerns, and you're not likely to find many people who voted for that reason.

And I have a big concern about that. I think that the political will has to be there to stop this nonsense.

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