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News & Publications

Q&A with atmospheric chemists Kristie Boering and Ron Cohen

Professor Ron Cohen

Professor Ron Cohen

The spring 2006 edition of the College of Chemistry’s NewsJournal features the global warming research of atmospheric chemists Kristie Boering and Ron Cohen. To accompany the article we’ve included this Q&A session with Boering and Cohen about climate change and its implications.

1. Does there remain any scientific basis for the viewpoint that global warming could be the result of natural (not man-made) forces?

A. No, not anymore. In year 2000 scientists were still cautious, but now we have six more years of data and the climate models are working well. You just can’t explain the pattern of temperatures without taking into account human-caused increases in greenhouse gases.

2. What advice would you give to a friend who was considering returning to New Orleans? Was hurricane Katrina a fluke, or is it a sign that global warming is producing bigger storms?

A. Independent of the global warming connection to hurricanes, the increase in population in coastal zones means that we are likely to see more devastation in the Gulf States in years to come. As for the climate effect on hurricanes, the scientific connection is just beginning to develop. It is true the gulf is warming, and a scientific case has been made for a connection between this warming and hurricane intensity. Critical thinking about these new results and a longer record of gulf storms (hopefully with less loss of life and property) will help us understand how storms are changing in response to other changes in climate.

boeringProfessor Kristie Boering

3. The preindustrial carbon dioxide level was about 280 part per million (ppm). It’s now about 380 ppm, and even very optimistic scenarios have levels stabilizing at around 500 ppm. Do you think this is achievable?

A. To achieve this we will require extremely aggressive reductions in emissions. More efficient use of energy can be a major contribution, but even with major efficiency improvements we also need new technologies for power generation including a mix of solar, wind, hydrogen, nuclear and other non-CO2 producing strategies. Capture and storage of CO2 is also a possibility.

4. The relationship between ozone air pollution and global warming is a positive feedback loop — as temperature and humidity rise, the chemical reactions in the atmosphere increase the production of ozone, leading to further climate change. Is this true for other greenhouse gases like carbon dioxide, nitrous oxide or methane?

A. The main positive feedback loop is water. As temperatures rise, the atmosphere can hold more of the main greenhouse gas water. There are both positive and negative feedback loops for the other greenhouse gases, and much of current research is aimed at identifying which one will win out.

5. One possible beneficial negative feedback loop is the more rapid growth of plants in an atmosphere with elevated amounts of carbon dioxide. But recent studies are less optimistic about faster plant growth. Will more rapid plant growth help solve the problem of global warming?

A. In the long run, you can’t store enough carbon in forests to continue burning fossil fuel indefinitely. Sooner or later the trees die, decompose and return that CO2 to the atmosphere. The hope was that there was room to grow forests now and forestall the need for other drastic measures. There remains significant potential for growing forests to slow the CO2 increase, but recent research says not quite as much potential as we might have hoped for.

6. Clouds can either help reflect light away from the earth, having a cooling effect, or help trap more heat close to the earth’s surface, having a warming effect. Do climate scientists understand the relationship between global warming and cloud formation well enough to say how clouds will affect global warming and vice versa?

A.  We still have a lot to learn about clouds and rain. This is an area where one of the largest uncertainties in climate science resides — and with it some of the most interesting chemistry and some of the most challenging computational science. We need to be able to predict from first principles whether human emissions are changing the number of particles in the atmosphere on which cloud droplets form. At the same time we need to observe the chemistry of clouds and confirm that predictions of a first principles model do indeed describe clouds and their properties.

7. The victims of Hurricane Katrina may be just the first of a coming wave of climate refugees — people forced to move because of rising sea levels, coastal flooding and more violent storms. Countries like Bangladesh and remote, low-lying island countries like Tuvalu are thought to be the most vulnerable. Will we see climate refugees become a political problem?

A. In some places, we are going to see massive engineering projects such as the New Orleans levees and the dikes in the Netherlands as countries try to preserve the land people are living on today. In other places, millions of people will eventually be forced to move.

8. In Europe, financial markets are starting to grow for globally traded carbon rights. These CO2 pollution permits limit the total amount of carbon that can be added to the Earth’s atmosphere, but can be traded between companies and countries. Do you think the U.S. will eventually be part of this trading system? How will compliance be monitored?

A. There is already a U.S. trading system in place on the Chicago exchange. California and many other states are developing policies to participate and require the participation of companies doing business in their states.

9. Should we be optimistic or pessimistic about the future? Will the necessary scientific and technical solutions, and the political will, be found to manage climate change?

A. We need to move aggressively to be more efficient, and to find alternate sources of energy so we get on a path to stabilizing greenhouse gas levels as quickly as possible. At the same time we need to develop new predictive capabilities that can describe the consequences of climate change on the regional scale — especially predictions of changes in the number of extreme events such as severe storms, flooding, or heat waves. Here in California we need to worry that the snow line will rise, affecting the availability of water during the late summer (not to mention skiing). We are optimistic that with continued progress in climate science and some important new sources of energy there will be a growing political will to manage climate change.

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