Science suggests that to mitigate the human contribution to global warming, we should reduce carbon dioxide and other greenhouse gas emissions. Because some additional warming is inevitable—even if we achieve significant greenhouse gas reductions quickly—we should make plans to adapt to coming climate change. If we are unable to control emissions and/or adapt to unavoidable changes quickly enough, a carefully selected geoengineering strategy could conceivably provide an emergency stopgap to slow global warming. As yet, however, several of the strategies being discussed are very risky and unproven.

Controlling Emissions
Controlling emissions is a large, complex, and potentially expensive problem that no single strategy will solve. On the other hand, the costs of uncontrolled global warming will probably also be significant. Many economists have concluded that putting existing scientific and technological strategies into place and developing new ones may stimulate the economy, and would also generate significant near-term benefits in public health through air pollution reduction.

The Carbon Mitigation Initiative, a university and industry partnership based at Princeton University, has identified strategies—based solely on existing technologies—that used in combination over the next 50 years, would keep the amount of carbon dioxide in the atmosphere from more than doubling the pre-industrial level. (Many scientists believe doubled carbon dioxide levels will cause a dangerous interference with the climate.) These strategies are:

1. Increase the energy efficiency of our cars, homes, and power plants while lowering our consumption by adjusting our thermostats and traveling fewer miles;
2. Capture the carbon emitted by power plants and store it underground;
3. Produce more energy from nuclear, natural gas, and renewable fuels—solar, wind, hydroelectric, and bio-fuels;
4. Halt deforestation and soil degradation worldwide, while reforesting more areas.

Some of those strategies will have to be put into place by governments and industry, but individuals can also do a lot on their own. On average, individual Americans emit 19 tons of carbon dioxide annually while driving our cars and heating our homes—more than people in any other country. If we can reduce our personal emissions by just 5 percent, total U.S. emissions would drop by 300 million tons. That reduction could be easily achieved by replacing appliances and light bulbs with more efficient ones, planning our automobile trips more carefully, driving more fuel-efficient cars, taking fewer flights, and so on.

By learning about global warming, by communicating with elected officials about the problem, and by making energy-conscious decisions, individuals will play a meaningful role in what must be a global effort to respond to global warming.

Adapting to Climate Change
Climate has been fluctuating throughout Earth’s history, and recently, humans have become one of the factors contributing to climate change. Changes related to human activity are already being felt. Even if we were to stop greenhouse gas emissions today, additional climate change from emissions already in the atmosphere would be inevitable. For this reason, many governments and industries are beginning to adapt policies, disaster response plans, or infrastructure to prepare for anticipated changes. While some adaptations are difficult and expensive, many are relatively inexpensive and offer immediate benefits.

Adaptation strategies vary from region to region, depending on the greatest threat posed by climate change locally. For example, coastal regions facing rising sea levels and increased coastal erosion might eliminate incentives to develop high-risk coastlines and encourage a “living buffer” of sand dunes and forest between the ocean and infrastructure. New York City has already integrated climate change into the process it uses to plan future development, reducing the need for expensive retrofitting later.

Local governments may adjust disaster response plans to accommodate changes in weather patterns. The city of Philadelphia recently implemented an emergency response plan to limit the health impact of increasingly frequent heat waves on its population. Philadelphia officials estimate that their heat response plan has already reduced heat-related deaths.

More extreme and expensive adaptations may become necessary in some regions. Thawing permafrost and increased storms, windiness and coastal erosion are now putting at least 166 communities at risk in Alaska. Moving each community to safer areas will cost an estimated 30 to 50 million dollars per village, estimates the U.S. Army Corps of Engineers. Six communities have already decided to relocate.

For individuals, governments, and businesses, adapting to climate change requires understanding and accepting the risks of regional climate change, assessing the immediate and long-term costs and benefits of adaptation strategies, and implementing adaptations that bring the most benefits relative to the cost and risk.

Geoengineering
Though risky and unproven, geoengineering could provide another near-term strategy for slowing global warming until carbon emissions can be reduced enough to prevent catastrophic climate change. In this context, geoengineering means deliberately altering the atmosphere, land, or ocean to counter the effects of global warming.

Many geoengineering schemes have been proposed, but all can be reduced to two main strategies: reduce the amount of greenhouse gases in the atmosphere (increase the amount of infrared radiation escaping to space) or reduce the amount of solar energy the Earth system absorbs. Two of the most common examples of these geoengineering strategies involve removing carbon from the atmosphere by adding fertilizer to selected regions of the ocean to increase phytoplankton growth and reflecting more sunlight by injecting tiny, non-absorbing particles (aerosols) into the upper atmosphere (stratosphere).

While both of these geoengineering examples might counter global warming for a time, they could also have significant drawbacks. Increased fertilizers and/or phytoplankton growth could have unintended consequences on ocean ecosystems, including increased ocean dead zones and toxic blooms. Adding aerosols to the upper atmosphere could modify the chemistry of the upper atmosphere, affecting ozone and thereby having possible unintended impacts on the lower atmosphere.

Because the impact of geoengineering on the complex global climate system hasn’t been extensively studied, any large-scale geoengineering strategy could have serious unexpected consequences. As a result, most scientists consider geoengineering only as a last-resort, emergency measure.

1. References

2. America’s Climate Choices. (2010, May). Adapting to the impacts of climate change. National Research Council of the National Academies. Accessed July 16, 2010.
3. Intergovernmental Panel on Climate Change. (2007). Summary for Policymakers. In: Climate Change 2007: Mitigation of Climate Change
   Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
4. Pacala, S., and Socolow, R. (2004) Solving the Climate Problem for the Next 50 Years with Current Technologies. Science, 305 (5686), 968-972.
5. Parkinson, C. L. (2010). Coming Climate Crisis? Consider the Past, Beware the Big Fix. Lanham, Maryland: Rowman & Littlefield Publishers.
6. Robock, A., Marquardt, A., Kravitz, B, and Stenchikov, G. (2009, October 2). Benefits, risks, and costs of stratospheric geoengineering. Geophysical Research Letters, 36, L19703.

7. Further Reading

8. The Carbon Mitigation Initiative, is a collaboration between Princeton University, BP, and Ford to find solutions to the global warming problem.
9. The Energy Star Website, published by the U.S. Department of Energy and the U.S. Environmental Protection Agency provides information for individuals and businesses on making energy-conscious choices.

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