Any attempt to curb global warming should include efforts to reduce natural and man-made greenhouse gases in addition to carbon dioxide, MIT researchers show in a report released today by the Pew Center on Global Climate Change.
Using a model developed at MIT, authors John M. Reilly, associate director for research at the MIT Joint Program on the Science and Policy of Global Climate Change; Henry D. Jacoby, professor at the Sloan School of Management; and Ronald G. Prinn, the Tepco Professor and head of the Department of Earth, Atmospheric and Planetary Sciences, show that including all greenhouse gases in a moderate emissions reduction strategy increases the overall amount of emissions reductions and also reduces the overall cost of mitigation.
Although carbon dioxide (CO2), a byproduct of fossil fuel combustion, is the principal greenhouse gas contributing to global warming, methane, nitrous oxide and man-made, industrial-process gases such as hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride also are important contributors to climate change.
From an environmental and an economic standpoint, effective climate strategies should address both CO2 and these other greenhouse gases, the report says.
Due to the high potency of the non-CO2 gases and the current lack of economic incentives, the researchers conclude that control of these gases is especially important and cost-effective in the near term.
"The non-CO2 gases contribute a great deal to climate change, yet there is currently little or no incentive to control these emissions," said Eileen Claussen, president of the Pew Center on Global Climate Change. "Curbing emissions of these greenhouse gases is both environmentally important and cost-effective."
The report, "Multi-Gas Contributors to Global Climate Change: Climate Impacts and Mitigation Costs of Non-CO2 Gases," discusses the sources and amounts of these emissions, the atmospheric interactions of the various gases, and the relative costs of reducing them. The researchers use a general equilibrium modeling framework to analyze the costs and climate impacts of controlling various greenhouse gas emissions.
The report discusses opportunities and difficulties associated with incorporating non-CO2 greenhouse gases into a climate policy framework.
If, for example, total greenhouse gas emissions in the United States were held at year 2000 levels through 2010, many cost-effective reduction opportunities would come from the non-CO2 greenhouse gases.
In developing countries like India and Brazil, non-CO2 gases currently account for more than half of total greenhouse gas emissions. Thus, any cost-effective effort to engage developing countries in climate change mitigation should also include these other gases.