Buying Time on Climate Change

While much of the discussion of climate change revolves around carbon dioxide because of its primary role in increasing average global temperatures, many other chemicals other than CO₂ can have an effect on the climate. Two such important contributors to global climate are the greenhouse gas methane (i.e. the primary component of natural gas) and black carbon (soot from incomplete burning). Methane is emitted by a variety of sources both natural and human such as wetlands and rice paddies, as I had discussed in a previous article about the methane cycle. Black Carbon is nothing more than the smoke common in wood fires or any kind of incomplete burning from diesel or coal burning. It also can absorb heat in the atmosphere and cause warming, and when deposited on snow or ice, can decrease its cooling ability by reducing its albedo or how much light it reflects. Both methane and soot have much shorter lifetimes than carbon dioxide in the atmosphere, at 11 years and weeks to months respectively compared to 170 years for carbon dioxide, making them attractive targets for short to medium term reductions in emissions related to climate change.

In addition to their effects on climate, methane and black carbon are also problematic emissions because they both act as precursors to photochemical smog and because black carbon is a big component of particulate emissions that are really bad for your lungs. Because reducing both these emissions would have a public health benefit beyond any changes to the climate, emission reductions of methane and black carbon could potentially be an important first stem to slowing climate change. In a recent Science article (gated), Drew Shindell, a NASA scientist, and a team of scientists and economists from around the world identified various technologies available now and possible regulations that could reduce methane and black carbon emissions immediately. They then calculating the costs of of implementing these new technologies and compared them to the potential benefits on public health, crop yields, and climate. The benefits of reducing both far outweighed the costs, in reduced impacts from changes in climate from differences in precipitation patterns, crop yields, and premature deaths. In particular, the reductions in black carbon resulted in an enormous benefit in terms of reduced premature deaths since particulate emissions such as black carbon are pretty bad for human health. Most of the benefits were realized in India and China (where black carbon emissions are much, much worse than in the United Stats or Europe) in the form of avoided changes in the precipitation patterns crucial for agriculture. However, the United States also benefited from potential increases in crop yields due to less photochemical smog from methane emissions. The ozone formed in photochemical smog, in addition to being a lung irritant, also reduces crop yields. Plants reduce atmospheric uptake in high concentrations of ozone because of its highly reactive nature, which can damage the inside of the plant as easily as it can damage your lung tissue.

For climate change, the full implementation of their recommended technologies and regulations would actually in the short to medium term help slow the pace of climate change relative to a "business as usual" scenario. This interactive graphic from NASA that accompanied this publication shows how under different "climate sensitivity" (how much the temperature changes in response to increased CO₂) scenarios the implementation of CH₄ (methane) and BC (black carbon) measures can reduce the expected warming. Depending on how sensitive the climate is to changes in CO₂ these measures delay the time it takes to reach 2^oC degree warming threshold that many scientists consider to be a dangerous threshold for the climate. This gives all of us some "breathing room" (so to speak) to develop alternatives to fossil fuel burning as a source of energy because even with these measures CO₂ is still the primary mover of climate change. Many times it's extremely under-appreciated just how challenging it is to develop alternatives to fossil fuels as it may be decades before a true alternative can be developed. This study gives us hope that we can eventually tackle climate change without dramatic changes to living standards or a halt to the increasing prosperity that free trade and liberalizing reforms are bringing to the developing world.

Related Links:
An interview with Drew Shindell, the primary author of this study