EmissionsIn a recent article for the New York Times, Justin Gillis tackles the “lesser of two climate evils,” pitting methane against CO2. Both greenhouse gases are bad for the environment, but how bad is a matter of (several) degrees.

That man-made emissions are contributing to global warming is past the point of debate. What is up for debate, Gillis writes, is how much damage emissions are doing and which emissions are in need of immediate reduction.

President Obama’s new climate change plan, released in early June, calls for the nation’s power plants to reduce their carbon dioxide emissions by 30 percent (from 2005 levels). This will necessitate the use of other energy sources – more renewables, preferably, but more natural gas undoubtedly.

But is this what’s best for the environment? Natural gas consists mostly of methane, a potent ingredient in global warming. It is released into the environment during the mining of coal, and in drilling for oil and gas. Agriculture is also a huge contributor, with global livestock accounting for about 14.5 percent of greenhouse gas emissions – 44 percent of which is in the form of methane.

Methane is a stronger gas than carbon dioxide, yet unlike carbon dioxide its lifespan in the atmosphere is much more brief. Whereas CO2 lingers in the atmosphere and moves throughout the ecosystem, methane dissipates after approximately 12 years.

Dr. Raymond T. Pierrehumbert, a climate scientist at the University of Chicago, puts it best: “[M]ethane is like a hangover that you can get over if you stop drinking. CO2 is more like lead poisoning — it sticks around, you don’t get rid of it, and it causes irreversible harm.”

Scientists that share Pierrehumbert’s view say that world governments should focus their efforts on reducing CO2. Methane emissions need to be dealt with as well, but methane’s long-term effects are not nearly as dire.

There are scientists who disagree, however. Drew Shindell, a NASA climate scientist, believes that, while methane dissipates faster than carbon dioxide, it is easier to deal with right now. “[O]ur success in controlling CO2 emissions is likely to make very little difference on temperature over the next 40 years,” he says.

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