Dear Umbra,

I have heard and am beginning to understand one of the biggest movements of social change occurring right now: we need to reduce our carbon footprint. I have also heard that while carbon is our most abundant greenhouse gas byproduct (by way of the burning of fossil fuels) other gases, such as methane, are actually far more potent in their ability to alter our global climate … What can I do to reduce my contributions of these other gases? Should I be concerned?

Jamie G.
Bingen, Wash.

Dearest Jamie,

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It’s right to be concerned about reducing our carbon footprint, and it’s good to learn details about what behaviors increase global warming gases in the atmosphere. It’s also easy for today’s concerned citizen to skip the details, and go directly to tips on reducing a carbon footprint. Because even though it’s called a “carbon” footprint, any decent set of instructions will include all relevant gases.

carbon footprint protest

Watch your step.

Let’s have a closer look at the gas issue, then talk about steps you can take.

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Human-produced greenhouse gases include carbon dioxide (CO2), which is the most prevalent by weight, methane (CH4), nitrous oxide (N2O), and fluorinated gases such as hydrofluorocarbons and perfluorocarbons. A simple place to start reading about these is on the EPA site. As you note, some of these gases alter the climate more than others, on a per-pound basis. Since climate modeling, policy, and conversation require a lot of math, climate scientists have developed standard units for comparing and examining the gases.

This here paragraph is for the truly committed; feel free to skip to the next one. Now then: One unit used to compare gases is Global Warming Potential. All greenhouse gases have the potential to contribute to radiative forcing/global warming at varying levels over the same period of time. So scientists assign a global warming potential value to each gas, which they use as a multiplier to convert it into carbon dioxide equivalent, or CO2E. Over 100 years, for example, carbon dioxide gets a Global Warming Potential of 1, and all other values are relative to that 1; e.g., methane has a 100-year GWP of 21. Having everything in carbon-equivalent units makes it possible to talk about global warming impacts without lots of parenthetical remarks, such as “We’d better not burn coal, as a ton of coal releases x amount of carbon dioxide (not to mention x amount of methane, a greenhouse gas twenty times more potent!).” You can get a better handle on these concepts at the Pew Center Climate Change site.

All that is to say that a good source of global warming activism information will include all the greenhouse gases in their recommendations for a greener life, perhaps even giving you impacts in CO2E rather than CO2. They just might not be telling you that’s what they’re doing. When in doubt, inquire.

As to what you can do: The production and consumption of coal and natural gas emit both CO2 and methane, so for most of us reducing our electricity use helps with both. Ruminants emit methane in their breath and poop, so as we cut back on eating cows, sheep, and goats and their products, we slim down our methane footprint as well as our CO2 footprint. Nitrous oxide is emitted from fossil fuel combustion, so using clean engines, and using them less, helps with N2O as well as carbon. A particularly methane-y thing you could cut back on is the amount of garbage you send to the landfill.

I’ll try to write about this more as we finish up March and move toward Earth Day ’09, so we can all get a little updated on what we should be doing about climate change.



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