CLIMATE CHANGE: what does it mean?

Day 5 - Greenhouse Gases

The characters in this seven-day dialogue are described in the Foreword. Please read it first to get a better appreciation of what they're saying.

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Chaud: Carbon dioxide is not the only greenhouse gas. Why is it the only one talked about?

Froid: There are many, but CO2 is the most important because of the large quantities stored in the oceans and produced by anthropogenic (human-made) activities each year. Its concentration in the atmosphere is currently about 400 parts per million (ppm). Methane (CH4) is next in importance. Even though its global warming potential is much higher than carbon dioxide, its concentration in the atmosphere is only about 2 ppm. Nitrous oxide (N2O) is third in importance. And although its global warming potential is much higher than both CO2 and CH4, its concentration in the atmosphere is much less than 1 ppm. So, CO2 being the biggest source gets the most attention.

Chaud: How much anthropogenic greenhouse gas do we emit into the atmosphere annually?

Froid: The 2010 emissions were: 31.1 billion tonnes of carbon dioxide, and the equivalent of 6.9 billion tonnes of CO2 in the form of methane. Therefore, methane accounts for about 22% of carbon dioxide emissions, or 17% of the combined total. They are not insignificant.

Chaud: Where do methane emissions come from?

Froid: The biggest contribution is from livestock and the second is from oil and gas extraction. Together, they account for more than two thirds of the total.

Chaud: I bet you that the biggest emitters of greenhouse gases are the Chinese because they burn so much coal and their cities are so polluted.

Froid: There's no disagreement on that one. With an annual rate of 8.3 billion tonnes per year, China is by far the biggest emitter of CO2 into the atmosphere. It accounts for about 25% of the world total. The U.S. is second with 5.4 billion tonnes per year, or 16% of the world total. However, on a per capita basis, the U.S. is still the biggest. The world average per capita emission of carbon dioxide is 4.9 tonnes per year. Over the past three decades, U.S. per capita emissions ranged between 18 and 20 tonnes per year. China's emissions more than doubled in the last decade, but at 6 tonnes per year they are less than a third of those in the U.S. Unfortunately, it's the Americans, not the Chinese that are the biggest emitters. Moreover, by exporting manufacturing jobs to China, the U.S. has also exported pollution and greenhouse gases to them, so now they can point to them and say, "They're the problem!"

Chaud: I know that coal is the biggest contributor to carbon dioxide emissions: what are the others?

Froid: According to the U.S. Environmental Protection Agency, electricity production accounts for 37% of U.S. emissions, most of which come from burning coal. Interestingly enough, transportation is a close second at 32%, most of which come from burning petroleum products. To complete the picture, manufacturing accounts for 15%, commercial and residential heating 10%, and natural sources 6%.

Chaud: Shutting down coal-fired plants would certainly have a significant impact. I'm amazed how small the contribution from humans and animals is. Even if the whole country went vegetarian it wouldn't make a significant difference.

Froid: Actually, it would make a significant difference to greenhouse gas emissions because livestock produce a lot of methane, which has a much higher global-warming potential. So going vegetarian would help reduce not only greenhouse gas emissions but also demand for clean water, which in some areas is already a major problem. California is a good example. In any case, if every American became a vegetarian, greenhouse gas emissions would be reduced by almost 5%. Promoting a vegetarian lifestyle would reduce the number of livestock raised to supply a protein-rich diet to an increasingly obese population. Not only would this be healthier for the population, it could also be beneficial for our biosphere.

Chaud: Are you saying that greenhouse gas emissions are largely due to America's lifestyle?

Froid: Although America is still a big part of the problem it's not alone. The American lifestyle has been exported throughout the Western world, so other members of the OECD are catching up to America's high-protein diet and overconsumption.

We cannot be serious about reducing greenhouse gas emissions, if we're not serious about reducing per capita consumption of not just energy, but everything. The "we" refers to OECD countries, the richest, and those most responsible for the problem.

Keep in mind that greenhouse gases may be saving us from the onset of the next ice age! Nevertheless, while they might delay, or advance, it by a century or so, eventually the cooling cycle will start again, as it has for billions of years, and the northern hemisphere will once again be covered with ice! There's nothing we can do about it. It's preordained by the celestial cycles!