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Last week we talked about the major emitters of carbon dioxide (CO2), but why does that matter? We’re talking about climate disruption, but why is CO2 the main indicator and at what level do we have to worry?


The greenhouse effect

There are many greenhouse gases in the atmosphere. The two with the biggest impact are water vapor and carbon dioxide. Why do we only talk about carbon dioxide? There is one major difference between the two gases. In the water cycle, water evaporates, then condenses, and falls back to the earth as precipitation. Any extra humans pump into the air falls out as rain within a couple of days. In the carbon cycle some carbon is emitted when vegetation decays, but it’s then re-absorbed by weathering rocks, the oceans, and plants. But humans add extra CO2 faster than it can be reabsorbed. This extra builds up in the atmosphere because it can’t just “rain” out.

Before the industrial revolution when we started to burn fossil fuels and deforest large areas, the atmospheric concentration was around 280 parts per million (ppm). Since then, CO2 has built up to nearly 400 ppm (and we’re adding about 2 ppm every year). With more CO2, the atmosphere traps more heat (like adding an extra blanket). We know average surface temperatures have risen about 0.8 degrees C. This is an average, so temperature in places like the Arctic and on land have risen more and places near the equator less.

Political consensus

Several years back, many countries got together and agreed to try to limit warming to 2 degrees C. This means that if we can limit the atmospheric concentration to 450 ppm, we’ll have a 50% chance at avoiding “very dangerous” climate change. That doesn’t sound like a very good gamble and we look unlikely to even hit the goal, but it’s been nearly impossible to get countries to agree to anything stricter.

So where does 350 come from?

2 degrees C of warming historically corresponds to many meters of sea level rise. This will probably be a slow increase; most estimates are an additional 2 to 3 feet rise by 2100. While not catastrophic to the world this will impose huge costs, cause millions to migrate higher, and could still wipe out low-lying countries and areas. Some scientists, including Jim Hansen, suggest that to stop this sea-level rise, we need to reduce the concentration to 350 ppm. This is how 350.org, the green group got its name.

In a Rolling Stone article, Bill McKibben made it clear that we’re in trouble. Since CO2 stays up in the atmosphere for hundreds of years, we can’t simply say that ppm CO2 will start decreasing once we stop emitting. It matters how fast we stop emissions. And fossil fuel companies currently claim to have five times as much fuel as we can burn before reaching 450 ppm. That means that if world leaders are serious about reaching that goal, then nearly 80% of all fossil fuel stocks are worthless because we will not be able to burn their products.

But what about CO2e?

In the last post, we talked about the unit CO2e. This converts other harmful greenhouse gases to a single measure. If we count other GHGs like methane and nitrous oxides, we’re already near 480 ppm CO2e.

FML, what can I do?

If you have an hour to explore these ideas further, check out climate scientist Dr. Kevin Anderson’s presentation about our current predicament. Then, I recommend you DO SOMETHING. We ultimately need government-level leadership, so start demanding climate action from your representatives. If you have the skill sets, start organizing for climate action or working on creating better technology solutions.

As comparatively wealthy citizens of the planet, I also suggest you try one or more of these personal actions suggested by David McKay. Many of these changes can make a big impact if enough people adopt them. Many can save you money and I can tell you that my quality of life is just as good after making some of these changes.

Any more ideas? Post them in the comments.