A central issue in dealing with climate change is determining how much carbon we can emit into the atmosphere before global temperatures increase too much. How much is too much? Most experts think that if average temperatures increase by more than 2 degrees Celsius (3.6 degrees Fahrenheit), the consequences will be severe and irreversible.
Despite lots of short-term climatic variability, the relationship between average global temperatures and the concentration of greenhouse gases in the atmosphere is fairly straightforward and the big problem is that much of the carbon we dump into the atmosphere will stay there for centuries.
So the concept emerges for a carbon budget. The most recent report by the Intergovernmental Panel on Climate Change puts the cumulative carbon emissions to date at over 500 billion tons. The world currently emits about 10 billion tons of carbon each year.
So how much more can we afford to emit without dire consequences? What is our carbon limit?
Unfortunately, there is not total agreement on this. The IPCC says we have 485 billion tons to go. The Earth Institute at Columbia University says 350 billion tons. A European consortium says 250 billion tons.
Furthermore, these models are couched in terms of probabilities of keeping global temperatures below the 2-degree rise, not certainties, and even that metric itself is not a guarantee of safety. In many ways, the effects of climate change are outpacing the simple rise in temperature. More important than any of these numbers, if our policy makers don’t put in place action plans, our problems are bound to increase.
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What Is the Carbon Limit? That Depends Who You Ask
Photo, posted September 21, 2014, courtesy of Peter Bowden via Flickr.
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Earth Wise is a production of WAMC Northeast Public Radio.