George Monbiot‘s book Heat covers the limits of our climate-changing actions and the actions that need to be taken immediately in order to avert catastrophe. Here’s the skinny: there is a limit to the amount of CO2 in the atmosphere before we set into motion devastating, irreversible consequences. If we reach this limit we will go past the “tipping point,” the global point of no return.
Malte Meinshausen, a climatologist at the Potsdam Institute for Climate Impact Research quoted in a ScienceNews article, says “If you want to limit the risk of exceeding 2 degrees C global warming to one in four, or 25 percent, then total CO2 emissions over the first half of the 21st century have be kept below 1,000 billion tons.” We’ve already emitted half of that, but that does leave a decent amount left to fill the gap (though we don’t need to fill the gap).
We’ve talked about this limit before: a concentration limit for atmospheric CO2. We want it back to 350ppm from the current level of 389ppm. There are other guesses to this number: some say 400ppm or 450ppm, while others insist we’ve passes it (remember 350ppm). If we continue on our current path without serious emission cuts we’ll hit this upper limit in just a few decades.