Balanced Climate Sensitivity: Framing the Future of Global Warming

For decades, scientists struggled to determine how much the Earth would warm for a given amount of carbon dioxide in the atmosphere. The term for this is Equilibrium Climate Sensitivity (ECS). The classic way to put it is to ask what happens if we double the amount of carbon dioxide in the atmosphere from the pre-industrial revolution level, which was 280 parts per million (ppm). (Today it is 415 ppm.)

Historically, the ECS has been estimated between 1.5 and 4.5 degrees Celsius, but in July 2020 a team of 25 scientists from around the world recalculated the ECS using more data than was previously available. They determined that the ECS is actually between 2.6 and 3.9 degrees Celsius. This is a narrower range than before, and the low is 1.1 degrees higher. This means that, without serious mitigation efforts, the Earth will warm faster than expected.

Based on current trends in energy consumption and taking into account the growth of renewable energy, some estimates predict that the concentration of carbon dioxide will reach 560 ppm (a doubling of 280) by 2050. If we take cautiously the lower end of the ECS range, this means that by the middle of the century, the planet’s average surface temperature will be at least 2.6 degrees warmer than pre-industrial levels. The Intergovernmental Panel on Climate Change (IPCC), representing the studies of climatologists around the world, said that at a rise of 2.0 degrees, the climate impact would be catastrophic with serious consequences for the world civilization.

Editor’s note: Dan Lennon distilled this track from Umair Irfan’s track on Scientists have moved away from the worst climate scenario – and the best too

Teresa H. Sadler