Would warming stop after greenhouse gas emissions end? Not quite

The latest IPCC report estimated our remaining “carbon budget” that would give us a chance of reaching the goal of keeping global warming below 2 degrees Celsius this century. That estimate was created using a simpler class of climate model that can crank out long or repeated simulations without tying up a supercomputer for a week. A new study using one of the most complex models, however, suggests that the simpler models get a key issue wrong: they overestimate how much carbon we can emit if we actually want to stay below 2 degrees Celsius over the centuries that follow.

A recent study used one of those simpler models (technically known as “Earth System Models of Intermediate Complexity," or EMICs) to look at how long it takes us to reap the benefits of cutting emissions. Rather than the oft-repeated estimate that there is a delay of about 40 years, the researchers found that the peak in temperature came just 10 years after emitting a simulated pulse of CO₂. However, they only modeled about a hundred years.

ETH Zürich’s Thomas Frölicher and David Paynter of NOAA’s Geophysical Fluid Dynamics Laboratory turned to a more complex model and a much longer timeframe to investigate a related question: what happens long after we stop emitting greenhouse gases?