Researchers use a computer simulation to find out that if humanity were to pull the climate emergency brake and abstain from all emissions overnight, this would accelerate global warming. However, the effect is only temporary.
What if all man-made emissions affecting the climate stopped immediately? The answer of a group of researchers from the University of Washington in Seattle is sobering. Global warming would still reach 1.5 degrees with a probability of around 42 percent. And that’s not all: if emissions were to be stopped immediately, warming would initially accelerate, the authors write in their study, which was published in the journal “Nature Climate Change”.
The reason for the accelerated warming: when coal, oil and natural gas are burned, aerosols are produced which contribute to cooling. “Tropospheric aerosols produced by fossil fuel burning and biomass burning have atmospheric lifetimes of days to weeks and currently exert a strong net cooling effect on climate (a negative radiative forcing).” With this cooling effect removed, rapid warming would occur before reductions in greenhouse gases lowered the temperature.
So far, climate researchers have focused on the effect that would arise from the absence of the greenhouse gas carbon dioxide (CO2). Because CO2 breaks down very slowly in the atmosphere, the CO2 concentration would remain high for a long time and the temperature would hardly change. Methane, on the other hand, is broken down in 10 to 20 years and other greenhouse gases are not as long-lived as CO2. Stopping emissions of these substances would therefore result in a gradual reduction in the average global temperature.
As in the United Nations Sixth World Climate Report, the reference period to which the temperature changes refer is the period 1850 to 1900. Dvorak’s team calculated that from 1850 to 2019 humans released an amount of 2290 billion tons of CO2 into the atmosphere. After a further 1080 billion tons from January 2021, the 1.5 degree limit will be reached, after 1980 billion tons the two degree limit. Amplification effects such as increased methane emissions from the thawing permafrost are not taken into account in the climate model, so the warming can also be higher.
The director at the Max Planck Institute for Meteorology in Hamburg, Jochem Marotzke, describes the study as “very well done”. He was the coordinating lead author of the Sixth World Climate Report and therefore knows the background very well. Simulations like the ones in this study would have been viewed with suspicion a few years ago, says Marotzke. “Today we know that these simulations with fairly simple models are very well suited for predicting the temperature development.”