SEATTLE (AP) – Even if all human-made emissions affecting the climate were stopped immediately, global warming could reach 1.5 degrees with a probability of about 42 percent. This is the result of a new simulation study.
The researchers also found that an immediate cessation of emissions would initially accompany faster warming because the cooling effect from aerosols from combustion of coal, oil, and natural gas would be lost; Only after a few years will the global temperature drop. The study, led by a group led by Michael Dvorak of the University of Washington in Seattle, was published in the journal Nature Climate Change.
The researchers stress that they want to look at two aspects of climate change separately:
For this reason, Dvorak and colleagues assumed in their simulations that all human-made climate-related emissions would abruptly stop at the beginning of 2021. In this way, they calculated that if emissions were not reduced to zero until 2029, the probability of exceeding the 1.5 degree limit increases to 66 percent.
No cooling effect
With the help of a computer model “FaIR”, developed by experts to balance Earth’s radiation, scientists have created a time series of 39 gases and short-lived drivers of climate change. It concluded that halting emissions immediately would accelerate global warming to approximately 1.5 degrees, because: “Tropospheric aerosols from burning fossil fuels and burning biomass have an atmospheric lifespan of days to weeks, and practice currently has a strong cooling effect. on climate (a negative radiative forcing).With this cooling effect removed, rapid warming will occur before reductions in greenhouse gases lower the temperature.
So far, climate researchers have focused on the effect an absence of carbon dioxide (CO2) would have. Since carbon dioxide decomposes very slowly in the atmosphere, the carbon dioxide concentration will remain high for a long time and the temperature will hardly change. On the other hand, methane degrades within 10 to 20 years, and other greenhouse gases don’t last as long as carbon dioxide. Thus, stopping the emissions of these substances will lead to a gradual decrease in the average global temperature.
As in the sixth United Nations Global Climate Report (IPCC), the reference period indicated by changes in temperature is the period from 1850 to 1900. Dvorak’s team calculated that from 1850 to 2019, humans released 2,290 billion tons of CO2 carbon in the atmosphere. . After another 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 thawing permafrost are not taken into account in the climate model, and thus warming could be higher as well.
Praise for studying
Joachim Marwitzky, director of the Max Planck Institute for Meteorology in Hamburg, describes the study as “very well done”. He was the coordinating lead author of the Sixth World Climate Report and thus knows the background well. Simulations like the one in this study might have been viewed with suspicion a few years ago, Marutzky says. “We know today that these simulations with fairly simple models are well suited to predicting temperature developments.”
The study is also of interest to Elmar Kreigler of the Potsdam Institute for Climate Impact Research, although the Sixth World Climate Report already takes into account the dynamics described in the study. Crigler has co-authored several reports for the Intergovernmental Panel on Climate Change. The study shows that it would be very difficult to keep global warming below 1.5 degrees. Even if the long-term goal of not exceeding the 1.5-degree threshold can be achieved, it is expected that this threshold will be “exceeded” for a few years. However, more policy action is needed than before: “Efforts to reduce climate change will be a struggle for every tenth of a degree.”
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