According to a study published in Science (ref.), reducing CO2 from the Earth‘s atmosphere might not reverse the climate change predicted by meteorological models in the most vulnerable areas. Korean researchers simulated how the removal of large amounts of carbon dioxide could affect the course of local climate changes.
Study, based on computer models, examined a hypothetical scenario in which carbon dioxide concentrations continued to rise from current levels for 140 years, then gradually decreased to initial levels for another 140-year period. The research aimed to understand how these changes would impact vulnerable subtropical regions, which notably suffer from increasingly frequent droughts as climate change progresses.
Starting today for results in 200 years
Study’s results suggest that the local climate in these areas would not return to normalcy for over 200 years after the decrease in carbon dioxide concentrations. For instance, the Mediterranean region, plagued by increasingly severe heatwaves, droughts, and fires, would continue to suffer and could become even drier, according to the study.
Researchers found changes in the air circulation pattern called the Hadley Cell. This carries moisture from the equatorial regions towards the tropics of Cancer and Capricorn. Scientists have known for years that the Hadley cell circulation responds to climate changes by expanding toward the poles. The moist air rising from the equator is deposited onto Earth at increasingly higher latitudes, causing worsened droughts in subtropical regions.
Modeling conducted by the Korean team found that after the removal of carbon dioxide, the Hadley cell does not recover its original shape and extent until 220 years later. In the Northern Hemisphere, the scenario is worse. The area where moisture arrives from tropical regions moves closer to the equator. This shift could make the Mediterranean region drier than it is today. In the Southern Hemisphere, the cell remains slightly expanded toward the South Pole, potentially altering precipitation patterns in Australia.
Ocean circulation and the Hadley cell
Lead author of the study, Seo-Yeon Kim, stated, “One of the main reasons for this asymmetric response of the Hadley cell is the different ocean response to ocean circulation. Ocean’s response is slower than the removal of carbon dioxide in the atmosphere. The speed at which the ocean responds determines the recovery of the Hadley cell.”
Team used current levels of carbon dioxide as a starting point and modeled a scenario in which concentrations increase by a factor of four before returning to the baseline level. They did not model a return to levels that were common in the pre-industrial era before humans began burning fossil fuels.
According to the United States National Oceanic and Atmospheric Administration (NOAA), carbon dioxide concentrations rose to 421 parts per million in 2022, over 50% above pre-industrial era concentrations (ref.). Current carbon dioxide concentrations are even higher than those during the Pliocene Climatic Optimum. A warm period in Earth’s history about 4.5 million years ago when sea levels were 25 meters higher than today.
Reduce CO2 now!
Despite climatologists’ warnings, the world is still behind in meeting CO2 reduction goals to curb progressive climate change. Humanity’s slow response is pushing research to discover other climate interventions, such as active carbon removal. There are two ways to remove carbon dioxide from the Earth’s atmosphere. Technologies that capture the warming gas from the air and sequester it in artificial stone, or reforestation and fertilization of ocean parts to promote algae growth.
Unfortunately, thousands of studies worldwide suggest that climate change is spiraling out of control. Antarctica experienced unprecedented sea ice extent during its winter this year, while extreme heatwaves plague parts of Europe and North America. Kim, however, emphasizes that model results show that even as we reduce CO2 to lower temperatures, climate change could continue to impact millions of people in vulnerable regions for centuries.
“I think the main message of our study is that we should reduce carbon dioxide emissions now because it will become increasingly difficult later. We can’t control nature; we can’t reverse the consequences so easily. We can’t fix nature as quickly as we imagine”.