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Professor Soon-Il An Atmospheric sciences

Long-lasting Effect of Carbon Dioxide on Surface Temperature And Precipitation Worldwide after Mitigation

Scientists from Korea find that certain climate variables undergo irreversible changes with global warming.

 

Research published online in Nature Climate Change in September 2022



Greenhouse gas emissions are causing the earth to warm up at a concerning rate. Recently, researchers from Korea and USA, led by Prof. An (left) showed that climate factors like precipitation and surface temperature undergo irreversible changes due to greenhouse emissions and do not return to their pre-warming states when atmospheric CO2 levels are reduced.

Image courtesy (right): Piyaset from Shutterstock.

Since the beginning of the industrial revolution, the earth's temperature has been rising at an alarming rate owing to the release of greenhouse gas emissions, particularly carbon dioxide (CO2), from human activities. In recent times, several international efforts have been made, notably the Paris Agreement, to reduce such emissions worldwide and mitigate the resulting climate change. However, recent research suggests that some of the most important climate variables, such as surface temperature and precipitation, do not revert to their pre-warming natural states even when CO2 emissions are reduced to their present level. In other words, the change experienced by these variables is distinct for increasing and decreasing CO2 concentrations, and often irreversible. This is an effect commonly known as “hysteresis.” However, there is a lack of data about this hysteresis effect on a regional scale over the globe. 

To address this issue, a research team led by Professor Soon-Il An and Ph.D. student Soong-Ki Kim from Yonsei University in Korea conducted a computational study to explore climate hysteresis and irreversibility on a regional scale. Their findings were published in Nature Climate Change and made available online on September 01, 2022.

The team employed a climate model simulation of the earth in which CO2 levels were increased by 1% per year for 140 years and then reduced by 1% every year for the same period. Using this model, they developed a method for visualizing the spatial patterns of hysteresis and irreversibility for surface temperature and precipitation. The results showed that regions in the Arctic and Southern and North Atlantic Oceans demonstrated irreversible changes in surface temperature. On the other hand, the tropical Pacific, the Himalayas, and monsoon regions worldwide saw irreversible changes in precipitation. Overall, 89% and 58% of places across the earth was estimated to experience irreversible changes in surface temperature and precipitation, respectively.

The results suggested that regions of Africa, South America, Northern India, and Greenland are less resilient to climate change and, therefore, more vulnerable. Additionally, the study showed that the irreversible changes in climate variables will impact other subsystems, such as mountain glaciers, rainforests, and sea ice.

“Our findings suggest that even if CO2 levels are reduced, the earth's climate does not return to its current condition. Furthermore, developing countries are more vulnerable to the potential harm produced by greenhouse gas emissions. Therefore, simply meeting the Paris Agreement's goal is not sufficient. We would need stronger policies for reducing CO2 levels,” concludes Prof. An.

In summary, the study highlights the potential long-term effects of greenhouse gas emissions on a regional scale. It suggests that the effects of greenhouse gas emissions go beyond the timescale of humans. Even if the CO2 levels return to pre-industrial levels, several climate variables will not return to pre-climate warming levels over many regions, which mostly encompass developing countries.

As a next step, the team plans to explore the hysteresis pattern for different climate models and various CO2 removal scenarios.

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