Frontiers of Science Look at the World, Learn to Understand the Universe
With the world warming at an unprecedented rate in recent decades, the question of whether anthropogenic climate change is reversible has become an important issue. The latest research shows that even with drastic cuts in atmospheric carbon dioxide levels from now on, the world's weather system will struggle to return to pre-industrial patterns, and humanity has gone too far down the path of climate change.
Through a series of climate model simulations, the researchers found that it would take a span of 140 years to first raise carbon dioxide levels to four times their current levels of 1468 ppm and then return to today's levels. And as carbon dioxide levels fall, the tropical convergence zone (ITCZ) will move southward, exhibiting strong lagging behavior that could lead to permanent changes in the global climate.
Studies have shown that the tropical convergence zone (ITCZ) does not respond linearly to carbon dioxide levels. Although the position of the ITCZ changes little during the rise in carbon dioxide levels, once the carbon dioxide levels begin to decline, the ITCZ center will shift southward and eventually be located in the southern hemisphere. ITCZ accounts for 32% of global rainfall, changes in ITCZ patterns will alter the entire Earth's atmospheric circulation, and temperatures in the Northern Hemisphere are expected to decrease as carbon dioxide levels fall, but the Southern Hemisphere will maintain weather patterns similar to those experienced in El Niño years, with persistent high temperatures.
Models show that even a drop in carbon dioxide levels can cause permanent changes in the climate in some parts of the world. For example, precipitation in North and South America will increase significantly by 15 percent, and the chance of flooding will increase. At the same time, the annual precipitation in southern Europe and the Sahara Desert will be reduced by 20%, which may lead to further drought and desertification.
Clearly, the carbon dioxide already emitted will have an irreversible, lasting, and far-reaching impact on the planet, and longer than expected. Even if carbon dioxide levels return to pre-industrial levels, global temperatures and precipitation will not return to the past, a warning of urgency to reduce carbon dioxide emissions. The researchers point out that these irreversible changes in weather systems should be taken into account in future climate change planning, making more common predictions of temperatures and rainfall on a global scale.
参考文献：Hysteresis of the intertropical convergence zone to CO2 forcing, Nature Climate Change, 2021, DOI: org/10.1038/s41558-021-01211-6.
Editor-in-charge: Zhu Zhang Hangyu