Improved Global Surface Temperature Simulation using Stratospheric Ozone Forcing with More Accurate Variability

Increasingly, studies have pointed out that variations of stratospheric ozone significantly influence climate change in the Northern and Southern hemispheres. This leads us to consider whether making the variations of stratospheric ozone in a climate model closer to real ozone changes would improve the simulation of global climate change. It is found that replacing the original specified stratospheric ozone forcing with more accurate stratospheric ozone variations improves the simulated variations of surface temperature in a climate model. The improved stratospheric ozone variations in the Northern Hemisphere lead to better simulation of variations in Northern Hemisphere circulation. As a result, the simulated variabilities of surface temperature in the middle of the Eurasian continent and in lower latitudes are improved. In the Southern Hemisphere, improvements in surface temperature variations that result from improved stratospheric ozone variations influence the simulation of westerly winds. The simulations also suggest that the decreasing trend of stratospheric ozone may have enhanced the warming trend at high latitudes in the second half of the 20th century. Our results not only reinforce the importance of accurately simulating the stratospheric ozone but also imply the need for including fully coupled stratospheric dynamical–radiative–chemical processes in climate models to predict future climate changes.

Stratospheric ozone loss over the Eurasian continent induced by the polar vortex shift

The Montreal Protocol has succeeded in limiting major ozone-depleting substance emissions, and consequently stratospheric ozone concentrations are expected to recover this century. However, there is a large uncertainty in the rate of regional ozone recovery in the Northern Hemisphere. Here we identify a Eurasia-North America dipole mode in the total column ozone over the Northern Hemisphere, showing negative and positive total column ozone anomaly centres over Eurasia and North America, respectively. The positive trend of this mode explains an enhanced total column ozone decline over the Eurasian continent in the past three decades, which is closely related to the polar vortex shift towards Eurasia. Multiple chemistry-climate-model simulations indicate that the positive Eurasia-North America dipole trend in late winter is likely to continue in the near future. Our findings suggest that the anticipated ozone recovery in late winter will be sensitive not only to the ozone-depleting substance decline but also to the polar vortex changes, and could be substantially delayed in some regions of the Northern Hemisphere extratropics.

Climate change can exert a significant effect on the ozone recovery. Here, the authors show that the Arctic polar vortex shift associated with Arctic sea-ice loss could slow down ozone recovery over the Eurasian continent.

Impacts of Polar Changes on the UV-induced Mineralization of Terrigenous Dissolved Organic Matter

Local climates in the Northern and Southern Hemisphere are influenced by Arctic Amplification and by interactions of the Antarctic ozone hole with climate change, respectively. Polar changes may affect hydroclimatic conditions in temperate regions, for example, by increasing the length and intensity of precipitation events at Northern Hemisphere midlatitudes. Additionally, global warming has led to the thawing of ancient permafrost soils, particularly in Arctic regions, due to Arctic Amplification. Both heavy precipitation events and thawing of permafrost are increasing the net transfer of terrestrially derived dissolved organic matter (DOM) from land to surface waters. In aquatic ecosystems, UV-induced oxidation of terrigenous DOM (tDOM) produces atmospheric CO2 and this process is one of several mechanisms by which natural organic matter in aquatic and soil environments may play an important role in climate feedbacks. The Arctic is particularly affected by these processes: for example, melting of Arctic sea ice allows solar UV radiation to penetrate into the ice-free Arctic Ocean and to cause photochemical reactions that result in bleaching and mineralization of tDOM. Open questions, in addition to those shown in the Graphical Abstract, remain regarding the resulting contributions of tDOM photomineralization to CO2 production and global warming.

Effects of stratospheric ozone depletion, solar UV radiation, and climate change on biogeochemical cycling: interactions and feedbacks

Solar UV radiation and climate change interact to influence and determine the environmental conditions for humans on planet Earth.