Deforestation (or afforestation) can alter the momentum, energy and water exchanges between the land and air via changes in surface properties (e.g., albedo and roughness) and thereby further influences local and regional climate; this is called the biophysical process of deforestation. It has been demonstrated that deforestation can impact mean and extreme temperatures through biophysical processes. In addition to the mean and extreme values, variability is also an important statistical metric measuring the rate of temperature changes at different time scales. In particular, daily temperature variability has broad impacts on ecosystem function, human health, and the socioeconomy. Academician Congbin Fu and his team from the School of Atmospheric Sciences for the first time revealed rapid changes in daily temperature variability over China under global warming (Wu et al., 2017). They further found that changes in daily temperature variability at the global scale are mainly attributed to anthropogenic greenhouse gases emissions (Xu et al., 2020). They also found that daily temperature variability dominates the outbreak of influenza in subsequent winter, and changes in daily temperature variability significantly increase the risk of future influenza outbreaks under global warming (Liu et al., 2020). However, the impacts of deforestation on daily temperature variability have rarely been investigated and remain largely unknown.

Using simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) and the CMIP6-endorsed subprojects as well as observations from 33 flux stations in North America and Europe, Professor Weidong Guo’s team and the collaborators performed a systematic study on the impacts of deforestation/afforestation on daily temperature variability. Based on an idealized global deforestation experiment, they find that deforestation can significantly increase daily temperature variability in the northern middle and high latitudes, especially in winter. The higher daily temperature variability further leads to a significant increase in the frequency of rapid warming or cooling events. The main mechanism for such effects is that deforestation reduces surface roughness and enhances near-surface horizontal wind speed. Simultaneously, the cooling effect of deforestation in the northern middle and high latitudes amplifies the meridional temperature gradient. These two effects collaborate to enlarge the near-surface horizontal temperature advection, consequently enhancing daily temperature variability.

The team also analysed the impacts of land use and land cover changes on daily temperature variability in the historical period and future scenarios under different shared socioeconomic pathways (SSPs) using the detection and attribution method. The results show that large-scale deforestation in North America since the Industrial Revolution has significantly increased daily temperature variability. At the regional scale, such a positive effect of deforestation even offsets the negative effect of other human activities, such as greenhouse gas and aerosol emissions, on daily temperature variability. In contrast, if a low-emission sustainable pathway (SSP1-2.6) is adopted, we project that large-scale afforestation in North America will decrease daily temperature variability by the end of this century. These results emphasize that impacts on not only terrestrial carbon sinks, mean temperature and extreme temperature but also daily temperature variability should be considered when large-scale afforestation is implemented in the northern mid- and high-latitude countries in the future.

This paper entitled “Deforestation intensifies daily temperature variability in the northern extratropics” was recently published in Nature Communications. Dr. Ge Jun and Dr. Qi Liu are co-first authors, and Dr. Ge Jun and Prof. Weidong Guo are co-corresponding authors. The other coauthors include Dr. Beilei Zan from Nanjing University of Information Science and Technology, Associate Professor Zhiqiang Lin from Chengdu University of Information Technology, Dr. Sha Lu from Nanjing University of Aeronautics and Astronautics, and Associate Professor Bo Qiu from Nanjing University. This work is supported by the Natural Science Foundation of China, Jiangsu Collaborative Innovation Center for Climate Change and the Frontiers Science Center for Critical Earth Material Cycling of Nanjing University.

Article link: https://doi.org/10.1038/s41467-022-33622-0 

Figure 1：Impacts of idealized global deforestation on daily temperature variability for each season.

References:

Ge J, Liu Q, Zan B, et al. Deforestation intensifies daily temperature variability in the northern extratropics. Nature communications, 2022, 13(1): 1-15.

Wu F T, Fu C, Qian Y, et al. High‐frequency daily temperature variability in China and its relationship to large‐scale circulation. International Journal of Climatology, 2017, 37(2): 570-582.

Liu Q, Tan Z M, Sun J, et al. Changing rapid weather variability increases influenza epidemic risk in a warming climate. Environmental Research Letters, 2020, 15(4): 044004.

Xu Z, Huang F, Liu Q, et al. Global pattern of historical and future changes in rapid temperature variability. Environmental Research Letters, 2020, 15(12): 124073.