Distinct Impacts of Land Use and Land Management on Summer Temperatures

Abstract

Land use has been recognized as an important anthropogenic forcing of climate change in recent studies. However, climatic effects of land management practices have been little discussed and compared to land-use impacts. As land-atmosphere interactions via surface fluxes are particularly strong during the warm season, we investigate the impacts of historical land use and present irrigation practices on summer temperatures in the Northern Hemisphere using the most recent version of Community Earth System Model. Our results suggest that historical land use leads to an overall cooling in the middle latitudes and a warming in the tropics, and the sign and magnitude of the changes in temperature depend on the type of land cover change. On the other hand, summer irrigation leads to a significant cooling over many irrigated areas due to enhanced evapotranspiration, and the local cooling is comparable to and even stronger than the land-use effects. Both land use and irrigation can also significantly influence the intensity and frequency of hot extremes. Land use shows stronger impacts during the night through ground heat flux feedback, while irrigation shows stronger impacts during the day through latent heat flux feedback. Our comparison demonstrates the importance of irrigation in local and regional climate, highlighting the necessity of considering such land management practices in future assessments of regional climate change and climate mitigation.

The Role of Irrigation Expansion on Historical Climate Change: Insights From CMIP6

“…One bias that the models could have is that irrigation quantities, even though realistic at the annual timescale (Thiery et al., 2017), might be applied in different months/seasons than the ones where irrigation is actually happening (Jha et al., 2022). For the air temperature, the annual maximum of monthly air temperature ( T max ) was considered instead, as previous studies have shown more significant irrigation impacts on hot extremes (Chen & Dirmeyer, 2020; Pitman et al., 2012; Thiery et al., 2020).…”

Land‐Atmosphere Interactions Exacerbated the Drought and Heatwave Over Northern Europe During Summer 2018

“…Thus, it is not usually a “hot spot” of L‐A coupling like the Great Plains of North America or the Sahel region of Africa (Koster et al., 2006). Not only can such areas experience magnified responses to droughts and heat waves, the local climate may also react more strongly to land cover changes, agricultural practices, and climate change (Chen & Dirmeyer, 2020; Dirmeyer et al., 2013). Given the concurrent dry and warm conditions during the summer of 2018, we pose the question: Did northern Europe enter an unprecedented regime of L‐A feedbacks—that is, did it become a coupling “hot spot” that may have intensified the heatwave?…”

Evolution of land surface feedbacks on extreme heat: Adapting existing coupling metrics to a changing climate

“…When each period's anomalies and standard deviations for temperature, sensible heat, and potential sensible heat are used for each model, the left panel shows that the multimodel median of the 90th percentile value of π shows a significant consensus change over portions of the globe. Decreases correspond largely to areas of land cover change: areas of agricultural expansion over the Americas, Northeast China, India, the Sahel, and Australia, but the correspondence between land use change and land-heat coupling has not been explicitly quantified in this study as it has been in others (e.g., Chen and Dirmeyer, 2019;Chen and Dirmeyer, 2020;Hu and Sun, 2022). Increases are largely confined to low latitudes, corresponding to areas of tropical deforestation but also in the subtropics of the Southern Hemisphere during austral summer (Figure 2) and, curiously, much of the Sahara.…”