Inconsistent Responses of Hot Extremes to Historical Land Use and Cover Change Among the Selected CMIP5 Models

Abstract

Land use and cover change (LUCC) is an important anthropogenic forcing of the climate system. Previous studies have demonstrated that LUCC significantly impacts both mean and extreme temperatures. In this study, we explored the multimodel performance of simulating LUCC‐induced asymmetric effects on the different percentiles of maximum temperatures (Tmax) as well as the possible reasons for these effects using results from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Four state‐of‐art Earth system models (which provide the necessary data) are selected for investigating this issue. In general, all the cases of the model from the Geophysical Fluid Dynamics Laboratory show robust asymmetric responses between the 90th (TX90P) and 10th percentiles (TX10P) of Tmax, mainly due to cropland expansions, especially over India, the Sahel, and some parts of North America. However, weak and insignificant responses are shown for both the TX90P and TX10P in other models. The different changes in the Tmax variability among the models are primarily responsible for the occurrence of asymmetric features. Furthermore, by decomposing the Tmax changes over three typical regions, we analyze the potential causes for the inconsistencies among these models' results and find two crucial processes, that is, the repartitioning of the turbulent heat fluxes and the changes of the diurnal cycle variability due to LUCC. Whether these processes are pronounced determines the occurrence of the asymmetric Tmax responses. Overall, this study provides a critical clue for reducing the uncertainties of the LUCC effects on temperature extremes, which should be evaluated against observations.

Anthropogenic land cover change impact on climate extremes during the 21st century

“…Some regions with extensive historical LCC (Eurasia and North America) have experienced biophysical decreases in annual mean temperature of a magnitude similar to the concomitant increase in greenhouse gases (de Noblet-Ducoudré et al 2012). However, considerable disagreement is evident in model responses; most models show mid-latitude decreases of most hot extreme indices , Christidis et al 2013, Li et al 2018, Chen and Dirmeyer 2019, while other models simulate increases (Avila et al 2012, Findell et al 2017, Lejeune et al 2018, Li et al 2018, Chen and Dirmeyer 2019 in response to historical LCC. For instance, three out of four models of the 'land-use and climate, identification of robust impacts' (LUCID) intercomparison project simulated a decrease in extremely warm daytime temperatures over the northern mid-latitudes during summer due to historical LCC .…”

The Nonradiative Effect Dominates Local Surface Temperature Change Caused by Afforestation in China

“…Climate models (Arora and Montenegro 2011;Bala et al 2007; Davin and de Noblet-Ducoudré 2010) simulate a warming effect while observations (Alkama and Cescatti 2016;Burakowski et al 2018;Duveiller et al 2018;Li et al 2015;Schultz et al 2017;Wang et al 2018) point to cooling. Recent studies also suggest afforestation can impact temperature extremes (Findell et al 2017;Skinner et al 2018;Teuling et al 2010) although modeling of these processes is very uncertain (Avila et al 2012;Li et al 2018;Pitman et al 2012). Despite these uncertainties, the biophysical effects of afforestation on climate need to be considered, especially at local and regional scales where afforestation strategies are being implemented, to avoid risk of maladaptation (Anderson et al 2011;Bonan 2008).…”

Reconciling the disagreement between observed and simulated temperature responses to deforestation

“…Compared with the impacts on precipitation, which are more complex and difficult to validate, the relationship between deforestation and temperature has been extensively investigated using both observational datasets and modeling approaches 4 . In particular, recent studies have suggested that historical LULCC (namely deforestation) can significantly influence local high temperature extremes [5][6][7][8][9][10] .…”

“…Satellite-based observations show that cleared lands are warmer than nearby forest in daily maximum temperature during summer [12][13][14] . On the contrary, results from CMIP5 (Coupled Model Intercomparison Project Phase 5 15 ) and LUCID (land use and climate: identification of robust impacts 16,17 ) tend toward a summer daytime cooling over the middle latitudes as a result of documented historical deforestation 6,11 . The disagreement of model results with observations has been claimed to be associated with parameterization issues in current land surface models, such as the changes in partitioning of available energy between latent and sensible heat fluxes due to LULCC 6,8,11 .…”