Uncertainty and hotspots in 21st century projections of agricultural drought from CMIP5 models

Abstract

Future climate changes could alter hydrometeorological patterns and change the nature of droughts at global to regional scales. However, there are considerable uncertainties in future drought projections. Here, we focus on agricultural drought by analyzing surface soil moisture outputs from CMIP5 multi-model ensembles (MMEs) under RCP2.6, RCP4.5, RCP6.0, and RCP8.5 scenarios. First, the annual mean soil moisture by the end of the 21st century shows statistically significant large-scale drying and limited areas of wetting for all scenarios, with stronger drying as the strength of radiative forcing increases. Second, the MME mean spatial extent of severe drought is projected to increase for all regions and all future RCP scenarios, and most notably in Central America (CAM), Europe and Mediterranean (EUM), Tropical South America (TSA), and South Africa (SAF). Third, the model uncertainty presents the largest source of uncertainty (over 80%) across the entire 21st century among the three sources of uncertainty: internal variability, model uncertainty, and scenario uncertainty. Finally, we find that the spatial pattern and magnitude of annual and seasonal signal to noise (S/N) in soil moisture anomalies do not change significantly by lead time, indicating that the spreads of uncertainties become larger as the signals become stronger.

Projected Impacts of Climate Change on Drought Patterns Over East Africa

“…Moreover, climate‐related uncertainty is associated with the inability to predict the scale, intensity, and impact of climate change on human and natural environments (Mehata et al 2019). Different sources of uncertainties exist in future climate projections, which include internal climate variability, GCM data sets and future climate scenarios (Lu et al, 2019; Meresa et al, 2016; Meresa & Romanowicz, 2017; Orlowsky & Seneviratne, 2013). By far, climate change projections are inherently uncertain due to assumptions made about the formulation, parameterization, and boundary conditions of the underlying factors in climate (Mackay et al, 2019; Meresa & Romanowicz, 2017).…”

Historical Changes in Surface Soil Moisture Over the Contiguous United States: An Assessment of CMIP6

“…However, there is still substantial model-to-model variation in CMIP6 and this may influence the uncertainty in conclusions regarding soil moisture trends. Lu et al (2019) reported large intermodel uncertainty in CMIP5 under future projections, which may be caused by differences in model resolution, physics, and parameterization. As one of the main CMIP6-Endorsed Model Intercomparison Projects, the Land Surface, Snow and Soil Moisture (LS3MIP) has been designed to identify the source of model disagreement in CMIP6 through enhanced diagnostic studies and experimental design.…”

“…Global climate models (GCMs), coupling both climate system and land surface processes, are especially useful for evaluating the impacts of weather and climate on soil moisture and the feedbacks from soil moisture to the atmosphere. However, accurately simulating soil moisture is challenging (Lu et al., 2019) because of the complicated interactions between solar radiation, temperature, precipitation, land surface conditions (e.g., topography, soil type, and land cover) and other factors (e.g., wind speed, humidity, and CO 2 ) (Crow et al., 2012; Roderick et al., 2015). For example, although soil moisture is mainly controlled by precipitation, some studies have shown that regional and global soil moisture trends do not match precipitation trends (Byrne & O'Gorman, 2015; Greve et al., 2014).…”

Regulation and Subfunctionalization of Flowering Time Genes in the Allotetraploid Oil Crop Brassica napus

“…Moreover, drought stress during flowering was found to be much more devastating than during vegetative development (Hohmann, 2017). Many rapeseed growing areas face increased likelihoods of droughts during rapeseed flowering times due to climate change (Lu et al, 2019). If the drought period is short, drought avoidance including later flowering can be a successful strategy , but this is highly dependent on synchronization of drought period and flowering time.…”