Increasing meteorological drought under climate change reduces terrestrial ecosystem productivity and carbon storage

Plants on land absorb about 30% of the CO2 produced by human activities each year, meaning they have mitigated, to some degree, the global warming impacts of human emissions. However, plants are also vulnerable to climate change. While increases in CO2 may have a "fertilizing effect" and increase plant growth and therefore CO2 absorption, other impacts of climate change, such as increasingly frequent and severe droughts, will harm plant growth. In this work, we show that, if the future is powered by fossil-fueled development and CO2 emissions continue to increase, the end of the century will see a 3.5-fold increase in the loss of vegetation productivity due to droughts, especially in cropland. Our results suggest that the "buffering" impact of plants on human CO2 emissions cannot be counted on in an increasingly warm planet and emphasize the importance of greenhouse gas mitigation for vegetation and cropland productivity

Increased risk of flash droughts with raised concurrent hot and dry extremes under global warming

Abstract Flash droughts pose large threats to crop yields and ecosystem services due to their sudden onset and rapid intensification, arousing wide public concern in a warming climate. Their long-term characteristics of change, underlying mechanisms, and especially potential impacts on agriculture, forests, and populations at a global scale, however, remain largely unknown. We used in situ observations, two observation-based global reanalysis data sets, and 22 Earth system models to determine that flash droughts are shifting toward more frequent, accelerated-onset, and longer duration. These changes increased the exposure of agricultural areas, forested areas, and populations to flash droughts by 20.3%, 17.1%, and 30.0%, respectively, during 2001–2020 compared to 1981–2000, with a disproportionate increase in integrated risks across the Amazon Basin and eastern and southern Asia. The increase in concurrent hot and dry climatic conditions driven by warming has been mostly responsible for enabling and intensifying flash droughts over large regions. State-of-the-art Coupled Model Intercomparison Project Phase 6 (CMIP6) models, however, failed to identify the acceleration of the onset time of flash droughts and widely underestimated the occurrence of flash droughts that are driven only by precipitation deficits or by heat waves, probably because they misrepresent the dependence between precipitation and temperature and underestimate the sensitivity of soil moisture to temperature and precipitation at short timescales (e.g., 5 days). These syntheses comprehensively advance our understanding of the characteristics and impacts of flash droughts but also highlight that the CMIP6 models need to be validated to represent the correct covariability between climatic variables at short timescales to provide more reliable projections of flash droughts