Advances in understanding large‐scale responses of the water cycle to climate change

Abstract

Globally, thermodynamics explains an increase in atmospheric water vapor with warming of around 7%/°C near to the surface. In contrast, global precipitation and evaporation are constrained by the Earth's energy balance to increase at ∼2-3%/°C. However, this rate of increase is suppressed by rapid atmospheric adjustments in response to greenhouse gases and absorbing aerosols that directly alter the atmospheric energy budget. Rapid adjustments to forcings, cooling effects from scattering aerosol, and observational uncertainty can explain why observed global precipitation responses are currently difficult to detect but are expected to emerge and accelerate as warming increases and aerosol forcing diminishes. Precipitation increases with warming are expected to be smaller over land than ocean due to limitations on moisture convergence, exacerbated by feedbacks and affected by rapid adjustments. Thermodynamic increases in atmospheric moisture fluxes amplify wet and dry events, driving an intensification of precipitation extremes. The rate of intensification can deviate from a simple thermodynamic response due to in-storm and larger-scale feedback processes, while changes in large-scale dynamics and catchment characteristics further modulate the frequency of flooding in response to precipitation increases. Changes in atmospheric circulation in response to radiative forcing and evolving surface temperature patterns are capable of dominating water cycle changes in some regions. Moreover, the direct impact of human activities on the water cycle through water abstraction, irrigation, and land use change is already a significant component of regional water cycle change and is expected to further increase in importance as water demand grows with global population.

Robust increase of Indian monsoon rainfall and its variability under future warming in CMIP6 models

“…Within the latest studies using global coupled models, there is a widespread consensus that the Indian monsoon rainfall will increase due to climate change in the 21st century (Chaturvedi et al, 2012;Menon et al, 2013;Lee and Wang, 2014;Asharaf and Ahrens, 2015;Mei et al, 2015;Sharmila et al, 2015;Varghese et al, 2020). This trend is found for various Coupled Model Intercomparison Project phase 5 (CMIP5) models (Menon et al, 2013), the multi-model mean (Chaturvedi et al, 2012), the mean of only the four best models (Lee and Wang, 2014) or the model with the best deep convection scheme (Varghese et al, 2020).…”

Suppressive myeloid cells are a hallmark of severe COVID-19

“…SARS-CoV-2 was identified as the causative agent of COVID-19 (Wu et al, 2020) and similar to SARS coronavirus, it uses ACE2 as the primary cellular entry receptor (Hoffmann et al, 2020; Li et al, 2003). SARS-CoV-2 has a tropism for the upper airways and the lung (Wölfel et al, 2020), despite rather low numbers of cells that co-express ACE2 and the essential cofactor for ACE2 binding, TMPRSS2 (Allan et al, 2020; Qi et al, 2020; Sungnak et al, 2020; Ziegler et al, 2020), but the expression of ACE2 and TMPRSS2 in airway epithelial cells are increased by type-I IFN stimulation (Ziegler et al, 2020). Single cell studies of bronchoalveolar lavage samples have suggested a complex dysregulation of the pulmonary immune response in severe COVID-19 (Liao et al, 2020).…”

PPDIST, global 0.1° daily and 3-hourly precipitation probability distribution climatologies for 1979–2018

“…Peak P intensities were markedly higher at low latitudes (<30°N/S; Fig. 2b), due to the higher air temperatures which lead to more intense P in accordance with the Clausius-Clapeyron relationship [55][56][57] . The highest 15-year return-period P intensities (>200 mm d −1 ) over land were found in parts of Central America, India, and Southeast Asia, along the western equatorial coast of Africa, and over oceans in the intertropical convergence zone (Fig.…”