Drylands are home to more than 38% of the world's population and are one of the most sensitive areas to climate change and human activities. This review describes recent progress in dryland climate change research. Recent findings indicate that the long‐term trend of the aridity index (AI) is mainly attributable to increased greenhouse gas emissions, while anthropogenic aerosols exert small effects but alter its attributions. Atmosphere‐land interactions determine the intensity of regional response. The largest warming during the last 100 years was observed over drylands and accounted for more than half of the continental warming. The global pattern and interdecadal variability of aridity changes are modulated by oceanic oscillations. The different phases of those oceanic oscillations induce significant changes in land‐sea and north‐south thermal contrasts, which affect the intensity of the westerlies and planetary waves and the blocking frequency, thereby altering global changes in temperature and precipitation. During 1948–2008, the drylands in the Americas became wetter due to enhanced westerlies, whereas the drylands in the Eastern Hemisphere became drier because of the weakened East Asian summer monsoon. Drylands as defined by the AI have expanded over the last 60 years and are projected to expand in the 21st century. The largest expansion of drylands has occurred in semiarid regions since the early 1960s. Dryland expansion will lead to reduced carbon sequestration and enhanced regional warming. The increasing aridity, enhanced warming, and rapidly growing population will exacerbate the risk of land degradation and desertification in the near future in developing countries.

Atmospheric aerosols influence the earth’s radiative balance directly through scattering and absorbing solar radiation, and indirectly through affecting cloud properties. An understanding of aerosol optical properties is fundamental to studies of aerosol effects on climate. Although many such studies have been undertaken, large uncertainties in describing aerosol optical characteristics remain, especially regarding the absorption properties of different aerosols. Aerosol radiative effects are considered as either positive or negative perturbations to the radiation balance, and they include direct, indirect (albedo effect and cloud lifetime effect), and semi-direct effects. The total direct effect of anthropogenic aerosols is negative (cooling), although some components may contribute a positive effect (warming). Both the albedo effect and cloud lifetime effect cool the atmosphere by increasing cloud optical depth and cloud cover, respectively. Absorbing aerosols, such as carbonaceous aerosols and dust, exert a positive forcing at the top of atmosphere and a negative forcing at the surface, and they can directly warm the atmosphere. Internally mixed black carbon aerosols produce a stronger warming effect than externally mixed black carbon particles do. The semidirect effect of absorbing aerosols could amplify this warming effect. Based on observational (ground- and satellite-based) and simulation studies, this paper reviews current progress in research regarding the optical properties and radiative effects of aerosols and also discusses several important issues to be addressed in future studies.

The Tibetan Plateau (TP) is located at the juncture of several important natural and anthropogenic aerosol sources. Satellites have observed substantial dust and anthropogenic aerosols in the atmosphere during summer over the TP. These aerosols have distinct effects on the earth's energy balance, microphysical cloud properties, and precipitation rates. To investigate the transport of summer dust and anthropogenic aerosols over the TP, we combined the Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS) with a non-hydrostatic regional model (NHM). The model simulation shows heavily loaded dust aerosols over the northern slope and anthropogenic aerosols over the southern slope and the east of the TP. The dust aerosols are primarily mobilized around the Taklimakan Desert, where a portion of the aerosols are transported eastward due to the northwesterly current; simultaneously, a portion of the particles are transported southward when a second northwesterly current becomes northeasterly because of the topographic blocking of the northern slope of the TP. Because of the strong upward current, dust plumes can extend upward to approximately 7–8 km a.s.l. over the northern slope of the TP. When a dust event occurs, anthropogenic aerosols that entrained into the southwesterly current via the Indian summer monsoon are transported from India to the southern slope of the TP. Simultaneously, a large amount of anthropogenic aerosol is also transported from eastern China to the east of the TP by easterly winds. An investigation on the transport of dust and anthropogenic aerosols over the plateau may provide the basis for determining aerosol impacts on summer monsoons and climate systems.

The rapid warming and consequent retreat of glaciers across the Tibetan Plateau (TP) have given rise to the debate on the ability of the atmospheric water supply to alleviate the depletion of surface water storage. We investigate long‐term changes in atmospheric water vapor balance across the TP using 40‐year fifth generation European Centre for Medium‐Range Weather Forecasts (ECMWF) (ERA5) reanalysis. Precipitation, water vapor convergence, and evaporation generally maintain an equilibrium but with different long‐term variation trends: 0.68, −0.18, and 0.69 mm/a, respectively. Results suggest the inability of the water vapor arriving from outside the TP to effectively replenish the surface water storage. Despite of huge changes in atmospheric water vapor balance during summer, the risk of water storage depletion is brought by other three seasons, especially the autumn. The climatology and long‐term trends of water vapor balance exhibit strong variation across the regions of TP. The surrounding areas of Yarlung Zangbo Grand Canyon experience sharp decrease in water vapor convergence, thus reducing precipitation. Moreover, increasing evaporation is expected to severely loss of surface water storage. For the Three Rivers Source Region with no significant changes in total precipitations, decrease in water transported from outside of TP overlaps increase in evaporation results in the possible depletion of surface water storage. Brahmaputra basin, inner TP, and Qilian Mountain exhibit significant wetting trends due to increases in both convergence of water vapor flux and evaporation. Above regional and seasonal characteristics of water vapor, balances across the TP are attributed by inhomogeneous variation of atmospheric heat source and complex changes of atmospheric circulations.