The Paris Agreement aims to limit global mean surface warming to less than 2 • C relative to pre-industrial levels 1-3 . However, we show this target is acceptable only for humid lands, whereas drylands will bear greater warming risks. Over the past century, surface warming over global drylands (1.2-1.3 • C) has been 20-40% higher than that over humid lands (0.8-1.0 • C), while anthropogenic CO 2 emissions generated from drylands (∼230 Gt) have been only ∼30% of those generated from humid lands (∼750 Gt). For the twenty-first century, warming of 3.2-4.0 • C (2.4-2.6 • C) over drylands (humid lands) could occur when global warming reaches 2.0 • C, indicating ∼44% more warming over drylands than humid lands. Decreased maize yields and runo , increased long-lasting drought and more favourable conditions for malaria transmission are greatest over drylands if global warming were to rise from 1.5 • C to 2.0 • C. Our analyses indicate that ∼38% of the world's population living in drylands would su er the e ects of climate change due to emissions primarily from humid lands. If the 1.5 • C warming limit were attained, the mean warming over drylands could be within 3.0 • C; therefore it is necessary to keep global warming within 1.5 • C to prevent disastrous e ects over drylands.After the Paris Climate Agreement was signed in April 2016 and approved by USA and China on the G20 summit in September 2016, policymakers agreed upon a goal to limit global mean surface warming (GMSW) to no more than 2 • C above pre-industrial levels 1 . Furthermore, the pursuit of a warming limit as low as 1.5 • C was proposed and the Intergovernmental Panel on Climate Change (IPCC) was invited to generate a special report by 2018 on the impacts of global warming of 1.5 • C and on related global greenhouse gas emissions pathways. As part of an ambitious and urgent plan, the necessity and benefits of half a degree less warming must be evaluated soon before a new decision is made.The GMSW level has already reached ∼0.9 • C above the preindustrial level 4 , leaving only ∼0.6 • C for further warming before reaching a 1.5 • C target. Thus, it is suggested that a 1.5 • C target is not likely to be achieved without an overshoot, given recent CO 2 emissions trends 2 . However, some studies found extreme temperature changes associated with the 2 • C target could be substantial and a 1.5 • C target may be desirable 3 .These global warming targets are for global mean surface temperatures averaged over both land and ocean surfaces. Greenhouse gas (GHG)-induced warming is much lower over oceans than over land, owing to evaporation over and vertical mixing within oceans 5 . Thus, warming over land will significantly exceed the GMSW target due to the lower warming over oceans, which cover ∼71% of Earth's surface.Warming over land is also not evenly distributed, and large regional differences have raised concerns 3,6-8 . Observations have shown enhanced warming over drylands 9-11 . The world's drylands occupy nearly half of Earth's land surface and sustain ∼38% ...

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Abstract. The Weather Research and Forecasting Model with chemistry (WRF-Chem model) was used to investigate a typical dust storm event that occurred from 18 to 23 March 2010 and swept across almost all of China, Japan, and Korea. The spatial and temporal variations in dust aerosols and the meteorological conditions over East Asia were well reproduced by the WRF-Chem model. The simulation results were used to further investigate the details of processes related to dust emission, long-range transport, and radiative effects of dust aerosols over the Taklimakan Desert (TD) and Gobi Desert (GD). The results indicated that weather conditions, topography, and surface types in dust source regions may influence dust emission, uplift height, and transport at the regional scale. The GD was located in the warm zone in advance of the cold front in this case. Rapidly warming surface temperatures and cold air advection at high levels caused strong instability in the atmosphere, which strengthened the downward momentum transported from the middle and low troposphere and caused strong surface winds. Moreover, the GD is located in a relatively flat, high-altitude region influenced by the confluence of the northern and southern westerly jets. Therefore, the GD dust particles were easily lofted to 4 km and were the primary contributor to the dust concentration over East Asia. In the dust budget analysis, the dust emission flux over the TD was 27.2 ± 4.1 µg m −2 s −1 , which was similar to that over the GD (29 ± 3.6 µg m −2 s −1 ). However, the transport contribution of the TD dust (up to 0.8 ton d −1 ) to the dust sink was much smaller than that of the GD dust (up to 3.7 ton d −1 ) because of the complex terrain and the prevailing wind in the TD. Notably, a small amount of the TD dust (PM 2.5 dust concentration of approximately 8.7 µg m −3 ) was lofted to above 5 km and transported over greater distances under the influence of the westerly jets. Moreover, the direct radiative forcing induced by dust was estimated to be −3 and −7 W m −2 at the top of the atmosphere, −8 and −10 W m −2 at the surface, and +5 and +3 W m −2 in the atmosphere over the TD and GD, respectively. This study provides confidence for further understanding the climate effects of the GD dust.

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Abstract:Absorbing aerosols can strongly absorb solar radiation and have a profound impact on the global and regional climate. Black carbon (BC), organic carbon (OC) and dust are three major types of absorbing aerosols. In order to deepen the overall understanding of absorbing aerosols over East Asia and provide a basis for further investigation of its role in enhanced warming in drylands, the spatial-temporal distribution of absorbing aerosols over East Asia for the period of 2005-2016 was investigated based on the Ozone Monitoring Instrument (OMI) satellite retrievals. Overall, high values of Aerosol Absorption Optical Depth (AAOD) mainly distribute near dust sources as well as BC and OC sources. AAOD reaches its maximum during spring over East Asia as a result of dust activity and biomass burning. Single-scattering albedo (SSA) is comparatively high (>0.96) in the most part of East Asia in the summer, indicating the dominance of aerosol scattering. Hyper-arid regions have the highest Aerosol Optical Depth (AOD) and AAOD among the five climatic regions, with springtime values up to 0.72 and 0.04, respectively. Humid and sub-humid regions have relatively high AOD and AAOD during the spring and winter and the highest SSA during the summer. AAOD in some areas shows significant upward trends, which is likely due to the increase of BC and OC emission. SSA shows overall downward trends, indicating the enhancement of the aerosol absorption. Analysis of emission inventory and dust index data shows that BC and OC emissions mainly come from the humid regions, while dust sources mainly distribute in drylands.