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% ...

Desertification is the impoverishment of arid, semiarid, and some subhumid ecosystems. The assessment of global scale desertification vulnerability to climate change and human activity is important to help decision makers formulate the best strategies for land rehabilitation and combat global desertification in sensitive areas. There is no global desertification vulnerability map that considers both climate change and human activities. The main aim of this study was to construct a new index, the global desertification vulnerability index (GDVI), by combining climate change and human activity, provide another perspective on desertification vulnerability on a global scale, and project its future evolution. Using the probability density function of the GDVI, we classified desertification vulnerability into four classes: very high, high, medium, and low. The results of the analysis indicated that areas around deserts and barren land have a higher risk of desertification. Areas with a moderate, high, and very high desertification risk accounted for 13%, 7%, and 9% of the global area, respectively. Among the representative concentration pathways (RCPs), RCP8.5 projected that the area of moderate to very high desertification risk will increase by 23% by the end of this century. The areas where desertification risks are predicted to increase over time are mainly in Africa, North America, and the northern areas of China and India.

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Understanding species responses to global change will help predict shifts in species distributions as well as aid in conservation. Changes in the timing of seasonal activities of organisms over time may be the most responsive and easily observable indicator of environmental changes associated with global climate change. It is unknown how global climate change will affect species distributions and developmental events in subtropical ecosystems or if climate change will differentially favor nonnative species. Contrary to previously observed trends for earlier flowering onset of plant species with increasing spring temperatures from mid and higher latitudes, we document a trend for delayed seasonal flowering among plants in Florida. Additionally, there were few differences in reproductive responses by native and nonnative species to climatic changes. We argue that plants in Florida have different reproductive cues than those from more northern climates. With global change, minimum temperatures have become more variable within the temperate-subtropical zone that occurs across the peninsula and this variation is strongly associated with delayed flowering among Florida plants. Our data suggest that climate change varies by region and season and is not a simple case of species responding to consistently increasing temperatures across the region. Research on climate change impacts need to be extended outside of the heavily studied higher latitudes to include subtropical and tropical systems in order to properly understand the complexity of regional and seasonal differences of climate change on species responses.