Editing IPCC:AR6/WGII/Cross-Chapter-Paper-3 (section)

===== Where are we going? Risks and adaptation under warming pathways =====

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'''Some drylands will expand by 2100, while others will shrink (''' '''''high confidence''''' '''). Climate change affects drylands through increased temperatures and more irregular rainfall, with important differences between areas with different rainfall distributions linked to the dominant climate systems in each location. Projections are nevertheless uncertain and not well supported by observed trends, while different methodological approaches and indices exhibit different strengths and weaknesses (''' '''''medium confidence''''' ''').''' A fundamental methodological challenge is how to attribute projected impacts to climate change when background climate variability in drylands is so high. Some projections show aridity (as measured by the Aridity Index, AI) to expand substantially on all continents, except Antarctica. Expansion of arid regions is probable in southwest North America, the northern fringe of Africa, southern Africa and Australia. The main areas of semiarid expansion are ''likely'' [[#footnote-000|2]] to occur on the north side of the Mediterranean, southern Africa and North and South America. India, parts of northern China, eastern equatorial Africa and the southern Saharan regions are projected to have shrinking drylands. Under Representative Concentration Pathway (RCP) 8.5, aridity zones could expand by one-quarter of the 1990 area by 2100, increasing to over half the global terrestrial area. Lower greenhouse gas emissions, under RCP4.5, could limit expansion to one-tenth of the 1990 area by 2100. Nevertheless, the utility of the AI in delineating dryland biomes is limited under an increasing CO 2 environment ( ''medium confidence'' ) and how well the index fits observed trends has been questioned in recent research. The impacts of climate change on sand and dust storm activity are projected to be substantial, however, there is large regional variability in terms of rainfall seasonality, land management practices and differences in rates of change and the scales at which the projections are undertaken. The characteristics and speed of human responses and adaptations also affect future risks and impacts ( ''high confidence'' ). Increased temperature and rainfall variability will significantly change the interannual variability in the global carbon cycle, which is strongly influenced by the world’s drylands and the ways they are managed ( ''medium confidence'' ). Increased variability of precipitation would generally contribute to increased vulnerability for people in drylands, intensifying the challenges that people living in deserts and semiarid areas will face for their sustainable development ( ''medium confidence'' ). {3.3.1, 3.3.2}

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