Editing IPCC:AR6/WGI/TS (section)

==== TS.4.2.1 Regional Fingerprints of Anthropogenic and Natural Forcing ====

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While anthropogenic forcing has contributed to multi-decadal mean precipitation changes in several regions, internal variability can delay emergence of the anthropogenic signal in long-term precipitation changes in many land regions ( ''high confidence'' ). At the regional scale, the effect of human-induced GHG forcing on extreme temperature is moderated or amplified by soil moisture feedback, snow/ice-albedo feedback, regional forcing from land-use/land-cover changes, forcing from aerosol concentrations, or decadal/multi-decadal natural variability. Changes in local and remote aerosol forcings lead to south–north gradients of the effective radiative forcing (hemispherical asymmetry). Along latitudes, it is more uniform, with strong amplification of the temperature response towards the Arctic ( ''medium confidence'' ). The decrease of SO <sub>2</sub> emissions since the 1980s reduces the damping effect of aerosols, leading to a faster increase in surface air temperature that is most pronounced at mid- and high latitudes of the Northern Hemisphere, where the largest emissions reductions have taken place ( ''medium confidence'' ). Links to chapters 1.3, 3.4.1, 6.3.4, 6.4.1, 6.4.3, 8.3.1, 8.3.2, Box 8.1, 10.4.2, 10.6, 11.1.6, 11.3

Multi-decadal dimming and brightening trends in incoming solar radiation at Earth’s surface occurred at widespread locations ( ''high confidence'' ). Multi-decadal variation in anthropogenic aerosol emissions are thought to be a major contributor ( ''medium confidence'' ), but multi-decadal variability in cloudiness may also have played a role. Volcanic eruptions affect regional climate through their spatially heterogeneous effect on the radiative budget as well as through triggering dynamical responses by favouring a given phase from some MoVs, for instance. Links to chapters 1.4.1, Cross-Chapter Box 1.2, 2.2.1, 2.2.2, 3.7.1, 3.7.3, 4.3.1, 4.4.1, 4.4.4, Cross-Chapter Box 4.1, 7.2.2, 8.5.2, 10.1.4, 11.1.6, 11.3.1

Historical urbanization affects the observed warming trends in cities and their surroundings ( ''very'' ''high confidence'' ). Future urbanization will amplify the projected air temperature under different background climates, with a strong effect on minimum temperatures that could be as large as the global warming signal ( ''very high confidence'' ) (Box TS.14). Irrigation and crop expansion have attenuated increases in summer hot extremes in some regions, such as central North America ( ''medium confidence'' ) (Box TS.6). Links to chapters Box 10.3, 11.1.6, 11.3

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