Editing IPCC:AR6/WGI/Chapter-10 (section)

==== 10.4.2.4 Assessment Summary ====

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The robustness of regional-scale attribution differs strongly between temperature and precipitation changes. While the influence of anthropogenic forcing on regional temperature long-term change has been detected and attributed in almost all land regions, a robust detection and attribution of human influence on regional precipitation change has not yet fully occurred for many land regions ( [[#10.4.3|Section 10.4.3]] ). Although the contribution of anthropogenic forcing to long-term regional precipitation change has been detected in some regions, a robust quantification of the contributions of different drivers remains elusive. The delayed emergence of the anthropogenic precipitation fingerprint with respect to temperature is likely due to the opposing sign of the fast and slow land precipitation forced responses and time-dependent SST change patterns (Sections 8.2.1 and [[#10.4.3|Section 10.4.3]] ), stronger internal variability ( [[#10.3.4.3|Section 10.3.4.3]] ) as well as larger observational uncertainty ( [[#10.2|Section 10.2]] ) and impact of model biases. The contribution of internal variability to the observed changes can also be very sensitive to the period length and level of spatial aggregation for the region under scrutiny ( [[IPCC:Wg1:Chapter:Chapter-4#4.4.1|Section 4.4.1]] and Cross-Chapter Box 3.1; [[#Kumar--2016|Kumar et al., 2016]] ). Finally, even in the case of temperature changes at multi-decadal time scale, internal variability can still be a substantial driver of regional changes due to cancellation between different external forcings ( [[#Nath--2018|Nath et al., 2018]] ).

To conclude, it is ''virtually certain'' ( ''robust evidence'' and ''high agreement'' ) that anthropogenic forcing has been a major driver of temperature change since 1950 in many sub-continental regions of the world. There is ''high confidence'' ( ''robust evidence'' and ''medium agreement'' ) that anthropogenic forcing has contributed to multi-decadal mean precipitation changes in several regions, for example western Africa, south-east South America, south-western Australia, northern central Eurasia, and South and East Asia. However, at regional scale, the role of internal variability is stronger while uncertainties in observations, models and external forcing are all larger than at the global scale, precluding a robust assessment of the magnitude of the relative contributions of greenhouse gases, including stratospheric ozone, and different aerosol species.

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