Editing IPCC:Wg1:Chapter:Chapter-1-comments (section)

==== 1.6.1.2 Scenario Generation Process for CMIP6 ====

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The scenario generation process involves research communities linked to all three IPCC Working Groups (Figure 1.27). It generally starts in the scientific communities associated with WGII and WGIII with the definition of new socio-economic scenario storylines ( [[#IPCC--2000|IPCC, 2000]] ; [[#O’Neill--2014|O’Neill et al., 2014]] ) that are quantified in terms of their drivers – i.e., GDP, population, technology, energy and land use – and their resulting emissions ( [[#Riahi--2017|Riahi et al., 2017]] ). Then, numerous complementation and harmonization steps are necessary for datasets within the WGI and WGIII science communities, including gridding emissions of anthropogenic short-lived forcers, providing open biomass-burning emissions estimates, preparing land-use patterns, aerosol fields, stratospheric and tropospheric ozone, nitrogen deposition datasets, solar irradiance and aerosol optical property estimates, and observed and projected GHG concentration time series (documented for CMIP6 through input4mips; Cross-Chapter Box 1.4, Table 2; [[#Durack--2018|Durack et al., 2018]] ).

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'''Figure 1.27 |''' '''A simplified illustration of the scenario generation process, involving the scientific communities represented in the three IPCC Working Groups.''' The circular set of arrows at the top indicates the main set of models and workflows used in the scenario generation process, with the lower level indicating the datasets.
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Once these datasets are completed, ESMs are run in coordinated model intercomparison projects in the WGI science community, using standardized simulation protocols and scenario data. The most recent example of such a coordinated effort is the CMIP6 exercise ( [[#1.5.4|Section 1.5.4]] ; [[#Eyring--2016|Eyring et al., 2016]] ) with, in particular, ScenarioMIP ( [[#O’Neill--2016|O’Neill et al., 2016]] ). The WGI science community feeds back climate information to WGIII via climate emulators (Cross-Chapter Box 7.1) that are updated and calibrated with the ESMs’ temperature responses and other lines of evidence. Next, this climate information is used to compute several high-level global climate indicators (e.g., atmospheric concentrations, global temperatures) for a much wider set of hundreds of scenarios that are assessed as part of the IPCC WGIII Assessment (WGIII Annex C). The outcomes from climate models run under the different scenarios are then used to calculate the evolution of climatic impact-drivers (Chapter 12), and utilized by impact researchers together with exposure and vulnerability information, in order to characterize risk to human and natural systems from future climate change. The climate impacts associated with these scenarios or different warming levels are then assessed as part of WGII reports (Figure 1.27).

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