The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6

Abstract

Abstract. Projections of future climate change play a fundamental role in improving understanding of the climate system as well as characterizing societal risks and response options. The Scenario Model Intercomparison Project (ScenarioMIP) is the primary activity within Phase 6 of the Coupled Model Intercomparison Project (CMIP6) that will provide multi-model climate projections based on alternative scenarios of future emissions and land use changes produced with integrated assessment models. In this paper, we describe ScenarioMIP's objectives, experimental design, and its relation to other activities within CMIP6. The ScenarioMIP design is one component of a larger scenario process that aims to facilitate a wide range of integrated studies across the climate science, integrated assessment modeling, and impacts, adaptation, and vulnerability communities, and will form an important part of the evidence base in the forthcoming Intergovernmental Panel on Climate Change (IPCC) assessments. At the same time, it will provide the basis for investigating a number of targeted science and policy questions that are especially relevant to scenario-based analysis, including the role of specific forcings such as land use and aerosols, the effect of a peak and decline in forcing, the consequences of scenarios that limit warming to below 2 • C, the relative contributions to uncertainty from scenarios, climate models, and internal variability, and long-term climate system outcomes beyond the 21st century. To serve this wide range of scientific communities and address these questions, a design has been identified consisting of eight alternative 21st century scenarios plus one large initial condition ensemble and a set of long-term extensions, divided into two tiers defined by relative priority. Some of these scenarios will also provide a basis for variants planned to be run in other CMIP6-Endorsed MIPs to investigate questions related to specific forcings. Harmonized, spatially explicit emissions and land use scenarios generated with integrated assessment models will be provided to participating climate modeling groups by late 2016, with the climate model simulations run within the 2017-2018 time frame, and output from the climate modelPublished by Copernicus Publications on behalf of the European Geosciences Union.

AerChemMIP: quantifying the effects of chemistry and aerosols in CMIP6

“…To detect the largest signal we choose the reference scenario to be SSP3-7.0 "Regional Rivalry" without climate policy (7.0 W m −2 at 2100, experiment ssp370), see , as this has the highest levels of short-lived climate pollutants and "Weak" levels of air quality control measures (O'Neill et al, 2016;Rao et al, 2017). The ssp370 ScenarioMIP simulation will need to have been run with the AerChemMIP setup and diagnostics, or repeated here.…”

Global drought and severe drought-affected populations in 1.5 and 2 °C warmer worlds

“…We used SSP1 scenario because it describes the storyline of a green growth paradigm with sustainable development and low challenges for adaptation and mitigation (Jones and O'Niell, 2016). The 1.5 and 2 • C warmer worlds clearly fit in this description and are thus considered under the 2015 Paris Agreement (UNFCCC Conference of the Parties, 2015;O'Niell et al, 2016). In this pathway, the world population would peak at around 2050s and then decline (Van Vuuren et al, 2017).…”

Compiled records of carbon isotopes in atmospheric CO<sub>2</sub> for historical simulations in CMIP6

“…Carbon isotopes will also be included in the simulation of future scenarios. In a separate paper, we will provide atmospheric 14 C and δ 13 C for future scenarios in CMIP6 created with a simple carbon cycle model (Graven, 2015) and CO 2 emission and concentration scenarios from ScenarioMIP (O'Neill et al, 2016).…”