Proposal for a new GeoMIP experiment for Chemistry Climate Model Ini8a8ve (CCMI) S. Tilmes, M.J. Mills, U. Niemeier, H. Schmidt, A. Robock, B. Kravitz, G. Pitari, J.-‐F. Lamarque, V. Aquila, J. English, R. Neely Ø Overview of GeoMIP and Results Ø Mo6va6on for GeoMIP experiment for CCMI Ø Setup of experiments Ø Science Ques6ons CCMI Workshop, 20-‐22 May 2014, Lancaster University, UK Idea of Using Geoengineered Aerosols to Cool the Earth’s Climate Injec8on of Stratospheric Sulfate Aerosols: Natural Experiment: for example 1991 Mt Pinatubo erup6on cools the Earth’s surface Geo-‐engineering: for example injec6on of 10 TgS per year = one million flights per year with a payload of 10 metric tons of aerosol (Rasch et al, 2008). Stratosphere warming cooling Troposphere SPARC 2006, Rasch et al, 2008 How effec6ve is geoengineering to counteract global warming? How does it change regional climate and precipita6on? What other side effects are likely? -‐> learn about the climate system GeoMIP (Geoengineering Model Intercomparison Project) Well defined sensi6vity experiments G1-‐G2, based on CMIP5 experiments to study the impact of solar radia6on management (SRM) on the Earth’s system. Ini$ators: Ben Kravitz, Alan Robock, Olivier Boucher, Hauke Schmidt, Karl Taylor, Georgiy Stenchikov, Michael Schulz G1, G2: balancing incoming LW forcing with reduced solar constant 1850 1850 G1: Baseline: CMIP5 4xCO2, Geoeng.: radia6ve forcing on top of the atmosphere is balanced (model specific based on the planetary albedo, could effects etc): 3.5-‐5.0% reduc8on necessary G2: Baseline: CMIP 1% /yr CO2 increase, Geoeng.: as G1, derived forcing from G1 experiment, termina6on aber 50 years GeoMIP (Geoengineering Model Intercomparison Project) ScienOfic Highlights (hRp://climate.envsci.rutgers.edu/GeoMIP/publicaOons.html) G1 and G2 solar dimming experiments (12 models par8cipated): • Global temperatures could be balanced • Con6nued but less warming of high la6tudes (e.g., Schmidt 2012, Kravitz et al., 2013) • Reduced sea-‐ice loss (Moore et al., 2013) • Reduc6on of extreme temperature changes (Curry et al., 2013) • Reduc6on of the hydrological cycle (Tilmes et al., 2013) • Reduc6on of crops (Xia et al., 2014) • Termina6on Effect (Jones et al., 2013) -‐> solar acts in the shortwave while greenhouse gases act in the longwave radia6on GeoMIP (Geoengineering Model Intercomparison Project) More “realis6c” sensi6vity experiments G3-‐G4 G3, G4: balancing the anthropogenic radia6ve forcing using stratospheric aerosols G3: Baseline: RCP4.5, Geoeng.: stratospheric aerosols in 2020 is increased gradually to balance the LW forcing, equatorial injec6on, termina6on aber 50 years G4: Baseline: RCP4.5, Geoeng.: fixed aerosol injec6on of 5 Tg SO2 per year, termina6on aber 50 years Stratospheric Ozone Response to Sulfate Geoengineering Pitari et al, 2014 Comparison of 4 different models that include chemistry-‐climate interac6ons, as well as interac6ons with aerosols Differences: • SO2 injec6on of 3 out of 4 models, one used prescribe AOD -‐> very different aerosol distribu8on • Stratospheric heterogeneous chemistry for 3 out of 4 models • 2 prescribed SST, 2 coupled models • Aerosol impact on photolysis: 3 out of 4 • Aerosol microphysics, one model How much of the differences is due to different aerosol distribu8on, transport/chemistry descrip8on, and variability? -‐> uniformly prescribed aerosol distribu8on would reduce differences and iden8fy significant changes to the climate system Aerosol Op6cal Thickness New GeoMIP experiment for Chemistry-‐Climate Model Ini8a8ve (CCMI) Simple G4-‐type experimental setup: • Sensi6vity run for REFC2: 2020-‐2100 • Use prescribed aerosol distribu6on derived previously using a microphysical model • 8 Tg SO2 injec6on: 1.09 W/m2 based on ECHAM, large varia6ons between models possible 8TgSO2/year 8 Tg SO2/yr injec6on Tilmes et al., 2014, to be submiRed to GMD New GeoMIP experiment for Chemistry-‐Climate Model Ini8a8ve (CCMI) GeoMIP prescribed aerosols Pressure (hPa) Aerosol distribu8on: • Model: ECHAM HAM 3D microphysical modal model, radia6ve interac6ons included, evaluated against observa6ons • Injec8on case: 8 Tg of SO2 per year, includes 2 years ramp-‐up: 2020-‐2021, and two years ramp-‐down: 2070-‐2071 • Available variables: aerosol mass, effec6ve and modal radius, AOD/ ex6nc6on, aerosol volume density • Zonal and and monthly mean distribu6on on pressure levels up to 1hPa La6tude CCMI data set for 1992 ^p://acd.ucar.edu/user/8lmes/CCMI/sulf/ geomip_ccmi_2020-‐2071_volc_v2.nc ([email protected]) La6tude Tilmes et al., 2014, to be submiRed to GMD Scien8fic Ques8ons Response of a con8nuous enhanced stratospheric aerosol layer: Same aerosol forcing between 2020-‐2070, but: Ø declining halogen burden Ø increasing greenhouse gases Ø reduc6on of future aerosols Ø changes in future NOx and CO emissions • Stratospheric dynamics, including BDC and QBO, stratospheric hea6ng rates • Stratospheric chemistry in par6cular ozone and its impact on UV • Tropospheric ozone, methane life6me • Tropospheric dynamics and temperatures (SAM, Hadley Circula6on) • Climate, surface temperatures and precipita6on • Agriculture and Ecosystem Impact on QBO depending on emission rate (in ECHAM5/HAM) Courtesy of H. Schmidt and U. Niemeier Pressure (hPa) No engineering year u (m/s) 8 Mt S/yr Pressure (hPa) Pressure (hPa) 4 Mt S/yr year Phase 1 Phase 2 year (see also Aquila et al., GRL, 2014) Mo8va8on to include Chemistry • Impact on Stratospheric Dynamics and Chemistry (Ozone, QBO) • Impact on UV, surface ozone and crops • Impact on tropospheric life6me of different tracers -‐> Impact on Climate Impact on UV depending on the amount of Very Short-‐Lived species Changes in 2050 la6tude Tilmes et al., 2012 la6tude Impact on tropospheric methane life8me Conclusions Proposal to run CCMI models with the same prescribed aerosol distribu8on to simulate geoengineering between 2020 and 2070. • Same aerosol distribu6on and aerosol proper6es will help to reduce differences between models • Easy to implement for models (same as volcanoes) • Baseline simula6on (RCP6.0 already done) • More significant results in changes in climate variables, if more models par6cipate • Comprehensive chemistry descrip6on in models allows to iden6fy important interac6ons • Models are evaluated within the CCMI project 8TgSO2/year Aerosol distribu$on: 2p://acd.ucar.edu/user/$lmes/CCMI/sulf/geomip_ccmi_2020-‐2071_volc_v2.nc Email Simone Tilmes ([email protected]) Addi8onal Slide Surface temperature response to G4 BNU-ESM GISS-E2-R HadGEM2-ES MIROC-ESM MIROC-ESM-CHEM RCP4.5 G4 strong response: HadGEM2-ES, BNU-ESM weak response: MIROC-ESM, MIROC-ESM-CHEM GeoMIP (Geoengineering Model Intercomparison Project) ScienOfic Highlights (hRp://climate.envsci.rutgers.edu/GeoMIP/publicaOons.html) G1 and G2 solar dimming experiments (12 models par8cipated): • Global temperatures could be balanced • Reduced sea-‐ice loss (Moore et al., 2013) • Reduc6on of extreme temperature changes (Curry et al., 2013) • Con6nued but less warming of high la6tudes (e.g., Schmidt 2012, Kravitz et al., 2013) • Reduc6on of the hydrological cycle (Tilmes et al., 2013) • Reduc6on of crops (Xia et al., 2014) G3 and G4 sulfur injec8on experiments (4-‐6 models with different setup): • Effects on stratospheric chemistry, dynamics and UV (Pitari et al., 2014) • Effects on the stratospheric dynamics (Niemeier et al., in prepara6on) • Effects on Southern Annual Mode (Philpps et al., in prepara6on) • Effects on Agriculture (Xia et al., in prepara6on) -‐> fewer models par8cipated, less robust results
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