Using Earth System Models to provide policy-relevant information (Couples therapy for the uneasy marriage between science and policy)‏ Gavin Schmidt NASA Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University QUEST/AIMES Edinburgh 2010

Scientists Policymakers

We speak the same language but.... we frame issues very differently: Scientists tend to focus on individual processes, abundance and concentrations Policymakers focus on individual actions, emissions Scientists are often single issue, Policymakers multi-tasking i.e. air quality and climate and biodiversity and... The Fundamental Issues

But isn't IPCC supposed to deal with this? Secret definition of the IPCC: Assessment of the science, by the scientists, for the scientists

Climate forcings (Scientists' viewpoint)‏ IPCC AR4 (2007)‏ (mostly same as TAR except for a 90º clockwise rotation)‏

But different forcings are linked! Each industrial or agricultural activity has a different emission profile Different emissions affect secondary forcings (ozone, sulphates) through atmospheric chemistry Net climate forcing or air quality impacts may be very different

Forcings Forcings or Feedbacks Calculated Climate processes

Some key atmospheric interactions Impact on SO 2 -> SO 4

Key interactions Competition for oxidants: CH 4 decreases OH and increases ozone => reduced oxidation of SO 2 NO x increases OH and ozone => increased oxidation of CH 4, SO 2 SO 2 decreases OH, decreases O 3, nitrate Competition for NH 3 (btw sulphate and nitrate) BC: direct affects (absorption) + semi-direct effects (local heating affecting clouds) + indirect impact on ice clouds

Shindell et al (Science, 2009)‏ Climate forcings (Emissions viewpoint)‏

Where do/will emissions come from? Residential fossil fuel Residential biofuel Industry Power Biomass Burning Transportation NOx CO VOCs SO Global Emissions 1995 and 2030

Examples: Transportation Surface On-road Transport (ORT)‏ Cars, trucks, trains CO 2, NO x, BC etc. Ground level, domestically controlled Aviation CO 2, NO x, SO 2, Contrails, water vapour Upper troposphere, international Shipping Bunker fuel high in SO 2 very visible indirect effects (ship tracks)‏ Oceanic, surface, international

Climate Impacts: On Road Transport and Power Generation (20 yr horizon) Unger et al (2009, Atm. Env)‏

Future scenarios: 50% reduction ORT emissions S1: (zero emission replacement source)‏ S2: (current power generation mix) 20-yr horizon Unger et al (2009, Atm. Env)‏

Temperature impacts of scenarios Temperature (mK)‏ US only Global Zero-emission replacement Current power sector profile 20-yr horizon Unger et al (2009, Atm. Env)‏

Pollutant impacts OzoneSulphate Zero-emission replacement Current PG replacement BC OC Unger et al (2009, Atm. Env)‏

Summary Surface transportation (US or Global) good target Unambiguous reductions in climate forcing: Regardless of replacement power source! Some non-CO 2 effects are more uncertain: Indirect aerosol effects (incl. BC)‏ Projected reductions in temperatures across NH Also reductions in Ozone and PM (BC)‏ Uncertainty in BC affects may impact results w.r.t. new diesel

Climate forcings by sector (Policy viewpoint)‏ Shindell et al (2008)‏ On 20-yr timescale, inclusion of short-lived species (ozone, black carbon, sulphates) changes relative importance of sectors N. Amer. transportation/Asian domestic better targets for reducing climate and air pollution effects

Regional impacts of sector-specific reductions

Can we identify win-win scenarios? Yes! 1) Domestic use of coal and biomass in Asia CO 2, CO, SO 2, soot => ozone, smog, health issues Electrification (even using modern coal plants)‏ reduced CO 2, reduced air pollution, reduced climate forcing, better health outcomes 2) Surface transportation in US/Europe CO 2, soot from diesel, NO x => ozone Move to less driving/plug-in hybrids reduce CO 2, reduced air pollution

Conclusions Models can provide key input to policy choices Sector specific simulations can give projections for air quality and climate and other impact Outside of current IPCC framework Emerging focus on short-term initialized decadal predictions untested and of unclear utility for policymakers Important uncertainties remain: Carbon cycle feedbacks, mixed phase aerosols Ice sheet response (for sea level rise)‏ Regional impacts

Scientists Policymakers We need to talk....