Using Earth System Models to provide policy-relevant information

(Couples therapy for the uneasy marriage between science and policy)

Gavin SchmidtNASA 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 1750-2000(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 SO2 -> SO4

Key interactions

Competition for oxidants:

CH4 decreases OH and increases ozone

=> reduced oxidation of SO2

NOx increases OH and ozone

=> increased oxidation of CH4, SO2

SO2 decreases OH, decreases O3, nitrate

Competition for NH3 (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 1750-2000(Emissions viewpoint)

Where do/will emissions come from?

Residential fossil fuel

Residential biofuel

Industry

Power

Biomass Burning

Transportation

NOx CO VOCs SO21995 2030 1995 2030 1995 2030 1995 2030

Global Emissions 1995 and 2030

Examples: Transportation

Surface On-road Transport (ORT) Cars, trucks, trains CO2, NOx, BC etc.

Ground level, domestically controlled Aviation

CO2, NOx, SO2, Contrails, water vapourUpper troposphere, international

ShippingBunker fuel high in SO2

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) Temperature (mK)

US only

Global

Zero-emission replacement Current power sector profile

20-yr horizonUnger et al (2009, Atm. Env)

Pollutant impacts Ozone Sulphate

Zero-emissionreplacement

Current PGreplacement

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-CO2 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

CO2 CH4 (direct) Short lived species

Total-80

-60

-40

-20

0

20

40

60

Impact of 30% reduction in emissions in Asian and N. Amer-ican sectors

N. America domesticN. America surface transporta-tionN. America industry and power Asia domesticAsia transportAsia industry and power

Ra

dia

tive

Fo

rcin

g m

W/m

2

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 sectorsN. 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

CO2, CO, SO2, soot => ozone, smog, health issues

Electrification (even using modern coal plants)

reduced CO2, reduced air pollution, reduced climate forcing, better health outcomes

2) Surface transportation in US/Europe

CO2, soot from diesel, NOx => ozone

Move to less driving/plug-in hybrids

reduce CO2, reduced air pollution

Conclusions

Models can provide key input to policy choicesSector specific simulations can give projections for air quality and climate and other impactOutside of current IPCC frameworkEmerging focus on short-term initialized decadal predictions untested and of unclear utility for policymakersImportant uncertainties remain:

Carbon cycle feedbacks, mixed phase aerosols

Ice sheet response (for sea level rise)

Regional impacts

Scientists

PolicymakersWe need to talk....