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Climate Models, Climate Forcing and Climate Change

Adler Planetarium Feb 25 2006. Gavin Schmidt NASA Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University. Climate Models, Climate Forcing and Climate Change. Climate Changes. Global Mean. 2005 Annual Mean January 2006.

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Climate Models, Climate Forcing and Climate Change

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  1. Adler Planetarium Feb 25 2006 Gavin Schmidt NASA Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University Climate Models, Climate Forcing and Climate Change

  2. Climate Changes.... Global Mean 2005 Annual Mean January 2006

  3. The Climate Pyramid FORCINGS VARIABILITY RESPONSE CLIMATOLOGY PROCESSES

  4. Climate processes Calculated Forcings or Feedbacks Forcings

  5. Climate forcings Orbital Solar Volcanic Greenhouse gases (CO2, CH4, N2O, CFCs) Aerosol effects (direct and indirect) Ozone (troposphere/stratosphere) Land use Aircraft Events Tectonics Exotica?

  6. Climate forcings 1750-2000 Hansen et al (2005) Solar Aerosols Greenhouse Gases Land Use Total Forcing: ~ 1.6 ± 1.0 W/m2

  7. 20th Century forcings...

  8. Climate Sensitivity... • How much does the Earth warm if we change things? • An emergent property of global climate • i.e. not a priori determinable from small scales • An equilibirium property that involves feedbacks => 20-30 years for effects to be fully felt • Models: 3±1°C for 2xCO2 ~ ¾°C/(W/m2) • Paleoclimate data? Peak of last ice age (20 kyrs ago): • Ice sheets/vegetation/GHG/dust • RoughlyΔF = -6.6±1.5 W/m2for 5°C cooling • => ~¾°C/(W/m2)

  9. Modelling uncertainties... • Cloud parameterisations still relatively crude • Regional climate change less well validated • Aerosol effects are still highly uncertain • Past estimates of forcing (pre-1979) uncertain: aerosol, O3 distributions/composition, solar irradiance • Ocean response in medium/long term (50 – 100 yrs) • Regional climate sensitive to dynamic patterns (forced?)- Arctic Oscillation/North Atlantic Oscillation, El Nino etc... • Need to validate simulations against past climate change...

  10. Volcanic forcing and response Mt. Pinatubo 1991 “Winter warming” Obs Model

  11. Last 2000 years?

  12. Solar forcing? Solar Min vs. Solar Max Longer term solar changes? Lean (2006)

  13. Solar response Observed response: Lag correlation with solar forcing Mann et al 99 reconstruction Waple et al (2001) Modelled response: strat. resolving model ozone+SST feedbacks Decrease in NAO Shindell et al, 2001, Science

  14. 20th Century climate (IPCC AR4) MSU4 SAT MSU3 Rad. Imbalance

  15. Greenhouse Gas Emissions Increasing emissions of CO2 are certain... but CH4, CFC growth rates have declined

  16. Future projections...

  17. Future temperatures?

  18. Conclusions Known radiative forcings can explain large part of climate change over last 150 years (GHGs, Solar, Aerosols, Ozone, etc.) Delay in climate response and radiative imbalance implies another 0.6°C warming “in pipeline” Increases in CO2 emissions will continue CH4, black carbon, CFCs growth rates more controllable Forcing is not yet (probably) at a “dangerous” level Climate change is a long term issue and it will not be going away anytime soon...

  19. Some relevant quotes... Prediction is difficult, particularly of the future. -Niels Bohr Grid models can't save us now!-Day after Tomorrow

  20. More lessons from the media... It’s not nonsense! My father’s a climatologist. He works for the government!

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