Integrated View of  Climate Change and Air Quality   Global Roundtable on Climate Change May 11-12, 2005     James E. Hans...
Dangerous Anthropogenic Interference <ul><li>What Determines Critical Global Warming Level ? </li></ul><ul><li>►  Sea Leve...
Global Climate Forcings <ul><li>Forcing Changes in the Industrial Era (1850-2000) </li></ul><ul><li>►  CO 2  Is Largest Fo...
An Alternative Climate Scenario <ul><li>Places Equal Weight On </li></ul><ul><li>►   Reducing Conventional Air Pollutants ...
Carbon Dioxide Emissions <ul><li>Flat Emissions (50 years), Declining 1.5 W/m 2  in 100 yrs. </li></ul><ul><li>►  Annual G...
CO 2  Trade-off w. Non-CO 2  Climate Forcings <ul><li>Alternatives Achieving 1.5 W/m 2  for 21 st  Century Forcing </li></...
21 st  Century Global Warming <ul><li>Climate Simulations for IPCC 2007 Report </li></ul><ul><li>►  Climate Model Sensitiv...
Workshop at East-West Center, Honolulu <ul><li>“ Air Pollution as Climate Forcing: A Second Workshop” </li></ul><ul><li>► ...
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03_Day_1_Hansen

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03_Day_1_Hansen

  1. 1. Integrated View of Climate Change and Air Quality   Global Roundtable on Climate Change May 11-12, 2005   James E. Hansen NASA Goddard Institute for Space Studies, The Earth Institute at Columbia University
  2. 2. Dangerous Anthropogenic Interference <ul><li>What Determines Critical Global Warming Level ? </li></ul><ul><li>► Sea Level Rise: Evidence from The Earth’s History </li></ul><ul><li>(+5 meters eemian period; +25 meters middle pliocene) </li></ul><ul><li>► Arctic Environment: Avoid Demise of Summer Sea Ice </li></ul><ul><li>(very sensitive because of positive albedo feedback) </li></ul><ul><li>► Regional Climate Disruptions: Avoid Drastic Changes </li></ul><ul><li>(+1ºC may be moderate change; +3ºC is a different planet) </li></ul><ul><li>Conclusion : Need to Keep Global Warming ≤ 1ºC </li></ul><ul><li>References : </li></ul><ul><li>► Defusing the global warming time bomb, Scientific American , March, 2004. </li></ul><ul><li>► A slippery slope: how much global warming constitutes “dangerous anthropogenic interference”?, Clim. Change , 68 , 269, 2005. </li></ul>
  3. 3. Global Climate Forcings <ul><li>Forcing Changes in the Industrial Era (1850-2000) </li></ul><ul><li>► CO 2 Is Largest Forcing </li></ul><ul><li>► Air Pollutants (O 3 , CH 4 , BC) Cause Large Forcing </li></ul><ul><li>► Aerosol Effects (direct + on clouds) Most Uncertain </li></ul><ul><li>Conclusion : CO 2 Largest Forcing, But Others Significant </li></ul><ul><li>References : </li></ul><ul><li>► Trends of measured climate forcing agents, Proc.Natl.Acad.Sci. , 98, 14778, 2001. </li></ul><ul><li>► Efficacy of climate forcings, J. Geophys. Res., in press, 2005. </li></ul>Estimated 1850-2000 climate forcings; circled forcings are prime contributors to air pollution.
  4. 4. An Alternative Climate Scenario <ul><li>Places Equal Weight On </li></ul><ul><li>► Reducing Conventional Air Pollutants Causing Warming </li></ul><ul><li>(Ozone, Ozone precursors, esp. CH 4 , Soot = Black Carbon) </li></ul><ul><li>► Flattening of CO 2 Emissions Rate </li></ul><ul><li>(declining CO 2 emissions by mid-century) </li></ul><ul><li>Conclusion: Need Integrated Climate Assessment </li></ul><ul><li>References : </li></ul><ul><li>► Global warming in the twenty-first century: an alternative scenario, Proc. Natl. Acad. Sci. , 97 , 9875-9880, 2000. </li></ul><ul><li>► A brighter future, Climatic Change , 52 , 435-440, 2002. </li></ul><ul><li>► Image Credit: Burke, Paul. First People . http://www.firstpeople.us/pictures/bear/A-Mothers-Special-Touch-1600x1200.html </li></ul>
  5. 5. Carbon Dioxide Emissions <ul><li>Flat Emissions (50 years), Declining 1.5 W/m 2 in 100 yrs. </li></ul><ul><li>► Annual Growth Rate Declined From 4-5% to 1.4% in 1970s </li></ul><ul><li>(price driven + efficiency regulations) </li></ul><ul><li>► Further Gains are Feasible, which Could Flatten Emissions </li></ul><ul><li>(untapped efficiencies, renewables, CO 2 seques., next gen. nuclear) </li></ul><ul><li>► Fuel Cost Too Low to Drive Greater Efficiency Gains </li></ul><ul><li>(Iowa economist approach: gift + tax = 0 = little guy gains) </li></ul><ul><li>Conclusion: Flat (Uncaptured) CO 2 Emissions Technically Feasible </li></ul><ul><li>References: </li></ul><ul><li>► On the Road to Climate Stability, http://www.columbia.edu/~jeh1 </li></ul><ul><li>► Can we defuse the global warming time bomb?, NaturalSCIENCE , 2003, http://www.naturalscience.com/ns/articles/01-16/ns_jeh.html </li></ul>
  6. 6. CO 2 Trade-off w. Non-CO 2 Climate Forcings <ul><li>Alternatives Achieving 1.5 W/m 2 for 21 st Century Forcing </li></ul><ul><li>► +0.5 W/m 2 Non-CO 2 (typ . IPCC)  Max CO 2 = 440 PPM </li></ul><ul><li>(infrastructure + current trends  440 ppm implausible) </li></ul><ul><li>► -0.5 W/m 2 Non-CO 2  Max CO 2 = 520 PPM </li></ul><ul><li>(520 ppm also permits larger on-going fossil fuel use) </li></ul><ul><li>Conclusion : Small Forcings Make Big Difference </li></ul><ul><li>References : </li></ul><ul><li>► Greenhouse gas growth rates, Proc. Natl. Acad. Sci. , 101 , 16109-16114, 2004. </li></ul>5-year mean growth rate of climate forcing by well-mixed greenhouse gases (O 3 and stratospheric H 2 O not included)
  7. 7. 21 st Century Global Warming <ul><li>Climate Simulations for IPCC 2007 Report </li></ul><ul><li>► Climate Model Sensitivity ~ 2.7ºC for 2xCO 2 </li></ul><ul><li>(consistent with paleoclimate data & other models) </li></ul><ul><li>► Simulations Consistent with 1880-2003 Observations </li></ul><ul><li>(key test = ocean heat storage) </li></ul><ul><li>► Simulated Global Warming < 1ºC as Alternative Scenario </li></ul><ul><li>Conclusion : Warming < 1ºC if additional forcing ~ 1.5 W/m 2 </li></ul><ul><li>References : </li></ul><ul><li>► Climate simulations with GISS modelE, to be submitted to J. Geophys. Res. </li></ul>Global surface temperature simulations extended through 21 st century.
  8. 8. Workshop at East-West Center, Honolulu <ul><li>“ Air Pollution as Climate Forcing: A Second Workshop” </li></ul><ul><li>► Multiple Benefits by Controlling CH 4 and O 3 - Precursors </li></ul><ul><li>(benefits climate, human health, agriculture) </li></ul><ul><li>► Multiple Benefits from Near-Term Efficiency Emphasis </li></ul><ul><li>(climate & health benefits, avoid undesirable infrastructure) </li></ul><ul><li>► Targeted Soot Reduction to Minimize Warming from Planned Reductions of Reflective Aerosols </li></ul><ul><li>(improved diesel controls, biofuels, small scale coal use) </li></ul><ul><li>Conclusion : Technical Cooperation Offers Large Mutual Benefits to Developed & Developing Nations. </li></ul><ul><li>References : </li></ul><ul><li>► Air Pollution as Climate Forcing: 2002 meeting: http://www.giss.nasa.gov/meetings/pollution02/ </li></ul><ul><li>► Air Pollution as Climate Forcing: 2005 Workshop: http://www.giss.nasa.gov/meetings/pollution2005/ </li></ul>April 4-6, 2005; Local Host: Intn’l. Center for Climate and Society, Univ. Hawaii

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