03_Day_1_Hansen
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03_Day_1_Hansen Presentation Transcript

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