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Monitoring Climate Change from Space

Monitoring Climate Change from Space. Richard Allan Department of Meteorology, University of Reading. Why Monitor Earth’s Climate from Space?. Global Spectrum Current Detection Understanding Prediction. The problem. IPCC: www.ipcc.ch/ipccreports/ar4-wg1.htm.

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Monitoring Climate Change from Space

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  1. Monitoring Climate Change from Space Richard Allan Department of Meteorology, University of Reading

  2. Why Monitor Earth’s Climate from Space? • Global • Spectrum • Current • Detection • Understanding • Prediction

  3. The problem... IPCC: www.ipcc.ch/ipccreports/ar4-wg1.htm

  4. Earth’s Radiation balance in space 4πr2 Thermal/Infra-red or Outgoing Longwave Radiation (OLR)=σTe4 πr2 S Absorbed Solar or Shortwave Radiation (S/4)(1-α) • There is a balance between the absorbed sunlight and the thermal/longwave cooling of the planet: (S/4)(1-α) ≈ σTe4 • How does it balance? Why is the Earth’s average temperature about 15oC? e.g. Lacis et al. (2010) Science

  5. Earth’s global annual average energy balance Solar Thermal 240 Wm-2 240 Wm-2 Efficiency ~61.5% 390 Wm-2 Surface Temperature = +15oC Radiating Efficiency, or the inverse of the Greenhouse Effect, is strongly determined by water vapour absorption across the electromagnetic spectrum

  6. Now double CO2 or reduce suns output: a “radiative forcing” Solar Thermal: less cooling to space 240 Wm-2 236 Wm-2 Efficiency ~60.5% 390 Wm-2 Surface Temperature = +15oC Radiative cooling to space through longwave emission drops by about 4 Wm-2 resulting in a radiative imbalance

  7. The climate system responds by warming Solar > Thermal 240 Wm-2 236 Wm-2 Efficiency ~60.5% Heating 390 Wm-2 Surface Temperature = +15oC

  8. The climate system responds by warming Solar = Thermal 240 Wm-2 240 Wm-2 Efficiency ~60.5% 397 Wm-2 Surface Temperature = +16oC The 2xCO2 increased temperature by about 1oC in this simple example. So what’s to worry about?

  9. But it’s not that simple… IPCC (2007)

  10. Climate forcing and feedback : a natural experiment

  11. 29/3/06 11.05am

  12. 29/3/06 12.26pm

  13. Clouds affect radiation fluxes • Radiation fluxes affect clouds

  14. Feedback loops or “vicious circles” amplify or diminish initial heating or cooling tendenciese.g. Ice “albedo” Feedback Melting ice and snow  CO2 Temperature Reduced reflection of suns rays Additional surface heating

  15. One of the strongest positive amplifying feedbacks involves gaseous water vapour  CO2  Water vapour Temperature  Greenhouse effect  Net Heating

  16. Cloud Feedback: a complex problem • Clouds cool the present climate • Will clouds amplify or reduce future warming?

  17. Monitoring Climate From Space

  18. file:///C:/Documents%20and%20Settings/Richard%20Allan/My%20Documents/CONTED/ANIMATIONS/200603_60min_DUST.movfile:///C:/Documents%20and%20Settings/Richard%20Allan/My%20Documents/CONTED/ANIMATIONS/200603_60min_DUST.mov

  19. Satellite measurements (1970, 1997) confirm the effect of increasing greenhouse gases IRIS/IMG spectra: Harries et al. 2001, Nature CH4 Stronger greenhouse effect CO2 O3 1/wavelength

  20. Monitoring Natural forcings: The Sun ACRIM/VIRGO IPCC WG1 2.7.1 (p.188-193) 0.2 Implied changes in global temperature 0.1 0.0 Lean (2000) Y.Wang (2005) See also: http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant

  21. Monitoring Sea level IPCC 2007 Fig. 5.13 (p. 410) Satellite altimetry Recontructed (proxy) Coastal tide gauges

  22. Current rises in global sea level Is sea level rising faster than projections made by numerical climate simulations? Research by Rahmstorf et al. (2007) Science, 4 May

  23. Monitoring sea surface temperature

  24. Monitoring Land Ice From Space Above: results from Gravity Recovery And Climate Experiment (GRACE) mission Right: NASA's ICE-Sat satellite - Ice, Cloud and land Elevation Satellite

  25. Arctic sea ice:recovery from 2007 minimum but robust downward trends in extent since 1979 measured by SSM/I satellite instruments NSIDC : http://nsidc.org/news

  26. Remote sensing clouds and aerosol from space: Cloudsat and CALIPSO • Radar: ~D6, detects large particles (e.g. ice) • Lidar: ~D2, more sensitive to thin cirrus, low-level liquid clouds and aerosol pollutants but signal is attenuated Cloudsat radar CALIPSO lidar Insects Aerosol Rain Supercooled liquid cloud Warm liquid cloud Ice and supercooled liquid Ice Clear No ice/rain but possibly liquid Ground Target classification Work by Dr. Julien Delanoë and Prof. Robin Hogan, University of Reading

  27. How will the water cycle change? Work by Dr. Ed Hawkins and Prof. Rowan Sutton, University of Reading

  28. Trenberth et al., work published in the Bulletin of the American Meteorological Society (2009) and Intergovernmental Panel on Climate Change (2007)

  29. Physical basis: water vapour • Physics: Clausius-Clapeyron • Low-level water vapour concentrations increase with atmospheric warming at about 7%/K • Wentz and Shabel (2000) Nature; Raval and Ramanathan (1989) Nature

  30. Large-scale rainfall events fuelled by moisture convergence e.g. Trenberth et al. (2003) BAMS  Intensification of rainfall (~7%/K?) Extreme Precipitation

  31. Global Precipitation is constrained by energy balance Precipitation ~2-3%/K Water vapour ~7%/K Allen and Ingram (2002) Nature

  32. Changing character of rainfall events Heavy rain follows moisture (~7%/K) Mean Precipitation linked to radiation balance (~3%/K) Precipitation  Light Precipitation (-?%/K) Temperature  See discussion in Trenberth et al. (2003) Bulletin of the American Meteorological Society

  33. Climate model projections (see IPCC 2007) Precipitation Intensity • Increased Precipitation • More Intense Rainfall • More droughts • Wet regions get wetter, dry regions get drier? • Regional projections?? Dry Days Precipitation Change (%)

  34. Using microwave measurements from satellite to monitor the water cycle Precip. (%) Allan and Soden (2008) Science

  35. The rich get richer… Wet Precipitation change (%) Observations Dry Models Allan et al. (2010) Environmental Research Letters

  36. Conclusions • Earth’s radiative energy balance drives climate change • It also provides a rich spectrum of information • Monitoring and detecting climate change • Understanding physical processes • Enabling and evaluating prediction • Challenges... • Clouds & Aerosol • Precipitation • Regional impacts

  37. Earth’s global average energy balance:no atmosphere Solar Thermal 240 Wm-2 240 Wm-2 Efficiency = 100% 240 Wm-2 Surface Temperature = -18oC

  38. Earth’s global average energy balance:add atmosphere Solar > Thermal 240 Wm-2 Heating 240 Wm-2 Temperatures rise

  39. Earth’s global average energy balance:present day Solar Thermal 240 Wm-2 240 Wm-2 Efficiency ~60% 390 Wm-2 Surface Temperature = +15oC The greenhouse effect helps to explain why our planet isn’t frozen. How does it work?

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