Joint Session CでのKevin Trenberthの講演を増田がメモしたものを、英語の箇条書きですが、ひとまずそのまま置きます。

Kevin Trenberth: Aspects of climate observing system: Energy and water

Tracking Earth's global energy: Where has global warming from increased GHGs gone?

• 2008 coldest since 2000
  • (peak 1998 or 2005)
  • (1997-2008 trend positive but not significant)
  • CO2 rises, rad. forcing also rises
• "Natural variability"
  • evolution of Pacific Nino SST indices
  • La Nina 2007-2008 (Jan 2008 coldest)
  • El Nino 2009 June-
  • Cooling can easily happen for a decade or so (Easterling et al. 2009 GRL)
• But where did the energy go?
  • We should be able to trace it!

Global energy balance

• Global energy balance
  • Trenberth et al. 2009
  • 2000-2005 CERES period
  • Net absorbed energy 0.9 W/m^2
  • A warming climate has a cause ... radiative forcing and response of climate
• forcing
  • CO2 +1.6 W/m^2
  • GHGs (incl. CO2) +3.0
  • aerosols -2.1 (?)
  • total +1.6 (?)
• feedbacks
  • water vapor +2.1
  • ice-albedo (included in above?)
  • radiation -2.8
  • ...
  • net -0.9
• Where does energy go? Can we track it?
  • 1. warming land & atmosphere
  • 2. heat storage in ocean (sea level)
  • 3. melting land ice (sea level)
  • 4. melting sea ice
  • 5. evaporation -> cloud -> reflection -> lost to space
• Energy content change
  • IPCC 2007 Fig 5.4 (1961-2003 and 1993-2003)
  • Ocean storage more than 90%
• Top-of-atmosphere budget: absolute value difficult
  • ERBS TOA radiation Wang et al. 2006
  • + ocean heat content Willis et al. 2004
• Sea level
  • rising
  • +3.1 +/- mm/yr since 1992 (total 48 mm) (Steve Nerem, U. Colo.)
  • data: altimetry (TOPEX-POSEIDON, Jason 1,2)
  • 1997/98 anomalous increase
  • 2007/08 anomalous decrease
    • cf. Oct 2007 - Mar 2008 extra rainfall over land remarkable
  • 60% expansion, 40% glacier melt
• Ocean heat content revised
  • (Levitus et al. 2009; Domingues et al. 2008; Ishii & Kimoto 2009)
  • 1969-2007 linear trend 0.3 W/m^2

• What about 2007-2008?
  • Quiet sun
    • data: SORCE
    • drop about 0.5 W/m^2 in TSI (total solar irradiance)
    • = drop about 0.1 in radiative forcing to climate
  • Snow cover and Arctic sea ice decreasing
    • 10^6 km x 1 m to 10 deg. C ... 3.4 x 10^20 J
    • globally 0.02 W/m^2 ... too small to account for the change
    • (locally large)

• sea level
  • (Willis, Chambers, Nerem 2008 JGR)
    • sea level <- altimeter
    • heat content <- Argo
    • mass <- GRACE
  • Heat content and mass both short of accounting sea level rise
  • also
    • (Cazenave et al. 2009 GPC)
    • (Leuliette & Miller 2009)
  • Reconciliation depends on glacial isostatic adjustment in GRACE

• energy balance
  • Cloud
    • ISCCP -2007, not homogeneous
    • HIRS cloud amount trends (Wylie et al. 2005)
  • CERES
    • official product 2000-2005.Oct stable
    • preliminary product -2009, MTSAT problem since 2005.Nov
    • "Flashflux" discontinuity in 2008Jan in OLR
  • Where did the energy go?
    • 1993-2003 ocean
    • 2004-2008 some ocean, some not explained
  • Need to know
    • 1% increase in clouds ... -0.5 W/m^2
    • need cloud/radiation data near real-time
  • Implication to geo-engineering
    • background knowledge poor
    • (risk of side effects is real)

Climate observing system

• observation
• analysis
• assimilation
• prediction
• attribution
• assessment
• decision making

(to be presented at World Climate Conference next week)

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