IPCC (2007) and the NAS/NRC Committee on Radiative Forcing Effects on Climate
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Transcript of IPCC (2007) and the NAS/NRC Committee on Radiative Forcing Effects on Climate
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INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC) Working Group I
IPCC (2007) and the NAS/NRC Committee on Radiative Forcing
Effects on Climate
Susan Solomon, co-chair, IPCC WGI
and senior scientist, NOAA Aeronomy Laboratory
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IPCC - WGI
IPCC (2001): Houghton (UK)and Ding (China), co-chairs
Climate Change 2007 The Physical Science Basis
IPCC (2007): Solomon (USA) and Qin (China), co-chairs
An NRC report that was an important input to the TAR
This committee: an important opportunity for similar synergy through dialogue
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IPCC - WGI
Time Line Issues
WGI panelJan 2007
Lead Author meeting 4 (TBD)Jun 2006
Second draft completeFeb 2006
Lead Author meeting 3 (Christchurch)Dec 2005
First draft completeAug 2005
Lead Author meeting 2 (Beijing)May 2005
Second scoping meeting Sep 2003
Zero order draft completeFeb 2005
Lead Author meeting 1 (Trieste)Sep 2004
Lead author teams selected by WGI BureauApr 2004
Panel approval of outlines for reportsNov 2003
First scoping meetingApr 2003We are here:
the outline is in final form and is about to be submitted to the Plenary for approval
This committee’s report is due just before WGI authors begin first formal draft
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IPCC - WGI
What does UNFCCC want?
• Strong scientific messages telling an integrated story – not a grab bag of topics
• Clear expository graphics, avoiding “mathematical magic”
• Clear explanation of uncertainties and limits to understanding
• Address key questions
• Skip unnecessary repetition of earlier reports (very important) - this forced tough choices
• Shorter and “more focussed”
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IPCC - WGI
Radiative Forcing: A key topic, as in past reports…assess anthropogenic and natural influences on radiative balance
• Review/update past and estimated future radiative forcing for greenhouse gases, and..
• ..for aerosols including indirect effects (sulfate, nitrate, organic, soot….)
• Land use/surface albedo effect
• Aviation (e.g., new studies on cloud interactions)
• Compare with natural forcings (solar, volcanic).
• Roles of short-lived vs long-lived species
• Forcing/response relations in the global mean - use and limits of the radiative forcing concept;
• GWP and other metrics for comparing emissions
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IPCC - WGI
CO2 Solar UT O3
LS
O3
An updated and improved assessment of:•Solar•Aviation•Land use•Aerosols!• esp. soot!• Gases!•GWPs and other metrics
Joshi et al (2003)
More information on dependence of climate change
on forcing mechanism
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IPCC - WGI
How to best convey our message?
Many key
warming agents
live for decades or more
All known coolin
g agents
are short-lived
AR4: stronger emphasis on timescales
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IPCC - WGI
Paleoclimate: More links to forcing • Use paleoclimatic information to provide greater clarity on what may be
natural versus manmade (globally and regionally)
• Illuminate key vulnerabilities to changes in radiative forcing
• Paleoclimate as a basis for testing cause and effect relationships (e.g., volcanoes and solar)
• What happened in the past and why – focus on observations and processes
• Discuss paleo measurements in greater depth - tree rings, ice cores, etc.
• More careful analysis of how anomalous the last century has been
• Review/ update what is known of abrupt climate changes – the potential wild card
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IPCC - WGI
Compare to models (including volcanoes, solar, and anthropogenic forcing) for more than 1000 years
7 NH records
Model with volcanoes, solar,
and GHG/aerosol Tambora
From Crowley, personal communication
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IPCC - WGI
Couplings between changes in the climate system and biogeochemistry: “Beyond radiative forcing”
• Describe the emerging linkages in understanding and simulating the fully coupled system
• Carbon cycle / climate interactions – increasing respiration vs photosynthesis, coupling of C and N biogeochemistry, aerosol/diffuse flux linkages….
• Global atmospheric chemistry and climate change - processes influencing global ozone and methane in a coupled system, coupling of stratosphere to surface change, ….
• Air quality and climate change - interactions on new scales, where increasing numbers of people live
• Aerosols – aerosol/hydrological cycle feedbacks; regional and global scale analyses of coupled aerosol/ chemistry / climate interactions, ….
• Land surface / hydrology including e.g., fires, dynamic vegetation models
• Should better identify possible ‘wild cards’ that could emerge in an altered climate state
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IPCC - WGI
One example of a coupled interaction:Sea-salt emissions = function (wind speed)Transport (advective, convective) and deposition =function(climate)==> “in my opinion an assessment is needed in AR4” - O. Boucher, Marrakech, 2003
A need to go “beyond radiative forcing” to the fully coupled system of human/climate interactions.
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IPCC - WGI
Interesting new papers on aerosol forcings and responses at various levels: A key assessment challenge for WG I
Menon et al.: black carbon (soot) and Asian precipitation.
How well understood are the forcings? Surface fluxes/TOA?
Aerosols potentially influence precipitation at microphysical level (precipitation efficiency); sub-grid scale (altered convection); and large scale (altered circulation patterns).
Rostayn and Lohmann: suggesting a link of aerosols to the drought in Africa. See also work by Rosenfeld and others on other aerosol processes that could play a role.
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IPCC - WGI
Some areas of focus that this committee may wish to consider:
• Definitional issues: How should we think about surface / tropopause / TOA forcings? What is a forcing and what is a feedback?
• Aerosols: direct and indirect effects; aerosol linkages to land use effects (e.g., biomass burning, wind stress, etc.)
• Air quality/climate: a two-way story• Solar and volcanic forcings: satellite era and before,
including paleo. What is a forcing and what is a feedback, across a range of time scales?
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IPCC - WGI
Top-of-the-atmosphere Surface (Wm-2)
March 97
Definitions:Radiative processes and their spatial distributions
Implications for radiative forcing?
And the more general question: what is a forcing and what is a feedback?
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IPCC - WGI
• Particle number, size, precipitation efficiency, liquid water content are all factors in climate
• Do continental clouds have different feedbacks to aerosols than marine clouds?
• New research on black carbon (soot) and on gradients in radiative forcing (sulfate)
• Coupling of land use/vegetation/fires/aerosols issues
Aerosols: A Major Issue
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IPCC - WGI
UN, World Urbanization ProspectsThe 2002 Revision
Air Quality/Climate: More people are living the experience
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IPCC - WGI
Mexico City from Satellites GOME NO2 December average
Data courtesy J. Burrows, U. BremenProcessing by S. Massie, NCAR
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IPCC - WGI
FAR SAR TAR AR4
Solar Forcing: Three full solar cycles of direct observations of the solar irradiance. What are the constraints on solar/volcanic effects over the past three cycles, compared to human activities?
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IPCC - WGI
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Past climates: what do they tell us about radiative forcing and responses, as well as feedbacks?
Last Ice age
Lastinterglacial
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IPCC - WGI
Concluding remarks
• There are many opportunities for synergy; this presentation is a ‘sampler’.
• Timing IPCC/NRC is complementary
• Thanks for this initial discussion