Transcript Aerosol/Climate Research Future Needs

Federal Science Research on the Role
of Aerosols in Climate Change
Sylvia A. Edgerton*
National Science Foundation
Workshop on Secondary Organic Aerosols, Reno NV
February 5, 2002
* Thanks to
Dr. Joel Levy, Atmospheric Chemistry Program Manager at
NOAA, for preparing many of the slides related to aerosols and climate.
Aerosols and Climate
• Aerosols are intimately and significantly linked to the workings of the
climate system
–
–
–
–
Historical view understates the role of aerosols in climate
Aerosols exert very large regional effects not reflected in global averages
Aerosols significantly influence surface energy flux budgets
Aerosols may significantly influence precipitation
• Focused aerosol/climate research is an essential for operational
climate prediction
– Critically selected measurements are required
– Research must be targeted at conceptual breakthroughs
Aerosol Radiative Forcing Mechanisms
• Direct Effect
– Light Scattering and Absorption
==> surface cooling, atmospheric warming
• 1st Indirect Effect (Twomey Effect)
– Decreased cloud droplet size
– Increased cloud droplet concentrations
==> brighter clouds
• 2nd Indirect Effect (feedback?)
– Increased cloud lifetime and/or thickness
==> suppression of drizzle
• Semi-Direct Effect (feedback?)
– Cloud burning due to atmospheric heating
IPCC(2001) Global and Annual Mean
Radiative Forcing
What’s not in this
picture?
• Aerosol 2nd indirect
effect omitted
• Aerosol semi-direct
effect omitted
• Regional character of
aerosol forcing not
represented
• Aerosol models are
largely unvalidated
Aerosol Indirect Radiative
Forcing
Indirect aerosol forcing is the single
largest source of uncertainty in the
radiative forcing of the climate
system.
IPCC 2001
What are aerosol indirect effects?
Aerosol-forced perturbations in cloud
optical properties, resulting from changes
in cloud drop concentration, physical
thickness, effective radius, and horizontal
extent (cloud fraction) that lead to a
change in the earth's cloud radiative
forcing
IPCC (1995) - Invoked aerosol cooling to offset
GCM overestimates of greenhouse warming
Crude Aerosol Model
• Sulfate only
• Light-scattering
only phenomenon
included
• Impact on albedo
computed off-line
Radiative Forcing by Species
Hansen (2001)
Optical Properties of Aerosols
Contribution of Chemical Components to Submicron
Extinction for ACE 1 and INDOEX Air Masses
(550 nm and 55% RH)
Contribution of Chemical Components to
Aerosol Optical Depth for TARFOX
1.0
Fractional Contribution to Aerosol Extinction
0.8
Fractional Contribution to AOD
(Dry, 450 nm)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Carbon
Scattering
Sulfate
Hegg et al (1997)
Carbon
Absorption
Seasalt
Sulfate
Organics
BC
Dust
0.8
0.6
0.4
0.2
0.0
Southern SH Indian
Ocean
Ocean
NH Indian
Ocean
Arabia
Data courtesy of Quinn
E India
Subcontinent
Results from recent field
programs suggest that
regional aerosol-induced
surface cooling is large!
Large-scale observational evidence for
suppression of precipitation by aerosols
Aerosol 2nd Indirect Effect
==> Small droplets coalesce less
efficiently than large droplets
• AVHRR image over Australia shows
pollution tracks from
– power plant (5), smelter (6), port (7),
refinery (8)
• Yellow denotes smaller cloud droplets
• Co-located measurements from
TRMM/PR show
– precipitation outside pollution tracks
– no precipitation inside pollution tracks
• Similar observations have been made
for biomass smoke and dust
D. Rosenfeld, Science 287, 1793 (2000)
Recommendations for future research from a
recent workshop on aerosol-climate interactions
Scripps Institution of Oceanography January 2002
• Characterize the sources, distribution, and properties of
aerosols and their influence on cloud formation and
rainfall, globally and a region-by-region basis
• Represent aerosol impacts in climate models by linking
their representation to these observations
• Quantify the relative importance of aerosols and
greenhouse gases for global warming
Science Management in the
Federal Government
Office of Science and Technology Policy
Office of Management and Budget
National Science and Technology Council
Committee on Environment and Natural
Resources (CENR)
Research Subcommittees
Air Quality
Ecological Systems
Global Change
Natural Disaster Reduction
Toxics and Risk
Member Agencies
Department of Agriculture
Department of Commerce
Department of Defense
Department of Energy
Department of Health and Human Services
Department of Housing and Urban Development
Department of State
Department of the Interior
Department of Transportation
Environmental Protection Agency
National Aeronautics and Space Administration
National Science Foundation
Office of Management and Budget
Office of Science and Technology Policy
Tennessee Valley Authority
Atmospheric Composition Program Element
Focuses on improving our understanding of the
global- and regional-scale impacts of natural and
human processes on the composition of the
atmosphere; and determining the effects of such
changes on air quality and human health.
OUR CHANGING PLANET
THE FY 2002
FY 2002
USGCRP
Annual Budget
Request to
Congress
U.S. GLOBAL CHANGE RESEARCH PROGRAM
A Report by the Subcommittee on Global Change Research,
Committee on Environment and Natural Resources
of the National Science and Technology Council
Interagency Air
Quality Research
Subcommittee
PM Strategy Goal:
Enhance the scientific
information base for
public policy that protects
the public health (of
primary importance) and
the environment from
harmful effects due to
airborne particulate
matter.
NARSTO PM Assessment
Targeted to provide a current
description of PM formation
and transport with an evaluation
of the science tools to support
implementation.
NARSTO PM Assessment
Support the 2003 review of the PM Canada Wide
Standards and the implementation of that standard.
Assist with the development of State
Implementation Plans in the U.S. starting in 2003.
Support the joint international work leading up to
negotiation of a PM Annex under the Canada/US Air
Quality Accord.
In Mexico it will support their PROAIRE program
to improve air quality in Mexico City.
NSF Atmospheric Chemistry Program
Primary Goals:
Characterize the chemical composition of the atmosphere
and its variability
Understand the processes by which chemicals are
transformed and transported in the atmosphere
Quantify the major fluxes of a wide variety of important
substances into and out of the atmosphere, and to
understand the processes controlling those fluxes
Understand the natural and anthropogenic causes of
atmospheric chemical variability, and the effects of
chemical change on climate.
NSF Atmospheric Chemistry Program
Crosscutting Goals:
Understand the role of atmospheric chemistry in the
radiation budget of the Earth, i.e. greenhouse gases,
stratospheric ozone, aerosols, cloud radiative forcing;
Provide information about the processes leading to the
emissions and atmospheric deposition of biologically
important chemicals, i.e. acid deposition, nutrient cycling,
biomass burning and its relationship to land use practices,
carbon cycle, etc.;
Understand how natural and anthropogenic emissions
interact with the atmospheric chemical system to affect
regional air quality.
FY01 ATC Program
Project Type
11%
3%
10%
25%
51%
Instrumentation Development
Field measurements
Laboratory studies
Numerical modeling
Other
FY01 ATC Program
Project Focus
4% 3%
45%
41%
7%
Atmospheric Aerosols
Biogeochemical Cycles
Regional Chemistry/Air Quality
Stratospheric Chemistry
Other