Transcript aerosols - climateknowledge.org

Climate Change: The Move to Action
(AOSS 480 // NRE 501)
Richard B. Rood
734-647-3530
2525 Space Research Building (North Campus)
[email protected]
http://aoss.engin.umich.edu./people/rbrood
Winter 2008
January 29, 2008
Class News
• A ctools site for all
– AOSS 480 001 W08
• This is the official repository for lectures
• Email [email protected]
• Class Web Site and Wiki
– Climate Change: The Move to Action
– Winter 2008 Term
• Wunderground Climate Page
– Posted Introduction of the New Rough Guide
– My recent series on models
Readings on Local Servers
• Assigned
– Stott: External Forcings of 20th Century Climate
– Andronova: Anthropogenic Forcing of 20th Century
Climate
• Of Interest
–
–
–
–
NASA Langley: Aerosol Fact Sheet
Terra Mission: Aerosol Fact Sheet
NASA SVS: Aerosols over South Asia (1)
NASA SVS: Aerosols over South Asia (2)
Lectures coming up
• http://www.snre.umich.edu/events
• MLK Day Keynote Speaker: Dr. Warren
Washington // Climate Modeling // Tuesday,
February 5, 2008 - 4:00pm to 5:30pm //Location:
Stamps Auditorium, North Campus, Charles R.
Walgreen, Jr. Drama Center
• Erb Speaker Series: Jim Nixon, Alcoa,
"Challenges for an Energy Intensive
Business in a Carbon Constrained World"
Tuesday, February 5, 2008 - 5:00pm to
6:30pm Ross School, Wyly 0750
Outline of Lecture
• Let’s talk about next Tuesday a bit.
– Warren Washington will be with us.
•
•
•
•
Radiative Balance of the Earth
Feedbacks: Responses to global warming
Aerosols
Introduction to Models
The Sun heats the Earth which cools to space
SOLAR
TERRESTRIAL
WATER (& BIO)
TERRESTRIAL
ICE
LAND & BIO
Gives us an atmosphere that looks like this
(near the surface)
COLDEST
WARMEST
WINTER POLE
SURFACE
SUMMER POLE
How does the climate respond?
• There is motion in the atmosphere and
ocean.
• Water circulates between ocean and land
and air.
– Between ice and liquid and vapor
• There is a dynamic balance of water and
temperature.
If we change something what happens to this balance?
• FEEDBACKS ....
– The idea that one thing causes a second thing
to happen.
• That second thing then does something to the first
thing
– It damps it, negative feedback
– It amplifies it, positive feedback
The Earth System: Feedbacks 1
Infrared Proportional to Temperature
Top of Atmosphere / Edge of Space
Assume that greenhouse gases remain the same
• Infrared emission is proportional to temperature
• Temperature increases  emission increases
• Equilibrium is maintained
ATMOSPHERE
(infrared)
SURFACE
Water Vapor Feedback
When it gets warmer more water, a greenhouse gas,
will be in the atmosphere
Top of Atmosphere / Edge of Space
• Higher temperature increases evaporation from land
and ocean
• Higher temperature allows air to hold more water
• Increase of water increases thickness of blanket –
increases temperature more
•This is a positive feedback
• Compensating circulation changes?
• Think deserts …
•Role of condensation and clouds??
ATMOSPHERE
(infrared)
SURFACE
THIS INCREASES
The Earth System: Feedbacks 3
Ice - Albedo
When it gets warmer less ice
Top of Atmosphere / Edge of Space
• Less ice means less reflection  warmer
• Warmer means less ice
• This could runaway!
• Cooler works the other way  ice-covered
ICE
The Earth System: Feedbacks 4
Clouds?
Clouds are difficult to predict or to figure out the
sign of their impact
Top of Atmosphere / Edge of Space
• Warmer  more water  more clouds
• More clouds mean more reflection of solar  cooler
• More clouds mean more infrared to surface  warmer
• More or less clouds?
• Does this stabilize?
• Water in all three phases essential to stable climate
CLOUD
ATMOSPHERE
(infrared)
SURFACE
Schematic Review
go?
CLOUD-RADIATIVE FEEDBACK
ICE-ALBEDO FEEDBACK
WATER VAPOR FEEDBACK
TEMPERATURE FEEDBACK
THE EARTH IS EXPECTED TO RESPOND TO THESE CHANGES
FEEDBACKS
POSITIVE: ACCELERATE WARMING
NEGATIVE: DAMP WARMING
Cloud-Ice-Atmosphere Feedback
• Some carry away messages
– This is where much of the discussion about scientific
uncertainty resides.
– The Earth is at a complex balance point
• That balance relies on water to exist in all three phases.
– Too warm could run away to “greenhouse”
– Too cold run away to “snowball” ice
vapor
– How clouds change is not completely understood and
much argued.
– Is there something in all of this that changes the sign;
namely, that CO2 warming will be compensated by
more cooling?
• The Iris Effect?
Is there a reason?
• Is there a reason for the Earth to maintain the
same average surface temperature in the
presence of increasing greenhouse gases?
dT
 H   (T  Tideal )
dt
IF YES, THEN:
A MAJOR MISSING ENERGY PROCESS
CONTROL BY A DIETY
OTHER ... ????
EVIDENCE FOR THIS?
Following Energy through the Atmosphere
• We have been thinking about
– Things that absorb
– Things that reflect
– Responses to energy  Feedbacks
• We have kept in our mind, mostly,
greenhouse gases.
– Need to introduce aerosols
Aerosols
• Aerosols are particulate matter in the
atmosphere.
– They impact the radiative budget.
– They impact cloud formation and growth.
Aerosols: Particles in the Atmosphere
Aerosols: Particles in the atmosphere.
• Water droplets – (CLOUDS)
• “Pure” water
• Sulfuric acid
• Nitric acid
• Smog
•…
• Ice
• Dust
AEROSOLS CAN:
• Soot
REFLECT RADIATION
• Salt
ABSORB RADIATION
• Organic hazes
CHANGE CLOUD DROPLETS
Earth’s aerosols
Dust and fires in Mediterranean
Forest Fires in US
The Earth System
Aerosols (and clouds)
Clouds are difficult to predict or to figure out the
sign of their impact
Top of Atmosphere / Edge of Space
• Warmer  more water  more clouds
• More clouds mean more reflection of solar  cooler
• More clouds mean more infrared to surface  warmer
• More or less clouds?
• Does this stabilize?
• Water in all three phases essential to stable climate
CLOUD
ATMOSPHERE
(infrared)
SURFACE
The Earth System: Aerosols
Top of Atmosphere / Edge of Space
Aerosols directly impact radiative balance
• Aerosols can mean more reflection of solar  cooler
• Aerosols can absorb more solar radiation in the
atmosphere  heat the atmosphere
• In very polluted air they almost act like a “second”
surface. They warm the atmosphere, cool the earth’s
surface.
AEROSOLS
ATMOSPHERE
?
(infrared)
SURFACE
Composition of aerosols matters.
•This figure is simplified.
•Infrared effects are not well quantified
South Asia “Brown Cloud”
• But don’t forget
– Europe and the US in the 1950s and 1960s
• Change from coal to oil economy
Aerosol: South & East Asia
http://earthobservatory.nasa.gov/Newsroom/NasaNews/2001/200108135050.html
Reflection of Radiation due to Aerosol
http://earthobservatory.nasa.gov/Newsroom/NasaNews/2001/200108135050.html
Atmospheric Warming: South & East Asia
WARMING IN ATMOSPHERE, DUE TO SOOT (BLACK CARBON)
http://earthobservatory.nasa.gov/Newsroom/NasaNews/2001/200108135050.html
Surface Cooling Under the Aerosol
http://earthobservatory.nasa.gov/Newsroom/NasaNews/2001/200108135050.html
The Earth System
Aerosols (and clouds)
Aerosols impact clouds and hence indirectly impact
radiative budget through clouds
Top of Atmosphere / Edge of Space
• Change their height
• Change their reflectivity
• Change their ability to rain
• Change the size of the droplets
CLOUD
ATMOSPHERE
(infrared)
SURFACE
Aerosols and Clouds and Rain
Some important things to remember about aerosols
• They can directly impact radiative budget through both reflection and
absorption.
• They can indirectly impact radiative budget through their effects on
clouds  both reflection and absorption.
• They have many different compositions, and the composition
matters to what they do.
• They have many different, often episodic sources.
• They generally fall out or rainout of the atmosphere; they don’t stay
there very long compared with greenhouse gases.
• They often have large regional effects.
• They are an indicator of dirty air, which brings its own set of
problems.
• They are often at the core of discussions of geo-engineering
Let’s take a breath
• We have now seen the basics of the climate
change problem
– reduced it to an energy balance that is altered by
changes in greenhouse gases and aerosols.
• Absorption and reflection.
– seen that there is significant natural variability in the
climate
– identified the role of the major components of the
physical climate system
– exposed the role of water in the physical climate
– exposed a set of feedbacks that might affect the
balance of the climate system
Still taking a breath
• We have not
– Really looked at what the atmosphere and
ocean look like observationally.
– Talked about how we measure climate
change
– Talked about how we predict climate change
– Talked about how we make attributions of
climate change to greenhouse gases
– Really addressed the role of “abrupt” climate
change
What do we know with significant certainty?
Greenhouse
Effect
(Observation and
Theory)
Observations of
the past. / Large
and small climate
shifts. / Relation
between CO2 and
Temperature
Anticipate
consequential rise in
global temperature /
Rapid enough to
disrupt society and
commerce
Rapid CO2
increase /
Comparable to ice
age – temperate
difference
Is this simply curious or important?
NO
Greenhouse Effect
(Observation and
Theory)
Anticipate
consequential rise in
global temperature /
Rapid enough to
disrupt society and
commerce
Observations of the
past. / Large and small
climate shifts. / Relation
between CO2 and
Temperature
Rapid CO2 increase
/ Comparable to ice
age – temperate
difference
Should we be concerned ?
YES
Modeling
Now Let’s Go To Models
• We have used heuristic models to develop some
conceptual understanding of the greenhouse effect.
• We have posed that the conservation equation is the
foundation of a physical model.
• There are also statistical models, which are based on the
observed behavior and extrapolating that behavior into
the future.
• Some modeling subsets
–
–
–
–
Mechanistic models
Component models
Coupled models
.....
What is a Model?
• Model
– A work or construction used in testing or perfecting a
final product.
– A schematic description of a system, theory, or
phenomenon that accounts for its known or inferred
properties and may be used for further studies of its
characteristics.
• Numerical Experimentation
– Given what we know, can we predict what will
happen, and verify that what we predicted would
happen, happened?
What do we do?
• We develop models based on the
conservation of energy and mass and
momentum, the fundamental ideas of
classical physics. (Budget equations)
For exampled, we considered the conservation of energy
and CO2 in the ice core data
CHANGES IN SOLAR HEATING
T
 Heating  Cooling  H  T
t
CHANGES IN CO2, WHICH
CHANGE THE RATE OF COOLING
CO 2
 PCO2  LCO2
t
The Earth System
SUN
CLOUD-WORLD
ATMOSPHERE
ICE
(cryosphere)
OCEAN
LAND
Symbolic Energy Balance Equation
Atmosphere:
Eat+t = Eat + t((Pa – LaEa) + (Traoil + Ma ))
Symbols
E = “Energy”
P = Production
L = Loss rate
Tr = Transfer
M = Motion
Superscripts
a is for atmosphere
o is for ocean
i is for ice
l is for land
Variables
t = time
t = time increment
Symbolic Energy Balance Equation
(Earth System)
Atmosphere:
Eat+t = Eat + t((Pa – LaEa) + (Traoil + Ma ))
Ocean:
Eot+t = Eot + t((Po – LoEo) + (Troail + Mo ))
Ice:
Eit+t = Eit + t((Pi – LiEi) + (Trioal + Mi ))
Land:
Elt+t = Elt + t((Pl – LlEl) + (Trloia + Ml ))
A point
• With this model we are now existing inside of the
climate system rather than sitting out in space
looking at the global balance.
– Inside – we are especially interested in what goes on
at the surface of the Earth
– Inside – we have to worry about the climate every
day, we don’t have the benefit of the average
– Inside – we have to deal with the complexity
• Conservation is still true, but you have to think
about being embedded in the system, not a
distant observer of the system
What do we do?
• We develop models based on the conservation
of energy and mass and momentum, the
fundamental ideas of classical physics. (Budget
equations)
• We determine the characteristics of production
and loss from theory and observations of, for
instance, the eruption of a major volcano and
the temperature response as measured by the
global observing system.
Consider just the Production and Loss Rate
(We call this forcing.)
Pa – LaEa
We can divide this, conceptually, into two:
 That in absence of the influence of the “industry” of humans
• Variability of the sun
• What volcanoes put in the atmosphere
• Greenhouse gases prior to industrial revolution
• Aerosols from, for instance, sea salt and desert dust
 That which includes the influence of the “industry” of humans
• Changes in greenhouse gases due to burning of fuel
• Aerosols from “industrial” emissions
• Changes in gases due to changes in what is growing
• Change in absorption and reflection due to land use change
• More?
What do we do?
• We develop models based on the conservation of energy
and mass and momentum, the fundamental ideas of
classical physics. (Budget equations)
• We determine the characteristics of production and loss
from theory and observations of, for instance, the
eruption of a major volcano and the temperature
response as measured by the global observing system.
• We attempt to predict the temperature (“Energy”)
response.
• We evaluate (validate) how well we did, characterize the
quality of the prediction relative to the observations, and
determine, sometimes with liberal interpretation, whether
or not we can establish cause and effect.
Schematic of a model experiment.
T
T
Start model prediction
Model prediction without
forcing
Model prediction with
forcing
Model prediction with
forcing and source of
internal variability
Observations or “truth”
Class News
• A ctools site for all
– AOSS 480 001 W08
• This is the official repository for lectures
• Email [email protected]
• Class Web Site and Wiki
– Climate Change: The Move to Action
– Winter 2008 Term
• Wunderground Climate Page
– Posted Introduction of the New Rough Guide
– My recent series on models
Readings on Local Servers
• Assigned
– Stott: External Forcings of 20th Century Climate
– Andronova: Anthropogenic Forcing of 20th Century
Climate
• Of Interest
–
–
–
–
NASA Langley: Aerosol Fact Sheet
Terra Mission: Aerosol Fact Sheet
NASA SVS: Aerosols over South Asia (1)
NASA SVS: Aerosols over South Asia (2)