Climate Change: The Move to Action (AOSS 480 // NRE 480)
Richard B. Rood Cell: 301-526-8572
2525 Space Research Building (North Campus) [email protected]
http://aoss.engin.umich.edu/people/rbrood
Winter 2014 February 6, 2014
Class News
• Ctools site: AOSS_SNRE_480_001_W14
• Reading: The World Four Degrees Warmer – New et al. 2011
• Something I am playing with – http://openclimate.tumblr.com/
Politics of Dismissal Entry Model Uncertainty
Description
First Reading Response
• The World Four Degrees Warmer – New et al. 2011
• Reading responses of roughly one page (single-spaced). The responses do not need to be elaborate, but they should also not simply summarize the reading. They should be used by you to refine your questions and to improve your insight into climate change.
• They should be submitted via CTools by next Tuesday and we will use them to guide discussion in class on Thursday. Assignment posted with some questions to guide responses.
This lecture:
• Projects? – Tuesday work on teams and specifics
• Energy – Absorption – Reflection
• Aerosols
But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F).
The sun-earth system (What is the balance at the surface of Earth?)
SUN
Earth
Based on conservation of energy: If the Earth did NOT have an atmosphere, then, the temperature at the surface of the Earth would be about -18 C ( ~ 0 F).
Radiative Balance. This is conservation of energy. Energy is present in electromagnetic radiation.
Let’s build up this picture
• Follow the energy through the Earth’s climate.
• As we go into the climate we will see that energy is transferred around. – From out in space we could reduce it to just
some effective temperature, but on Earth we have to worry about transfer of energy between thermal energy and motion of wind and water.
Building the Radiative Balance
What happens to the energy coming from the Sun?
Energy is coming from the sun. Two things can happen at the surface. In can be:
Reflected
Top of Atmosphere / Edge of Space
Or Absorbed
Building the Radiative Balance What happens to the energy coming from the Sun?
We also have the atmosphere. Like the surface, the atmosphere can:
Top of Atmosphere / Edge of Space
Reflect
or Absorb
Building the Radiative Balance What happens to the energy coming from the Sun?
In the atmosphere, there are clouds which :
Top of Atmosphere / Edge of Space
Reflect a lot
Absorb some
Building the Radiative Balance What happens to the energy coming from the Sun?
For convenience “hide” the sunbeam and reflected solar over in “RS”
Top of Atmosphere / Edge of Space RS
Building the Radiative Balance What happens to the energy coming from the Sun?
Consider only the energy that has been absorbed.
What happens to it?
Top of Atmosphere / Edge of Space RS
Building the Radiative Balance Conversion to terrestrial thermal energy.
1) It is converted from solar radiative energy to terrestrial
thermal energy. (Like a transfer between accounts)
Top of Atmosphere / Edge of Space RS
Building the Radiative Balance Redistribution by atmosphere, ocean, etc.
2) It is redistributed by the atmosphere, ocean, land, ice, life. (Another transfer between accounts)
Top of Atmosphere / Edge of Space RS
Building the Radiative Balance Terrestrial energy is converted/partitioned into three sorts
SURFACE
3) Terrestrial energy ends up in three reservoirs
(Yet another transfer )
Top of Atmosphere / Edge of Space
ATMOSPHERE CLOUD
RS
WARM AIR (THERMALS)
PHASE TRANSITION OF WATER
(LATENT HEAT)
RADIATIVE ENERGY
(infrared or thermal)
It takes heat to • Turn ice to water • And water to “steam;”
that is, vapor
Building the Radiative Balance Which is transmitted from surface to atmosphere
SURFACE
3) Terrestrial energy ends up in three reservoirs
Top of Atmosphere / Edge of Space
ATMOSPHERE CLOUD
RS
(THERMALS) (LATENT HEAT) (infrared or thermal)
CLOUD
Building the Radiative Balance And then the infrared radiation gets complicated
SURFACE
Top of Atmosphere / Edge of Space
ATMOSPHERE CLOUD
RS
(THERMALS) (LATENT HEAT) (infrared or thermal)
CLOUD
1) Some goes straight to space
2) Some is absorbed by atmosphere and re-emitted downwards 3) Some is absorbed by clouds and re-emitted downwards
4) Some is absorbed by clouds and atmosphere and re-emitted upwards
Thinking about the greenhouse A thought experiment of a simple system.
SURFACE
Top of Atmosphere / Edge of Space
ATMOSPHERE
(infrared or thermal)
1) Let’s think JUST about the infrared radiation • Forget about clouds for a while
2) More energy is held down here because of the atmosphere
• It is “warmer”
3) Less energy is up here because it is being held near the surface.
• It is “cooler”
Thinking about the greenhouse A thought experiment of a simple system.
SURFACE
Top of Atmosphere / Edge of Space
ATMOSPHERE
(infrared or thermal)
T effective
1) Remember we had this old idea of a temperature the Earth would have with no atmosphere.
• This was ~0 F. Call it the effective temperature. • Let’s imagine this at some atmospheric height.
2) Down here it is warmer than T effective T > T effective
3) Up here it is cooler than T effective T < T effective
Thinking about the greenhouse Why does it get cooler up high?
SURFACE
Top of Atmosphere / Edge of Space
ATMOSPHERE
(infrared or thermal)
1) If we add more atmosphere, make it thicker, then
2) The part coming down gets a little larger. • It gets warmer still.
3) The part going to space gets a little smaller • It gets cooler still.
The real problem is complicated by clouds, ozone, ….
Think about that warmer-cooler thing.
• Addition of greenhouse gas to the atmosphere causes it to get warmer near the surface and colder in the upper atmosphere.
• This is part of a “fingerprint” of greenhouse gas warming.
• Compare to other sources of warming, for example, more energy from the Sun.
Think about a couple of details of emission.
• There is an atmospheric window, through which infrared or thermal radiation goes straight to space. – Water vapor window
• Carbon dioxide window is saturated – This does not mean that CO2 is no longer able to absorb. – It means that it takes longer to make it to space.
Thinking about the greenhouse Why does it get cooler up high?
SURFACE
Top of Atmosphere / Edge of Space
ATMOSPHERE
(infrared or thermal)
3) Additional CO2 makes the insulation around the window tighter.
1) Atmospheric Window 2) New greenhouse gases like N20, CFCs, Methane CH4 close windows
The real problem is complicated by clouds, ozone, ….
So what matters?
Things that change
reflection Things that
change absorption
Changes in the sun
If something can transport energy DOWN from the surface.
THIS IS WHAT WE ARE DOING
Think about the link to models
• energy reflected = (fraction of total energy reflected) X (total energy)
• energy absorbed = total energy - energy reflected = (1-fraction of total energy reflected) X (total energy)
• fraction of total energy reflected à – Clouds – Ice – Ocean – Trees – Etc.
CLOUD-WORLD
The Earth System
ATMOSPHERE
LAND
OCEAN ICE (cryosphere)
SUN Where
absorption is important
CLOUD-WORLD
The Earth System
ATMOSPHERE
LAND
OCEAN ICE (cryosphere)
SUN Where reflection
is important
CLOUD-WORLD
The Earth System
ATMOSPHERE
LAND
OCEAN ICE (cryosphere)
SUN
Possibility of transport of energy down from the
surface
CLOUD-WORLD
Earth System: Sun
ATMOSPHERE
LAND OCEAN ICE (cryosphere)
SUN
Lean, J., Physics Today, 2005
SUN: • Source of energy • Generally viewed as stable • Variability does have discernable signal on Earth • Impact slow and small relative to other changes
Lean: Living with a Variable Sun
CLOUD-WORLD
Earth System: Atmosphere
ATMOSPHERE Change CO2 Here
LAND OCEAN ICE (cryosphere)
SUN
The Atmosphere: • Where CO2 is increasing from our emissions • Absorption and reflection of radiative energy • Transport of heat between equator and pole • Weather: Determines temperature and rain
What are the most important greenhouse gasses? • Water (H2O) • Carbon Dioxide (CO2) • Methane (CH4)
CLOUD-WORLD
Earth System: Cloud World
ATMOSPHERE
LAND OCEAN ICE (cryosphere)
SUN
Cloud World: • Very important to reflection of solar radiation • Very important to absorption of infrared radiation
• Acts like a greenhouse gas • Precipitation, latent heat • Related to motion in the atmosphere
Most uncertain part of the climate system. • Reflecting Solar Cools
• Largest reflector • Absorbing infrared Heats
CLOUD-WORLD
Earth System: Land
ATMOSPHERE
LAND Change Land
Use Here OCEAN ICE
(cryosphere)
SUN
Land: • Absorption of solar radiation • Reflection of solar radiation • Absorption and emission of infrared radiation • Plant and animal life
• Impacts H2O, CO2 and CH4 • Storage of moisture in soil • CO2 and CH4 in permafrost
Land where consequences are, first and foremost, realized for people. • What happens to atmospheric composition if permafrost thaws? • Can we store CO2 in plants? • Adaptability and sustainability?
CLOUD-WORLD
Earth System: Ocean
ATMOSPHERE
LAND OCEAN ICE (cryosphere)
SUN
Ocean: • Absorption of solar radiation • Takes CO2 out of the atmosphere • Plant and animal life
• Impacts CO2 and CH4 • Takes heat out away from surface • Transport of heat between equator and pole • Weather regimes: Temperature and rain
What will the ocean really do? • Will it absorb all of our extra CO2? • Will it move heat into the sub-surface ocean? • Changes in circulation?
Does it buy us time? Does this ruin the ocean? Acidification
Doney: Ocean Acidification
Today
• Scientific investigation of the Earth’s climate: Foundational information – Radiative Balance – Earth System – Aerosols
Following Energy through the Atmosphere
• We have been concerned about, almost exclusively, greenhouse gases. – Need to introduce aerosols
• Continuing to think about – Things that absorb – Things that reflect
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 • Soot • Salt • Organic hazes
AEROSOLS CAN: REFLECT RADIATION ABSORB RADIATION CHANGE CLOUD DROPLETS
The Earth System Aerosols (and clouds)
SURFACE
Top of Atmosphere / Edge of Space
ATMOSPHERE
(infrared)
Clouds are difficult to predict or to figure out the sign of their impact • Warmer à more water à more clouds • More clouds mean more reflection of solar à cooler • More clouds mean more infrared to surface à warmer • More or less clouds?
• Does this stabilize? • Water in all three phases essential to “stable” climate
CLOUD
The Earth System: Aerosols
SURFACE
Top of Atmosphere / Edge of Space
ATMOSPHERE
(infrared)
Aerosols directly impact radiative balance • Aerosols can mean more reflection of solar à cooler • Aerosols can absorb more solar radiation in the atmosphere à heat the atmosphere
• In very polluted air they almost act like a “second” surface. They warm the atmosphere, cool the earth’s surface.
AEROSOLS
?
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
• Coal emits sulfur and smoke particulates
• “Great London smog” of 1952 led to thousands of casualties. – Caused by cold inversion layer
à pollutants didn’t disperse + Londoners burned large amounts of coal for heating
• Demonstrated impact of pollutants and played role in passage of “Clean Air Acts” in the US and Western Europe
Asian Brown Cloud (But don’t forget history.)
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
http://earthobservatory.nasa.gov/Newsroom/NasaNews/2001/200108135050.html WARMING IN ATMOSPHERE, DUE TO SOOT (BLACK CARBON)
Surface Cooling Under the Aerosol
http://earthobservatory.nasa.gov/Newsroom/NasaNews/2001/200108135050.html
Volcanoes and Climate
• Alan Robock: Volcanoes and Climate Change (36 MB!)
Alan Robock Department of Environmental Sciences
NET COOLING
Stratospheric aerosols (Lifetime ≈ 1-3 years)
Ash
Effects on cirrus clouds
absorption (IR)
IR Heating
emission
emission
IR Cooling
More Downward
IR Flux
Less Upward IR Flux
forward scatter
Enhanced Diffuse Flux Reduced
Direct Flux
Less Total Solar Flux
Heterogeneous → Less O3 depletion Solar Heating
H2S SO2
NET HEATING
Tropospheric aerosols (Lifetime ≈ 1-3 weeks)
SO2 → H2SO4
→ H2SO4
CO2
H2O
backscatter absorption (near IR)
Solar Heating
More Reflected Solar Flux
Indirect Effects on Clouds
Alan Robock Department of Environmental Sciences
Robock and Mao (1995)
Superposed epoch
analysis of six largest
eruptions of past 120
years
Year of eruption
Significant cooling follows
sun for two years
Alan Robock Department of Environmental Sciences
The Earth System Aerosols (and clouds)
SURFACE
Top of Atmosphere / Edge of Space
ATMOSPHERE
(infrared)
Aerosols impact clouds and hence indirectly impact radiative budget through clouds • Change their height • Change their reflectivity • Change their ability to rain • Change the size of the droplets
CLOUD
Some important things to know about aerosols
• They can directly impact radiative budget through both reflection and absorption.
• They can indirectly impact radiative budget through their effects on clouds à 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
Scientific investigation of Earth’s climate
SUN: ENERGY, HEAT EARTH: ABSORBS ENERGY
EARTH: EMITS ENERGY TO SPACE à BALANCE
Sun-Earth System in Balance
The addition to the blanket is CO2
SUN EARTH
EARTH: EMITS ENERGY TO SPACE à BALANCE
PLACE AN INSULATING
BLANKET AROUND EARTH
FOCUS ON WHAT IS
HAPPENING AT THE
SURFACE
Increase of Atmospheric Carbon Dioxide (CO2)
Data and more information
Primary increase comes from burning fossil fuels – coal, oil, natural gas
Temperature and CO2: The last 1000 years
Surface temperature and CO2 data from the past 1000 years. Temperature is a northern hemisphere average. Temperature from several types of measurements are consistent in temporal behavior.
q Medieval warm period
q “Little ice age”
q Temperature starts to follow CO2 as CO2 increases beyond approximately 300 ppm, the value seen in the previous graph as the upper range of variability in the past 350,000 years.
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