climate change: the move to action (aoss 480 // nre...

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

Let’s focus on the balance of the energy at the Earth’s surface

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:


Reflect

or Absorb


In the atmosphere, there are clouds which :


Reflect a lot

Absorb some


For convenience “hide” the sunbeam and reflected solar over in “RS”

Top of Atmosphere / Edge of Space RS


Consider only the energy that has been absorbed.

What happens to it?


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)


Building the Radiative Balance Redistribution by atmosphere, ocean, etc.

2) It is redistributed by the atmosphere, ocean, land, ice, life. (Another transfer between accounts)


Building the Radiative Balance Terrestrial energy is converted/partitioned into three sorts

SURFACE

3) Terrestrial energy ends up in three reservoirs

(Yet another transfer )


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


ATMOSPHERE CLOUD

RS

(THERMALS) (LATENT HEAT) (infrared or thermal)

CLOUD

Building the Radiative Balance And then the infrared radiation gets complicated

SURFACE


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

Want to consider one more detail

•  What happens if I make the blanket thicker?

Thinking about the greenhouse A thought experiment of a simple system.

SURFACE


ATMOSPHERE


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


ATMOSPHERE


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


ATMOSPHERE


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


ATMOSPHERE


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.

Radiation Balance Figure In this figure out = in

Radiative Balance (Trenberth et al. 2009) In this figure out does not = in

This lecture:

•  Energy –  Absorption –  Reflection

•  Aerosols

CLOUD-WORLD

The Earth System

ATMOSPHERE

LAND

OCEAN ICE (cryosphere)

SUN

CLOUD-WORLD

The Earth System

ATMOSPHERE

LAND


SUN Where

absorption is important

CLOUD-WORLD

The Earth System

ATMOSPHERE

LAND


SUN Where reflection

is important

CLOUD-WORLD

The Earth System

ATMOSPHERE

LAND


SUN Solar Variability

CLOUD-WORLD

The Earth System

ATMOSPHERE

LAND


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


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)

Cloudy Earth

CLOUD-WORLD

Earth System: Cloud World

ATMOSPHERE


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


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

Earth’s aerosols

Dust and fires in Mediterranean

Forest Fires in US

The Earth System Aerosols (and clouds)

SURFACE


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


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.)

Current Anthropogenic Aerosol Extreme

•  South Asian Brown Cloud

Aerosol: South & East Asia

http://earthobservatory.nasa.gov/Newsroom/NasaNews/2001/200108135050.html

Reflection of Radiation due to Aerosol


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


Natural Aerosol

Earth’s aerosols

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


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


The Earth System Aerosols (and clouds)

SURFACE


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

Aerosols and Clouds and Rain

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

Iconic and Fundamental Figures

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.

CLOUD-WORLD

The Earth System

ATMOSPHERE

LAND


SUN

Radiation Balance Figure

Radiative Balance (Trenberth et al. 2009)

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