Climate Change The Move to Action AOSS 480

Climate Change: The Move to Action (AOSS 480 // NRE 501) Richard B. Rood 734 -647 -3530 2525 Space Research Building (North Campus) rbrood@umich. edu http: //aoss. engin. umich. edu. /people/rbrood Winter 2008 January 22, 2008

Class News • A ctools site for all – AOSS 480 001 W 08 • This is the official repository for lectures • Email climateaction@ctools. umich. edu • Class Web Site and Wiki – Climate Change: The Move to Action – Winter 2008 Term • Thursday I’m going to ask: “Have you been thinking about projects? ”

Class News: Get the registration right • If you signed up for AOSS 480 or NRE 501 (Climate Change: The Move to Action), and that is what you wanted to do, then that is all good. • If you signed up for AOSS 480, but want the Quik. Climate course on the physical climate system (AOSS 605), then you should change over to 605. • This course has been “approved” by SNRE as permanent! Hence, there may be a 501 number change. – Stay tuned, if you need to do anything. • If you signed up for AOSS 605 or AOSS 480 and have decided that you want to take both, then my advice would be to register for both.

Readings on Local Servers • Assigned – IPCC Working Group I: Summary for Policy Makers • Of Interest – Lean: Living with a Variable Sun – Doney: Ocean Acidification

Outline of Lecture • Greenhouse effect • Radiative Balance of the Earth • Earth’s Climate System – Atmosphere • Clouds – Oceans – Land – Ice (Cryosphere)

The Conservation Principle • The idea that some basic quantities are conserved. – Energy obeys a conservation equation. – Carbon dioxide obeys a conservation equation • Analysis of the conservation equation is a counting problem – the calculation of a budget. – The amount that you have is equal to the amount that you started with, plus the amount that you acquired (income or production), minus the amount that you got rid of (expense or loss)

Basic mathematical form of the conservation principle. HEATING COOLING Proportional to how hot it is.

If the energy from Earth is in balance • Then T (temperature is not changing) This is the essence of the global warming problem. What is the balance of heating and cooling?

Look at the Earth from Space

Conservation principle Energy from the Sun Stable Temperature of Earth could change from how much energy (H) comes from the sun, or by changing how much we emit, related to l. Earth at a certain temperature, T Energy emitted by Earth (proportional to T)

The Greenhouse Effect SUN 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). Earth But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). This greenhouse effect is well known. This temperature, which is higher than expected from simple conservation of energy, is due to the atmosphere. The atmosphere distributes the energy vertically; making the surface warmer, and the upper atmosphere cooler, which maintains energy conservation.

The Greenhouse Effect SUN 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). Earth But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). This greenhouse effect in not controversial. This temperature, which is higher than expected from simple conservation of energy, is due to the atmosphere. The atmosphere distributes the energy vertically; making the surface warmer, and the upper atmosphere cooler, which maintains energy conservation. We are making the atmosphere “thicker. ”

Energy conservation of Earth • If we change the heating or the cooling rate then we will change the equilibrium. Will ultimately reach a new equilibrium. Changing a greenhouse gas changes this

Energy conservation for Earth • We reach a new equilibrium Can we measure the imbalance when the Earth is not in equilibrium? Changes in orbit or solar energy changes this

Some aspects of the greenhouse effect • Greenhouse warming is part of the Earth’s natural climate system. – It’s like a blanket – it holds heat near the surface for a while before it returns to space. – We have been calculating greenhouse warming for a couple of centuries now. • Water is the dominant greenhouse gas. • Carbon dioxide is a natural greenhouse gas. – We are adding at the margin – adding some blankets • Or perhaps closing the window that is cracked open. • N 20, CH 4, CFCs, . . . also important. – But in much smaller quantities.

Something of a summary • We know that CO 2 in the atmosphere holds thermal energy close to the surface. Hence, more CO 2 will increase surface temperature. – Upper atmosphere will cool. – How will the Earth respond? • Is there any reason for Earth to respond to maintain the same average surface temperature? • Why those big oscillations in the past? – They are linked to solar variability. – Release and capture of CO 2 by ocean plausibly amplifies the solar oscillation. • Solubility pump • Biological pump • What about the relation between CO 2 and T in the last 1000 years? – Look to T (temperature) variability forced by factors other than CO 2 • • Volcanic Activity • Solar variability • CO 2 increase Radiative forcing other than CO 2? – Other greenhouse gases – Aerosols (particulates in the atmosphere)

Radiative Balance of The Earth • Over some suitable time period, say a year, maybe ten years, if the Earth’s temperature is stable then the amount of energy that comes into the Earth must equal the amount of energy that leaves the Earth. – Energy comes into the Earth from solar radiation. – Energy leaves the Earth by terrestrial (mostly infrared) radiation to space. • (Think about your car or house in the summer. )

Radiation Balance Figure

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.

The sun-earth system (What is the balance at the surface of Earth? ) SUN 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). Welcome Back Earth But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). Radiative Balance. This is conservation of energy, which is present in electromagnetic radiation.

Building the Radiative Balance What happens to the energy coming from the Sun? Top of Atmosphere / Edge of Space Energy is coming from the sun. Two things can happen at the surface. In can be: Reflected Or Absorbed

Building the Radiative Balance What happens to the energy coming from the Sun? Top of Atmosphere / Edge of Space We also have the atmosphere. Like the surface, the atmosphere can: Reflect or Absorb

Building the Radiative Balance What happens to the energy coming from the Sun? Top of Atmosphere / Edge of Space In the atmosphere, there are clouds which : Reflect a lot Absorb some

Building the Radiative Balance What happens to the energy coming from the Sun? RS Top of Atmosphere / Edge of Space For convenience “hide” the sunbeam and reflected solar over in “RS”

Building the Radiative Balance What happens to the energy coming from the Sun? RS Top of Atmosphere / Edge of Space Consider only the energy that has been absorbed. What happens to it?

Building the Radiative Balance Conversion to terrestrial thermal energy. RS Top of Atmosphere / Edge of Space 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. RS Top of Atmosphere / Edge of Space 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 Top of Atmosphere / Edge of Space RS It takes heat to • Turn ice to water • And water to “steam; ” that is, vapor 3) Terrestrial energy ends up in three reservoirs (Yet another transfer ) CLOUD ATMOSPHERE PHASE TRANSITION OF WATER RADIATIVE ENERGY (infrared) (LATENT HEAT) SURFACE WARM AIR (THERMALS)

Building the Radiative Balance Which is transmitted from surface to atmosphere Top of Atmosphere / Edge of Space RS 3) Terrestrial energy ends up in three reservoirs CLOUD (LATENT HEAT) (infrared) SURFACE ATMOSPHERE (THERMALS)

Building the Radiative Balance And then the infrared radiation gets complicated Top of Atmosphere / Edge of Space RS 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 CLOUD (LATENT HEAT) (infrared) SURFACE 4) Some is absorbed by clouds and atmosphere and re-emitted upwards ATMOSPHERE (THERMALS)

Put it all together and this what you have got. The radiative balance

Thinking about the greenhouse A thought experiment of a simple system. Top of Atmosphere / Edge of Space 1) Let’s think JUST about the infrared radiation • Forget about clouds for a while 3) Less energy is up here because it is being held near the surface. • It is “cooler” ATMOSPHERE (infrared) 2) More energy is held down here because of the atmosphere • It is “warmer” SURFACE

Thinking about the greenhouse A thought experiment of a simple system. Top of Atmosphere / Edge of Space 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. 3) Up here it is cooler than T effective ATMOSPHERE 2) Down here it is warmer than T effective (infrared) SURFACE T < T effective T > T effective

Thinking about the greenhouse Why does it get cooler up high? Top of Atmosphere / Edge of Space 1) If we add more atmosphere, make it thicker, then 3) The part going to space gets a little smaller • It gets cooler still. ATMOSPHERE 2) The part coming down gets a little larger. • It gets warmer still. (infrared) SURFACE The real problem is complicated by clouds, ozone, ….

Changes in the sun So what matters? THIS IS WHAT WE ARE DOING Things that change reflection Things that change absorption If something can transport energy DOWN from the surface.

The Earth System SUN CLOUD-WORLD ATMOSPHERE ICE (cryosphere) OCEAN LAND

The Earth System SUN CLOUD-WORLD ATMOSPHERE Where absorption is important ICE (cryosphere) OCEAN LAND

The Earth System Where reflection is important SUN CLOUD-WORLD ATMOSPHERE ICE (cryosphere) OCEAN LAND

The Earth System Solar Variability SUN CLOUD-WORLD ATMOSPHERE ICE (cryosphere) OCEAN LAND

The Earth System SUN CLOUD-WORLD ATMOSPHERE ICE (cryosphere) OCEAN LAND Possibility of transport of energy down from the surface

From Warren Washington

Transport of heat poleward by atmosphere and oceans • This is an important part of the climate system • One could stand back far enough in space, average over time, and perhaps average this away. • This is, however, weather. . . and weather is how we feel the climate day to day – It is likely to change because we are changing the distribution of average heating

While Building the Radiative Balance Figure Redistribution by atmosphere, ocean, etc. RS Top of Atmosphere / Edge of Space 1) The absorbed solar energy is converted to terrestrial thermal energy. 2) Then it is redistributed by the atmosphere, ocean, land, ice, life. CLOUD ATMOSPHERE SURFACE

Another important consideration. Latitudinal dependence of heating and cooling Top of Atmosphere / Edge of Space CLOUD ATMOSPHERE After the redistribution of energy, the emission of infrared radiation from the Earth is ~ equal from all latitudes. Because of tilt of Earth, Solar Radiation is absorbed preferentially at the Equator (low latitudes). SURFACE South Pole (Cooling) Equator (On average heating) North Pole (Cooling)

Transfer of heat north and south is an important element of the climate at the Earth’s surface. Redistribution by atmosphere, ocean, etc. Top of Atmosphere / Edge of Space This predisposition for parts of the globe to be warm and parts of the globe to be cold means that measuring global warming is difficult. Some parts of the world could, in fact, get cooler because this warm and cool pattern could be changed. CLOUD ATMOSPHERE heat is moved to poles cool is moved towards equator SURFACE This is a transfer. Both ocean and atmosphere are important!

Hurricanes and heat: Sea Surface Temperature

Weather Moves Heat from Tropics to the Poles HURRICANES

Mid-latitude cyclones & Heat

The Earth System SUN CLOUD-WORLD ATMOSPHERE ICE (cryosphere) OCEAN LAND

Earth System: Sun 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 ATMOSPHERE OCEAN LAND ICE (cryosphere)

SUN What are the most important greenhouse gasses? • Water (H 2 O) • Carbon Dioxide (CO 2) • Methane (CH 4) Earth System: Atmosphere The Atmosphere: • Where CO 2 is increasing from our emissions • Absorption and reflection of radiative energy • Transport of heat between equator and pole • Weather: Determines temperature and rain CLOUD-WORLD ATMOSPHERE Change CO 2 Here OCEAN LAND ICE (cryosphere)

Cloudy Earth

SUN Most uncertain part of the climate system. Earth System: Cloud World: • Very important to reflection of solar radiation • Very important to absorption of infrared radiation • Acts like a greenhouse gas • Precipitation, latent heat • Reflecting Solar Cools • Largest reflector • Absorbing infrared Heats CLOUD-WORLD ATMOSPHERE OCEAN LAND ICE (cryosphere)

Earth System: Land SUN Land where consequences are, first and foremost, realized for people. • What happens to atmospheric composition if permafrost thaws? • Can we store CO 2 in plants? • Adaptability and sustainability? OCEAN Land: • Absorption of solar radiation • Reflection of solar radiation • Absorption and emission of infrared radiation • Plant and animal life • Impacts H 2 O, CO 2 and CH 4 • Storage of moisture in soil • CO 2 and CH 4 in permafrost CLOUD-WORLD ATMOSPHERE LAND Change Land Use Here ICE (cryosphere)

SUN What will the ocean really do? • Will it absorb all of our extra CO 2? • Will it move heat into the sub-surface ocean? • Changes in circulation? Earth System: Ocean: • Absorption of solar radiation • Takes CO 2 out of the atmosphere • Plant and animal life • Impacts CO 2 and CH 4 • Takes heat out away from surface • Transport of heat between equator and pole • Weather regimes: Temperature and rain CLOUD-WORLD ATMOSPHERE Does it buy us time? Does this ruin the ocean? Acidification OCEAN Doney: Ocean Acidification LAND ICE (cryosphere)

Do you know about the Younger Dryas? Lamont-Doherty: Abrupt Climate Change

Bubbles of gas trapped in layers of ice give a measure of temperature and carbon dioxide 350, 000 years of Surface Temperature and Carbon Dioxide (CO 2) at Vostok, Antarctica ice cores Ø During this period, temperature and CO 2 are closely related to each other Ø It’s been about 20, 000 years since the end of the last ice age

Younger Dryas POSSIBLE EVIDENCE OF CHANGE IN OCEAN CIRCULATION WHAT DOES THIS MEAN?

Earth System: Ice SUN ICE: • Very important to reflection of solar radiation • Holds a lot of water (sea-level rise) • Insulates ocean from atmosphere (sea-ice) Ice impacts both radiative balance and water – oceans and water resources on land. . • Large “local” effects at pole. • Large global effects through ocean circulation and permafrost melting. • Might change very quickly. OCEAN CLOUD-WORLD ATMOSPHERE LAND ICE (cryosphere)

The Earth System: ICE (Think a little more about ice) non-polar glaciers and (Greenland) snow (Antarctica) Impacts regional water supply, agriculture, etc. sea-ice Solar reflection, Ocean-atmosphere heat exchange Solar reflection, Ocean density, Sea-level rise (Tour of the cryosphere, Goddard Scientific Visualization Studio)

The Cryosphere • TOUR OF CRYOSPHERE: MAIN NASA SITE