Climate Change: The Move to Action (AOSS 480 // NRE 501) Richard B. Rood 734-647-3530 2525 Space Research Building (North Campus) [email protected] ./people/rbrood.

Climate Change: The Move to Action(AOSS 480 // NRE 501)

Richard B. Rood734-647-3530

2525 Space Research Building (North Campus)[email protected]

http://aoss.engin.umich.edu./people/rbrood

Winter 2008January 31, 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– McCarty: Ecological Consequences of Climate

Change– Walther: Ecological Response to Climate Change

• Of Interest– Osborn: Spatial Extent of Current Warming– Francis: Sea Ice and Water Vapor Feedback– Anderson: Little Ice Age/Baffin Island

QuikClimate AOSS 605

• First specific readings for Quikclimate (Physical Climate Course)– Hartmann: Chapter 5: Hydrological Cycle– Oort & Rasmusson: Chapter 12: Hydrological

Cycle

• Short meeting after class today.

Projects

• Next Thursday: Projects discussion– What topics are being discussed?– Are groups organizing?– Present a prospectus?

Lectures coming up

• http://www.snre.umich.edu/events

Outline of Lecture

• Models and Attribution– Consistency of data and predictions in the

past 100 years.

• Predictions for the next 100 years

• The nature of abrupt climate change

Figure TS.23

Figure SPM.4

Ocean

• Time scales in ocean much longer

• Oceanography and ocean modeling has shorter history of comprehensive observations and modeling.

• Exchanges in ocean and atmosphere not fully characterized:– Are they adequately “constrained” by

knowledge?

Atlantic Ocean Surface Temperature

Related to Hurricane Arguments

Heat in the Ocean

Calculated Radiative Forcing

Radiative Forcing IPCC 2007

Comparison of “Change” to Balance

IF WE CHOOSE TO DO SOMETHING ABOUT THIS, THEN CHANGE ENERGY BALANCE CHANGE ABSORPTION OF RADIATIVE ENERGY CHANGE REFLECTION OF RADIATIVE ENERGY

~2 out of 340 W / m2

Changes in Precipitation

Observed Precipitation Change: Late 20th Century

Start to think about the 2100 predictions

As people sitting here on earth, what climate parameters/events do we care about?

• Temperature• Water

– Precipitation– Evaporation– Humidity

• Air Composition– Air quality– Aerosols– Carbon dioxide

• Winds• Clouds / Sunlight

• Sea-level Rise

• Droughts• Floods

• Extreme Weather

Remember the simple model

Note: There isconsistency from many models, many scenarios, that there will be warming. (1.5 – 5.5 C)

Also, it’s still going up in 2100!

IPCC 2001

B1

B2

A1B

Temperature Projections 2100

B1

?B2

A1B

IPCC 2007

Temperature Projections 2100

IPCC 2007

Remember the simple model

Note: There isconsistency from many models, many scenarios, that there will be warming. (1.5 – 5.5 C)

Also, it’s still going up in 2100!

IPCC 2001

B1

B2

A1B

Temperature in 2100 for different scenarios

Temperature when CO2 equilibrium is achieved. (Longer prediction)

Again, all predictions are of warming.

IPCC 2001

IPCC 2001

Temperature Predictions 2100

IPCC 2007

Systematic Temperature Changes

• Global Temperature increase 1.5 – 4.5 C

• Poles warm more faster than globe, especially the North Pole.

• Land warms faster than ocean.

• Night warms faster than day

• Spring starts earlier

• Autumn starts later

IPCC 2001: Has this changed significantly?

IPCC 2001

Precipitation Prediction 2100

IPCC 2007

Water

• Water vapor in atmosphere will increase (It’s a greenhouse gas.)

• Precipitation will increase

• Evaporation will increase (It’s warmer.)

• Snow cover will be less over most continents.

• Snow could increase in Greenland and Antarctica?

IPCC 2001: Has this changed significantly?

Surface Elevation Change of Ice Caps

Sea Level Projections 2100

IPCC 2007

IPCC 2007: A2 0.23-0.51

IPCC 2007: B2 0.20-0.43

Sea level predictions

• This was most controversial part of the report among scientists at the time of release.– Note the report is heavily qualified

• “do not include full effects of changes in ice sheet flow”

– Basis lacking in literature.– “Larger values cannot be excluded ...”

• If the current trend remains and is linear add 0.1 – 0.2 meters.

Changes in Weather

Very Wet Days

With confidence

• The surface temperature will rise.• Sea level will rise

– Ice will melt• Weather will change

– Precipitation intensity and spatial distribution will change

– Evaporation will increased because it is warmer• I would posit, this has been observed, and to be

consistent with model predictions for the past 150 years. Going into the future these predictions are robust in the sense of sign, and approximate magnitude.

• The predictions and observations so far are either in the sense of:– Relatively small changes in the dynamic

balance of the climate system– Incremental changes to the stable climate.

• What about “abrupt” climate change?

Abrupt climate change

Abrupt climate change

• Changes in the ocean circulation.– Remember Younger Dryas in Lecture 6

• Remember the ice-age turn around:– Need some sort of positive feedback to amplify the solar forcing

• Ice-albedo feedback // – Sea ice collapse in Arctic?– Land ice sheet collapse sea level rise

• Sudden release or absorption of greenhouse gas from ocean

• Sudden release or absorption of greenhouse gas from land– Permafrost

• Sudden change in the biological balance of plants and animals– Ocean temperature and acidification

Abrupt Climate Change

• Most scenarios of abrupt climate change are related to a phase change in some way or another. Does the albedo change quickly? Is there a change in the fresh water in the ocean? Is there a release of gas stored in something that is frozen?

• It is also possible to define rapid changes in ocean (land?) ecosystems, that leads to composition changes in the atmosphere. Biology – sensitive to temperature, water, salinity, ph, etc.

Lamont-Doherty: Abrupt Climate Change

When people talk about sudden climate change, what do they mean? (An excursion to the North Atlantic)

• Remember that the atmospheres and ocean carry heat from the equator to the pole.– This is done at preferential locations.– One especially important mechanism of heat transport is the

Gulf Stream, along the eastern coast of the U.S, which transports heat to the North Atlantic. This keeps much of Europe much warmer than it would be based on the position of the sun.

– The Gulf Stream is part of a large organized circulation in the oceans.

• Connects north and south• Connects top and bottom of ocean (which is not very common)

– This organized circulation is sometimes called the ocean “conveyor” belt. It is named the thermohaline circulation because it depends on both the thermal structure and the saltiness (“haline”) of the water.

The Thermohaline Circulation (THC) (Global, organized circulation in the ocean)

(The “conveyer belt”, “rivers” within the ocean)

Where there is localized

exchange of water between

the surface and the deep

ocean (convection)

From Jianjun Yin, GFDL, see J. Geophysical Research, 2006

Warm, surface currents.

Cold, bottom currents.

Green shading, high saltBlue shading, low salt

Some aspects of the thermohaline circulation

• Salt is important to the density of sea water.• Warm, salty water on the surface moves to high northern and

southern latitudes, where it sinks.• The area where there is strong, localized exchange, bottom water

currents develop which return cold water towards the equator (heat exchange).

• The area where there is strong localized exchange is significantly warmer than it would be in the absence of the ocean currents. (see next figure)

• Saltiness is very important. If the North Atlantic were flooded with fresh water from Greenland ice melting or much more precipitation, then the thermohaline circulation might shut down.– There is evidence that this has happened before (look up the Younger

Dryas)– Hence melting of Greenland impacts both sea-level rise and the

thermohaline circulation

Importance of the Thermohaline Circulation in the Present Climate

• The deviation of the surface air temperature from the zonal average

(NCAR/NCEP reanalyses);• The THC is responsible for most northward heat transport in the Atlantic

(> 1 PetaWatts = 1015 Watts);• High surface air temperature over the North Atlantic and Europe

If the

thermohaline

circulation

shut down,

then the

climate, the

mean surface

temperature,

would be

abruptly and

significantly

changed.

From Jianjun Yin, GFDL, see J. Geophysical Research, 2006

Some model predictions of what would happen if the thermohaline circulation shutdown

• From From Jianjun Yin, GFDL, see J. Geophysical Research, 2006

• Fresh water is added in the model simulation to the North Atlantic, in the vicinity of Greenland and Iceland.

• With the addition of fresh water the thermohaline circulation shuts down

• There are global consequences– See plots below.

Predicted Sea Surface Temperature• Bipolar Seesaw 3oC decrease NA• Extension of icy seawater and sea ice

coverage in North Atlantic • Spread of warmer seawater via ACC• Feedback on the THC intensity • (This dipole has the characteristic of a

dynamical response)

Predicted Sea Surface Salt (SSS)• 1.2 psu decrease in 50~70oN belt• SA and Gulf of Mexico become more

saline • Sharp SSS gradient at 40oN• Labrador Sea: the most susceptible

region to freshwater perturbation

Predicted Sea Ice• Thickness increases and coverage

extends in the Labrador Sea• Thickness decreases in the Nordic

Seas the Barents Sea and the Weddell Sea due to enhancement of deep convection (part of a dynamical response?)

From Jianjun Yin, GFDL, see J. Geophysical Research, 2006

Abrupt Climate Change

• This is a subject of current high interest.– Is there a “dangerous” threshold that could

have extremely rapid, decades, impact?– Is there a dangerous threshold that we could

avoid by mitigation?– Should we plan for this contingency?