This Week: Future Climate

Future CO2 Forcing

Climate Sensitivity – Feedbacks

Natural Short and Long-term Forcings

Global Warming Impacts

Announcements

• See handout and website for details regarding paper and poster content

• Poster Sessions: March 12 and 13 in Mary Gates Commons 10:30 – 11:20

• Monday March 17 8:30 AM, Final Exam, JHN 075 (here)

• Papers and descriptions of 3 other posters due Wednesday March 19

Kaya Identity Model

kaya identity model

Future Atmospheric CO2

One emission scenario

Range of predictions suggest double pre-industrial by mid-century

Figure 10.20

Stabilization Scenarios

2000 23002100 2200

What our emissions can be for different constant CO2 levels.

What do these tell us about future biosphere and ocean sinks?

Committed to Warming: Time Response

Figure 10.4

A Long View of Fossil Fuel Perturbation

Figure 7.12

Climate Sensitivity-All about Feedbacks

T = F

is climate sensitivity parameter

units: K “per” W/m2

determined by feedbacks!

Estimates of Climate Sensitivity

Box 10.2, Figure 1

T change for a 4 W/m2 forcing (i.e. “double CO2”)

Most probable ~ 0.75 K/(W/m2)

Announcements

• Get a handout on paper/poster guidelines

• Brian’s office hours today canceled, moved to Thursday 5-6pm

• My office hours are today, 3:30 – 4:30pm in 506 ATG

Feedbacks

Initial ForcingState Variable

Process or coupling

+/-

+/-

+ increases state variable- decreases state variable

“feedback loop”

Ice-Albedo Feedback

Initial Forcing(e.g. GHG)

Temperature

Ice melts, dark soils exposed

Example of a positive feedback

+ Albedo -

+

More solar radiation absorbed

Water Vapor-Temperature Feedback

Initial Forcing(e.g. GHG, solar radiation)

Temperature+

Water Vapor +

+

More evaporation, saturation vapor pressure increase

Increased Greenhouse effect

Atmosphere—Protector of the Oceans?

water trap

If H2O reaches top of atmosphere it is blown apart by UV radiation

H atoms escape to space, never to return

Probable cause for no H2O on Venus

IR Flux-Temperature Feedback

Initial Forcing(e.g. GHG)

Temperature

Example of a negative feedback

+ Outgoing IR flux increases+

-

Phytoplankton-DMS-Marine Cloud Feedback

Initial Forcing(decreased clouds)

Solar Radiation(Temperature)

+ Biogenic Sulfur Emissions

+

-

Charlson, Lovelock, Andreae, Warren“C.L.A.W.” Hypothesis

Photosynthesis

+

aerosols and cloudiness+

Cloud Forcings and Feedbacks

Low altitude thick clouds

Stratus

High altitude thin ice clouds

Cirrus

Aircraft emit particles (and particle precursors) which can nucleat clouds.

This activity gives rise to a

Posi

tive

radia

tive

for..

.

Neg

ativ

e ra

diat

ive

fo...

43%

57%1. Positive radiative

forcing2. Negative

radiative forcing

Aviation Contrails—Positive Forcing

October 2004

Clouds and Climate—a complex problem

Cirrus: Not so reflective, but absorb and emit at cold T

Low Clouds: Absorb IR but emit like warm surface. Reflective

Clouds and Cloud Feedbacks

Initial Forcing(e.g. GHG, solar radiation)

Temperature

Temperature

+

+

Low Clouds+

High Clouds+

-

+

Atmosphere holds more water

Atmosphere holds more water

Uncertain!

Increased greenhouse effect

Albedo

+

Predicted Changes in Cloud Forcings

Figure 10.11

IPCC 2007

Sunspots – Cyclic Changes in Solar Output

~11 year Sunspot Cycle

Radiative Forcing by Solar Cycle

The solar cycle forcing has increased from -0.1 to 0.2 W/m2 since 1900. This forcing can explain ____ of 1oC increase in global Avg. T

since 1900

60

- 70%

40

- 50%

20

- 30%

5%

75%

20%

1. 60 - 70%2. 40 - 50%3. 20 - 30%

False Assertions: Sun – Global Warming

Originally from WSJ Article written by two chemists named Robinson

WRONG Solar Cycle

WRONG T record

False Assertions: Sun – Global Warming

Correct cycleLaut 2003

T Response After Major Eruptions

FAQ 8.1, Figure 1

Natural and Anthropogenic Forcings

Figure 6.13

El Nino Southern Oscillation-ENSO

Neutral Walker Circulation

Neutral

El Nino/La Nina State Flip-Flop

El Nino/La Nina Circulation Patterns

Very Strong El NinoStrong La Nina

ENSO “Periodicity”

El Niño years

La Niña years

El Nino Global Impacts

El Nino Impact on Fish

Normal El Nino

Climate History

18O Ratios in Sediment and Ice Core

Pleistocene Glacial and Interglacials

Reconstruction of land and sea ice 21,000 years ago (last glacial maximum)

February

July

Records of NH GlaciationsGeological Records: glacial deposits, scarring, larger scale

Cordilleran Ice SheetLake MissoulaSpokane Floods (from Lake Missoula)

Milankovitch—Before sediment cores

Predicts glacial and interglacial transitions based on variations in Earth’s orbit

His results suggested many such transitions in ~ 1 million yrs (he was right)

—at the time, no observable records show that many, so his work widely criticized

Milutin Milankovitch

Milankovitch Continued

“I do not consider it my duty to give an elementary education to the ignorant, and I have also never tried to force others to use my theory, with which no one could find fault.”

While lacking patience for critics, he did not lack confidence

Milutin Milankovitch

Orbital Forcing Summary

FAQ 6.1, Figure 1

Eccentricity

Tilt

Precession

IPCC 2007

Orbital Forcing Summary Cartoon

• orbital forcings

Currently NH summer takes place at aphelion, in about 12,000 years, NH summer

will occur at perihelion. At this time, SH seasonality will be

stro

nger

wea

ker

54%

46%

1. stronger2. weaker

Solar Insolation at 65N and Glaciation

Recent UW Research

Time rate of change of ice volume and solar insolation

The Key For Glaciation

Solar insolation in NH summer appears to be key maintaining glaciation. Ice sensitive to melting!

Initial ForcingWeaker NH summer insolation

T- Albedo

+

-

Ice Coverage

+

Positive Feedback—Destabilizing Climate

Same old ice-albedo feedback, just different initial forcing

Questions—In Class Activity

1. Given the behavior of CO2 and CH4 is there a positive or negative feedback with T?

2. Provide a feedback involving marine biota which might explain CO2’s behavior.

3. Suppose marine biota are the cause of CO2’s behavior, is this support for or against Gaia theory?

4. When’s the next glacial maximum? Do you think we’ll get there?

Eccentricity: More to Less Circular

Obliquity: More or Less Seasonality

Precessional Cycle: Tilt and Eccentricity

Current situation