Nicolas Gruber

Environmental Physics, Institute of Biogeochemistry and Pollutant Dynamics,ETH Zürich, Switzerland

Science, policy, and politics of global climate change

Results from WS'06 survey

1. How large do you think was the observed global surface temperature increase from 1900 to 2000?

Questionnaire

Average: 0.9 ± 0.4 °C

Range: 0.4 - 1.5 °C

2. How strongly are you convinced that the observed warming in the 20th century is due, in part, to human influences (1: not convinced; 5 strongly convinced)

Questionnaire (cont)

Average: 4.6 ± 0.5

Range: 4 - 5

Questionnaire (cont)

3. Which evidence do you find most convincing do demonstrate this human influence (up to three choices possible)

a. Instrumental temperature record (14)

b. Satellite temperature record (6)

c. Proxy temperature reconstruction for the last 1000 years (18)

d. Retreat of tropical glaciers (8)

e. Detection studies with models (1)

f. Sea-ice retreat (3)

g. Antarctic shelf-ice breakup (10)

h. Stratospheric cooling (0)• Day-night warming pattern (0)

j. Your favorite choice (name) (5) CO2 record

Global change: Ice-sheet breakdown

Larsen ice-sheet in Antarctica

January 31, 2002 March 5, 2002

Global change: Glacier retreat

Rhone glacier

ca 1850 2004

Global change: Glacier retreat2004 ~1900

2004 2004

Rhone glacier in Switzerland

Questionnaire (cont)

4. Please rank the following components to radiative forcing in terms of their contribution to global warming. Do one ranking for now and one for what you think the situation will be in 50 years from now?

TODAY

a. CO2 (33)b. CH4 (20)c. CFCs (10)d. Aerosols (direct) (6)• Aerosols (indirect) (5)f. Solar forcing (3)

FUTURE

a. CO2 (26)b. CH4 (20)c. CFCs (3)d. Aerosols (direct) (4)• Aerosols (indirect) (7)f. Solar forcing (5)

Note: water vapour is not considered a radiative forcing

Questionnaire (cont)

5. How much different do you expect global mean temperature to be in 2030, 2050 and 2100 in comparison to now?

2030 2050 2100

Average: 0.7 ± 0.5 1.6 ± 1.5 2.8 ± 1.8

Range: 0.05 to 1.5 0.5 to 6 0.7 to 6.5

Projected warming (2071-2100)

Projected changes in precipitation

Questionnaire (cont)

6. What do you think will be the primary driver(s) for setting this temperature (rank 1-3)?

a. Population changes (14)

b. Economic development (16)

c. Technological development (16)

d. Earth system feedbacks (28)

What determines future climate?

∆T = · ∆CO2atm

climate sensitivity (function of feedbacks)∆CO2

atm future atmospheric CO2 concentration

Npop Populationrenergy Energy consumption per capitaICO2 CO2 intensity of energy source

E= Npop · renergy · ICO2

∆CO2atm = ƒ(E · fair)

E Anthropogenic CO2 emissionsƒair airborne fraction (function of carbon system feedbacks)

∆T = · ƒ(fair · Npop · renergy · ICO2)

What determines future climate?

physical climate system (feedbacks)

bgc climate system (bgc feedbacks)

Socio-economic factors (health, education, etc)

Economical-political-technical factors

Technical/economical factors

OUR CHOICE

We have a choice!

Questionnaire (cont)

7. How do you rank the importance of global climate change vs. these other problems?

a. Climate Change (17)

b. HIV/Aids (5)

c. Malnutrition (29)

d. Sanitation and Water (31)

e. Migration (2)

f. Terrorism (0)

Ranking by the Copenhagen Consenus

Questionnaire (cont)

8. Do you think we know enough in order to act upon the issue

of global warming?

a. Science is unsettled, need to do more research before

acting (1)

b. Scientific evidence is relatively clear, but we have other

priorities (1)

c. Scientific evidence is relatively clear, and we should act

even in the presence of other important issues. (12)

d. Scientific evidence is unsettled, but we should act now

regardless. (0)

Questionnaire (cont)

9. What do you view as the most effective role of scientists in this debate?

a. Write peer reviewed articles and rely on the public to pick up

the information (1)

b. Give public lectures, write essays for the general public (11)

c. Get involved in IPCC (2)

d. Become a scientific activist (0)

Policy versus Politics

Policy: Prudence or wisdom in the management affairs or high-level plan embracing the general goals and acceptable procedures

Politics: Art or science of government or art or science of guiding government policies.

IPCC mandate: policy guiding but not prescriptive!

The role of science and scientists

• Public obligation versus academic freedom (curiosity driven research)

• Academic standing versus activism

• Science policy versus scientific politics

Questionnaire (cont)

10. If (physical) climate scientists had another 1 B $ at hand, what would you spend it on?

a. Climate observations (1)

b. Process studies (6)

c. Model development and scenario testing (2)

d. Method development (4)

e. Something else (please specify) (1) lobbying