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Global%20Warming:%20The%20Debate

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Global Warming: The Debate Objectives: Define the uncertainties Describe the scientific process Analyze available data Explore solutions – PowerPoint PPT presentation

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Title: Global%20Warming:%20The%20Debate


1
Global Warming The Debate Objectives Define
the uncertainties Describe the scientific
process Analyze available data Explore solutions
2
Four debates
  • Is the climate changing?
  • Are humans responsible?
  • How severe will it be?
  • What should we do about it?

Science
Science
Science/Policy
Policy
3
Why trust science?
  • The scientific method

Carbon dioxide is increasing
Is the world getting warmer?
The world is warmer today than in 1750
Measure tree rings, ice cores
Yes, tree rings and thermometers show a warming
trend
Theory ? Law
4
Why trust science?
  • The scientific method is objective
  • Science is peer-reviewed by experts
  • Ideas are funded, not particular answers

5
Science funding
Taxpayer
Congress
Private foundation
Business
Govt Agency
Peer Review
Scientist
Scientific Method
Results
Peer Review
6
The Intergovernmental Panel on Climate Change
(IPCC)
7
The Greenhouse Effect (Fourier 1824)
  • Sunlight warms the earth
  • The earth cools by radiating heat
  • Greenhouse gases in atmosphere trap heat and
    re-radiate it back to surface

Slide from M. S Torn, LBL
8
1. Is the climate changing? YES
9
Climategate
Michael Mann
Phil Jones
  • Issues data manipulation and sharing
  • Tree ring data do not match thermometers
  • No evidence that data were altered
  • Evading and disparaging skeptics is
    counterproductive
  • Public is losing confidence in climate science

10
Temperature has risen by 1.5 F over land 9 of
the hottest years of the century occurred in
last 10 years
11
2. Are humans responsible? YES
Charles David Keeling
CO2 concentrations are rising
12
Can warming be explained by natural causes? No.
Climate Model Simulations ? (a) with only
natural processes (solar, volcanoes) ? (b) with
also anthropogenic gases and aerosols
13
Major Findings of IPCC-4
  • Unequivocal that Earths climate is warming
  • Greenhouse gases at highest levels in 650,000
    years
  • Very Likely that increased greenhouse gases
    have caused most of the rise in temperatures
    since 1950

14
3. How severe will climate change be?It depends
California, relative to last three decades
15
Expect a lot of change relative to the past
16
Impacts on the biosphere feedback loops
CO2
Plant Growth
Warming
Nutrients
Decomposition
Negative
Positive
17
Temperature increase by 2100
Soil carbon
18
Warming experiment
Alaskan boreal forest
19
Measuring soil carbon loss
20
Warming reduces microbial activity
21
We find negative feedbacks
CO2
Plant Growth
Warming
Nutrients
Decomposition
Negative
Positive
22
Different results in permafrostBig soil carbon
losses
23
Also consider ocean feedbacks
24
4. What can we do?
  • Mitigate slow the rate of increase of
    greenhouse gases
  • Adapt change infrastructure to deal with
    climate change
  • Manage actively manage climate and
    atmospheric composition

Increasing knowledge required
25
Mitigation options
Pacala and Socolow, 2004
26
Mitigation options
Pacala and Socolow, 2004
27
Mitigation options
Pacala and Socolow, 2004
28
Summary
  • Climate change is happening
  • Humans are the likely cause
  • The biosphere may respond in unpredictable ways
  • There are options to avoid climate change
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