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IPCC Third Assessment Report (TAR)
Climate Change 2001: The Scientific Basis
Briefing on WGI contribution
Bonn: Tuesday 17 July 2001
The Scientific Basis
Sir John Houghton
Overview of WGI findings, observations,
radiative forcing
Dr John Mitchell
Model evaluation, detection and attribution
Dr Bob Watson
The carbon cycle
Dr Ulrich Cubasch
Climate projections (including regional
projections and sea level)
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IPCC Website
http://www.ipcc.ch
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Structure of IPCC 1997 - 2001
United Nations
WMO
UNEP
World Climate
Programme
IGBP
Global Climate
Observing
system etc
Subsidiary
bodies of the
framework
convention on
climate change
IPCC
IPCC
Bureau
WGI
Science
WGII
Impacts and
adaptation
WGIII
Mitigation
Lead Authors, Contributors, Reviewers
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COP/FCCC
Climate Change 2001: The Scientific Basis
WGI contribution to IPCC Third Assessment Report
Summary for Policymakers (SPM)
Drafted by a team of 59
Approved ‘sentence by sentence’
by WGI plenary (99 Governments and 45 scientists)
14 chapters
881 pages
120 Lead Authors
515 Contributing Authors
4621 References quoted
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Key steps in preparation of Working Group I (science)
component of Third Assessment Report
Bad Munsteriefel
Scoping Meeting
Vienna
Shanghai
VII
WORKING GROUP I
SESSION
VIII
Paris
1
LEAD AUTHORS
MEETING
Arusha
2
Auckland
3
Victoria
4
Shanghai
5
New
York
TS / SPM
DRAFTING
INFORMAL REVIEW
EXPERT REVIEW
GOVERNMENT
REVIEW
1998
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1999
2000
2001
What is global warming about ?
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Variations of the Earth’s surface temperature
for the past 140 years
SPM 1a
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Variations of the Earth’s surface temperature
for the past 1,000 years
SPM 1b
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Concentration of Carbon Dioxide and Methane Have
Risen Greatly Since Pre-Industrial Times
Carbon dioxide: 33% rise
BW 5
The MetOffice. Hadley Center for Climate Prediction and Research.
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Methane: 100% rise
700
CO2 in 2100
(with business as usual)
Double pre-industrial CO2
500
Lowest possible CO2
stabilisation level by 2100
400
CO2 now
300
10
Temperature
difference
200
0
from now °C
–10
100
160
120
80
Time (thousands of years)
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Now
CO2 concentration (ppmv)
The last 160,000 years
(from ice cores) and
the next 100 years
600
The Greenhouse Effect
Solar radiation
Long-wave radiation
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The Enhanced Greenhouse Effect
Solar (S) and longwave (L) radiation in Wm-2 at the top of the atmosphere
S
236
L
236
S
236
L
232
S
236
L
236
T = -18°C
TS = 15°C
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CO2 x 2
CO2 x 2
TS = 15°C
DTS ~ 1.2K
S
236
L
236
CO2 x 2
+ Feedbacks
H2O (+60%) Ice/Albedo
(+60%)
Cloud?
Ocean?
DTS ~ 2.5K
Variations of the Earth’s surface temperature; 1000 to 2100
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The Carbon Cycle
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Human Perturbation of the Carbon Cycle
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Partitioning of CO2 uptake using O2 measurements
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Changing Land Use
Changing land use could influence
atmospheric CO2 concentration.
Hypothetically, if all of the carbon released
by historical land-use changes could be
restored to the terrestrial biosphere over
the course of the century (e.g., by
reforestation), CO2 concentration would be
reduced by 40 to 70 ppm.
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Radiative Forcing
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SPM 3
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Estimated solar irradiance variations 1750-2000
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Main climate changes
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
Sea level rise

Higher temperatures - especially on land

Hydrological cycle more intense

Changes at regional level
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Sea-level transgression scenarios for Bangladesh
Adapted from Milliman et al. (1989).
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Percent of the continental USA with a much above
normal proportion of total annual precipitation from
1-day extreme events (more than 2 inches or 50.8mm)
BW 7
Karl et al. 1996
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Patterns of Climate Response
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The 1997/98 El Niño Strongest on Record*
El Niño years
La Niña years
BW 14
*As shown by changes in sea-surface temperature (relative to the 1961-1990 average) for
the eastern tropical Pacific off Peru
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Global ocean circulation
Cooling
Warm
surface
current
Intermediate
waters
Warm and less saline
Antarctic circumpolar current
A simplified view of the global thermohaline conveyor belt, showing cooling and downwelling in the North Atlantic,
warming and freshening in the southern hemisphere, and return flow as a warm surface current.
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Stabilisation of Climate
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UNITED NATIONS FRAMEWORK CONVENTION ON CLIMATE CHANGE
Rio de Janeiro : June 1992
ARTICLE 2: OBJECTIVE
The ultimate objective of this Convention .... is to achieve, .…
stabilization of greenhouse gas concentrations in the atmosphere at a
level that would prevent dangerous anthropogenic interference with the
climate system.
Such a level should be achieved within a
time-frame sufficient :


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to allow ecosystems to adapt naturally
to climate change.
to ensure that food production is not
threatened, and
to enable economic development to
proceed in a sustainable manner.
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CO2 emissions for SRES and stabilisation scenarios
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