ipcc (wg1) overview
TRANSCRIPT
IPCC (WG1) Overview
Thomas StockerOeschger Centre for Climate Change ResearchPhysics InstituteUniversity of Bern
~3,900 H2 O molecules ~ 280 CO2 molecules~ <1 CH4 molecule
this raises temperature
from –18°C to +15°C
before year 1750 1,000,000 molecules of air contained:
+195 H2 O molecules +105 CO2 molecules
+1 CH4 molecule
in year 2007 1,000,000 molecules of air contain:
how much more warming
and other changes ?
CO2 : higher levels and faster rise
(IPCC, 2007, Fig. SPM-1)
Sie
gent
hale
r et a
l., (2
005)
Joos
& S
pahn
i (20
08)
last 10,000 years
last 200 years
last 50 years
CO2 : higher levels and faster rise
(Fig. 2.3, IPCC 2007)
CO2 increase is due to fossil fuel burning
UN Intergovernmental Panel on Climate Change
• 152 Authors• 450 Contributors• 40 Countries• ~600 Reviewers• 4 years of work
Report (WG1): 996 p.
SPM (WG1): 18 p.
www.ipcc.ch
very high confidence that the [] net effect of human activities since 1750 has been one of warming
(IPCC, 2007, Fig. SPM-2)
Change in many climate variables
The warming in the
climate system is
unequivocal, ...
(IPCC, 2007, Fig. SPM-3)
Arctic sea ice reduces rapidly
(Stro
eve
et a
l., 2
007)
Warmth of the last half century is unusual
(IPC
C, 2
007,
Fig
. TS-
20)
Warming rates similar throughout atmosphere
°C per decade (1979-2005)
(IPC
C, 2
007,
Fig
. TS-
6)
Fingerprint of climate change in atmosphere
2080-2099
60°S 60°NEQ
800
600
400
200
1000
Climate sensitivity now better constrained
IPCC TAR IPCC AR4
Equilibrium Climate Sensitivity
range:1.5 to 4.5°C
most likely valueabout 3°C
very unlikely <1.5°C
likely range:2.0 to 4.5°C
(IPC
C, 2
007,
Box
10.
2, F
ig. 1
c)
Equilibrium Climate Sensitivity (°C)
The key question:
Has the warming anything to
do with the increase of
greenhouse gases ?
Causal link between increasing CO2 and warming
(IPCC, 2007, Fig. SPM-4)
How good are IPCC projections ?
(IPC
C, 2
007,
Fig
. TS-
26)
Global warming depends on scenario
Emissions „high"
(IPCC, 2007, Fig. SPM-5)
Emissions „low"
„low
"„h
igh"
Gre
enho
use
gas
emis
sion
s
(IPCC, 2007, Fig. SPM-6)
Global warming depends on scenario
(IPCC, 2007, Fig. 10.19)
Heat waves very likely to become more frequent
Sea level rise: Very long-term – large uncertainties
(IPCC, 2007, Fig. 10.33)
(IPCC, 2007, Fig. 10.38)
Very likely reduction of the Atlantic MOC
(IPC
C, 2
007,
Fig
. 10.
15)
Water resources will change worldwide
(IPC
C, 2
007,
Fig
. SP
M-7
)
Conclusions 1: Robust findings
• Geographic patterns of temperature increase
• Long-term sea level rise
• Large-scale changes of precipitation
• Significant decrease of glaciers
• Acceleration of snow cover reduction in Arctic
• Slow down of the Atlantic MOC
• More frequent heat waves, fewer frost days
• Higher risk of droughts
Conclusions 2: Key Uncertainties
• Abrupt change, „tipping points“
• Extremes in precipitation
• Frequency and strength of tropical cyclones
• Response of climate modes (ENSO, NAO, AMO)
• Carbon cycle feedbacks
• Ocean acidification
• Ice sheet instabilities: Greenland, WAIS
• Possible irreversible changes
Switzerland: Great Aletsch Lake in 2100 ?
M. Bader, Sonntagszeitung 31.12. 2006