Download Grüne Bildungswerkstatt Tirol, 22-23 February 2008

Anthropogenic climate change,
scenarios and acceptance
Hans von Storch
Institute for Coastal Research, GKSS Research Center
and KlimaCampus*, Hamburg University, Germany
*The German Excellence Center for Climate Science
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Detection and attribution
The IPCC’s (TAR)
attribution
argument
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Assessment: Is Global Warming real?
Climate scientists
have been
surveyed about
their view about
climate change.
We can say for certain that
global warming is a process
already underway.
2/3 are convinced
that most of the
observed ongoing
warming is related
to human action
Bray, D. and H. von Storch,
2007: Climate Scientists’
Perceptions of Climate
Change Science. GKSSReport 11/2007
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disagree
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agree
Which weather elements change? Not all.
Regional temperature
(example: Denmark)
consistent with
anthropogenic global
mean temperature rise,
but storms do not change
at the same time.
Temperature
Frequency of storms
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Damages and extreme weather
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Losses from Atlantic
Hurricanes
The increase in damages
related to extreme
weather conditions is
massive – but is it because
the weather is getting
worse?
Hardly
“Great Miami”, 1926,
Florida, Alamaba – damages
of 2005 usage - in 2005
money: 139 b$
Katrina, 2005: 81 b$
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Pielke, Jr., R.A., Gratz, J., Landsea, C.W.,
Collins, D., Saunders, M., and Musulin, R.,
2008. Normalized Hurricane Damages in
the United States: 1900-2005. Natural
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February
2008
Hazards
Review
Damages and extreme weather
• 2006 meeting of scientists and re-insurances
(Munich Re; Hohenkammer, May 2006)
• Consensus statement:
„1. Climate change is real, and has a significant
human component related to greenhouse gases.
2. Direct economic losses of global disasters have
increased in recent decades with particularly large
increases since the 1980s.
8. Analyses of long-term records of disaster
losses indicate that societal change and economic
development are the principal factors responsible
for the documented increasing losses to date.
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Visioning futures
Future anthropogenic climate change, or Global Warming
is described by scenarios.
Alternative scenarios about economic and social
developments in the coming 100 years are made; from
these assumptions emissions of greenhouse gases are
estimated; the climatic effect of these are assessed by
running climate models.
The resulting knowledge are not forecasts, but
conditional predictions given certain emissions.
If, however, all scenarios point to the same development,
then they collectively become predictions – namely that
temperatures as well as sea level will rise.
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IPCC SRES Scenarios
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IPCC SCRES Scenarios
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Asessement: Does the IPCC reflect consensus?
The scientific
community finds that
contemporary
scientific knowledge
about climate and
climate change
is well assessed
by the IPCC
(Intergovernmental
Panel on Climate
Change).
Bray, D. and H. von Storch,
2007
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To what extent do you agree or disagree
that the IPCC reports accurately reflect
the consensus of thought within
the scientific community?
disagree
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agree
The question of consensus
There is indeed broad consensus among scientists on some
issues, in particular on
- the ongoing emissions of greenhouse gases into the
atmosphere cause elevated concentrations in the atmosphere
and changes in the statistics of weather (i.e., climate).
- reducing the emissions will lead to smaller changes of climate.
- stronger climate change will be associated with more severe
impacts.
With respect to other issues, such as tipping points, tropical
storms, future sea level and the fate of Grønland, there is no
consensus.
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Possible Reponses to
Anthropogenic Climate Change
In the interacting environment-and-society system, we have to options for
response
• trying to avoid man-made changes („mitigation“),
• or to adapt to man-made changes („adaptations“).
In principle, mitigation is preferable over adaptation, but complete mitigation
seems impossible so that the best strategy is to mitigate as much as
affordable and to minimize negative consequences by adaptation.
Even if the very ambitious 2o-goal of the EU would be achieved, a significant
adaption pressure will emerge – greatly enhanced thinking about options of
adaption not only in Europe but in particular in more vulnerable parts of the
world are needed.
The goal of limited warming in 2100 to 2o relative to preindustrial levels (1850)
and to reach stabilization of climate is politically motivated, and most climate
scientists consider the chances of success of being remote.
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