Download climate change - Hans von Storch

Hans von Storch
Institute of Coastal Research, Helmholtz Zentrum Geesthacht, Germany
BACC and IPCC –
global and regional assessments of
knowledge about climate, climate change
and climate impact
Mission: determine present status of scientific knowledge,
and its consensus – not: discover “truth” about climate change
Intergovernmental
Panel on Climate
Change
Global temperature
derived from
thermometer data (CRU)
Explaining global mean surface air
temperature
Only natural
factors
Additional ly man
made factors
„observations“
IPCC 2007
Scenarios, not predictions
Zentrale Aussagen aus dem Bericht der Arbeitsgruppe
I des UNO Klimarats IPCC
- Temperatur steigt überall, aber verschieden schnell
- Ohne einen signifikanten Beitrag durch CO2 können
wir die Temperaturentwicklung nicht beschreiben.
Consensus among climate
scientists
Bray, 2010
Climate scientists agree more and more that
a) the world is warming („manifestation“)
b) and that this warming can not be explained without referring to
increased GHG levels („attribution“)
Survey by Dennis Bray, CLISCI 2013
The IPCC
- is needed as an impartial institution to provide
relevant knowledge for decision makers.
- has documented strong consensual evidence
(1) that the human emissions of greenhouse gases
(GHG) in the past, and foreseeable future has, and will
continue to warm the climate system, and
(2) most of this warming can not be explained without
the increase in GHG concentrations – with the present
knowledge.
Die Wissenschaft wird sich immer einiger, während die Reaktion in der Öffentlichkeit
beschränkt bleibt – offenbar eine Entkopplung von Wissenschaft und von manchen
gewünschter Mobilisierung der Öffentlichkeit.
Thus, on the global scale, the
knowledge about climate, climate change
and climate impact is mostly well
documented, but what about the regional
scale?
This should be an effort of the regional
scientific community – thus a task for
the regional efforts such as “Baltic Earth”
BACC as „regional IPCC“
BALTEX Assessment of Climate Change for the
Baltic Sea basin - BACC
An effort to establish which scientifically
legitimized knowledge about climate change
and its impacts is available for the Baltic Sea
catchment.
The assessment has been
accepted by the intergovernmental HELCOM
commission as a basis
for its judgment and
recommendations.
Östersjöfondens
pris 2014
BACC- Principles
→ The assessment is a synthesis of material drawn comprehensively
from the available scientifically legitimate literature (e.g. peer
reviewed literature, conference proceedings,
reports of scientific institutes).
→ Influence or funding from groups with a political,
economical or ideological agenda is not allowed;
however, questions from such groups are welcome.
→ If a consensus view cannot be found in the above
defined literature, this is clearly stated and the
differing views are documented. The assessment thus
encompasses the knowledge about what scientists agree on but
also identify cases of disagreement or knowledge gaps.
→ The assessment is evaluated by independent scientific reviewers.
BACC (2008) results – in short
→ Presently a warming is going on in the Baltic Sea
region, and will continue throughout the 21st century.
→ BACC considers it plausible that this warming is at
least partly related to anthropogenic factors.
→ So far, and in the next few decades, the signal
is limited to temperature and directly related variables,
such as ice conditions.
→ Later, changes in the water cycle are expected to
become obvious.
→ This regional warming will have a variety of effects on
terrestrial and marine ecosystems – some predictable
such as the changes in the phenology others so far
hardly predictable.
Overall Summary of BACC-2 (2013)
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New assessment finds results of BACC I valid
Significant detail and additional material has been found and assessed.
Some contested issues have been reconciled (e.g. sea surface temperature
trends)
Ability to run multi-model ensembles seems a major addition; first signs of
detection studies, but attribution still weak
Regional climate models still suffer from partly severe biases; the effect of
certain drivers (aerosols, land use change) on regional climate statistics
cannot be described by these models.
Data homogeneity is still a problem and sometimes not taken seriously
enough
The issue of multiple drivers on ecosystems and socio-economy is
recognized, but more efforts to deal with are needed
In many cases, the relative importance of different drivers, not only
climate change, needs to be evaluated.
Overall Summary of BACC-2 (2013)
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Estimates of future deposition and fluxes of substances like sulphur and nitrogen
oxides, ammonium, ozone, carbondioxide depend on future emissions and climate
conditions. Atmospheric factors are relatively less important than emission changes.
In the narrow coastal zone, where climate change and land uplift act together plant
and animal communities had to adapt to changing environment conditions.
Climate change is a compounding factor to major drivers of freshwater
biogeochemistry, but evidence is still often based on small scale. The effect of climate
change cannot be quantified yet on a Baltic Basin wide-scale.
Scenario simulations suggest that most probably the Baltic Sea will become more acid
in the future.
Increased oxygen deficiency, increased temperature, changed salinity and increased
acidification will impact the marine ecosystem in several ways and may erode the
resilience of the ecosystem.
Increasing need for adaptive management strategies (forestry, agriculture, urban
complexes) in the Baltic Sea Basin that deal with both climate change but also
emissions of nutrients, aerosols, carbondioxide and other substances.
Past change: air
temperature
The warming of the low level atmosphere
is larger in the Baltic Sea regions than
the global mean for the corresponding
period.
Warming
• continued for the last decade but not
in winter
• largest in spring
• largest for northern areas
Data sets
Year
Winter
Spring
Summer
Autumn
Northern area
0.11
0.10
0.15
0.08
0.10
Southern area
0.08
0.10
0.10
0.04
0.07
1 Linear surface air temperature trends (K per decade) for the period 1871-2011 for the Baltic Sea
Basin. Northern area is latitude > 60°N. Bold numbers are significant at the 0.05 level.
Data updated for BACCII from the CRUTEM3v dataset (Brohan et al. 2006)
Same for
1871-2004
(BACC I):
Annual and seasonal mean surface air temperature
anomalies for the Baltic Sea Basin 1871-2011, Blue colour
comprises the Baltic Sea basin to the north of 60°N, and red
colour to the south of that latitude.
Range of projected change of: Temperature – at the end of the century
Range of projected change of: precipitation amount – at the end of the century
Range of projected change of: maximum wave speed at the end of the century
Marine ecosysteme
Higher Temperature are expected to go along with
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Stronger growth
Earlier plankton blooms
Modification of species composition
Possibly advantages for blue algae
Invading of foreign species
Threatening of ringed seals (loss of ice cover)
and lower salinity
 Changing species composition; immigration of new species
 Reduced oxygen supply in deeper waters, which may be associated with problems for fisheries
(cod)
 Changed distribution and composition of zooplankton (food for small fish and fish larvae) and
bottom-dwelling organisms.
Detection and Attribution
→ Detection of non-natural influence on regional warming. Can be
explained only by increased greenhouse gas concentrations. Present
trend consistent with model scenarios.
→ Detection of non-natural component in trends of precipitation amounts;
present trends much larger than what is anticipated by models; thus no
consistent explanation for the time being.
→ Lack of studies on detection of changes in other variables
(e.g. snow cover, runoff, sea ice)
→ Lack of studies of the effect of other drivers (reduction of industrial
aerosols, land use change)
Regional attribution
Observed CRU, EOBS (1982-2011)
Projected GS signal, A1B scenario
10 simulations (ENSEMBLES)
Observed and projected
temperature trends
(1982-2011)
The observed (grey)
trends are consistent with
what the regional climate
models (green) suggest as
response to elevated GHG
levels in DJF and MAM,
but not in JJA and SON.
However, the observed
warming was in all
seasons larger than what
the models suggested.
Regional attribution
Observed 1972-2011 (CRU, EOBS)
Projected GS signal (ENSEMBLES)
Observed (grey) and
projected (green)
precipitation trends (19722011)
The observed changes are in
all seasons, except for SON,
larger than those suggested by
the regional climate models.
The observed changes in DJF ,
JJA und SON are inconsistent
with the models’ suggestion.
In SON observation and
projection even contradict
each other.
Assessing Scientific Reports: The BACC report
How well do you feel your area of expertise was represented
1 = not at all 7 = very well
Past and current climate change
Projections of future anthropogenic climate change
Change in terrestrial - freshwater ecosystems
Change in marine ecosystems
Sea level rise
other
no
Bray, 2010, pers. comm.
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2
3
4
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level of representation
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Climate science has provided sufficient
knowledge for societies to decide about
limiting climate change
• Yes, climate is changing,
We can not explain this change in terms of temperature
without referring to elevated greenhouse gases
When looking at change in general, global climate
change is one factor; others may be at work as well,
sometimes dominantly so.
Climate change represents a challenge for human
societies and ecosystems
Climate change can be limited by limiting the
accumulation of greenhouse gases in the atmosphere.
• Whether societies agree on joining to actually limit climate
change is legitimately a matter of policymaking, of values, of
societal choices.
Knowledge assessments reports
–
a significant component to any
climate service („Deutung“)
Entering the realm of
social and cultural sciences
Conditions of climate servicing:
Recognition that Climate science is in a
post-normal state
• Postnormal science: Jerry Ravetz, Silvio Funtovicz, 1986
and earlier.
• When facts are uncertain, values in dispute, stakes high
and decisions urgent, science is not done for reasons for
curiosity but is asked for as support for preconceived
value-based agendas.
• Climate science is in a post-normal state.
Analysis under
postnormal conditions requires
• Analysis of two bodies of knowledge claims, namely
(dominantly) scientifically constructed knowledge, and
(dominantly) culturally constructed knowledge.
• Analytical support by cultural sciences needed.
• Discrimination between scientifically solid core of
knowledge vs. added politically convenient (contested)
knowledge claims.
Two different construction of „climate change“ –
scientific and cultural – which is more powerful?
Cultural: „Klimakatastrophe“
Scientific: man-made change is
real, can be mitigated to some
extent but not completely avoided
Lund and Stockholm
Ideal climate science /policy interaction
policies
mitigation, adaptation costs
„Linear model“: Consolidated knowledge (consensus) leads to
policy. Depoliticization of politics.
Competition of knowledge claims
IPCC
BACC
NGOs
Economic
interests
Knowledge assessment - an opportunity for
building and exerting societal power
• Typical: „science tells us to …“, „scientific truth“ .
Scientific knowledge decides about political decisions
• Associated with emergence of elites, which steer
acceptance and rejection of views, insights and
determine speakers / leaders.
• Tendency of “circling wagons” (not a conspiracy but
“normal” social behavior, cf. “ClimateGate”)
• Scientific curiosity and openness limited by the need to
support “right” policy.
• Quasi-colonial positioning, in educating (informing,
teaching, “helping”) scientifically “less literate” social
actors (in particular in the third world).
What to do about it ?
1. Recognition that science and knowledge assessment is
a social process.
2. Accompanying social and cultural science efforts
needed to study these processes
3. Increase the number of degrees of freedom
– radical exchange of personal involved in ongoing
efforts (IPCC, BACC)
– have regional efforts whenever possible (like BACC)
– limited global assessment (like IPCC) to issues,
where a truly global view is needed – such as sea level,
sensitivity of the climate system.
– describe contested issues as contested
4. More measures ?