Hans von StorchInstitute 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)

IPCC 2007

Additional ly man-made factors

Only natural factors

„observations“

Explaining global mean surface air temperature

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.

Climate scientists agree more and more thata) the world is warming („manifestation“)b) and that this warming can not be explained without referring to

increased GHG levels („attribution“)

Bray

, 201

0

Consensus among climate scientists

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”

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 inter-governmental HELCOM commission as a basis for its judgment and recommendations.

BACC as „regional IPCC“

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.

→ 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.

BACC (2008) results – in short

• 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)

• 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.

Overall Summary of BACC-2 (2013)

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

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.

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):

Past change: air temperature

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

Higher Temperature are expected to go along with 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.

Marine ecosysteme

→ 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)

Detection and Attribution

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.

Observed CRU, EOBS (1982-2011)

Projected GS signal, A1B scenario 10 simulations (ENSEMBLES)

Regional attribution

Observed 1972-2011 (CRU, EOBS)

Projected GS signal (ENSEMBLES)

Observed (grey) and projected (green) precipitation trends (1972-2011)

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.

Regional attribution

Assessing Scientific Reports: The BACC reportHow well do you feel your area of expertise was represented

1 = not at all 7 = very well

2 3 4 5 6

not a

t all

very

well

level of representation

other

Sea level rise

Change in marine ecosystems

Change in terrestrial - freshwater ecosystems

Projections of future anthropogenic climate change

Past and current climate change

Bray, 2010, pers. comm.

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.

Lund and Stockholm

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

mitigation, adaptation costs

policies

„Linear model“: Consolidated knowledge (consensus) leads to policy. Depoliticization of politics.

Ideal climate science /policy interaction

Competition of knowledge claims

IPCCBACC

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 ?