Studying climate change in the Baltic Sea Region Hans von Storch Institut für Küstenforschung Helmholtz Zentrum Geesthacht with material from Sirje Keevalik (Tallinn), Anders Omstedt (Göteborg), Markus Meier (Norrköping) and Marcus Reckermann (Baltic Earth Secretariat) Deutsch-Polnische Wissenschaftliche Begegnung, in Warszawa, 12. Juni 2014

BALTEX, BACC, Baltic Earth The Baltic Sea region, The catchment of the Baltic Sea Temperate to subarctic climate Different cultures Joint history Until 1991 divided into two different, partly hostile parts of the world. Atmospheric scientists began building a joint platform for bridging the divide – BALTEX Beginning in 2003, another effort for uniting scientific communities – the BACC effort In 2013, in recognition of the Earth System science character, BALTEX is renewed as “Baltic Earth”

Overcoming the big divide Sirje Keevalik, Tallinn

The beginning … 3-8 August 1992, Tallinn International Radiation Symposium Bringing scientist from East and West together Making the Baltic Sea region another site for the international GEWEX program with its emphasis on the regional energy and water cycle – named BALTEX Bringing together meteorologists, hydrologists and oceanographers

Basis of knowledge: Temperature, precipitation, river runoff, salinity, and ice The first BALTEX phase

Sirje Keevalik, Tallinn

Additional: Connecting climate and environmental changes: Carbon and nutrient cycles The second BALTEX phase

Achievements of 20 years of BALTEX overcoming the division between East and West Synergistically combining forces from West and East consolidating data bases novel observational databases coupled atmosphere-ice-ocean models novel reanalysis products outreach and communication activities like the homepage, study conferences and summer schools organized and coordinated by the International BALTEX Secretariat several working groups, e.g. BALTEX Assessment of Climate Change for the Baltic Sea Basin (BACC)

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.

interdisciplinary and international collaboration (study conferences, workshops, etc.) holistic view on the Earth System of the Baltic Sea region, encompassing processes in the atmosphere on land and in the sea and also in the anthroposphere 'service to society'‘= thematic assessments of knowledge gaps education (Summer schools) 2013: A new science and outreach program for the Baltic Sea region: Baltic Earth

Societal challenges in the Baltic Sea Region for which scientific knowledge is needed Climate change Eutrophication Pollution Habitat degradation Invasive species Overfishing

1.Salinity dynamics in the Baltic Sea. 2.Land-Sea biogeochemical feedbacks in the Baltic Sea region. 3.Natural hazards and extreme events as the key factor in understanding and predicting natural disasters in the Baltic Sea region. 4.Understanding sea Ievel dynamics using new technologies (remote sensing). 5.Anthropogenic changes and how the Earth system of the Baltic Sea region is affected. 6.Understanding regional/local variability of water and energy exchanges Suggested Grand Challenges

The BACC effort: How does climate change affect the Baltic Sea Region?

IPCC: Global temperature development during “instrumental times”

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“) Bray, 2010 Consensus among climate scientists

Thus, on the global scale, the knowledge about climate, climate change and climate impact is well documented, but what about the regional scale? This should be an effort of regional scientific communities – thus a task for BALTEX and, now, 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. Approximately 80 scientists from 12 countries have documented and assessed the published knowledge in 2008 in BACC 1; in 2014 BACC-2 comes out, with about 130 contributing authors.

A truly Baltic Sea Region effort …

→Presently a warming is going on in the Baltic Sea region, and will continue throughout the 21 st 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 Annual and seasonal mean surface air temperature anomalies for the Baltic Sea Basin , 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 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 (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 wind 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 ( ) The observed (grey) trends are mostly consistent with what the regional climate models (green) suggest as response to elevated GHG levels. However, the observed warming was in all seasons larger than what the models suggested. Observed CRU, EOBS ( ) Projected GS signal, A1B scenario 10 simulations (ENSEMBLES) Regional attribution

Observed (CRU, EOBS) Projected GS signal (ENSEMBLES) Observed (grey) and projected (green) precipitation trends ( ) The observed changes are in all seasons, except for fall (SON), larger than those suggested by the regional climate models. The observed changes in winter (DJF), summer (JJA) und fall (SON) are inconsistent with the models’ suggestion. In fall (SON) observation and projection even contradict each other. Regional attribution

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.

Independently of mitigation, a need for adaptation remains – this is a regional and local issue We have not done our homework -to study ongoing and possible future change. -to separate the different causes for observed change. Climate science needs to deal more with options of adaptation to prepare for societal decisions. The more successful the climate change limitation policy is, the less adaptation is needed – but adaptation is needed, and is useful in any case, if vulnerability is reduced. The regional scientific community is asked to generate the needed knowledge. The eventual decisions needed are again a matter of policymaking, of values, of societal choices.