Jannica Haldin: The Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) assesses the latest scientific knowledge about the impacts of climate change on ocean, coastal, polar and mountain ecosystems, as well as on us humans who depend on them. It is a mirror, with which we can look back to see what has changed from past to present. However, it also lets us look into the future, projecting what changes we can expect in the sea, depending on the amount of greenhouse gases we continue producing.
When looking at what has already changed, we can see that the rate of ocean warming – the sea taking in and storing heat – has more than doubled, as has global mean sea level rise. In fact, to date, the ocean has taken up more than 90 percent of the excess heat in the climate system. It is also clear that over the last decades, global warming has led to mass loss of ice sheets and glaciers, reductions in snow cover, and Arctic sea ice extent and thickness. In response to ocean warming, sea ice and biogeochemical changes such as oxygen loss, marine species have undergone shifts in geographical range and seasonal activities. This has already resulted in changes in species composition, abundance and biomass production of ecosystems and altered interactions between species, causing cascading impacts on ecosystem structure and functioning.
But the report also looks forward, up to 80 years into the future. Our future ocean is projected to transition to unprecedented conditions, a combination of increased temperatures, greater upper ocean stratification, further acidification, oxygen decline, and altered net primary production – for instance linked to algal blooms – as well as reduced sea ice extent. As a consequence, over the 21st century, we can expect a further decrease in global biomass of marine animal communities and in their production, a shift in species composition, and a decline in fisheries catch potential. In turn, this is projected to affect income, livelihoods, and food security. Projected ecosystem responses include further losses of species habitat and diversity, and degradation of ecosystem functions.
The SROCC report also makes clear that impacts of climate change are already a reality, and when the pressures exerted by climate change are combined with pressures stemming from other human activities, the latter have the potential to intensify the warming-induced ecosystem impacts. The capacity of organisms and ecosystems to adjust and adapt to change is better the lower the total pressure on the system is. This means that the sea has a better chance to handle the changes under lower emissions but it also means that we need to work to manage other human activities to limit their negative effects, to give the ecosystem a fighting chance.
Although the report looks at the global situation, it is highly relevant for our own sea. The Baltic Sea is a shallow, Northern sea, partially covered by sea ice and with a high coast to sea ratio. If they changes outlined in the report come to pass, they will impact a significant proportion of the approximately 85 million people living in the catchment. The report directly states that the effects of warming will be more pronounced on high latitudes and for temperate shallow estuaries with limited exchange with the open ocean, of which the Baltic is used as prime example. This translates into that the changes outlined globally will occur faster and with more impact here than in other places.
In addition to the changes which affect larger areas, the report outlines some changes where Baltic Sea specific information is available. This includes increased risk of water-borne disease in the Baltic Sea, with a nearly two-fold predicted increase in suitable conditions for Vibrio bacteria which can cause cholera. Wave height in the Baltic is also predicted to increase, and extreme sea level projections show a rise of up to 0.35 m towards the end of the century along the Baltic Sea coast. Long-term loss and degradation of marine ecosystems compromise the sea's role in cultural, recreational, and intrinsic values important for our identity and well-being.
Overall, HELCOM aims at strengthening the sea's resilience and own coping mechanisms, by improving the capacity of the Baltic Sea's ecosystem to recover from stress and disturbance resulting from climate change impacts. HELCOM is a regional environmental policy maker, working on developing common environmental objectives and actions for the whole region, as well as providing information about the state of and trends in the marine environment. Both the objectives and the trend information can then form the basis for decision-making in the Baltic Sea countries and in other international fora. HELCOM strives to make climate change increasingly visible in marine policy making, as well as incorporate it into the day to day work of the Commission.
In practice, climate change work within HELCOM is focusing on understanding and communicating what climate change means for the marine and coastal environment. Climate change has a multitude of effects so it needs to be approached in that way, not from one single topic, but from every angle of possible importance to the sea.
To compile the available climate change information, HELCOM, together with Baltic Earth, earlier this year established a Joint Climate Change expert network (EN CLIME), currently consisting of over 60 experts from the entire region. Right now, EN CLIME is working on a Baltic Sea climate change fact sheet, to make sure that decision makers have the latest science on climate change and its impacts. Similarly to the IPCC report, the fact sheet will provide key messages on what has already happened and what we can expect in the future. However, the fact sheet will look specifically at our own region, covering a large number of topics, from how much it might rain, to what we can expect for seabirds, to possible impacts on maritime traffic.
What the IPCC report did on a global scale, the fact sheet will do at the regional level – empowering decision makers to tackle the transition facing the region and help underpin timely, ambitious and coordinated action. The statement from the IPCC report is as valid for the Baltic Sea as it is globally:
"The more decisively and earlier we act, the more able we will be to address unavoidable changes, manage risks, improve our lives and achieve sustainability for ecosystems and people – today and in the future."