IPCC Special Report attests dramatic consequences of climate change for the ocean and cryosphere

The new IPCC special report shows that climate change is already having severe impacts on the earth's ocean and cryosphere. It is an appeal to the international community to take more effective climate action before very serious consequences occur or even tipping points are reached, which will accelerate climate change further. The risks both for humanity and nature will increase significantly with greater global warming. The special report, unanimously adopted by IPCC member states in Monaco, has been presented today in Berlin by Federal Environment Minister Svenja Schulze and her colleague Federal Research Minister Anja Karliczek.

Federal Environment Minister Svenja Schulze commented: "The Intergovernmental Panel on Climate Change provides evidence that the impact of climate change can be proven and is experienced by people and nature already today. There are more floods and storm surges, tropical storms are ever more devastating. The new IPCC report shows also quite clearly what the consequences would be if the international community does not implement the Paris Agreement. It would be a totally different world from what we know today. Sea level could rise by metres, glaciers could melt and permafrost thaw, releasing significant additional amounts of CO₂. Some island states and coastal regions where today large part of the world’s population live, would be threatened by floods or even become uninhabitable. The international community must certainly act more decisively as otherwise future generations will face extreme and partly irreversible climate consequences."

Federal Research Minister Anja Karliczek said: "The new IPCC special report illustrates impressively the pressure the earth's ocean and cryosphere are experiencing due to climate change. There is no doubt that we will manage to achieve our ambitious climate goals only by means of technological and social innovation. The more we can rely on research in this field, the more scope of action will remain for our societies and our economies alike. The Federal Ministry of Education and Research (BMBF) will therefore contribute not only by providing important approaches concerning the reduction of CO₂ emissions for the German government’s Climate Action Programme 2030, but also by expanding its research into the changes occurring in the ocean and cryosphere. The Polarstern expedition in the Arctic which just started last week shows how we approach this: based on science and in close international cooperation."

The SROCC lists evidence for the dramatic change occurring in the oceans worldwide: ocean warming and acidification are on the rise while the oxygen content of the ocean is decreasing. Glaciers, snow, ice and permafrost are declining significantly on a global scale: glaciers and ice sheets in polar regions are losing mass, ice cover and permafrost are retreating. With further warming, extreme weather events like storm surges and tropical cyclones will become more intense and frequent.

According to the IPCC, the rate of sea level rise has accelerated in recent decades. Without effective climate action, the sea level rise will reach 61 to 110 centimeter (global average) by the end of this century as compared to 2000. These figures are higher than those given in the last IPCC Assessment Report 2013 as new insights indicate a higher contribution by melting water from the Antarctic ice sheet. Sea level will continue to rise for centuries, in a scenario without effective climate action possibly even by several meters.

The ocean and cryosphere play a key role in the global climate system. Currently, the ocean buffers the atmospheric warming by absorbing around 30 percent of anthropogenic CO₂ emissions and around 90 percent of the additional energy caused by the greenhouse effect. Ice and snow surfaces reflect sun rays, thereby reducing global warming. Global ocean currents act as gigantic circulation pumps transporting heat and freshwater, thus influencing regional climate conditions.

Reaching what are known as tipping points, for example instabilities in Antarctic ice sheets, the collapse of the Atlantic circulation (of which the Gulf Stream is part) or the massive release of greenhouse gases due to thawing permafrost, would bring about dramatic and mostly irreversible consequences. There remain major uncertainties with regard to the probability and the temperature thresholds of these processes. However, it cannot be excluded that specific tipping points might already be reached in this century with a temperature increase of 1.5 to 2 Degrees Cels compared to pre-industrial times.

Global warming is causing further shifts in climatic zones on land and at sea, but species and ecosystems might not always be able to follow these shifts. Climate change will also have a progressive impact on fisheries, in particular in tropical regions. There will be regional scarcity of fresh water due to shrinking mountain glaciers. The repercussions for infrastructure, food security, coastal defence and tourism will probably be grave. Changes in the ocean and cryosphere due to unrestricted greenhouse gas emissions may outpace the adaptability of ecosystems and societies in some areas already by mid-century.

It will only be possible to significantly curb these risks in the framework of climate resilient and sustainable developments if immediate and coordinated systematic climate action is taken, together with initiatives for adaptation to the consequences of climate change that probably cannot be prevented.