IPCC stands for Intergovernmental Panel on Climate Change; it is an intergovernmental body of the United Nations body for assessing the science related to climate change. It provides regular assessments of the scientific basis of climate change, its impacts ad future risks, and options for adaptation and mitigation. The lead authors are nominated and they volunteer their time. Lead authors work with hundreds of Contributing Authors with specific knowledge or expertise so that the full range of scientific views is reflected in the report.
I am an environmental scientist and I have been researching environmental vulnerability and adaptation options in low-lying coastal areas at UNU-EHS for 12 years. I currently lead the Environmental Vulnerability and Ecosystem Services (EVES) section and based on this was nominated as a lead author for chapter 4, which is the chapter focusing on sea level rise in The Ocean and Cryosphere in a Changing Climate (SROCC) report. While my research led to my appointment it is important to note that the job of an IPCC lead author is not to conduct research, but to assess the current state of global research; in that sense it has also been an interesting shift of perspective.
What makes the SROCC special is its integrative nature. Firstly, we are not only looking at how our environment is changing, but we are also paying attention to the social dimension, so the vulnerability and exposure of communities as well as adaptation. Secondly, the report brings together the cryosphere, which is the frozen part of our planet, with the ocean, which gives justice to its interconnected nature. In simple terms, the water that we lose at the poles and in the high mountains puts communities at the low-lying coast at risk.
If I want people to take away one main message, I would tell them that we know that sea level rise is here to stay. In a wonderful, but unrealistic scenario where we would stop all greenhouse gas emissions by tomorrow, we would still be confronted with sea level rise. Sea level rise lags behind global warming mainly because of the large heat capacity of the oceans. This means we need both mitigation – so a dedicated commitment to cutting down carbon emissions now – and the implementation of effective adaptation solutions.
By 2050 we will have a mean global sea level rise of 20 to 40 cm. There will be regional differences but all parts of the world will be affected. While this amount of sea level rise sounds manageable it is important to keep in mind that other factors contribute to the challenge. If we take the example of the megacity of Jakarta, which is subsiding, these 20 to 40 cm can already become a crucial challenge. At the end of the century and beyond we face two very different futures: If we stick to the Paris agreement and our commitment to cutting down carbon emissions, we can keep sea level rise at bay with a global mean rise of 50 cm. If we continue with the current emission scenario, we will face 1 meter sea level rise by 2100 and up to 4 meters by 2300.
As someone who has spent a big part of her life researching disaster risk reduction, the increased frequency with which we will be hit by extreme events worries me the most. A simple analogy I use is the one of a bath tub which is full with water. If you create waves here, you will have flooding in your entire bathroom. Sea level rise will work the same way. Extreme events, such as flooding caused by storms, which we are currently categorizing as events that occur once in a hundred years, will become an annual event in many places. This has tremendous implications for communities living near the coasts, for our ecosystem and for people’s livelihoods.
The science is very clear: the dominant cause of global mean sea level rise is global warming caused by our emissions. What is new since the last IPCC report in 2014, is that the melting of the ice sheets is now the primary contributor to sea level rise, while thermal expansion of the ocean comes now second. Mass loss from the ice sheets tripled from the Antarctic and doubled from Greenland over the period 2007–2016 relative to 1997–2006.
Today impacts are mostly felt in places where sea level rise combines with subsidence (sinking land) or other hazards. In the report we use case studies to give some examples. In Nadi Town, Fiji, for instance, river and coastal flooding is caused by a combination of heavy rainfalls, elevated sea levels and the subsidence of the river delta. People and houses in the Nadi River flood plain are already affected.
I have worked quite a lot in tropical deltas, for example the Mekong delta, which is also sinking. I have seen that in the dry season salt water can intrude as far was 100 km inland, which is a combined effect of low river flows in the dry season, changes in the river bed, and sinking land caused by e.g. ground water pumping. Sea level rise adds to these pressures and will increase salt water intrusion and flooding in the delta. Along the coast this causes drinking and irrigation water to become salty. This also sets off the process of land use change. People for example decide that they want to use the salt water and switch from rice farming to shrimp farming as shrimp can yield higher income. What they however often do not take into consideration is that shrimp farming is a lot more risky, so while you will not become rich with rice farming it can provide a financial stability that shrimp farming mostly can’t. The issue is that land conversion to salt-water based aquaculture is largely irreversible. So it is critical that land use is well-thought-out and well planned. For example, in areas where salt water influences land use and available agricultural options, allocating space for ecosystems, which can buffer against coastal hazards and help to prevent erosion can be an effective solution. Studies show that mangroves and coastal wetlands stabilize land, capture sediments and can keep up with current level sea level rise.
As a scientist, I see a window of opportunity to enhance the understanding for and take-up of ecosystem-based solutions as one part of the overall adaptation strategy at the coast. As a mother, I see and sense the spirit and determination of young people, including my own two sons, who question the actions of us grown-ups and who are demanding change. When children start asking their parents the hard questions about the choices related to the family’s carbon footprint, this is a very effective driver towards a household’s transformation toward sustainability. So I hope that all of us will hold each other accountable for the decisions we are making for our fascinating and beautiful planet.
Find out more about Dr. Sebesvari here.