Researchers from the Geological Survey of Denmark and Greenland (GEUS) have led a new study, which shows that we can expect much larger sea-level rise by 2150 than previously thought. The researchers have included both historical observations of sea level and the changes predicted by the UN's climate panel, IPCC, in their latest report on the consequences of climate change, and focused on four Danish cities: Copenhagen, Aarhus, Esbjerg and Hirtshals.
”Our research shows that if we continue in the climate scenario with the highest emissions of greenhouse gases – defined by the IPCC as SSP5-8.5 – we can expect sea level changes of 123 cm at Esbjerg, 117 cm at Copenhagen, 115 cm at Aarhus and 99 cm at Hirtshals by 2150,” says William Colgan, Senior Researcher at GEUS and lead-author of the study. He continues:
”However, if we meet or exceed the ambitions of the Paris Climate Agreement and move to the climate scenario with the lowest emissions of greenhouse gases – defined by the IPCC as SSP1-1.9 – we can expect sea level changes of between 29 and 55 cm across the four cities based on our current knowledge.”
According to the researchers behind the study, the wide span in the expected sea level rise under the different climate scenarios underline the potentially great effect it will still have to implement climate mitigation measures.
Extreme sea-level events will be more common
The researchers have also studied the impact that changes in the average sea level could have locally in the case of extreme water-level events, for example storm flooding. At Aarhus, a 100-year extreme sea-level event – i.e. an extreme event which statistically only occurs once every 100 years - has been estimated as +163 cm above mean sea level. However, as sea levels around Denmark rise, such extreme events are expected to occur far more often.
”In a high-emission scenario, the extreme sea-level events that currently occur every 100 years, will occur every 1 to 5 years by the year 2100,” says William Colgan.
Expected sea level is rising as scientific understanding develops
The new study also reviews previously published prognoses for sea-level rise in Denmark and found that the best estimate, for planning purposes, of sea-level rise at Copenhagen increased 50 cm during the last two decades.
“Information on sea-level rise changes all the time - among other things, because the science develops, and climate models become more sophisticated. Newer results generally show increases in expected sea-level rise. This indicates that there is a continual need for updated sea-level prognoses using real and up-to-date information and to make these prognoses applicable to local interests,” says Kristian K. Kjeldsen, Senior Researcher at GEUS and co-author of the study.