A warming of just 2 degrees Celsius will be enough to trigger a sea-level rise of more than 6 metres. This was the conclusion of researchers who participated in a workshop in Bern, Switzerland. Their study assessed past warm periods on our planet. Elke Bunge reports.
Under the Paris Agreement, the world’s nations agreed to limit global warming to no more than 2 degrees Celsius by 2100 above pre-industrial levels. But many experts doubt that this will be enough.
Fifty-nine scientists from 17 countries met at a workshop in Bern, Switzerland, to discuss their research on climate change. They took a new approach in which they assessed long-term data on global climate developments. Their study was published in the latest issue of Nature Geoscience.
Using paleoclimate data
Led by the University of New South Wales in Australia, the University of Bern in Switzerland, and Oregon State University in the U.S., the project integrated paleoclimate data to develop a new climate model.
Studies have shown that the Earth has experienced several time intervals over the past 3.5 million years that were 0.5 to 2 degrees Celsius warmer than the so-called preindustrial temperatures of the 19th century – precisely the upper limit allowed for in the Paris Agreement.
CO2 emissions rising drastically
One consequence of the higher temperatures is that the ice at the polar caps melted and even larger parts of the permafrost thawed. As a result, more greenhouse gases were released, which in turn led to further global warming.
The scientists are concerned that this information from the past has not been included in short-term climate models.
“It is worrisome that these models likely underestimate climate change under higher emission scenarios, such as a ‘business as usual’ scenario, and especially over longer time scales,” said lead author Kathrin Meissner from the Climate Change Research Centre at the University of New South Wales.
If such long-term data is not included in our climate models, the 2-degree target set out in the Paris Agreement could simply fall short of curbing global warming. This is especially the case given that many signatory states – including the major industrial ones – appear unable to meet their own climate targets.
Shifting ecosystems and climate zones
Ecosystems and climate zones will generally shift poleward or to higher altitudes in the event of such warming. Polar ice caps will melt even further and large parts of Greenland will thaw. The additional carbon dioxide and methane released into the atmosphere will exacerbate the greenhouse gas effect, driving additional warming. In the long term, a sea-level rise of more than 6 metres is expected to last for thousands of years, the study found.
“We are already beginning to see the effects of rising sea level,” said Alan Mix of Oregon State University. “This rise may become unstoppable for millennia, impacting much of the world’s population, infrastructure, and economic activity that is located near the shoreline”.
According to the researchers, this underscores the urgency of reducing CO2 emissions soon to meet the goals of the Paris Agreement in this century and beyond.