Climate change: Wet feet for our descendants

For every degree of warming, the sea level rises more than two meters in the long term

Antarctic © NOAA
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Our climate sins today will give our descendants still wet feet in hundreds of years. For every degree of warming more, the sea level will rise by a good two meters in the next 2, 000 years. This shows a new model calculation of climate researchers. Because the increase of the level starts now only slowly, but will accelerate strongly in the future. The main sources of additional water are then no longer the mountain glaciers, but the ice of Greenland and the Antarctic, according to the scientists in the journal "Proceedings of the National Academy of Sciences".

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"CO2, once released by the burning of fossil fuels, remains in the atmosphere for a terribly long time, " says Anders Levermann, lead author of the study and head of research at the Potsdam Institute for Climate Impact Research (PIK). "Consequently, the warming it causes remains as well." The oceans and ice sheets are slow to respond to climate change, simply because of their enormous mass. Therefore, the sea level is currently only rising very gradually - it is still measured in millimeters per year. In the entire 20th century, the levels increased by about 0.2 meters and even the worst future scenarios start from less than two meters in this century.

But that will change significantly in the distant future. "The problem is: Once unbalanced, the rise is unstoppable - unless the temperature drops, " says Levermann. With their study, the researchers wanted to find out to what point we bring sea-level rise through our present-day action and anthropogenic climate change. They have been underestimating the impact of short-term changes in temperatures on the long-term response of the oceans.

2.30 meters more for each degree of warming

Levermann and his colleagues tested this using computer simulations and data on the behavior of the oceans in the history of the earth. For the latter, they analyzed sediment cores from the seabed and past shorelines from various coasts worldwide. "Our estimates combine physical understanding with climate archive data - they seem to be robust, " the researchers said. display

The result: The sea level rise will intensify in the distant future. Any degree of temperature could then increase the ocean level by 2.30 meters. And the sources of additional water are also changing: while the thermal expansion of the sea and the melting of mountain glaciers are today the main causes of rising seas, this will change in the next 2, 000 years. In the long term, the Greenlandic and Antarctic ice sheets are the dominant factors, according to the study. Half of this increase is likely to be caused by ice losses in the Antarctic, which currently contribute less than 10 percent to global sea-level rise.

It can not be done without adaptation

Specifically, if the global average temperature rises four degrees from pre-industrial times, which could be reached as much as 2100 in a business-as-usual scenario, the Antarctic ice sheet will be in the next two Millennia contribute about 50 percent of sea-level rise, Greenland an additional 25 percent. The thermal expansion of seawater, currently the largest contributor to sea-level rise, will only contribute 20 percent and the proportion of mountain glaciers will be less than five percent, given that many of them will have shrunk to a minimum.

"There will have to be an adjustment, " says Levermann. "Increasing sea-level rise is something we can not avoid if global temperatures do not recede. While measured in terms of terms, it may be slow, but inevitable and therefore important for almost everything we build in the near future and for many generations to come. ( Proceedings of the National Academy of Sciences, 2013; doi: 10.1073 / pnas.1219414110)

(Potsdam Institute for Climate Impact Research (PIK), 17.07.2013 - NPO)