"In the year 6565, if man is still alive" was the text of a famous pop song of the seventies and in a Science-fiction-movie of the nineties ("Waterworld") Kevin Kostner portrayed a aquatic world in a fictive future in which the survivors of a global climate change mainly live on the water and former cities like New York, Hamburg or London are beneath the shore of the oceans. It seems as if mankind is on its best way to fullfill darkest visions: in a recent study German and British scientists from the University of Tuebingen, University of Southhampton and University of Bristol developed a model which predicts the rise of the sea level for the coming millenia. Their conclusion: in some thousand years Earth will have a sea level alike in the pliocene (3-5 million years ago).

 

Usually the research for climate change and sea level rise focusses on the next hundred years. It is predicted that mankind will face a sea level rise of one meter or more. But prognoses for the coming millenia are difficult because glaciers melt down slowly  even if the temperature rises quickly.

 

 

Comparing earth climate history with future climate changes

 

The scientists compared the CO2-concentrations in fossile antarctic ice samples for the last 520.000 years with the sea level changes determined for that time period. Due to the latest results it seems that during the last 5 ice age periods there was a close coherence between global temperatures, carbon dioxide content in the air and the sea level. When the scientists extrapolate these values for the coming millenia they conclude a much more dramatic sea level rise of 25 meters, more than was assumed until now.

Anthropogenic emissions of CO2 has lead during the last 100 year to a concentration of the greenhouse gas in our recent athmosphere (387 ppmv=387 parts of CO2 in 1 million parts of air) which compares to that of a period which is 3-5 million years ago (the pliocene). In the pliocene the sea level was 25 meters above the nowadays level. The context  the model reveals - published in the present study -  suggests, that even if we managed to freeze every CO2-emission immediately the rise of sea level would hardly be to stop.

 

 

"Waterworld" for our childrens children?

 

Thus will in the year 10.000 mankind blame their ancestors (us) for living on a tropical planet with few land left to live on?
In the movie "Waterworld" the performers eventually reach a remote islands of hope. Maybe for our progeny with billions of individuals there won't be enough islands remaing to live on.
It is so our responsibility to decide in what world our childrens children will live in because we are the first generation to understand what is going on and maybe the last one that still can change things.

 

Source:
- E. J. Rohling, K. Grant, M. Bolshaw, A. P. Roberts, M. Siddall, Ch. Hemleben and M. Kucera: Antarctic temperature and global sea level closely coupled over the past five glacial cycles. Nature Geoscience, 2009
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- idw-online.de