Feature Links:

cop21 cover ytb 260px cop21 part2 ytb 260px bru pearce biomass 260 146px

Equilibrium Sea Level Rise by 2100

Source: Potsdam Institute for Climate Impact Research (PIK)


Sea-levels worldwide will likely rise by 50 to 130 centimeters by the end of this century if greenhouse gas emissions are not reduced rapidly.

This is shown in a new study led by the Potsdam Institute for Climate Impact Research that, for the first time, combines the two most important estimation methods for future sea-level rise and yields a more robust risk range. A second study, like the first one to be published in the USProceedings of the National Academy of Sciences, provides the first global analysis of sea-level data for the past 3000 years. It confirms that during the past millennia sea-level has never risen nearly as fast as during the last century. Together, the two studies give critical information for coastal planning. For expert assessments of future sea-level rise, the authors make the tool available online.

 

“With all the greenhouse-gases we already emitted, we cannot stop the seas from rising altogether, but we can substantially limit the rate of the rise by ending the use of fossil fuels,” says Anders Levermann, Research Domain Co-Chair for Adaptation at the Potsdam-Institute for Climate Impact Research (PIK), scientist at Columbia University’s Lamont-Doherty Earth Observatory,  and co-author of the study on future sea-level rise. “We try to give coastal planners what they need for adaptation planning, be it building dikes, designing insurance schemes for floodings, or mapping long-term settlement retreat.”

Even if the Paris Agreement is implemented, adaptation is a challenge

The scientists will make the computer simulation code available online so experts can use the information and the estimation tool for risk assessments. Even if ambitious climate policy follows the 2015 Paris Agreement, sea levels are projected to increase by 20 to 60 centimeters by 2100 – hence the relevance for coastal protection. “This is quite a challenge, but less expensive than adaptation to unabated sea-level rise which in some regions is impossible”, Levermann adds. “If the world wants to avoid the greatest losses and damages, it now has to rapidly follow the path laid out by the UN climate summit in Paris a few weeks ago.”

For future sea-level rise, the scientists combine two approaches. To forecast sea-level rise, some scientists use  process-based computer simulations that calculate the contribution of melting glaciers, ice sheet mass loss and the thermal expansion of sea-water from physical laws – warmer water takes more space. These simulations are computationally costly and slow. As an alternative, statistical analyses have been used to assess future sea-level rise quickly at low computational cost. “We designed our tool in a way it is consistent both with the past observations of sea-level rise and the long-term physical processes in the different elements of the Earth system,” says lead-author Matthias Mengel from PIK. “Importantly, our calculation method is fast, which makes it easy to reproduce and allows for a lot of simulation runs to provide probabilities of sea-level rise."

The likely future sea-level rise cannot be brought down to just one number, but is represented as a range, which at first sight might seem large. “The range allows for a risk assessment,” says Ben Marzeion from the University of Bremen, Germany. “Coastal Planners need to know how a reasonable worst-case scenario as well as a well-founded best-case scenario look like to weigh chances and costs. The best available science is now converging towards a common uncertainty range of future sea-level rise. Curbing greenhouse gas emissions now gives us the chance to prevent sea level rise to accelerate further.”

During past millennia sea-level has never risen as fast as during the last century

The study on future sea-level rise turns out to be confirmed by the other one on past sea-level rise: they yield nearly identical sea-level rise estimates for the 21st century. Also, the new estimates overlap with those of the latest IPCC report.

“Our study is for sea level what the now well-confirmed famous ‘hockey stick’ diagram was for global temperature,” says Stefan Rahmstorf, co-author of the paper on past sea-level rise and Co-Chair of PIK’s research domain Earth System Analysis. “We can confirm what earlier, more local sea-level data already suggested: during the past millennia sea-level has never risen nearly as fast as during the last century.” Based on the analysis of the past millennia of natural sea-level variations, the new study was also able to estimate how much human activities have contributed to modern sea-level rise: Almost certainly more than half of the 20th Century rise has been caused by human activity, possibly even all of it.

Confirming previous assumptions, as boring as it might sound, is of key relevance for the progress of science. “We can now show the effect in an unprecedentedly robust way, based upon the statistical analysis of a global database of regional sea-level reconstructions,” says Rahmstorf. “The new sea-level data confirm once again just how unusual the age of modern global warming due to our greenhouse gas emissions is – and they demonstrate that one of the most dangerous impacts of global warming, rising seas, is well underway.”


Article on future sea-level rise: Mengel, M., Levermann, A., Frieler, K., Robinson, A., Marzeion, B., Winkelmann, R. (2016): Future sea-level rise constrained by observations and long-term commitment. Proceedings of the National Academy of Sciences (PNAS) [DOI:10.1073/pnas.1500515113]

Weblink to the article on future sea-level rise: www.pnas.org/cgi/doi/10.1073/pnas.1500515113

Weblink to source code for future sea-level rise approximation tool:https://github.com/matthiasmengel/sealevel

Article on past sea-level rise: Kopp, R.E., Kemp, A.C., Bittermann, K., Horton, B.P., Donnelly, J.P., Gehrels, W.R., Hay, C.C., Mitrovica, J.X., Morrow, E.D., Rahmstorf, S. (2016): Temperature-driven global sea-level variability in the Common Era. Proceedings of the National Academy of Sciences (PNAS) [DOI:10.1073/pnas.1517056113]
Weblink to the article on past sea-level rise:http://www.pnas.org/cgi/doi/10.1073/pnas.1517056113

 

 

More posts by Nick Breeze

Interview by Nick Breeze with Dr Natalia Shakhova and Dr Igor Semiletov

A new scientific paper published in Nature Communication Journal demonstrates that the mechanisms of destabilisation of subsea permafrost, contrary to previous claims, provide new insights into increased emissions from the worlds largest deposits of methane, that exists in the East Siberian Arctic Shelf (ESAS).

The subsea permafrost has for thousands of years acted as a seal, restricting the flow of gas through the water column to the atmosphere. This paper clearly shows that permafrost degradation and the occurrence of gas migration pathways are key factors in controlling the emissions.  

 

Comment: Watching our recent interview with Christiana Figueres, David Tattershall (Envisionation Limited) responded with considered concern with respect to her answer to the question on the reduction of emissions from the aviation industry.

Just to recap, here is the transcripted answer with Tattershall's response below:

 

The lady who ushered in the Paris Agreement now wants to ramp up the pace and ensure the world reaches peak emissions by 2020, leading to total decarbonisation by 2050. The whole campaign hinges on the a new report that cites 2020 as a critical milestone for stemming the effects of climate change.

Christiana Figueres is persuasive and influential but in light of recent world events that include the destabilisation of the EU as a political block, and the openly anti-climate action administration of President Trump, it is very clear that the world has changed since Paris.

READ THE COMMENT: Does Figueres interview give clues as to why we went backwards from Copenhagen to Paris?

 

Centre for Science and Policy (CSaP): 2017 Climate Change Seminar Series

Science, politics, knowledge management, innovation and markets all play a role in climate change action, but what is the role of the University of Cambridge as an ‘anchor institution’ for these? Bringing together speakers spanning the worlds of research and policy, this series of events will explore how the multifaceted aspects of climate change action can come together to help us make the right decisions for the long run.  

The window of opportunity is closing… but the price of failure is still too high!

The rate of ecological destruction is now so bad that the fate of our civilisation literally hangs in the balance. The loss of the Arctic polar ice cap, the melting from above and below of Antarctica, the culling and collapse of forests and dying oceans, failing ecosystems, our atmosphere burdened with hundreds of billions of tonnes of extra greenhouse gases, and still each week scientists report more broken links in the chains of interconnectedness that sustain each one of us, rich and poor, on this planet. Despite all this, the great human enterprise built on a foundation of carbon, rumbles on in search of new fixes.

 

Peter Wadhams has achieved many accolades and held positions such as Director of the Scott Polar Institute in Cambridge Uk, among a great many others. He has been on more than 50 research trips to the polar regions and, of special interest to those studying the demise of the Arctic ice cap, he has been under the ice on 6 submarine expeditions.