Global warming: New study shows even modest temperature increases will raise sea levels by several meters

1 meter sea level rise would subject New York to severe flooding every 3 years

When the impacts of melting ice sheets are added to thermal expansion, sea level rise from global warming becomes a dicey proposition. Photo by Bob Berwyn.

By Summit Voice

SUMMIT COUNTY —Sea-level increases of several feet are likely in the coming centuries even if global warming is held to two degrees Celsius, the target for current efforts to cap heat-trapping greenhouse gas emissions.

“Due to the long time it takes for the world’s ice and water masses to react to global warming, our emissions today determine sea levels for centuries to come.” said  Michiel Schaeffer, of Climate Analytics and Wageningen University, and the lead author of a new study that tries to pinpoint the long-term outlook for sea levels.

“Sea-level rise is hard to quantify, yet a critical risk of climate change,” Schaeffer said, adding that the results demonstrate the benefits of capping and cutting greenhouse gas emissions.

Limiting global warming to less than 1.5 degrees Celsius and subsequent temperature reductions could halve sea-level rise by 2300, compared to a 2-degree scenario. If temperatures are allowed to rise by 3 degrees, the expected sea-level rise could range between 2 and 5 metres, with the best estimate being at 3.5 metres.

The potential impacts are significant.

“As an example, for New York City it has been shown that one metre of sea level rise could raise the frequency of severe flooding from once per century to once every three years,” said Stefan Rahmstorf, of the Potsdam Institute for Climate Impact Research and co-author of the study.

The scientists further assessed the rate of sea-level rise. The warmer the climate gets, the faster the sea level climbs.

“Coastal communities have less time to adapt if sea-levels rise faster,” Rahmstorf said. “In our projections, a constant level of 2-degree warming will sustain rates of sea-level rise twice as high as observed today, until well after 2300,” Schaeffer added. “But much deeper emission reductions seem able to achieve a strong slow-down, or even a stabilization of sea level over that time frame.”

Previous multi-century projections of sea-level rise reviewed by the Intergovernmental Panel on Climate Change were limited to the rise caused by thermal expansion of the ocean water as it heats up, which the IPCC found could reach up to a metre by 2300.

However, this estimate did not include the potentially larger effect of melting ice, and research exploring this effect has advanced considerably in the last few years.

The new study uses a complementary approach based on using the connection between observed temperature and sea level during past centuries in order to estimate sea-level rise for scenarios of future global warming.

“Of course it remains open how far the close link between temperature and global sea level found for the past will carry on into the future,” Rahmstorf said. “Despite the uncertainty we still have about future sea level, from a risk perspective our approach provides at least plausible, and relevant, estimates.”

Weblink to the article when it is published on June 24th: http://dx.doi.org/10.1038/NCLIMATE158

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4 Responses

  1. At current rates of emission, the atmosphere will contain over 10,000ppm of CO2 by 2300. The sea level won’t matter when nobody (including most plants) will be able to breath. Enjoy your extinction!

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