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Sea-levels will keep rising even with the Paris Agreement, latest findings show

Published: 6 April 2018
Sea-levels continue to rise
Latest findings show sea-levels will keep rising

What will the world look like with 1.5°C of warming? That has been the focus of investigation in three recently published studies led by the University of Southampton.

The Paris Agreement, aiming to hold global average temperatures to ‘well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C’ does not take account the longevity of sea-level rise.

These new studies indicate that early climate change mitigation can reduce sea-level rise by approximately 0.40-0.50m by 2100 and 1.0-2.0m by 2300. This approximately halves the land area exposed by 2300 compared with a non-mitigation scenario.

Between 1.5% and 5.4% of the world’s population may be exposed to coastal flooding by 2300. Moreover, low-lying deltas are particularly vulnerable to the effects of sea-level rise.

To generate a range of scenarios of sea-level rise, the project team used an innovative climate modelling approach which reflected different magnitudes and rates of long term climate change.

The team found significant benefits of mitigating for climate change, particularly in the immediate future.

The lead author of the first study, Dr Philip Goodwin, lecturer in Ocean and Earth Science at the University of Southampton, found that climate change mitigation was very important in reducing sea-level rise in a centennial timescale. This paper, published in Earth’s Future, is titled ‘Adjusting Mitigation Pathways to stabilize climate at 1.5 and 2.0 °C rise in global temperatures to year 2300’.

Dr Goodwin said: “We compared the amount that sea-levels could rise by analysing mitigation scenarios for 1.5°C and 2.0°C. This indicated that by 2100, sea-levels could rise to 0.40m and 0.46m respectively, and by 2300, 1.00m and 1.26m. Compared with a non-mitigation scenario, mitigation reduced sea-level rise by 3.2m by 2300.”

Lead-author of the other two studies focussing on climate change is Dr Sally Brown, Senior Research Fellow at the University of Southampton.

Dr Brown’s papers, ‘Quantifying land and people exposed to sea-level rise with no mitigation and 1.5 and 2.0 °C rise in global temperatures to year 2300’ and ‘What are the implications of sea-level rise for a 1.5°C, 2°C and 3°C rise in global mean temperatures in the Ganges-Brahmaputra-Meghna and other vulnerable deltas?’ featured in Earth’s Future and Regional Environmental Change, respectively.

Dr Brown said: “Around 100 million people are exposed to flooding today and this could approximately double by 2100, and increase three fold by 2300, even taking account of climate change mitigation. Adaptation in coastal, and particularly delta areas, is challenging given the geographic scale, and continued efforts to reduce risk by governments and other national and international organisations is required.”

Many areas of the world are already sensitive to extreme water levels, such as delta regions, home to millions of people world-wide. An equivalent of a 1.5°C rise in sea-level will mean more extremes and is likely to lead to more wide spread and deeper flooding unless adaptation is undertaken.

Dr Ivan Haigh, co-author of the studies and Associate Professor in Coastal Oceanography at the University of Southampton, said: “The implications of sea-level rise has important consequences for society for hundreds of years to come. Extreme water levels affect thousands of people around the world today, and this will increase with sea-level rise.

“These papers make an important contribution to determine who what or will be subject to long-term flood risk even under stringent climate change mitigation.”

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