Coastal flooding across the world is set to rise by almost 50 per cent due to climate change in the next 80 years, endangering many millions of people and resulting in trillions of euro in damage to cities and coastal infrastructure, according to the latest projections.
Among the most vulnerable regions is northwest Europe, including Ireland, concludes an international team led by researchers at the University of Melbourne and the University of East Anglia.
Their findings, generated in a complex modelling exercise, shows land area exposed to an extreme flood event will increase by more than 250,000sq km globally; an increase of 48 per cent – or more than 800,000sq km.
Without investment in flood defences or a reduction in greenhouse gas emissions, the figures indicate coastal flooding could have major implications for the global population and economy by 2100.
Areas that could be at risk of extensive flooding include southeast China; Australia's Northern Territories, Bangladesh, West Bengal and Gujurat in India, the US states of North Carolina, Virginia and Maryland and northwest Europe – where east coast UK, northern France and northern Germany are most threatened.
The authors suggest the global population exposed to coastal flooding could be up to 287 million by 2100 (4.1 per cent of the world’s population) – 600 million people live in low-lying areas.
This would mean about 77 million more people will be at risk of experiencing flooding, a rise of 52 per cent to 225 million. The economic risk in terms of the infrastructure exposed will rise by up to €12 trillion, representing 20 per cent of global GDP, they predict.
The analysis published on Thursday in Springer Nature’s journal Scientific Reports is based on a climate scenario where carbon-dioxide concentrations in the atmosphere continue to rise rapidly.
"A warming climate is driving sea-level rise because water expands as it warms, and glaciers are melting. Climate change is also increasing the frequency of extreme seas, which will further increase the risk of flooding," said lead author Ebru Kirezci of the University of Melbourne.
“What the data and our model is saying is that compared with now, what we see as a one-in-100-year extreme flood event will be 10 times more frequent because of climate change.”
Lead UK author Prof Robert Nicholls, director of Tyndall Centre for Climate Change Research at the University of East Anglia, said: "This analysis shows the urgency of action to address sea-level rise via both climate mitigation to reduce the rise and adaptation such as better coastal defences, as some of the rise is unavoidable."
University of Melbourne infrastructure engineering researcher Prof Ian Young said that although northwest Europe including Ireland is particularly exposed to rising flood risk, the study shows other major risk areas in every continent, with "hot spots" in Australia, New Zealand, China, India, southeast Asia, southeast Africa and North America.
“This is critical research from a policy point of view because it provides politicians with a credible estimate of risks and costs we are facing, and a basis for taking action,” Prof Young added.
“This data should act as a wake-up call to inform policy at global and local government levels so that more flood defences can be built to safeguard coastal life and infrastructure.”
The analysis does not take account of existing flood defences that are in places such as northern Europe already providing significant protection. But researchers warn the extent of the increased risk highlighted by their study shows how vulnerable large parts of the world will become unless action is taken both to mitigate climate change effects and expand flood defences.
“Our research shows large parts of communities residing in low-lying coastal areas are at risk of being devastated so we need urgent action. Vulnerable areas need to start building coastal defences, we need to increase our preparedness and we need to be following strategies to mitigate climate change,” Ms Kirezci said.
The research factors in sea-level rise estimates under different greenhouse gas emission scenarios – including the impact of melting ice-sheets in polar regions as well as episodic coastal flooding events caused by extreme storms.
The study included input from specialists at Vrije Universiteit Amsterdam and the Global Climate Forum in Germany.