Coastal flooding predicted to rise by up to 50 per cent by 2100

Coastal flooding globally is set to rise by around 50 per cent due to climate change in the next 80 years, a new study predicts.

UK and Australian researchers conducted climate change scenarios where carbon dioxide concentrations in the atmosphere continue to rise rapidly. 

They found the associated flooding, due to the melting of polar ice, would endanger millions of people and cost more than £10 trillion.  

Land exposed to extreme flooding will increase by more than 96,500 square miles globally – up 48 per cent or more than 308,000 square miles from today.  

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 areas predicted to be most impacted by flooding are north-west Europe, south-east and east Asia, north-east US and northern Australia.  

Global distribution of projected 100-year return period extreme sea levels. Rises are expressed in metres and colour-coded 

A catastrophic climate-related event that would usually only happen once every 100 years would also happen 10 times as often under this scenario. 

‘A warming climate is driving sea level rise because water expands as it warms, and glaciers are melting,’ said study lead author Ebru Kirezci at the University of Melbourne.

‘Climate change is also increasing the frequency of extreme seas which will further increase the risk of flooding.

‘Our research shows that large parts of communities residing in low-lying coastal areas are at risk of being devastated so we need urgent action. 

This map compares global distribution of the historical 100-year return period extreme sea level at vulnerable coast locations, based on the team's model data, which ran from 1979 to 2014

This map compares global distribution of the historical 100-year return period extreme sea level at vulnerable coast locations, based on the team’s model data, which ran from 1979 to 2014

‘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.’ 

The study should be a ‘wake-up call’ for governments to implement flood defences, safeguard coastal life and infrastructure and combat carbon dioxide emissions. 

‘This is critical research from a policy point of view because it provides politicians with a credible estimate of the risks and costs we are facing, and a basis or taking action,’ said co-author Professor Ian Young, also at the University of Melbourne.    

The research team, which included personnel from the University of East Anglia (UEA), combined data on global sea levels during extreme storms from 1979 to 2014 with projections of sea level rises under different greenhouse gas emission scenarios.   

They then used this data to model maximum sea levels that may occur by 2100 and combined this with topographic data – the physical physical features of land surface – to identify areas at risk of coastal flooding. 

Also using data on global population distribution and GDP in affected areas, they estimated the population and assets at risk from flooding. 

Regional areas showing the projected flooding associated with a 100-year return period extreme sea level event for 2100. Coloured dots show the magnitude of the projected extreme sea level at the coast. Flooding extent shown by blue shading

Regional areas showing the projected flooding associated with a 100-year return period extreme sea level event for 2100. Coloured dots show the magnitude of the projected extreme sea level at the coast. Flooding extent shown by blue shading

With high greenhouse gas emissions and no sufficient flood defences implemented, land affected by coastal flooding could increase by 48 per cent at the turn of the next century, they reveal.     

A total of 68 per cent of the global coastal area flooded will be caused by tide and storm events, with 32 per cent due to projected regional sea level rise.

Areas that could be at risk of extensive flooding include south-eastern China, Australia’s Northern Territories, Bangladesh, West Bengal and Gujurat in India, the US states of North Carolina, Virginia and Maryland.

In Europe, particularly at-risk regions are the north-west of the continent, including the UK, northern France and northern Germany. 

The global population exposed to coastal flooding could be up to somewhere between 225 million and 287 million by 2100 – the latter of which would represent an alarming 4.1 per cent of the world’s population. 

Infrastructure exposed to flood water could cost of up to $14.2 trillion (£10.8 trillion), which represents 20 per cent of global GDP. 

‘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,’ said Lead UK author Prof Robert Nicholls, director of the Tyndall Centre for Climate Change Research at UEA. 

The analysis does not take account of existing flood defences that in places like northern Europe already provide significant protection.  

But without investment in flood defences or a reduction in greenhouse gas emissions, coastal flooding could have calamitous implications for the humans of 2021, many of whom have already been born. 

The study has been published in Scientific Reports

GLACIERS AND ICE SHEETS MELTING WOULD HAVE A ‘DRAMATIC IMPACT’ ON GLOBAL SEA LEVELS

Global sea levels could rise as much as 10ft (3 metres) if the Thwaites Glacier in West Antarctica collapses. 

Sea level rises threaten cities from Shanghai to London, to low-lying swathes of Florida or Bangladesh, and to entire nations such as the Maldives. 

In the UK, for instance, a rise of 6.7ft (2 metres) or more may cause areas such as Hull, Peterborough, Portsmouth and parts of east London and the Thames Estuary at risk of becoming submerged.

The collapse of the glacier, which could begin with decades, could also submerge major cities such as New York and Sydney.

Parts of New Orleans, Houston and Miami in the south on the US would also be particularly hard hit.

A 2014 study looked by the union of concerned scientists looked at 52 sea level indicators in communities across the US.

It found tidal flooding will dramatically increase in many East and Gulf Coast locations, based on a conservative estimate of predicted sea level increases based on current data.

The results showed that most of these communities will experience a steep increase in the number and severity of tidal flooding events over the coming decades.

By 2030, more than half of the 52 communities studied are projected to experience, on average, at least 24 tidal floods per year in exposed areas, assuming moderate sea level rise projections. Twenty of these communities could see a tripling or more in tidal flooding events.

The mid-Atlantic coast is expected to see some of the greatest increases in flood frequency. Places such as Annapolis, Maryland and Washington, DC can expect more than 150 tidal floods a year, and several locations in New Jersey could see 80 tidal floods or more.

In the UK, a two metre (6.5 ft) rise by 2040 would see large parts of Kent almost completely submerged, according to the results of a paper published in Proceedings of the National Academy of Science in November 2016.

Areas on the south coast like Portsmouth, as well as Cambridge and Peterborough would also be heavily affected.

Cities and towns around the Humber estuary, such as Hull, Scunthorpe and Grimsby would also experience intense flooding. 

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