Since 2015, almost every country on Earth has been bound by the Paris Agreement to try and keep global warming below 1.5°C.
But climate scientists now warn that this limit is too high – and could spark ‘mass inland migration’.
Researchers from the University of Durham say that the world needs to stay within just 1°C of the pre-industrial average to avoid a catastrophic sea level rise.
With current warming levels already at 1.2°C, that means the world needs to seriously cool down to avoid disaster.
While the researchers recognise that 1.5°C is an ‘admirable’ goal, they found there was ‘no evidence to suggest it will halt or even slow the rate of SLR [Sea Level Rise] from the world’s ice sheets.’
Lead author Professor Chris Stokes told MailOnline that the ‘best case scenario’ for current targets is one where sea levels continue to show ‘slow and steady’ increases.
‘The problem of sea-level rise is here to stay and will affect future generations, even if we limit warming to 1.5°C,’ he said.
‘If the current rate of acceleration continues, then we could see [sea level rises of] 10 mm per year towards the end of this century – that’s within the lifetime of our youngest children.’
Climate scientists have warned that the 1.5°C target of the Paris Climate Agreement is too high to save the world’s ice sheets. Pictured: The Vanderford Glacier, Antarctica
By comparing modern melt rates, computer simulations, and evidence from warm periods in Earth’s history, scientists calculated what would happen to the Earth’s ice sheets at 1.5°C above the pre-industrial average. Pictured: Researchers drill for ice cores on the East Antarctica Ice Sheet
This chart shows how the world’s declining ice sheets have contributed to rising sea levels. The amount of ice gained or lost each year is shown for the East Antarctic Ice Sheet in black, West Antarctic Ice Sheet in red and Greenland Ice Sheet in turquoise. The dark blue line shows cumulative sea level rise over time
The Paris Agreement is a legally binding treaty which requires signatories to limit the increase in the global average temperature to well below 2°C above pre-industrial levels – the average temperature between 1850 and 1900.
The agreement also requires countries to pursue efforts to ‘limit the temperature increase to 1.5°C above pre-industrial levels’.
This is because going beyond 1.5°C has been determined by the Intergovernmental Panel on Climate Change (IPCC) to risk unleashing far more severe consequences such as increased flooding, droughts, heatwaves, and storms.
In their new paper, published in the journal Communications Earth & Environment, Professor Stokes and his co-authors investigated what this would mean for the world’s ice sheets.
Meltwater from these ice sheets is the biggest contributor to rising sea levels, and, together, they hold enough water to increase sea levels by a whopping 65 metres.
Even at current rates of warming, the mass loss from these ice sheets has quadrupled since the 1990s, with 370 billion tonnes of ice melting each year.
The researchers combined this data with computer simulations of how ice sheets might lose mass in different warming levels, and evidence from slightly warmer periods in Earth’s history caused by natural variations in how the planet orbits the sun.
Together, this evidence suggests that 1.5°C of warming is too high to save the world’s ice sheets.
At current levels of warming, ice melt will trigger several metres of sea level increases. This will be an ‘existential threat’ for the 230 million people living within one metre of sea level. Pictured: Glaciers from the Illulissat Glacier, Greenland
This chart shows how much ice melt from the Antarctic ice sheet will contribute to global mean sea level increase in a scenario with +1.5°C of warming (black) vs no additional warming (dashed lines). The blue shading indicates the degree of certainty in the model
Co-author Professor Andrea Dutton, of the University of Wisconsin-Madison, says: ‘Evidence recovered from past warm periods suggests that several metres of sea level rise – or more – can be expected when global mean temperature reaches 1.5°C or higher.
‘Furthermore, this evidence also suggests that the longer those warm temperatures are sustained, the greater the impact on ice melt and resulting sea-level rise.’
Sea-level increases on this scale will be extremely difficult and hugely expensive for the world to adapt to.
Current estimates suggest that there are 230 million people living within one metre of sea level.
The researchers say this melting ice represents an ‘existential threat’ to entire communities and nations lying in this zone.
But even smaller increases will be devastating, as one recent study estimates that just a 20cm rise in sea levels by 2050 would lead to average global flood losses of $1 trillion or more per year for the world’s 136 largest coastal cities.
What makes this especially worrying is that ice melt is essentially irreversible, meaning every millimetre of sea level increase is permanent.
Co-author Professor Rob DeConto, of the University of Massachusetts Amherst, says: ‘It is important to stress that these accelerating changes in the ice sheets and their contributions to sea level should be considered permanent on multi-generational timescales.
The researchers stress that any loss of the ice sheet will be permanent on the scale of multiple human generations, meaning we need to act now to prevent ice from being lost and increasing the sea level. Pictured: Scientists overlooking the edge of Mawson Glacier, East Antarctica
‘Even if the Earth returns to its pre-industrial temperature, it will still take hundreds to perhaps thousands of years for the ice sheets to recover. If too much ice is lost, parts of these ice sheets may not recover until the Earth enters the next ice age.’
This is why the researchers say it is so important to act now to limit warming in the first place, before the world’s ice sheets are lost for good.
Although they say that more research is needed to discover the ‘safe’ temperature for the ice sheets, aiming for a temperature increase of just 1°C is a good place to start.
Professor Stokes adds: ‘Put another way, and perhaps it is a reason for hope, we only have to go back to the early 1990s to find a time when the ice sheets looked far healthier.
‘Global temperatures were around 1°C above pre-industrial back then and carbon dioxide concentrations were 350 parts per million, which others have suggested is a much safer limit for planet Earth.
‘What is very clear is that the sooner we slow and stop the warming, the easier it will be to return to safe levels.’
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