WASHINGTON, May 22 – Global sea levels can rise two feet (6.5 feet) and displace tens of millions of people by the end of the century, according to new forecasts that double the UN estimates.
The enormous icy roofs of Greenland and Antarctica contain enough frozen water to lift the world's oceans to tens of meters. Expansion of water, as the oceans are warm, also contributes to raising sea levels.
But predicting the speed at which it melts as the planet heats up is known to be difficult.
The Intergovernmental Panel on Climate Change (IPCC) has said its Fifth Assessment Report in 2013 that under current emissions scenarios, a "normal business" scenario known as RCP8.5, is likely to increase to 1 meter 2100 years.
Since then, this forecast has been seen as conservative as the greenhouse gas emissions that warm the planet continue to increase each year, and satellites show accelerated meltdown rates from the massive ice sheets of Antarctica and Greenland.
This week, a group of leading global glacier scientists published an expert assessment of the situation using their own experiences and observations.
Although there is still a significant error, they believe it is "plausible" that in the business emission scenario, as usual the increase in sea level may exceed two meters by 2100.
The authors argue that the land lost to the ocean may be equivalent to that of France, Germany, Spain and the UK together and will displace more than 180 million people.
"Raising sea levels of this magnitude would obviously have profound consequences for mankind," they say.
The Paris Climate Agreement, concluded between countries in 2015, aims to limit the rise in global temperature to well below two degrees Celsius and encourages countries to work for a 1.5C limitation.
In October, the IPCC released a remarkable climate report, calling for a drastic and immediate takeover of coal, oil and gas to halt the rapid rise in greenhouse gas levels in the atmosphere.
However, this report does not include revised sea level increases.
The earth has already warmed 1C from pre-industrial time, contributing approximately 3mm to sea level each year.
The authors of the new study, published Monday in the magazine Notifications of the National Academy of Sciences, claim that the IPCC sea level forecast is too limited, focusing on what is "likely" to happen.
At greater probabilities, 5-95% probability, they found that at 2C the warming seas could rise 36-126cm to 2100 years.
In the world that has warmed by 5C – unlikely, but certainly not impossible, given the predicted demand for fossil fuels over the coming decades – they calculate a five per cent altitude risk at sea level of two meters, reaching 238 centimeters.
Willie Aspinal of Bristol's Earth Sciences School said he hoped the study could provide politicians with a more accurate scenario with the worst scenario "decisive for making decisive decisions."
"Limiting attention to the" probable "range, as was the case in the IPCC Fifth Assessment Report, may be misleading and likely lead to a bad assessment of real risks," he added. – AFP