May 20 (UPI) — Rising sea levels caused by man-made climate change will see hundreds of millions of people forced to flee inland from coasts even if the rise in the global temperature stays within the 1.5 degrees Celsius target of the Paris Climate Agreement, a British and American team of scientists said Tuesday.
With an estimated 1 billion people around the world living less than 33 feet above sea level and around 230 million at 3 feet 3 inches or less, even 8 inches of rise by 2050 would result in average global flood losses of $1 trillion or more a year for the world’s 136 largest coastal cities, according to their study published in the Communications, Earth and Environment journal.
The scientists from the universities of Durham, Bristol, Wisconsin-Madison and Massachusetts Amherst synthesized multiple lines of evidence to show that a 1.5 degrees Celsius would result in unmanagable sea level rise and that even if it remained at the current 1.2 degrees Celsius of heating a rise of several meters could be expected in the coming centuries.
With the melting ice sheets of Greenland and Antarctica now exceeding thermal expansion of the oceans as the main driver, that level of sea rise would cause extensive loss and damage to coastal populations and make adaptation measures, which have long lead times, more challenging to implement.
Analysis of previous periods when the Earth was in a warming phase, recent audits of ice-sheet mass and numerical modeling indicate that even current temperatures could “trigger rapid ice sheet retreat” that would push to the limit any mitigation from adaptation measures.
Even the current 1.2 degrees Celsius of warming might generate “high” rates of sea level rise — categorized as greater than 0.4 of an inch a year — sufficient to create problems that would be very difficult to adapt to.
A cooler global mean temperature was therefore imperative to maintain ice sheet equilibrium because a rapid collapse of one or more ice sheets would result in a sea level rise of several meters with “catastrophic consequences for humanity.”
“To avoid this requires a global mean temperature that is cooler than present and which we hypothesise to be at or below 1 degree Celsius above pre-industrial, which is similar to the 1980s when ice when ice sheets were broadly in balance, but further work is urgently required to more precisely determine a ‘safe limit’ for ice sheets,” said the study.
The scientists said some of the worst impacts could be avoided by cutting carbon emissions to rapidly reduce global mean temperatures to below +1.5 degrees Celsius, which the average surface air temperature reached in 2024 for the first time.
However, the study found that even overshooting temperature thresholds temporarily could result in sea level rises of several meters, referencing another piece of research that found that even under a “net zero” emissions scenario sea level rise in the year 2300 would be 1.6 inches higher for each decade the the temperature stays above 1.5 degrees Celsius.