Climate reporter, BBC News
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Experts have issued a warning that even achieving the ambitious goal of limiting global warming to 1.5°C may not prevent dangerous sea-level rise of several meters over the coming centuries.
Almost 200 nations have committed to striving for the 1.5°C target, yet researchers caution that this should not be regarded as “safe” for coastal communities.
Their conclusions are based on a review of the latest studies regarding ice sheet changes and historical data.
The scientists emphasize that minimizing even slight degrees of warming can significantly reduce risks.
Current projections indicate a trajectory towards nearly 3°C of warming by the century’s end, compared to pre-industrial levels, driven by existing government policies aimed at reducing fossil fuel emissions.
However, even maintaining a rise of 1.5°C would still initiate ongoing melting of Greenland and Antarctica, with temperature changes requiring centuries to fully affect these vast ice masses, according to the researchers.
“Our primary message is that reaching the 1.5°C goal would constitute a significant achievement; it should remain our objective—but it won’t halt or even slow sea-level rise or the melting of ice sheets,” stated lead author Prof Chris Stokes, a glaciologist from Durham University.
The 2015 Paris Agreement set aims to keep global warming “well below” 2°C—with the ideal limit being 1.5°C.
This has frequently been oversimplified as implying that 1.5°C is “safe,” a notion that glaciologists have warned against for years.
The new paper, published in *Communications Earth and Environment*, presents three key lines of evidence supporting this warning.
Firstly, fossil records indicate significant melting during previous warm periods, with sea levels much higher than present, especially around 125,000 years ago.
The last occurrence of similar atmospheric carbon dioxide levels occurred about 3 million years ago, when sea levels were approximately 10-20 meters higher.
Secondly, ongoing observations show a growing rate of ice melting, though this can vary annually.
“We are observing some quite dramatic changes in both West Antarctica and Greenland,” remarked co-author Prof Jonathan Bamber, director of the Bristol Glaciology Centre.
For the time being, East Antarctica appears to be more stable.
“We are beginning to witness some of the worst-case scenarios unfolding right in front of us,” added Prof Stokes.
Lastly, scientists utilize computer simulations to predict how ice sheets might react to future climate conditions. The outlook they present is disconcerting.
“Very few models indicate a slowdown in sea-level rise even if warming stabilizes at 1.5°C, and none suggest that sea-level rise will cease,” Prof Stokes said.
A major concern is the potential acceleration of melting beyond critical “tipping points” due to human-induced warming, although the specifics of these processes and thresholds remain unclear.
“The strength of this study lies in its use of various lines of evidence to demonstrate that our climate is in a condition comparable to those periods when several meters of ice melted historically,” stated Prof Andy Shepherd, a glaciologist from Northumbria University who was not associated with the new research.
“The resulting impact on coastal communities would be catastrophic,” he added.
Approximately 230 million people currently reside within one meter of today’s high tide levels.
Determining a “safe” warming limit is notably complex, as certain populations are more susceptible than others.
Projected sea-level rise of a centimeter or more per year by the century’s conclusion, largely due to ice melt and warming oceans, may challenge even affluent nations’ capacities for adaptation, researchers suggest.
“Reaching that threshold would make adaptation strategies exceedingly formidable, leading to mass displacement on a scale unseen in modern history,” Prof Bamber contended.
Nevertheless, researchers assert that this grim outlook should not dissuade action.
“Increased rates of warming will lead to faster ice loss and an accelerated rate of sea-level rise,” Prof Stokes noted.
“Every fraction of a degree is crucial for ice sheets.”
Additional reporting by Phil Leake
