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Even if the world manages to meet the 1.5°C global warming limit set by the Paris Agreement in 2015, the threat of rising sea levels will continue to escalate, endangering coastal cities and millions of people. A recent study published in Communications Earth & Environment reveals that moderating global warming to this ambitious target won't prevent increasingly severe ocean encroachment.

Research utilizing satellite data, comparisons with ancient climates, and advanced projections indicates that even minimal levels of warming could activate feedback loops in the planet's ice sheets. This would push sea level rise to unmanageable extremes. Over the past 30 years, sea levels have risen at twice the previous rate, and this trend is set to double again by 2100. If current trends persist, oceans could rise by one centimeter per year within a few generations.

Chris Stokes, the study's lead author and a professor at Durham University in the UK, emphasizes that while achieving the 1.5°C target would mitigate many severe climate effects, it still wouldn't halt the acceleration of sea level rise. With over 230 million people living within a single meter of today's sea level and over a billion within ten meters, a relatively small rise could result in devastating urban flooding, mass migrations, and economic losses reaching trillions by mid-century.

One particularly concerning revelation from the study is the vulnerability of the Greenland and West Antarctic ice sheets. Together, these ice sheets hold enough water to raise sea levels by 65 meters and are currently losing ice at a rate of 400 billion tonnes per year. Previously, scientists believed that Greenland’s ice sheet wouldn't be significantly affected until global temperatures rose by 3°C. The new consensus suggests that tipping points for irreversible ice sheet collapse may occur at around 1.5°C.

Historical climate data compounds these concerns. Around 125,000 years ago, during the last interglacial period, sea levels were 2 to 9 meters higher than today, despite lower temperatures and CO2 levels. Going further back, some three million years ago, when atmospheric CO2 matched today's levels at 424 parts per million, sea levels were 10 to 20 meters higher. These comparisons indicate that our current trajectory could commit the planet to significant long-term sea level rise, despite any immediate reductions in emissions.

The study's findings make it clear that significant investment in coastal defenses and sweeping changes to global energy systems are urgently needed. Professor Stokes concludes that slowing sea level rise to a manageable level would necessitate long-term global temperatures close to +1°C, underscoring the immense challenge humanity faces without drastic changes in policy and behavior.