A new U.N. report warns of the dire consequences of rising sea levels | Joe Raedle/Getty Images
Limiting climate change to 1.5 degrees would limit but not entirely eliminate those threats.
MONACO — Unchecked global warming could lead to sea level rises of more than a meter by the end of the century, people abandoning coastal homes and low-lying islands, a collapse in fisheries, droughts in mountain regions and more frequent hurricanes, according to a landmark U.N. scientific report.
Temperatures are already 1 degree Celsius above pre-industrial levels, which has had drastic effects on ecosystems, the Intergovernmental Panel on Climate Change (IPCC) warned. “The ocean is warmer, more acidic and less productive. Melting glaciers and ice sheets are causing sea level rise, and coastal extreme events are becoming more severe.”
Limiting climate change to 1.5 degrees — the aspirational goal of the 2015 Paris Agreement — would limit but not entirely eliminate those threats.
“If we reduce emissions sharply, consequences for people and their livelihoods will still be challenging, but potentially more manageable for those who are most vulnerable,” said Hoesung Lee, chair of the IPCC.
But getting there won’t be easy. It requires “unprecedented transitions in all aspects of society,” said Debra Roberts, one of the lead scientists involved in the report.
The political difficulty was starkly illustrated on Monday, when a U.N. climate summit meant to get countries to commit to more radical climate measures fell short of the expectations set by Secretary-General António Guterres. Governments find it difficult to undertake expensive measures that could slow economic growth, despite growing calls for action from climate protesters.
Stark conclusions
The U.N. report will almost certainly pile pressure on policymakers.
Last October, the IPCC published a report that described the differences between a world where warming is halted at 1.5 degrees and one where it gets to 2 degrees. Although both targets are out of reach if current trends continue, the report was so disturbing about a warmer planet that it dominated discussions at last December’s COP24 climate summit.
This report is likely to have a similar effect on the COP25 talks taking place in Chile at the end of the year.
The report last year had to run the gauntlet of oil-producing nations, which tried to water down its conclusions. The same thing happened in Monaco this year. Saudi Arabia pushed back on referencing the 1.5-degree report in this assessment’s conclusions, worried about the impact on oil and gas sales, and partly succeeded.
Even so, the report makes for grim reading.
It’s the first time that the U.N.’s science panel — pulling together 100 authors from 37 countries — has zoomed in on oceans, part of a growing realization that the world’s seas can’t easily shake off decades of pollution.
“For the vast history of people on this planet, we have thought about the ocean as being so immense, endlessly bountiful … that it was simply too big to fail,” said Jane Lubchenco, a marine biologist and a former head of the U.S. National Oceanic and Atmospheric Administration.
Even the current level of warming is having a drastic impact, the IPCC warned.
Rising seas
Melting glaciers are causing sea levels to rise. They went up by around 15 centimeters during the last century, and they are “currently rising more than twice as fast — 3.6mm per year — and accelerating,” the scientists said. It could reach from 30 centimeters to 60 centimeters by 2100 — even if countries step up emissions cuts and global warming is limited to well below 2 degrees.
Sea levels would rise around 60 centimeters to 1.1 meters by the end of the century “if greenhouse gas emissions continue to increase strongly,” the report warned.
That’s a catastrophe for the 680 million people living in low-lying coastal areas. They will be buffeted by freak tides and intense storms. “Events that occurred once per century in the past will occur every year by mid-century in many regions,” the report said.
Fisheries will collapse as oceans become more acidic and warmer.
“The ocean has been acting like a sponge absorbing carbon dioxide and heat to regulate temperatures, but it can’t keep up,” Ko Barrett, the U.N. panel’s vice chair, said at a press conference in Monaco’s Oceanographic Museum, perched on a cliff overlooking the sea.
The 670 million people living in mountain regions also face a drier future with glaciers shrinking or disappearing in Europe, eastern Africa, the Andes and Indonesia.
Arctic ice will continue to thin. If warming is kept to 1.5 degrees, then the Arctic Ocean would be ice-free once a century; at 2 degrees that would happen every three years.
Known unknowns
The report also contains a lot of uncertainties. A big risk factor is what happens to the permafrost. The vast areas of the planet that are permanently frozen contain huge amounts of carbon dioxide and methane, which is released by melting — potentially speeding up global warming. Even a sub-2-degree scenario could see a quarter of the permafrost thaw. Much warmer than that, and 70 percent could melt.
The difference in outcomes between a 1.5-degree world and one that’s warmer underscores the need for action, the report’s authors said.
“The more decisively and the earlier we act, the more able we will be to address unavoidable changes, manage risks, improve our lives, and achieve sustainability for ecosystems and people,” said Roberts, the climate scientist.
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