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Japan Today
22-05-2025
- Science
- Japan Today
Rising seas to severely test humanity's resilience in second half of 21st century
The Greenland ice sheet holds enough frozen water to lift global oceans by five metres. By Marlowe HOOD Rising seas will severely test humanity's resilience in the second half of the 21st century and beyond, even if nations defy the odds and cap global warming at the ambitious 1.5 degrees Celsius target, researchers say. The pace at which global oceans are rising has doubled in three decades, and on current trends will double again by 2100 to about one centimeter per year, they reported in a study. "Limiting global warming to 1.5C would be a major achievement" and avoid many dire climate impacts, lead author Chris Stokes, a professor at Durham University in England, told AFP. "But even if this target is met," he added, "sea level rise is likely to accelerate to rates that are very difficult to adapt to." Absent protective measures such as sea walls, an additional 20 centimeters of sea level rise -- the width of a letter-size sheet of paper -- by 2050 would cause some $1 trillion in flood damage annually in the world's 136 largest coastal cities, earlier research has shown. Some 230 million people live on land within one meter of sea level, and more than a billion reside within 10 meters. Sea level rise is driven in roughly equal measure by the disintegration of ice sheets and mountain glaciers, as well as the expansion of warming oceans, which absorb more than 90 percent of the excess heat due to climate change. Averaged across 20 years, Earth's surface temperature is currently 1.2C above pre-industrial levels, already enough to lift the ocean watermark by several meters over the coming centuries, Stokes and colleagues noted in the journal Communications Earth & Environment. The world is on track to see temperatures rise 2.7C above that benchmark by the end of the century. In a review of scientific literature since the last major climate assessment by the U.N.-mandated Intergovernmental Panel on Climate Change (IPCC), Stokes and his team focused on the growing contribution of ice sheets to rising seas. In 2021, the IPCC projected "likely" sea level rise of 40 to 80 centimeters by 2100, depending on how how quickly humanity draws down greenhouse gas emissions, but left ice sheets out of their calculations due to uncertainty. The picture has become alarmingly more clear since then. "We are probably heading for the higher numbers within that range, possibly higher," said Stokes. The scientist and his team looked at three baskets of evidence, starting with what has been observed and measured to date. Satellite data has revealed that ice sheets with enough frozen water to lift oceans some 65 meters are far more sensitive to climate change than previously suspected. The amount of ice melting or breaking off into the ocean from Greenland and West Antarctica, now averaging about 400 billion tonnes a year, has quadrupled over the last three decades, eclipsing runoff from mountain glaciers. Estimates of how much global warming it would take to push dwindling ice sheets past a point of no return, known as tipping points, have also shifted. "We used to think that Greenland wouldn't do anything until the world warmed 3C," said Stokes. "Now the consensus for tipping points for Greenland and West Antarctica is about 1.5C." The 2015 Paris climate treaty calls for capping global warming at "well below" 2C, and 1.5C if possible. The scientists also looked at fresh evidence from the three most recent periods in Earth's history with comparable temperatures and atmospheric levels of CO2, the main driver of global warming. About 125,000 years ago during the previous "interglacial" between ice ages, sea levels were two to nine meters higher than today despite a slightly lower average global temperature and significantly less CO2 in the air -- 287 parts per million, compared to 424 ppm today. A slightly warmer period 400,000 ago with CO2 concentrations at about 286 ppm saw oceans 6-to-13 meters higher. And if we go back to the last moment in Earth's history with CO2 levels like today, some three million years ago, sea levels were 10-to-20 meters higher. Finally, scientists reviewed recent projections of how ice sheets will behave in the future. "If you want to slow sea level rise from ice sheets, you clearly have to cool back from present-day temperatures," Stokes told AFP. "To slow sea level rise from ice sheets to a manageable level requires a long-term temperature goal that is close to +1C, or possibly lower." © 2025 AFP
Japan Today
07-05-2025
- Science
- Japan Today
World's richest 10% caused two thirds of global warming: study
Researchers say there is a direct link between ultra-high net worth individuals and the climate By Marlowe HOOD The world's wealthiest 10 percent of individuals are responsible for two thirds of global warming since 1990, researchers said on Wednesday. How the rich consume and invest has substantially increased the risk of deadly heatwaves and drought, they reported in the first study to quantify the impact of concentrated private wealth on extreme climate events. "We link the carbon footprints of the wealthiest individuals directly to real-world climate impacts," lead author Sarah Schoengart, a scientist at ETH Zurich, told AFP. "It's a shift from carbon accounting toward climate accountability." Compared to the global average, for example, the richest one percent contributed 26 times more to once-a-century heatwaves, and 17 times more to droughts in the Amazon, according to the findings, published in Nature Climate Change. Emissions from the wealthiest 10 percent in China and the United States -- which together account for nearly half of global carbon pollution -- each led to a two-to-threefold rise in heat extremes. Burning fossil fuels and deforestation have heated Earth's average surface by 1.3 degrees Celsius, mostly during the last 30 years. Schoengart and colleagues combined economic data and climate simulations to trace emissions from different global income groups and assess their impact on specific types of climate-enhance extreme weather. The researchers also emphasised the role of emissions embedded in financial investment rather than just lifestyle and personal consumption. "Climate action that doesn't address the outsized responsibilities of the wealthiest members of society risk missing one of the most powerful levers we have to reduce future harm," said senior author Carl-Friedrich Schleussner, head of the Integrated Climate Impacts Research Group at the International Institute for Applied Systems Analysis near Vienna. Owners of capital, he noted, could be held accountable for climate impacts through progressive taxes on wealth and carbon-intensive investments. Earlier research has shown that taxing asset-related emissions is more equitable than broad carbon taxes, which tend to burden those on lower incomes. Recent initiatives to increase taxes on the super-rich and multinationals have mostly stalled, especially since Donald Trump regained the White House. Last year, Brazil -- as host of the G20 -- pushed for a two-percent tax on the net worth of individuals with more than $1 billion in assets. Although G20 leaders agreed to "engage cooperatively to ensure that ultra-high-net-worth individuals are effectively taxed," there has been no follow-up to date. In 2021, nearly 140 countries agreed on work toward a global corporate tax for multinational companies, with nearly half endorsing a minimum rate of 15 percent, but those talks have stalled as well. Almost a third of the world's billionaires are from the United States -- more than China, India and Germany combined, according to Forbes magazine. According to anti-poverty NGO Oxfam, the richest 1 percent have accumulated $42 trillion in new wealth over the past decade. It says the richest one percent have more wealth than the lowest 95 percent combined. © 2025 AFP
