REUTERS: As 1.5C warming limit nears, interest in sun-dimming tech heats up

Climate-cooling technology could help rein in global heating and its impacts, say backers, but critics warn it carries serious and unknown risks, with some calling for research to stop

LONDON, July 18 (Thomson Reuters Foundation) - As fossil fuel use continues apace and a hotter planet edges close to passing safety limits, some scientists are exploring a controversial technological stopgap: spraying chemicals into the atmosphere to reflect away some of the sun's warmth.


Deploying the technology, using special planes, would be relatively cheap and simple, costing a few billion dollars a year, its backers say.


And it could - if maintained - hold down global average temperatures, potentially staving off increasingly deadly climate-change impacts such as heatwaves, they argue. "I do see it as a likely option" if plans to cut emissions fall short and dangers grow, said Emmi Yonekura, a researcher on the risks of climate "geoengineering" at RAND Corporation, a military-focused policy think-tank, during an online event.


But the technology, which mimics the sky-darkening effect of volcanic eruptions, also carries serious and unpredictable risks, critics say - with some scientists so worried that they believe research should stop and outdoor tests be banned.


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Scientists with the Intergovernmental Panel on Climate Change (IPCC) have warned that if global average temperatures exceed 1.5C above pre-industrial times, the world could see changes that will be hard to adapt to.

Those could include surging hunger as crops fail, as well as growing water shortages, migration and conflict.


Deaths and financial losses from worsening heatwaves, wildfires, droughts, floods, hurricanes and sea level rise could also increase, affecting rich countries as well as poor.

More heat could melt Arctic and ocean permafrost that holds climate-heating methane, turbo-charging temperature rise and launching the planet into a vicious heating cycle that would be hard to reverse, scientists say.


Some impacts of passing 1.5C - such as likely losses of many of the world's coral reefs - "will be irreversible, even if global warming is reduced", warned Thelma Krug, a climate scientist and vice chair of the IPCC.


With the World Meteorological Organization projecting that the 1.5C threshold could be passed, at lest temporarily, within five years, a Climate Overshoot Commission of 16 world leaders was launched in May.


It will look at controversial sun-dimming technologies, alongside efforts to remove carbon dioxide from the atmosphere and to adapt to new conditions.


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