geoengineering 'dangerous and unproven'
Boats pumping out clouds and thousands of mirrors in space are among geoengineering ideas outlined by the Royal Society.
The society's latest report, Geoengineering the climate: Science, governance and uncertainty, states Earth's future rests on these and other 'dangerous and unproven' geoengineering schemes unless we tackle emissions now.
Released last Tuesday (1 September) the report says unless efforts to cut greenhouse gas emissions are much more successful than they have been, geoengineering will be the only way to cool the planet.
The report lists a host of geoengineering technologies which it considers 'technically possible' and even 'potentially useful' to mitigate climate change by reducing emissions.
However, the report identified major uncertainties regarding their effectiveness, costs and environmental impacts.
The report assesses the two main kinds of geoengineering techniques Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM).
CDR techniques are seen as the best for tackling rising C02 and have fewer risks as, according to the report, they work to return the Earth to a more normal state.
They considered preferable to SRM techniques overall, but as they're not yet seen as effective or affordable much more research would be needed before they could be taken forward.
SRM techniques, while cheaper, act by reflecting the sun's energy away from Earth, meaning they lower temperatures rapidly, but do not affect C02 levels.
However, uncertainties about their regional consequences, and they only reduce some, but not all, of the effects of climate change, while possibly creating other problems.
CDR techniques assessed by the report included:
C02 capture from ambient air, enhanced weathering, improved land use and tree planting.
SRM technologies assed were:
Stratospheric aerosols, like volcanic eruptions, could create a cover that would block out the sun for a short time.
However, there are some serious questions over adverse effects, particularly depletion of stratospheric ozone.
Space-based methods were considered to be a potential SRM technique for long-term use, such as mirror to reflect the sun rays.
But, at the moment present the techniques remain prohibitively expensive, complex and would be slow to implement.
Cloud albedo techniques , such as ships pumping clouds into the sky, could localise the impacts on regional weather patterns and ocean currents.
But, again little research into the schemes has been carried out.
Professor John Shepherd, who chaired the Royal Society's study, said: "It is an unpalatable truth that unless we can succeed in greatly reducing C02 emissions, we're headed for a very uncomfortable and challenging climate future.
"And geoengineering will be the only option left to limit further temperature increases.
"Our research found some geoengineering techniques could have serious unintended and detrimental effects on many people and ecosystems - yet we are still failing to take the only action that will prevent us from having to rely on them.
"Geoengineering and its consequences are the price we may have to pay for failure to act on climate change."
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