More than 60 policy experts and scientists said on Monday that planetary-scale engineering schemes designed to cool Earth's surface and lessened the impact of global heating are potentially dangerous and should be blocked by governments.
They argued in an open letter that the consequences of turning back a critical fraction of the Sun's rays could outweigh any benefits.
The letter supports a commentary in the journal WIREs Climate Change that says that solargeoengineering deployment cannot be governed globally in a fair, inclusive and effective manner.
"We therefore call for immediate political action from governments, the United Nations and other actors to prevent the normalization of solar geoengineering as a climate policy option."
An increase of 1.1 degrees Celsius above mid-19th century levels has already boosted the intensity, frequency and duration of deadly heat waves.
The world's nations have committed to capping the rise in Earth's surface temperature to 1.5C above mid-19th century levels, but UN-backed scientists say that threshold will be broken within a decade.
The failure to reduce the greenhouse gas emissions that drive global heating has led some policy makers to embrace solargeoengineering in order to buy time for a more durable solution.
It has been known for a long time that injecting a large amount of reflective particles into the upper atmosphere could cool the planet.
Earth's average surface temperature was lowered for more than a year because of debris from the 1991 eruption of Mount Pinatubo.
There are a number of reasons to reject such a course of action.
Artificially dimming the Sun's radiative force is likely to disrupt monsoon rains in South Asia and western Africa, and could ravage the rain-fed crops upon which hundreds of millions depend for sustenance.
Unintended consequences.
The Intergovernmental Panel on Climate Change said in its most recent scientific assessment thatspheric sulfate injection weakens the African and Asian summer monsoons.
A study last year concluded that the risk of drought in southern Africa could be greatly reduced by the use of SRM.
If seeding the atmosphere with Sun-blocking particles were to suddenly stop, scientists worry about a so-called termination shock.
The Intergovernmental Panel on Climate Change said there is high confidence that surface temperatures would increase rapidly if SRM were terminated.
The chemistry of the ocean is changing because of the continued build up of atmospheric CO2, and the technology wouldn't do anything to stop it.
The open letter cautions that raising hopes about a quick fix for climate can make it harder for governments, businesses and societies to achieve decarbonization or carbon neutrality as soon as possible.
There is currently no global governance system to monitor or implement solargeoengineering schemes, which could be set in motion by a single country, or even a billionaire with rockets.
The open letter calls for an international non-use agreement that would block national funding, ban outdoor experiments, and refuse to grant patent rights for SRM technologies.
The letter said that the agreement would not prohibit atmospheric or climate research.
Other forms of solar radiation modification include seeding marine clouds with salt particles from the ocean, and placing giant mirrors in space to reflect away Earth-bound sunlight.
Whitening rooftops and road surfaces are less controversial than lightening the color of crop leaves.
Frank Biermann, a professor of global governance at Utrecht University, Aarti Gupta, a professor of global environmental governance at Wageningen University, and ProfessorMelissa Leach, director of the Institute of Development Studies in England, are some of the signatories to the open letter.
Agence France-Presse.
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