Cooling Earth artificially could be disastrous, warn scientist

London: Proposals to counter the effects of global warming by imitating volcanic eruptions could lead to natural disasters in different parts of the world, warn scientists.

Geoengineering - the intentional manipulation of the climate to counter the effect of global warming by injecting aerosols artificially into the atmosphere - has been mooted as a potential way to deal with climate change. But such measures could have a devastating effect on regions prone to either tumultuous storms or prolonged drought, according to the study published in the journal Nature Communications.

Targeting geoengineering in one hemisphere could have a severely detrimental impact for the other, the study said. "Our results confirm that regional solar geoengineering is a highly risky strategy which could simultaneously benefit one region to the detriment of another," said study lead author Anthony Jones from University of Exeter in Britain. "It is vital that policymakers take solar geoengineering seriously and act swiftly to install effective regulation," Jones said.

While injections of aerosols in the northern hemisphere would reduce tropical cyclone activity - responsible for such recent phenomena including Hurricane Katrina - it would at the same time lead to increased likelihood for drought in the Sahel, the area of sub-Saharan Africa just south of the Sahara desert, the study said.

The findings suggest that policymakers worldwide must strictly regulate any large scale unilateral geoengineering programmes in the future to prevent inducing natural disasters in different parts of the world.

The research centred on the impact solar geoengineering methods may have on the frequency of tropical cyclones. The controversial approach, known as stratospheric aerosol injection, is designed to effectively cool the Earth's surface by reflecting some sunlight before it reaches the surface. The proposals mimic the aftermath of volcanic eruptions, when aerosols are naturally injected into the atmosphere.

In the study, the researchers used sophisticated simulations to investigate the effect of hemispheric stratospheric aerosol injection on North Atlantic tropical cyclone frequency.
They found that injections of aerosols in the northern hemisphere would decrease North Atlantic tropical cyclone frequency, while injections contained to the southern hemisphere may potentially enhance it.

"Our results are likely to be generally applicable owing to the large body of evidence that if a climate model is forced by cooling one hemisphere, the ITCZ (Inter-Tropical Convergence Zone) and associated precipitation will migrate towards the opposite hemisphere," the study said.

"This is because the cross-equatorial energy transport adjusts to transport energy away from the warmer hemisphere while the transport of moisture at lower levels in the atmosphere acts in the opposite direction," it added.