To retard the process of human-induced global warming, the concerned UN bodies have been working hard to prevail upon nations to limit their levels of carbon emission. But despite commitments and promises from the main contributors to global warming, cooperation from the developed and fast growing developing nations is not forthcoming as expected. But scientists are not sitting idly by, while the politicians are taking the world to the brink of self-destruction. Some of these climate scientists are working on a novel idea of cooling the earth by spraying large amounts of aerosol into the stratosphere, the layer of the atmosphere that lies approximately 10 km to 50 km above the surface of the earth. These scientists hold that if this chemical substance is sprayed for long enough, it can reflect sunlight and cool the atmosphere. So, this can be a recipe for combating global warming.
This idea is part of solar geoengineering, a set of technologies that aims to manipulate earth's climate to mitigate the impact of climate change. Interestingly, these set of technologies are gaining traction among lawmakers, academics and even the UN bodies like IPCC (Intergovernmental panel on climate change) that assesses climate change and provides related scientific information to policymakers. However, there are also strong opponents of this idea who consider it a dangerous gamble on a planetary scale, since no one knows what would be the long-term effect of spraying aerosol, a suspension of liquid or solid particles in a gas such as air. Suspended chlorofluorocarbon (CFC) and Hydro chlorofluorocarbon (HCFC) particles that constitute aerosol, if sprayed into the atmosphere, will rise up to the ozone layer, which is part of the stratosphere. The chlorine in the chlorofluorocarbon, once released from the aerosol container, reacts with ozone gas and depletes it. The proponents of the method of aerosol spraying believe that by this means sunrays can be blocked from reaching the earth and thereby lower earth's temperature. Used over a long period of time, the method at a stage would bring down earth's temperature to the pre-industrial level, proponents of this process of Solar Radiation Management (SRM) or geoengineering believe.
This approach is obviously acceptable to the fuel oil producing countries and the businesses in this sector. Industries dependent on fossil fuel will also welcome the process. But the opponents think, here lies the real danger. Because by creating a hole in the ozone layer and expanding it further by continuously spraying CFC into it, ultraviolet (UV) rays, as generally believed, would flood the earth destroying plant and animal life. This is a common fear among scientists that led to banning of the use of CFC-rich aerosols in 1994 in the USA. And ultimately, the ban was introduced across the globe. Small wonder that, the proposal of using geoengineering like SRM as an answer to global warming has been greeted with such controversy among the scientific community. Even so, the SRM is being given serious consideration by many scientists including those in the IPCC. The reason is, the reduction of the solar heat being trapped by the earth at the expected level is not possible by the method of Carbon Dioxide Removal (CDR) now in use. In fact, the energy imbalance the earth is experiencing is approximately 1 watt per square metre of the earth's surface area. This is more than 25 times the amount of energy humans use globally. In that case, the target of limiting global temperature rise to 1.5 degrees Celsius above the pre-industrial level by 2050 does not appear to be an achievable one. Hence is this present focus of climate scientists on SRM as a possible tool of climate action.
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