Imagine a future where, despite all our efforts to curb greenhouse gas emissions, global temperatures are sky-high, the glaciers are melting, and several other repercussions are slamming the earth, one by one. That day is not far off. Already, compared to the 1800s, the Earth is about 1.1°C warmer (see Figure 1). Global temperature is projected to rise by about 1.5 degrees Celsius by 2050 and by about 3 degrees Celsius by 2100 if we are not careful. The Paris Agreement's goal to cap the rise of global temperatures at about 1.5°C to fight global warming, is highly unlikely to be met if the current policies and methods continue.
We can’t wait any longer. We must start implementing drastic measures soon.3 astrophysicists recently came up with the wild idea of shooting Moon dust into the space between Earth and the Sun that may act as a barrier to protect the earth from intense solar radiation. Researchers believe this measure could reduce the power of sunlight by more than 1.5%. This is supposed to be one of the ways of geoengineering the planet. So, what exactly is Geoengineering?
Geoengineering refers to the emerging technologies that are currently being developed to counter global climate change. It can be broadly classified into 2 types - Carbon Geoengineering or Carbon Dioxide Removal (CDR) and Solar Geoengineering or Solar Radiation Management (SRM).
Carbon Geoengineering aims to reduce the carbon dioxide content in the atmosphere through its removal.
Solar Geoengineering involves reducing the intensity of sunlight reaching the earth by reflecting some of it back into space, thereby attempting to cool the planet.
The idea of solar geoengineering is gaining popularity in many developed nations. In the year 2021, a report by the US National Academy of Sciences suggested that the United States form a coalition to conduct a detailed study on the viability of solar geoengineering as a stopgap measure to address the global climate change crisis.Solar Reflective Roof Coating involves the application of radiation-reflective paints onto the rooftops of large buildings to decrease the temperatures within the buildings. The French Startup Cool Roof France has developed this green cooling technology which has a reflective, thermal white paint that prevents buildings from getting overheated and reduces the need for ACs, which can cut down on CO2 emissions.
Marine Cloud Brightening is a method in which marine clouds or the low clouds hanging over the ocean are made to reflect sunlight back into space by spraying them with sea salt.
Cirrus Cloud Thinning involves seeding the high-altitude atmospheric clouds with aerosol particles to thin them out so they don’t trap much heat within and also emit long-wave radiation from the earth back into space.
Space-based Technologies involve placing sun shields in space that reflect sunlight away from the earth.
Stratospheric Aerosol Injection is an attempt to scatter sunlight back into space by introducing tiny reflective particles like sulfate aerosols or calcium carbonate particles into the upper atmosphere (see Figure 2). It can be done using aerostat systems, such as balloons or specialized airplanes. The US startup Make Sunsets claims to have sent up two weather balloons filled with helium and Sulphur dioxide above Mexico’s Baja California recently. There they are said to have burst, dispersing sun-reflecting sulfur dioxide particles into the stratosphere and cooling the Earth a bit.
Of all the different types of solar radiation modification that have been proposed, stratospheric aerosol injection is considered to be the cheapest and the most effective.