Alexander Lewis
Feb 23, 2024
When soaring temperatures, extreme weather and catastrophic wildfires hit the headlines, people start asking for quick fixes to climate change.
The underlying problem has been known for decades: Fossil-fuel vehicles and power plants, deforestation and unsustainable agricultural practices have been putting more carbon dioxide into the atmosphere than the Earth’s systems can naturally remove, and that’s heating up the planet.
Geoengineering, theoretically, aims to restore that balance, either by removing excess carbon dioxide from the atmosphere or reflecting solar energy away from Earth.
But changing Earth’s complex and interconnected climate system may have unintended consequences. Changes that help one region could harm another, and the effects may not be clear until it’s too late.
Risks of solar radiation management
When people hear the term geoengineering, they typically think of solar radiation control. These technologies, many of which are still under development, seek to reflect solar radiation away from the surface of the Earth.
For instance, the concept behind stratospheric aerosol injection is to fill the high atmosphere with billions of microscopic particles that directly reflect sunlight into space.
Cirrus cloud thinning tries to lessen the effect of high-altitude, wispy clouds that trap energy in the atmosphere by increasing the size, weight, and precipitation likelihood of their ice crystals.
Cloud brightening, on the other hand, tries to enhance the frequency of brighter, lower-level clouds that reflect sunlight, maybe by sprinkling seawater into the air to boost the concentration of water vapour.
Some researchers have proposed going further and putting in space mirror arrays that may reduce global temperature by reflecting solar energy.
While theoretically capable of cooling the planet, solar radiation management could have drastic side effects by shifting patterns of global atmospheric circulation that can lead to more extreme weather events.
It also does nothing to reduce the harms of excess greenhouse gases, including ocean acidification.
A 2022 study published in the scientific journal Nature predicted that stratospheric aerosol injection could alter global precipitation patterns and reduce agricultural productivity.
Cloud brightening, while effective in theory, also needs more research to make sure that efforts to expand lower-level reflective clouds that can help cool Earth’s surface do not also increase the prevalence of the high-altitude clouds that warm the planet.
Space mirrors placed between the Sun and Earth could theoretically block 2% of incoming solar radiation and stabilise global temperature.
But the technology is at least 20 years away from implementation and would cost trillions of dollars. More importantly, the overall global impact of shading Earth’s surface is largely unknown.
It will decrease regional ocean and air temperatures in ways that may affect changes in the jet stream, rainfall, snow cover, storm patterns and possibly even monsoons. Much more research is needed to clarify these uncertainties.
