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Climate engineering could be our last weapon against global warming

Engineering to the rescue

While some people still debate the veracity of climate change data, most scientists (read, smart people), have not only accepted it but also have a very bleak outlook. While on the one hand, the US pulls out of the Paris accord, on the other, you have studies telling us that we have failed miserably and that mitigation and mere reduction tactics aren’t going to cut it anymore.

There’s a need for something more drastic, and climate engineering might just be that solution! It involves us directly and intentionally intervening with the climate system using a host of cutting-edge technologies. Yes, we know it sounds like the beginning of a sci-fi novel, but it’s not as far-fetched as it sounds.

Broad approaches

Before we begin, let’s make one thing clear – climate engineering should never be viewed as a substitute for climate change mitigation. It is an add-on to help us when we fail to meet targets, and when disasters such as the US going rogue happen. Climate engineering solutions can be broadly divided into two kinds of approaches: solar radiation management and carbon dioxide removal. As in, removing carbon from our atmosphere and keeping some of the sun’s intense heat away from the earth.

CO2 Removal

At this point, through climate engineering, experiments have aimed to remove CO2 from the atmosphere and park it in the oceans, terrestrial biosphere, geological reservoirs, or commercial materials. In this area, there are a couple of approaches that we’ve tried or are trying now.

Ocean fertilisation using iron

This approach involves cultivating phytoplankton on the surface of the ocean by dropping iron into the water bodies. This phytoplankton, spread across the ocean surface, will absorb atmospheric CO2 and release oxygen. The problem with this process is that once the phytoplankton dies en masse, digesting bacteria that are attracted to their bodies can rid a large portion of the ocean of its oxygen, rendering it unlivable for most aquatic life. Such a phenomenon has already happened in the Gulf of Mexico due to nitrates from fertilizers running down the Mississippi River inducing dead zones that cover as much as 22,500 square kilometres!

A “red tide” off the coast of La Jolla,
San Diego, California.

Direct air capture (DAC)

A more effective approach, with fewer side effects, involves sucking the CO2 directly out of the atmosphere and putting it to other uses. While the obvious place to start seems to be at major generation sites like factories with post-combustion gathering, this wouldn’t affect the CO2 already in the atmosphere much – which is our primary concern at this point.

Direct removal of CO2 has to be combined with the long-term storage to be effective in bringing down the level of carbon dioxide in the atmosphere. There are a couple of techniques to do that.

Direct Air Capture Process Flow Diagram using NaOH as the absorbent and including
solvent regeneration

For instance, using a chemical process known as carbonation, CO2 can be bound to substrates. There are other chemical reactions that can be employed for this purpose too. And all of these have potential real-life applications. Projects include an artificial tree concept that can convert atmospheric CO2 to bicarbonates as well as an operating commercial plant in Switzerland by Climeworks AG that filters atmospheric CO2 and supplies it to buyers.

Solar Radiation management

Our only true source of energy in our solar system is our sun, and thanks to the proliferation of greenhouse gases and the subsequent depletion of the ozone layer, we’ve been getting a little too much of that energy. This is where solar radiation management (SRM) comes in as an approach to bring down the temperature of the planet. Overall, its objective is to reflect some of the sunlight away from Earth, in some pretty creative ways!

Aerosols in the stratosphere

Out of all the methods to reflect sunlight away from the planet, the widespread insertion of aerosols into the upper atmosphere has received the most amount of attention. Models based on this method have shown the ability to offset heating caused by a potential doubling of CO2 levels (which is the standard used for measuring the effectiveness of such strategies). Due to the pre-existing examples of volcanic eruptions, sulphates are the prime candidates for this process. Risks in this method include changes in the precipitation cycle on the planet and even the depletion of the ozone layer.

A representation of aerosol injection
using balloons

Marine cloud brightening

Taking reusability to a whole new level, this method involves spraying seawater into the atmosphere to increase cloud reflectivity. The extra condensation nuclei created by the spray will change the size distribution of the drops in existing clouds, essentially making them thicker and whiter.

Difference between the reflectivity of a normal cloud and a ‘brightened’ cloud

Space mirrors, lenses and moondust

Quite obviously, space-based solutions for solar radiation management are deemed unfeasible in comparison to the other techniques. But due to their effectiveness and ingenuity, they’re definitely worth the attention:

  • Space mirrors: having one large or several small (mesh) mirrors floating around the planet to act as reflectors to a certain percentage of sunlight without causing complete darkness underneath.
  • Space lens: using dispersive methods in space has been proposed quite a while back. Back in 2004, physicist and sci-fi writer Gregory Benford calculated that a concave rotating Fresnel lens a few mm thick but 1000 kilometres across located at the L1 point between the earth and the sun would reduce the solar energy reaching the Earth by approximately 0.5% to 1%. Additionally, he also estimated that this would cost around US$10 billion up front, and another $10 billion in supportive cost during its lifespan. The total would still be less than 4% of what the US government spent on the military in 2017.

    Representation of a space lens and its effect
  • Mining moondust: This has actually been proposed to create a shielding cloud that would be far enough to not aggravate the greenhouse effect.


As with any major scientific project, most climate engineering plans also face their own share of roadblocks even before they’ve properly begun. To start off, most of these require coordination and communication between multiple nations across the planet – and we’ve seen how pathetic we are at that! Some of these, like the injection of sulphates in the upper atmosphere, could be highly risky for particular nations depending on where it is done (above the equator, near the poles, etc.).

Additionally, most of these projects have significant risks and side effects. For example, the same sulphate injection plan could cause even worse warming if it were to be stopped, due to any possible reason. Which lays further emphasis on how important precise coordination around the world is for this. But sadly, in a world where different nations, developing and developed, superpowers and minnows, cannot reach an agreement about the same measurement units of climate change, there really is no hope to a collaboration towards saving this little blue dot that we call home!

Arnab Mukherjee

Arnab Mukherjee

A former tech-support desk jockey, you can find this individual delving deep into all things tech, fiction and food. Calling his sense of humour merely terrible would be a much better joke than what he usually makes.