A school of fish swim above a finger coral colony as it grows on the Great Barrier Reef off the coast of Cairns, Australia October 25, 2019.
| Photo Credit: Reuters

It might sound like science fiction, but “marine cloud brightening” is being seriously considered as a way to shield parts of the ocean from extreme heat.

We’re using water cannons to spray seawater into the sky. This causes brighter, whiter clouds to form. These low marine clouds reflect sunlight away from the ocean’s surface, protecting the marine life below from the worst of climate change.

Australia’s Reef Restoration and Adaptation Program – a collaboration between several universities, CSIRO and the Australian Institute of Marine Science – is exploring whether cloud brightening could reduce coral bleaching. As an oceanographer and engineer I lead the program’s research into cooling and shading techniques.

We started exploring cloud brightening after the mass bleaching event in 2016. First, we needed to develop and test the underlying technologies in the lab. Then we began pilot testing in the central Great Barrier Reef near Townsville during January 2020. After several iterations we have now moved beyond “proof of concept” to investigating the response of the clouds themselves.

A bright idea

British cloud physicist John Latham originally proposed cloud brightening in 1990 as a way to control global warming by altering Earth’s energy balance. He calculated that brightening clouds across the most susceptible regions of the world’s oceans could counteract the global warming caused by a doubling of preindustrial atmospheric carbon dioxide. That’s a level likely to be reached by the year 2060.

Recently, scientists have begun to consider regional rather than global application of cloud brightening. Could brightening clouds directly over the Great Barrier Reef for a few months reduce coral bleaching during a marine heat wave?

Modelling studies are encouraging and suggest it could delay the expected decline in coral cover. This could buy valuable time for the reef while the world transitions away from fossil fuels.

Lowering the heat stress on the ecosystem would produce other benefits when combined with other reef interventions – such as improved control of invasive crown of thorns starfish and planting of corals with increased heat tolerance.

But these studies also show there’s a limit to what can be achieved. Long-term benefits are only possible if the cloud brightening activity occurs alongside aggressive emissions reductions.

Cloud brightening does have risks as well as benefits, but the prospect of intermittent regional use is very different to large-scale “solar geo-engineering” proposals for shading and cooling the whole planet.

We expect the regional effect will be short-lived and reversible, which is reassuring. The technology must be operated continuously to modify clouds and could be stopped at any time. The sea salt particles sprayed in the process typically only persist in the atmosphere for one to several days.

How do you brighten a cloud?

A warm cloud (as opposed to an ice cloud) is a collection of small water droplets floating in the air.

A cloud of many small droplets is brighter than one with fewer large droplets – even if both clouds contain the same amount of water overall.

Every droplet begins with the condensation of water vapour around a nucleus, which can be almost any kind of tiny particle suspended in air.

Typically, in the lower atmosphere over land there are thousands to tens of thousands of these tiny particles suspended in every cubic centimetre of air. We call these airborne particles “aerosols”.

Aerosols may be natural such as dust, sea salt, pollen, ash and sulphates. Or they may come from human activity such as burning fossil fuels or vegetation, manufacturing, vehicle exhaust and aerosol spray cans.

In very clean maritime air, the aerosols available to form clouds are mainly sulphates and sea salt crystals. And they are few and far between, only a few hundred per cubic centimetre.

When a cloud forms under these conditions, water vapour is forced to condense around fewer nuclei, creating larger droplets and fewer of them. Large droplets reflect less light for the same volume of cloud water.

To brighten such clouds, we can spray large quantities of microscopic seawater droplets into the air. This process of atomising seawater mimics the generation of sea salt aerosols by wind and waves in the ocean. If these are incorporated into a cloud and create extra droplets, the cloud will be brightened.

Sea salt also provides additional shade by direct scattering of light.

Testing the theory

Although scientists have researched cloud brightening for more than 30 years, no one had ever directly tested the theory. In Australia, we have now developed technology to a point where we are starting to measure the response of the clouds.

We are beginning such tests with the support and permission of Traditional Owners, who have sustainably managed their Sea Country for tens of thousands of years.

Our research program involves more than 15 research institutions and has multiple levels of governance and oversight.

Not so far-fetched

Most people probably don’t realise we are already inadvertently brightening the clouds. The Intergovernmental Panel on Climate Change estimates humanity’s unintentional release of aerosols offsets around 30% of the warming effect due to greenhouse gases.

Sulphates in ship exhaust are such a potent source of aerosols for droplet formation, the passage of ships leaves cloud trails called ship tracks.

When the International Maritime Organisation introduced new rules limiting the sulphur content of marine fuels, the number and extent of ship tracks drastically reduced, especially in the Northern Hemisphere. A recent study even suggests the devastating heat wave that swept the Northern Hemisphere earlier this year was worsened by the absence of ship tracks.

The world-first research we are conducting in Australia aims to determine if we could harness the clouds in an effective, environmentally responsible and socially acceptable manner for the future conservation of one of our most precious ecosystems.

A facility for capturing CO2 from air of Swiss Climeworks AG is placed on the roof of a waste incinerating plant in Hinwil, Switzerland July 18, 2017. Controversial technologies intended to offset the effects of atmospheric carbon should banned until properly assessed, a group of politicians and scientists have warned.
| Photo Credit: Reuters

Controversial technologies intended to offset the effects of atmospheric carbon should banned until properly assessed, a group of politicians and scientists have warned, even as they urged developed nations to lead in cutting CO2 emissions.

A report by the Climate Overshoot Commission, chaired by former WTO boss Pascal Lamy and formed in 2022, said it was increasingly likely the world would exceed the target to keep temperature rises within 1.5 degrees Celsius above pre-industrial levels.

It said richer countries needed to take the initiative to cut CO2 emissions and mobilise finance for poorer countries to adapt. Carbon removal technologies that minimise the risks of CO2 leaking back into the atmosphere should be promoted, the report said.

Also Read | What is solar geoengineering? 

But potentially dangerous experimental geoengineering methods – including controversial “solar radiation modification” – need to be halted until they have been researched thoroughly, the report said.

“Countries should adopt a moratorium on the deployment of solar radiation modification and large-scale outdoor experiments that would carry risk of significant transboundary harm,” it said.

Solar radiation modification refers to a range of proposed technologies designed to reflect sunlight away from the earth, including the direct injection of sulphates into the atmosphere. Last year, 60 scientists launched a global initiative aimed at banning all kinds of solar geoengineering.

Also Read | Geoengineering is not a quick climate fix, but a costly gamble 

“The world does not yet know enough to make informed decisions about solar radiation modification,” the report said, adding that routine international reviews should take place to assess the potential risks.

“Early scientific evidence suggests that solar radiation modification could reduce some climate risks but would also introduce significant new risks,” it said.

The report said slashing emissions should be a priority but will not be enough on its own and efforts need to be made to adapt to global warming, and deploy technologies to remove CO2 and “create space for the least industrialised countries to pursue their clean and sustainable energy transitions while fighting poverty and fulfilling their development imperatives.”

The Climate Overshoot Commission also includes senior politicians from Canada, India, Pakistan, Spain and China.

A facility for capturing CO2 from air of Swiss Climeworks AG is placed on the roof of a waste incinerating plant in Hinwil, Switzerland July 18, 2017. Controversial technologies intended to offset the effects of atmospheric carbon should banned until properly assessed, a group of politicians and scientists have warned.
| Photo Credit: Reuters

Controversial technologies intended to offset the effects of atmospheric carbon should banned until properly assessed, a group of politicians and scientists have warned, even as they urged developed nations to lead in cutting CO2 emissions.

A report by the Climate Overshoot Commission, chaired by former WTO boss Pascal Lamy and formed in 2022, said it was increasingly likely the world would exceed the target to keep temperature rises within 1.5 degrees Celsius above pre-industrial levels.

It said richer countries needed to take the initiative to cut CO2 emissions and mobilise finance for poorer countries to adapt. Carbon removal technologies that minimise the risks of CO2 leaking back into the atmosphere should be promoted, the report said.

Also Read | What is solar geoengineering? 

But potentially dangerous experimental geoengineering methods – including controversial “solar radiation modification” – need to be halted until they have been researched thoroughly, the report said.

“Countries should adopt a moratorium on the deployment of solar radiation modification and large-scale outdoor experiments that would carry risk of significant transboundary harm,” it said.

Solar radiation modification refers to a range of proposed technologies designed to reflect sunlight away from the earth, including the direct injection of sulphates into the atmosphere. Last year, 60 scientists launched a global initiative aimed at banning all kinds of solar geoengineering.

Also Read | Geoengineering is not a quick climate fix, but a costly gamble 

“The world does not yet know enough to make informed decisions about solar radiation modification,” the report said, adding that routine international reviews should take place to assess the potential risks.

“Early scientific evidence suggests that solar radiation modification could reduce some climate risks but would also introduce significant new risks,” it said.

The report said slashing emissions should be a priority but will not be enough on its own and efforts need to be made to adapt to global warming, and deploy technologies to remove CO2 and “create space for the least industrialised countries to pursue their clean and sustainable energy transitions while fighting poverty and fulfilling their development imperatives.”

The Climate Overshoot Commission also includes senior politicians from Canada, India, Pakistan, Spain and China.

When soaring temperatures, extreme weather and catastrophic wildfires strike the headlines, population get started asking for quick fixes to climate change. The U.S. executive simply introduced the first awards from a US$3.5 billion fund for initiatives that guarantee to tug carbon dioxide out of the breeze. Policymakers also are exploring extra invasive types of geoengineering − the planned, large-scale manipulation of Earth’s herbal methods.

The underlying infection has been identified for many years: Fossil-fuel automobiles and gear vegetation, deforestation and unsustainable agricultural practices were placing more carbon dioxide into the circumstance than the Earth’s methods can naturally take away, and that’s heating up the planet.

Geoengineering, theoretically, targets to revive that balance, both by way of putting off huge carbon dioxide from the circumstance or reflecting solar power clear of Earth.

However converting Earth’s complicated and interconnected situation device will have accidental aftereffects. Adjustments that backup one area may hurt any other, and the consequences will not be unclouded till it’s too past due.

Also Read | EU calls for global talks on climate geoengineering risks

As a geologist and situation scientist, I consider those aftereffects aren’t but sufficiently understood. Past the prospective bodily aftereffects, international locations don’t have the prison or social constructions in park to supremacy each its importance and the fallout when issues advance mistaken. Alike considerations were highlighted by way of the Intergovernmental Panel on Climate Change, the United Nations Situation Programme, the National Academy of Sciences and the National Oceanic and Atmospheric Administration, among others.

The White House Place of business of Science and Generation Coverage additionally mentioned those considerations in its July 2023 research plan for investigating doable situation interventions.

Dangers of sun radiation control

When population pay attention the pledge “geoengineering,” they almost certainly image sun radiation control. Those applied sciences, lots of them nonetheless theoretical, attempt to mirror solar power clear of Earth’s floor.

The theory of stratospheric aerosol injection, for instance, is to seed the higher circumstance with billions of little debris that mirror daylight without delay out to dimension. Cirrus cloud thinning targets to shed the affect of high-altitude, wispy clouds that lure power inside the circumstance by way of making their ice crystals higher, heavier and much more likely to precipitate. Every other, cloud brightening, targets to extend the superiority of brighter, lower-level clouds that mirror daylight, in all probability by way of spraying seawater into the breeze to extend H2O vapor focus.

Some scientists have steered going additional and putting in arrays of space mirrors that might shed international temperature by way of reflecting solar power away ahead of it reaches the circumstance.

Hour theoretically able to cooling the planet, sun radiation control could have drastic side effects by way of transferring patterns of world atmospheric circulate that may govern to extra terminating climate occasions. It additionally does not anything to shed harms of huge greenhouse gases, together with ocean acidification. A 2022 find out about revealed within the medical magazine Nature predicted that stratospheric aerosol injection may regulate international precipitation patterns and shed agricultural productiveness.

Cloud brightening, month efficient in principle, additionally wishes more research to produce certain that efforts to extend lower-level reflective clouds that may backup cool Earth’s floor don’t additionally building up the superiority of the high-altitude clouds that heat the planet.

Range mirrors positioned between the Solar and Earth could theoretically block 2% of incoming sun radiation and stabilize international temperature. However the era is no less than two decades clear of implementation and would price trillions of greenbacks. Extra importantly, the overall global impact of shading Earth’s floor is in large part unknown. It’s going to shorten regional ocean and breeze temperatures in techniques that can affect changes within the jet current, drizzle, snow preserve, typhoon patterns and in all probability even monsoons. A lot more analysis is had to explain those uncertainties.

Also Read | IISc scientists receive grant to study impact of solar radiation modification as proposed intervention to climate change

Eliminating carbon dioxide from the breeze

Carbon dioxide removing applied sciences usually lift debase dangers than manipulating solar power.

Carbon capture and storage eliminates carbon dioxide from energy vegetation and factories and retail outlets it underground in deep geological reservoirs. This has confirmed doable, but it surely raises considerations that leaks would possibly contaminate aquifers, hurt folk fitness and in the end fail to hold carbon out of the circumstance.

The era is also expensive and depends upon the proximity of appropriate reservoirs for vault.

Direct breeze seize, designed to tug carbon out of the breeze, is still in its early stages however offer the good thing about having the ability to shed current ranges of carbon dioxide within the circumstance. This, too, is pricey, at upward of $600 per metric ton of carbon dioxide captured these days, however innovators are getting funding from the U.S. government.

There also are herbal techniques to take away carbon. Planting trees, for instance, can take away carbon without delay from the circumstance, however that is not enough. If all of the land to be had for reforestation have been replanted, it will nonetheless not be enough to opposite stream international warming tendencies.

Ocean fertilization is any other geoengineering hack supposed to spice up carbon sequestration, however research is at an early stage. The methodology supplies vitamins reminiscent of iron to extend the expansion of phytoplankton, which importance dissolved carbon from the circumstance to develop their shells and tissue. Nevertheless it may additionally have unintended effects for the meals chain that might hurt ocean generation.

The prison void

Past protection, any other remarkable query comes to duty.

There’s a just right anticipation that geoengineering supposed to backup one area would hurt others. That’s as a result of ocean and climate methods are globally interconnected.

So, who gets to decide which initiatives can advance forward? Presently, that’s a prison void.

There is not any regulatory framework that may decide who’s liable if one thing is going mistaken. Multinational alliances, particular person states, companies or even affluent prosperous folks can act independently without consulting anyone. Within the tournament of damage that crosses nationwide limitations, there’s these days deny unclouded trail for recourse.

Hanging the fitting stability

None of that is to mention that the sector must brush aside geoengineering.

Carbon dioxide removing tactics, reminiscent of planting bushes and extending soil carbon sequestration – protecting extra natural carbon in fruitful grounds – might handover extra advantages to ecosystem services by way of expanding species range and boosting agricultural productiveness. Those are all sure results and must be a part of a world situation reaction.

Some methods of stratospheric aerosol injection would possibly keep away from the destruction of ozone and feature decrease generation spans within the circumstance. On the other hand, extra rigorous analysis, clear international governance and strong legal and ethical frameworks to supremacy dangers and assure fairness are wanted first.

I consider all of the applied sciences will have to be complemented by way of deep and sustained efforts to reduce emissions and transform the power device to keep away from the worldwide affects of sea-level get up, hovering temperature, droughts, storms, floods, fires, famine, species extinction and extending human war.

As Riley Duren, a systems engineer from NASA, mentioned in an interview with the dimension company: “Geoengineering is not a cure. At best, it’s a Band-Aid or tourniquet; at worst, it could be a self-inflicted wound.”