How blocking the sun could help fix climate

Taking the heat out of it: Sun-dimming may be the best way to counter global warming. © Getty

Is it a good idea? As a new report shines light on a radical idea to cool the Earth, some scientists warn that solar geoengineering might actually cause more problems than it solves.

All around the world, humans are struggling to survive.

The crisis talks are over. The politicians failed. They could not agree to stop polluting the Earth. Now the planet has reached its boiling point – it is too hot for people to live here anymore. And every year, the temperatures keep rising.

It sounds horrifying, but this is the future climate scientists worry about every day.

Now they have come up with a backup plan to cool down the Earth if world leaders fail to stop global warming by reducing carbon emissions.

In a new report released last week, the US national science academy recommended that the country spend at least £73m over five years to research a series of radical ideas to block out the sun.

So how exactly would this work?

The academy’s report highlights three of the most common ways researchers believe they could engineer the sky. The first two – injecting tiny reflective particles into the stratosphere and using small particles to brighten marine clouds – would work by stopping incoming sunlight from reaching the Earth.

The third idea – thinning cirrus clouds – would allow more heat to escape the planet’s surface. All three would eventually help cool the Earth.

For environmental lecturer Kevin Surprise, one thing is clear: “Solar geoengineering can no longer be considered on the fringes of climate policy or a futuristic proposal that we can worry about down the road.”

Indeed, it may seem like science fiction, but sun dimming may soon be a reality. This June, scientists backed by Bill Gates hope to release a large balloon that could one day deposit a kilogram of chalk dust into the stratosphere over the Swedish arctic.

Not everyone is excited. Sceptics warn that solar geoengineering might have terrible consequences. Dimming the sun could alter weather patterns, drying up the monsoon rains relied upon by thousands of farmers across India.

And while the sunsets would be spectacular, the daytime sky could change from blue to white. Moreover, if geoengineering suddenly stopped, there could be a drastic overnight rise in global temperatures.

Even the scientists themselves are worried. Fossil fuel guzzling nations might use their plan as an excuse to delay cutting carbon emissions. If blocking the sun is necessary, experts say, it should be used alongside other measures to remove carbon from the atmosphere, not instead of them.

And while most people agree that the US has a responsibility to help tackle the climate crisis, few would accept that one country should have the power to deliberately alter the climate of the entire planet.

“If you’re not unsettled by the prospect of sun dimming, then you’ve not understood either what is being proposed or the reasons it’s being considered at all,” says Andy Parker from the University of Bristol.

“Solar radiation management is like chemotherapy. It’s horrible, it’s risky, no one in their right mind would consider it… unless the alternative is worse.”

Is blocking the sun a good idea?

Last resort

Definitely not, say some. This is a crazy suggestion. Even the scientists behind the plan to test solar geoengineering in Sweden say the thought of a large scale project is “terrifying”. Blocking the sun could have terrible side effects. The right thing to do is encourage nations to fix the root cause of the climate crisis by cutting emissions, not give them a new way to ignore the problem.

It may be our only option, say others. Nobody wants to block out the sun, not even the scientists who are working to make it possible. But one day, if politicians fail to solve this problem, solar geoengineering may be necessary to ensure the survival of the human race. We need to do the research now so that in the future, global leaders can make informed decisions on the fate of our planet.

You Decide

  1. Who should make the final decision on whether or not to block the sun?
  2. Is fixing the symptoms of a problem ever preferable to solving its cause?


  1. Write a dramatic scene for a play about a group of scientists and world leaders who must decide whether or not to block the sun.
  2. The American report concludes that not enough is being done to regulate geoengineering. Create a list of five rules you think scientists and governments should follow while they research ways to dim the sun.

Some People Say...

“We’ve engineered every other environment we live in – why not the planet?”

Lowell Wood (1941 – ), American astrophysicist and inventor

What do you think?

Q & A

What do we know?
It is generally agreed that the best way to make sure the Earth remains habitable long term is to cut carbon emissions. In 2018, one climate change panel warned that “limiting global warming to 1.5C would require rapid, far-reaching and unprecedented changes in all aspects of society”. The inconvenience of cutting emissions, combined with the relatively cheap cost of geoengineering, has prompted fears that politicians may choose to block the sun rather than address the cause of the issue.
What do we not know?
One main area of debate surrounds who should fund research on solar geoengineering. Currently, most of the research is paid for by private donors such as philanthropist Bill Gates. Some believe governments are reluctant to discuss geoengineering for fear of being accused of failing to act on carbon emissions. Now, the new US report says it is vital that this research is publicly funded to ensure transparency and accountability as scientists carry out tests that could alter the climate.

Word Watch

Carbon emissions
Carbon dioxide released into the atmosphere is one of the main causes of global warming. The five countries that produce the most carbon dioxide are China, the US, India, Russia and Japan.
The second layer of the Earth’s atmosphere, extending to about 50km above Earth’s surface.
Cirrus clouds
Short, wispy clouds found at high altitudes. They are named after the Latin word “cirrus”, meaning a ringlet or curl of hair.
Any deliberate large-scale manipulation of the Earth’s climate. Solar radiation management is one form of geoengineering.
Bill Gates
The co-founder of Microsoft is the world’s third richest person. He and his wife have donated £33bn to charity.
Fossil fuel
Fossil fuels, including coal, oil and natural gas, supply about 80% of the world’s energy. They release carbon dioxide when burned, and are one of the primary causes of climate change.
An aggressive form of chemical drug therapy used to treat cancer, known for causing unpleasant side effects.


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