Using Volcanoes to Pause Climate Change

An engineer and a climate scientist walk into a bar. The engineer says, “Why can’t we just pipe volcanic sulphur dioxide into the stratosphere and cool the planet?” The climate scientist rolls their eyes, “Surely, it’s not that simple!”.

This happened to me on a date last year.  My date, the engineer, had read about this geoengineering solution in a book called SuperFreakonomics .  The authors, economists Steven D. Levitt and Stephen J. Dubner, proposed that suspending a hose into the sky to inject sulfur dioxide high into the stratosphere could cheaply and quickly counteract the effect of global warming.

I was certain there had to be a catch. It couldn’t be a good idea to pump tonnes of toxic gas into the atmosphere.

What would to do?

The primary effect is simple enough to understand.  Sulphur dioxide and ash are naturally ejected from erupting volcanoes.  If the eruption is powerful enough by a volcano near the equator, the small particles reach into high into the stratosphere and spread around the world, tens of kilometres above the surface.  Particles remain in the stratosphere for a couple of years because there is no weather to wash out the particles.  The sulfur dioxide reflects some sunlight back into space that would usually warm the Earth’s surface and lower atmosphere.  When less energy enters the Earth, global temperatures would cool.

What eruptions have inspired this?

Injecting sulphur into the stratosphere would mimic large volcanic eruptions which have historically lead to a couple of degrees of cooling for a few years after.  Global temperatures time series show cooler temperatures following years with large volcanic eruptions. 

There are examples of throughout history.  one of the largest was The Year Without a Summer.  In 1816, the Indonesian volcano, Mount Tambora, erupted caused average global temperatures to fall three degrees Celsius below normal.  

Pinatubo 1991 is the most recent significant volcanic eruption to spew sulphur dioxide and ash high up into the stratosphere. 

By Giorgiogp2, CC BY-SA 3.0,


What happened naturally?

The stormy, dark and gloomy Year Without a Summer led to failing crops and famine.  Agriculture not only struggled due to the cold and the darkness, but also made acid rain as the sulfur combined with rain as it descended out of the atmosphere. The tumultuous gloomy summer was linked to masterpieces including Frankenstein, and also the invention of the bicycle as horses were too expensive to feed. 

The 1991 eruption of Mount Pinatubo cooled global temperatures by half a degree Celsius, and disrupted normal weather including Asian rainfall patterns.

Whiplash back to normal

After a few years, once all the sulphur rains back to the surface, the climate and global temperatures would rapidly return to what they would’ve been without intervention.  For sulphur dioxide injection to be a long term solution, the supply would need to be continually replenished.  If it stops, the subsequent sudden warming could be more detrimental to ecosystems and environments compared to if they had more time to gradually adjust to the global warming.

Climate change is more than global warming

Since the industrial revolution, burning fossil fuels has released tonnes of carbon dioxide and other greenhouse gases into the atmosphere.   Not only does carbon dioxide in the atmosphere increases the greenhouse effect, it mixes into the ocean, making the ocean acidic.  Sea life like coral and shellfish suffer because they cannot make shells or structures in acidic water.

Coral bleaching due to ocean acidification photo by Caitlin Seaview Survey –, Public Domain,

What’s the value of a garden hose in the sky?

Using a huge hose to pump toxic gas into the sky would cool temperatures, but at a significant and unpredictable cost to the environment.  SuperFreakonomics focus on the direct financial costs and the primary positive outcomes while dismissing the complications.

Like much of climate change, it is complicated.  From an ethical point of view, it isn’t ethical to create extra pollution, or to unevenly change other countries’ weather.  This solution also feeds into a psychological problem which might make people think because we have paused global warming, it’s fine to keep burning fossil fuels.  That could slow climate mitigation progress, thus further accelerating climate change.

As a climate scientist, I feel like the doctor refusing to do harm.  I explain to the engineer, that from my perspective, even though there is a chance for a payoff, the issues are too complex, too international, and too risky.  We should focus on reducing our emissions and removing excess carbon dioxide from the atmosphere.

[Feature photo by Photo by T. J. Casadevall, U.S. Geological Survey. –, Public Domain,]


The Conversation: Blocking out the sun won’t fix climate change – but it could buy us time

One Response to “Using Volcanoes to Pause Climate Change”

  1. Kaih Mitchell says:

    While it does sound like a quick fix, I can see why it would cause more problems than it solves. Maybe the engineer should focus their efforts on large scale carbon sequestration projects than polluting our planet further.