Scientists to test idea to dim the Sun’s rays
Radical tactic to cool planet met with fears of tinkering with nature, writes Robert Matthews
Scientists are preparing to test a radical new way of tackling climate change by dimming sunlight. Researchers from Harvard University plan to next year release a balloon into the skies over the south-west US.
Once it reaches an altitude of 20 kilometres, the balloon will release a chalky material to bounce the sun’s heat back into space.
Only a tiny amount of material will be released, and the effects will be limited to a few square kilometres. Even so, the experiment has reignited concern about such geo-engineering to tackle climate change.
The fear is that such schemes may have unintended consequences, but there is also mounting concern that time is running out to deal with climate change.
At the UN climate change conference in Poland last week, scientists insisted that emissions of carbon dioxide needed to be cut by almost 50 per cent in barely a decade to avert disastrous consequence.
Four former UN climate conference presidents went further, saying decisive action is needed in two years.
Scientists have been issuing such dire warning for decades. But despite repeated calls on governments to take action, emissions are expected to reach record levels this year.
And evidence of the need for action continues to mount. Seventeen of the 18 warmest years on record have occurred since 2001, with the past four being the hottest of all.
The impact of the rise in global temperatures is also growing. The UN says the cost of climate-related disasters last year was more than $500 billion (Dh1.83 trillion).
With such apocalyptic statistics, the reluctance of the major emitters of carbon dioxide – mainly the US, China and India – to act is prompting growing interest in radical measures. And they don’t come much more radical than giving the Earth a sunscreen.
Scientists already know it can work because nature has done it countless times with massive volcanic eruptions.
In 1991, the eruption of Mount Pinatubo in the Philippines injected about 20 million tonnes of sulphur dioxide gas into the stratosphere.
This bounced back so much of the sun’s light that the Earth’s average temperature dipped by 0.5°C for 18 months.
Given the huge size of the atmosphere, the effectiveness of this way of cooling the planet is astounding. In effect, adding barely one part for every billion of reflective matter to the atmosphere cancelled a century’s worth of global warming.
But that also highlights a key concern about geo-engineering – the risk of the Butterfly Effect. First coined in the 1960s, this describes how the atmosphere has a way of amplifying even small tweaks, such as the flap of a butterfly’s wings, into big consequences.
During the 1980s, average temperatures over mainland Europe started to rise far more rapidly than expected using global warming models.
Scientists traced the surge to the clean air campaigns that forced factories to cut the amount of matter they pumped into the air. But this also cut the amount of light-reflecting gas and dust they emitted, allowing more of the Sun’s heat through and causing a jump in temperature. That highlights the other concern about geo-engineering – its ability to trigger what the Germans call a schlimmbesserung, a “worse bettering”.
Nature again provides worrying insights into some of the potential unintended consequences of dimming the sun. After the Mt Pinatubo eruption, the darker skies led to cuts in the yields of crops such as rice, wheat and maize.
Some consequences are less obvious. The sulphur dioxide from the volcano cut visible light levels but also boosted levels of harmful ultraviolet light because of its effect on the ozone layer, which protects us from this radiation.
The eruption may also have affected the jet stream, which are the fast-moving currents of air in the stratosphere that can lead to bizarre weather across continents.
The scientists behind the planned experiment are fully aware of these lessons from nature and have taken every precaution to prevent nasty surprises. Initial tests will release ice into the stratosphere from the balloon to check that all of the systems are working.
The team then plans to move to calcium carbonate dust to study its ability to bounce back sunlight. The amounts involved are so small they will only affect the air around the balloon and will vanish in a matter of hours.
But critics of the experiment fear it will have a permanent impact by legitimising geo-engineering to politicians.
The attraction of this method has been boosted by a recent UN report suggesting that deliberate solar dimming could cut global temperatures by 1.5°C for as little as $1bn a year.
The prospect of a cheap and quick remedy to the effects of carbon dioxide on global warming is likely to be hard for politicians to resist.
Yet the very success of solar dimming could lead to the most disastrous consequence – by convincing politicians they need do nothing about carbon dioxide levels.
While their effect on global warming might be reduced, ever greater levels of carbon dioxide would end up in the world’s oceans, making them increasingly acidic, with as yet unknown consequences.
In the end, the only way to find out the truth is through carefully planned scientific experiments. On the face of it, that is exactly what the Harvard team is planning.
And it is far preferable to politicians suddenly waking up to the threat and demanding an instant fix that proves to be anything but.
Scientists already know it can work because nature has done it countless times with massive volcanic eruptions