Why dimming the Sun would be an effective tool in the fight against climate change

By Peter Irvine, UCL

It’s becoming increasingly clear that we will fail to meet our climate goals. We were already at 1.26°C of warming in 2022 and are on track to blow through 1.5°C in the mid-2030s. Research even suggests that current climate policy will lead to more than 2.5°C of warming by the end of this century.

Warming of this magnitude would devastate vulnerable communities and ecosystems around the world. It’s time we consider something radically new that could stop climate change in its tracks.

After powerful volcanic eruptions, like Tambora (Indonesia) in 1815 and Pinatubo (Philippines) in 1991, global temperatures dip for a few years. Major eruptions create a hazy layer of microscopic particles in the upper atmosphere that last for several years, dimming the Sun temporarily. We could copy this effect to fight climate change.

The Earth is warmed by the Sun, but it is kept warm by greenhouse gases that trap the heat our planet gives off. The warming effect of our CO₂ emissions could be countered by creating a persistent, artificial haze like those seen following major volcanic eruptions. Research has found that we would only need to dim the Sun by around 1% to cool the planet by 1°C.

This may sound unlikely. But every engineering assessment to date has concluded that it would be feasible and relatively cheap to do using a fleet of high-flying jets to release reflective particles into the upper atmosphere.

So we could dim the Sun – but should we?

Cooling the planet would work

Dimming the Sun wouldn’t perfectly reverse climate change. The Sun’s warming effect is strongest during the day, in the summer and at the Tropics, whereas greenhouse gases warm everywhere and at all times.

However, we could create an even cooling effect across the world by adjusting where we release the particles. Research suggests that such an approach would greatly reduce climate risks.

Rising temperatures really matter. Species around the world are on the move, tracking familiar temperatures polewards as the planet warms up.

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