New Scientist - USA (2021-02-27)

27 February 2021 | New Scientist | 41

shield only lasts a year or so because the

particles drift slowly back to the surface.

Only once we are capable of pulling huge

amounts of carbon out of the atmosphere

can we let the shield come down for good,

which brings us to our next investment.

We have to remove a good chunk of the

CO 2   we have released into the atmosphere.

Here I would fund two different approaches:

technologies designed to suck up CO 2 and

good old-fashioned tree planting.

For all its world-changing power, CO 2

is a trace gas, making up just 0.04 per cent

of the atmosphere. That makes it difficult

to extract. We can do it on a small-scale now

but we need to do it on a planetary scale.

Carbon capture

Climeworks is a Swiss firm trialling a

number of carbon-capture projects, the

most ambitious of which is in Iceland.

There, carbon-capture units running on

the country’s geothermal energy collect

50 tonnes of CO 2 a year and pump it

underground where it reacts with basalt

and turns to stone. But 50 tonnes per year

is nothing. In 2018 alone, humans emitted

37 gigatonnes of CO 2. Climeworks says it

wants to capture 1 per cent of global CO 2

emissions by the mid-2020s, which would

of the sunlight reaching the surface of the

planet and thereby cool global temperatures.

Let’s imagine we stump up a few hundred

million dollars for testing one such approach,

that of seeding the skies with sulphate

particles, which are considered the most

plausible planetary sunscreen. After extensive

trials, we find that it doesn’t wreck the

monsoon in South Asia, for example, and

that the benefits of a temperature decrease

aren’t offset by a reduction in crop yields.

Let’s also imagine that our trials, scaling up

each time, have garnered enough positive data

and political and social support to drive the

drawing up of a manifesto of responsibility

and the agreement of an international treaty

for a global solar geoengineering effort. We

will need specially made aircraft that fly high

in the stratosphere and release their sulphate

payloads. Following research by Wake Smith

at Yale University and Gernot Wagner at New

York University, we will commission a fleet

of autonomous drones with giant wingspans,

capable of cruising in the stratosphere,

steadily releasing their sulphur payload.

We will purchase an island, build a port to

receive shipments of sulphur and a runway

from which we can launch thousands of flights

to seed the skies. We will allocate $6 billion for

all this. That isn’t much. The trouble is that

if we started it, we couldn’t stop. A sulphate >

Stop climate

change

Climate change is a global tragedy unfolding

in front of our eyes. If we don’t keep

temperatures from rising more than 1.5°C

above pre-industrial levels, we could be locked

into devastating sea level rise, droughts,

famines and conflict. We urgently need to

cut emissions. That is the only way to stop the

disaster getting worse. But we have available,

right now, the means to cool the planet and

remove carbon dioxide from the atmosphere.

We will want to invest in geoengineering,

defined as any deliberate intervention of a

nature and scale capable of counteracting

human-made climate change and its

knock-on effects. We will focus on one of the

most promising ideas, solar geoengineering,

comprising methods to screen out some

Men planting trees in

Inner Mongolia, China.

Afforestation is

expensive but pays

huge dividends

We need to extract

carbon dioxide from

the atmosphere

on a massive scale

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