Silver bullet tech solutions to climate change can't save our planet

Joanne Bentley is a researcher at the African Climate and Development Initiative at the University of Cape Town.

We are now at a critical stage where our decisions on how we tackle greenhouse gas emissions will greatly influence the trajectory of our planet’s future. 

To put it very simply, there are two broad choices ahead of us for staying within global warming limits agreed by the world’s governments.

In one, society takes immediate and rapid actions to reduce greenhouse gas emissions by around 40% by 2030 and to near zero by mid-century.

This would allow us to teeter along at or slightly above our globally agreed warming limit of 1.5 degrees Celsius or “well below” 2C, and then settle at our target.  To achieve this, we must stop burning fossil fuels. 

In the other, the phasing-out of fossil fuels is further delayed, which causes us to drastically overshoot our targeted global warming limits.

To bring global temperature back down in line with the Paris Agreement, we then roll out technologies at colossal scales to pull carbon dioxide out from the atmosphere. 

Both scenarios, in theory at least, could limit global warming to below 2C by the end of the century. 

But there is a catch: A  global warming overshoot could thrust us into spiralling species extinction, ecosystem transformation, and disruption of our physical climate system.

To avoid ecosystem collapse and human suffering, the temperature journey is as important as the final destination.

This is our warning of over-relying on unproven carbon removal technology in a few decades’ time to compensate for government inaction now. 

Our new research shows that the risks to nature of first overshooting temperature targets before bringing them back down could be devastating.

Many more species could be pushed to extinction by dangerous climate conditions during an overshoot. Worryingly, these risks to species survival may remain for far longer than the duration of the temperature overshoot period. 

Should we fail to make the necessary fossil fuel cuts now, a number of interventions will be needed to remove enough carbon from the atmosphere to bring temperatures back down.

One is ‘nature-based’, which can include growing trees in degraded forests or in land not previously forested. These trees capture carbon emissions from the atmosphere and store it within the trees themselves. 

More controversial interventions include technologies such as bioenergy with carbon capture and storage (BECCS).

This is where crops are grown to capture carbon from the atmosphere and burned to create energy. The carbon released during this process is then directly captured and stored for a very long time in unused underground oil wells and other geological formations.

Carbon can also be directly sucked from the atmosphere and pumped into storage, a process called direct air capture.

Using these interventions, it is suggested that millions of tons of carbon can be removed from the atmosphere, energy can be generated through combustion, and the carbon can be locked away for millennia.

Silver bullet solution or red herring?

But, as the adage goes, if it sounds too good to be true, it’s probably because it is.

To use BECCS at the scale needed, vast tracts of land – along with significant water and fertiliser – would be needed to grow bioenergy crops.

Not only could this further endanger biodiversity through the replacement of natural land with monocultures, but it could also put pressure on global food security as food-producing land is converted to bioenergy cropland. 

At local scales, this land transformation may threaten water security and worsen land degradation and desertification, endangering indigenous peoples and other people who live there and depend on the land - particularly those with insecure land tenure. 

Subtropical and tropical regions, because of their good climates and long growing seasons, have been identified as ideal locations for bioenergy crop production.

However, biodiversity in these regions is already under severe risk from habitat loss, deforestation, overconsumption, hunting, and climate change. Additional pressure on these ecosystems could push them to breaking point.

None of these carbon removal technologies have yet been shown to work at the scales needed.

Right now, the bioenergy conversion process is inefficient and expensive, and the lifecycle emissions of BECCS are not well understood. Direct air capture technologies are in their infancy and their potential use in the future is, at this point, speculative. 

While nature-based approaches do not suffer the same technical constraints, storage in trees is often temporary compared to the permanent storage needed to reverse global warming.

Forests are vulnerable to human actions and future climate change. For instance, droughts and runaway forest fires could release tons of carbon stored in trees. 

While some amount of carbon dioxide removal will be essential for mopping up emissions that are leftover once we’ve reduced all possible emissions from fossil fuels, an over-reliance on unproven technologies is very risky.

Even if these interventions could be deployed quickly and at large scales, they will not be able to simply reverse the devastation to species, ecosystems, and human livelihoods catalysed by worsening climate change.