The report says natural CO2 removal processes like forests and soil are not going to be enough to stop temperature rises. Photo: 123rf
By Jonah Fisher, BBC Environment Correspondent
Technology to remove the planet-warming greenhouse gas CO2 from our atmosphere must be urgently ramped up, leading climate experts say in a new report.
Scientists say big cuts in CO2 emissions would not be enough to limit global warming. And nature alone would not remove enough of it from the air.
CO2 is the most important gas warming the planet, and is emitted when fossil fuels such as gas and oil are burnt.
"To limit warming to 2C or lower, we need to accelerate emissions reductions. But the findings of this report are clear: we also need to increase carbon removal too," said lead author Dr Steve Smith from Oxford University.
"Many new methods are emerging with potential."
There is consensus among scientists that the world is warming primarily because emissions of CO2 (estimated at 33 billion tonnes in 2021) far exceed the amount being removed (this report suggests two billion tonnes a year).
Until emissions and removals are balanced - so called "net-zero" - global temperatures are predicted to rise.
But getting there would not be easy. The latest UN climate reports said to fully achieve "net zero" there would need to be some CO2 removal, so called "negative emissions", to compensate for sectors that could not easily decarbonise.
Currently almost all of the world's removal of CO2 from the atmosphere occurred through natural processes. That's primarily plants and trees taking in CO2 from the air, and the soil absorbing and storing it.
But there were limits to how much nature could do. For example, how much more of the world could realistically be given over to forests?
Some optimistic scenarios suggest that natural CO2 removal could be doubled by 2050, but that was still only about 4 billion tonnes of CO2 a year.
Technological solutions?
The new report, titled The State of Carbon Dioxide Removal, said that to restrict and reduce global temperatures in the future there needed to be investment in developing technological solutions now.
The methods it cited were all fairly new, and at different stages of development and deployment. Put together they currently only make up a tiny fraction of the worlds CO2 removal.
One, known as BECCS, involved incorporating CO2 capture into biomass-based electricity-generation, in which organic matter such as crops and wood pellets were burned to produce power.
Other options included: huge facilities where carbon could be extracted from the air before being stored in the ground; the use of specially treated charcoal (biochar) that could lock in carbon; and "enhanced rock weathering" - loosely based on the carbon removal that occurred with natural erosion.
Biochar is a specially produced type of charcoal that locks in carbon and can be used as a fertiliser. Photo: CC BY-SA 4.0/ K.salo.85
The use of CO2 removal technologies was not without its critics.
Some campaigners doubt that they could be cost effective and fear that they could be an excuse to defer and delay the transition away from fossil fuel use.
This report stressed that removing CO2 should not be seen as a "silver bullet" to tackle climate change but that meeting the UN's climate goals would require technology as well as nature to reduce greenhouse gas levels.
That all assumes that global CO2 emissions from burning fossil fuels would - as pledged at numerous climate summits - fall rapidly. So far yearly emissions were yet to start a downward trend.
- BBC