Countries’ plans to take carbon dioxide back out of the atmosphere will not be enough to comply with goals to limit global warming to 1.5C, research warns.

Scientists have taken the UN’s approach of assessing the “emissions gap” between national climate protection plans and what is needed to limit warming to 1.5C as agreed under the global Paris treaty – and applied it to moves to remove key greenhouse gas carbon dioxide from the atmosphere.

The first-of-its-kind analysis found there was a gap of up to 3.2 billion tonnes of carbon dioxide (CO2) between what is planned by countries for removing carbon and what is needed by 2050 to curb dangerous global warming.

While cutting emissions, including from deforestation, is the main way society can curb rising temperatures, removing CO2 from the atmosphere will also have an important role to play, scientists said.

Removal of the gas includes planting trees or restoring other carbon-storing habitats as well as new technologies such as capturing the gas from the air directly and burning bioenergy such as wood pellets for power while catching and storing the CO2, known as Beccs.

The research, published in the journal Nature Climate Change, compared national action plans with scenarios based on the UN’s climate science body assessments for limiting warming to 1.5C to avoid the worst impacts of heatwaves, floods, droughts, melting ice and sea level rise.

If national targets are fully implemented, annual removals of CO2 could increase by a maximum of 1.9 billion tonnes by 2050.

Under one scenario for reducing fossil emissions and rapidly expanding renewables, annual carbon removals must still increase by 5.1 billion tonnes from today’s levels by 2050, leaving a gap of 3.2 billion tonnes of CO2.

Under another scenario, which assumes a significant reduction in global energy demand, there would need to be a lower increase, of 2.3 billion tonnes a year by 2050, so the gap would be smaller, at around 400 million tonnes.

The UK’s overall carbon pollution in 2023 was around 300 million tonnes.

Lead author Dr William Lamb, of the Berlin-based Mercator Research Institute on Global Commons and Climate Change, said that in the UN emissions gap reports, carbon removals are only accounted for indirectly.

“The usual benchmark for climate protection pledges is net emissions, ie emissions minus removals.

“We are now making transparent the specific ambition gap in scaling up removals,” he said.

Co-author Dr Naomi Vaughan, of the Tyndall Centre for Climate Change Research at University of East Anglia, said: “Carbon dioxide removal methods have a small but vital role to play in achieving net zero and limiting the impacts of climate change.

“Our analysis shows that countries need more awareness, ambition and action on scaling up carbon dioxide removal methods together with deep emissions reductions to achieve the aspirations of the Paris Agreement.”

The scientists warn that there were sustainability issues in scaling up efforts to remove carbon from the atmosphere, with demand for land potentially jeopardising wildlife and food security.

Meanwhile new techniques have hardly been promoted to date, and remove just a fraction of the CO2 that is being taken out of the atmosphere by conventional methods such as creating new forests.

The researchers also warned there was a lack of transparency, with many countries having commitments to reduce emissions to zero overall – known as net zero – but providing little information on the role carbon removal will play.

And they responded to concerns that carbon removal would be used as an excuse to do little to cut emissions at source, saying their assessment “in no way underplays the need for rapid, immediate and deep emissions reductions across all sectors”.

That includes a rapid decrease in fossil fuel use and the halting of deforestation, they said, adding that the longer such reductions are delayed, the higher the carbon removal requirements, and the wider the gap becomes.