Efforts to halt global warming depend on cutting net greenhouse gas emissions to zero, yet the world is moving in the opposite direction. Carbon dioxide emissions hit a record high last year, and for the first time global temperatures briefly exceeded 1.5 °C above preindustrial levels. The Intergovernmental Panel on Climate Change (IPCC) warns that keeping warming below 2 °C will require vast amounts of carbon removal to pull CO₂ out of the atmosphere and lock it away for centuries.
Traditional approaches to carbon removal include reforestation, afforestation, and storing more carbon in soils. These methods are relatively inexpensive, but they face serious limitations. Forests can burn, succumb to disease, or be cut down, releasing their stored carbon. Soil carbon is gradually broken down by microorganisms, and both strategies are constrained by the amount of land available. Pulverizing minerals to accelerate natural weathering can also sequester carbon, but it likewise demands large areas to sink each tonne of CO₂.
New industrial methods aim to fill the gap. Direct air capture (DAC) facilities use powerful fans or pumps to chemically strip CO₂ from the air or seawater, then inject it deep underground. Geological surveys show there are ample underground reservoirs capable of holding many trillions of tonnes of CO₂ for centuries. About 51 megatonnes of CO₂ are already stored each year, and announced projects could increase that figure sevenfold in the next decade. However, almost all current storage comes from capturing emissions at fossil-fuel facilities, not from the atmosphere. DAC’s contribution remains tiny.
The scale of the challenge is staggering. A 2018 review led by the Mercator Research Institute estimates that between 525 and 755 gigatonnes of CO₂ must be removed from the atmosphere by 2100 to stay below 2 °C of warming—and even more if emissions continue rising. From 2019 to 2023 only 9 gigatonnes were removed, 99.9 percent through managed forestry. Novel technologies such as DAC, biochar, and enhanced rock weathering collectively eliminated less than 2 million tonnes over those years, equal to just 0.004 gigatonnes. DAC’s share was a microscopic 0.00001 gigatonnes.
IPCC scenarios depend on a rapid scale-up. By the end of the century, DAC and other new techniques would need to remove 6 to 12 gigatonnes of CO₂ annually, supplementing the 2 to 5 gigatonnes expected from soils and forests. Achieving that would demand enormous energy: researchers in Saudi Arabia calculate that sustaining 10 gigatonnes of DAC each year would require an extra 4.4 terawatts of carbon-free electricity and heat—more than the total global supply of clean energy in 2024. Some existing DAC plants already struggle to offset the emissions from their own operations.
In short, every feasible method of carbon removal must expand dramatically, but each carries trade-offs in cost, land use, and energy demand. Meeting climate targets will require unprecedented investments, rapid innovation, and vigilant oversight to ensure that the drive for large-scale carbon removal does not create new environmental or social problems while attempting to solve the old ones.