On Wednesday this week, the concentration of carbon dioxide in the atmosphere was measured at 415 parts per million (ppm). The level is the highest in human history, and is growing each year.

Amid all the focus on emissions reduction, the Intergovernmental Panel on Climate Change (IPCC) says it will not be enough to avoid dangerous levels of global warming. The world must actively remove historical CO₂ already in the atmosphere – a process often described as “negative emissions.”

CO₂ removal can be done in two ways. The first is by enhancing carbon storage in natural ecosystems, such as planting more forests or storing more carbon in soil. The second is by using direct air capture (DAC) technology that strips CO₂ from the ambient air, then either store it underground or turn it into products.

US research published last week suggested global warming could be slowed with an emergency deployment of a fleet of “CO₂ scrubbers” using DAC technology. However, a wartime level of funding from government and business would be needed. So is direct air capture worth the time and money?

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