Dr David T. Ho is a Professor in the department of Oceanography at the University of Hawaii. He has worked in earth sciences since earning his doctorate at Columbia University in 2001.

Dr Ho’s article in NATURE makes numerous important points:

• All pathways to limit global warming to 1.5–2 °C above pre-industrial levels require rapid decarbonization to start now.

• CO₂ must be removed from the atmosphere because we won’t be able to eliminate carbon emissions entirely on the required time scales. ‘Hard to abate’ sectors such as aviation and shipping will remain large sources of greenhouse gases even in the most optimistic scenarios. 

• After some small-scale demonstrations of ‘direct air capture’ (DAC) technology, the US is developing four DAC hubs, but deploying them to remove CO₂ from the atmosphere is pointless until society has almost completely eliminated its polluting activities.

• We must stop talking about deploying CDR as a solution today, when emissions remain high — as if it somehow replaces radical, immediate emission cuts.

• Humanity has never removed an atmospheric pollutant at a global, continental or, even, regional scale — we have only ever shut down the source and let nature do the clearing up.

• The scale of the challenge is immense. We must slow the carbon clock to a crawl before we can turn it back.