The short answer is yes, they can.

First, a little background: atmospheric concentrations of carbon dioxide have been rising significantly since the beginning of the Industrial Revolution. In May, the Mauna Loa Observatory in Hawaii reported an average monthly level of carbon dioxide above 415 ppm, the highest concentration of atmospheric carbon dioxide in millions of years (I,II). This accumulation represents an additional 135 ppm of carbon dioxide in the atmosphere since the Industrial Revolution, which equates to one trillion tons* of carbon dioxide, or one teraton (III). **

To avoid the harshest effects of these additional greenhouse gases in the atmosphere, we must reduce current emissions – but even that will not be enough. Even if all countries meet their commitments under the Paris Agreement, and all companies meet their individual commitments, atmospheric carbon dioxide levels will continue to climb, reaching an estimated 580 ppm by the end of the century (IV). This uncertain future cannot be averted with a business-as-usual mindset, nor a middle of the road effort. Drawing down atmospheric carbon dioxide is necessary to begin undoing the damage.