Work in David Keith’s group is funded by a variety of public and philanthropic sources. Over the decade funding has come from the US NSF, Canada’s NSERC, a series of gifts from Bill Gates via the Fund for Innovative Climate and Energy Research (FICER), Harvard start-up funds, and Harvard grants: The Star Family Challenge for Scientific Research, The Weatherhead Initiative Research Cluster in International Affairs, and The Harvard Climate Solutions Fund. Harvard's Solar Geoengineering Research Program also provides funding.

We strongly oppose commercial work on solar geoengineering. The narrow engineering costs are so cheap that, if anything, one problem might be it is too cheap. In any case, we do not need private competition to make it cheaper. We do need transparency about risks and performance that are best provided in an academic, open, and public setting.

From October 2009 to November 2013 David was president of Carbon Engineering and currently serves as its Executive Chairman. Carbon Engineering is a private company developing technology for direct capture of CO2 from the atmosphere with a focus on making carbon-neutral transportation fuels. Because of concerns about conflict of interest David now does little academic work on direct air capture. While often referred to as "geoengineering", air capture is distinct and very different from solar geoengineering. The Keith Group's aim is to work solely on the latter, so there is no direct conflict of interest. It is an open research question under which circumstances even talk of solar geoengineering could lead to an increased or decreased willingness to mitigate carbon. The two clearly are no substitutes. We must decrease CO2 emissions to zero regardless of what happens on the solar geoengineering front.