What if the day comes that humans need to make massive, intentional changes to the earth in order to ensure the survival of the species? Perhaps the solar radiation from the sun increases, or the orbits of the planets shift, or greenhouse gases accumulate to fatal levels. These changes could result in the kind of intense warming that happened during the cretaceous, when palm frond and freshwater ferns dominated the polar landscapes. According to some, the best strategy for avoiding this kind of cataclysmic change is to, quite literally, block out the sun.  It sounds risky, pre-apocalyptic, and almost hubristic. Who are these humans who think on a planetary scale, and refuse to turn away from the challenge of engineering the atmosphere? Our guest today, Harvard professor Dr. David Keith, is an illustrative example of the field. While he studies what sorts of interventions could be used to turn down the intensity of incident solar radiation, in the next breath he’ll be the first to suggest that perhaps spraying sulfuric acid, aluminum, titanium, or diamond dust into the atmosphere isn’t a very good idea.   Our conversation covers all aspects of solar geoengineering. The state of the field, the incentives for developing systems that can change global climates, the likelihood of private actors taking matters into their own hands, and much more.   Subscribe & like so we can keep bringing the best conversations!!!  More readings from us: https://demystifyingscience.com/blog Join the DemystifyingScience mailing list:  http://eepurl.com/gRUCZL Let's talk!  @DemystifySci Twitter: https://twitter.com/demystifysciInstagram: https://www.instagram.com/demystifysciFacebook:  https://www.facebook.com/demystifysci~~~~~~~~~~~~~~ Music: ~~~~~~~~~~~~~~ Shilo Delay:  https://soundcloud.com/laterisgone