James Hansen

“A few geologists continue to speak as if they expect Earth to proceed into the next glacial cycle, just as it would have if humans were not around. That glacial period would begin with an ice sheet developing and growing in northern Canada. But why would we allow such an ice sheet to grow, and flow, and eventually crush major cities, when we could prevent it with the greenhouse gases from a single chlorofluorocarbon factory? Humans are now “in charge” of future climate. It is a trivial task to avoid the negative net climate forcing that would push the planet into an ice age (moving conditions toward the left in figure 30). But it is not an easy task to find a way to stop the growth of atmospheric greenhouse gases, most notably carbon dioxide (which moves conditions toward the right in figure 30), as we have been discussing.”
― James Hansen, Storms of My Grandchildren: The Truth About the Coming Climate Catastrophe and Our Last Chance to Save Humanity