Basically, we have to remove CO2 from the atmosphere if we don't want "ruinous" damage to the planet; even in the best case, renewable energy will not solve our problems.
Interesting, albeit not altogether surprising, how immediately dismissive they are of legislative solutions.
'Unfortunately, not every Google moon shot leaves Earth orbit. In 2011, the company decided that RE<C was not on track to meet its target and shut down the initiative. The two of us, who worked as engineers on the internal RE<C projects, were then forced to reexamine our assumptions.'
'Hansen set out to determine what level of atmospheric CO2 society should aim for “if humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted.” His climate models showed that exceeding 350 parts per million CO2 in the atmosphere would likely have catastrophic effects. We’ve already blown past that limit.'
'So our best-case scenario, which was based on our most optimistic forecasts for renewable energy, would still result in severe climate change, with all its dire consequences: shifting climatic zones, freshwater shortages, eroding coasts, and ocean acidification, among others. Our reckoning showed that reversing the trend would require both radical technological advances in cheap zero-carbon energy, as well as a method of extracting CO2 from the atmosphere and sequestering the carbon.'
'To reverse climate change, our society requires something beyond today’s renewable energy technologies. Fortunately, new discoveries are changing the way we think about physics, nanotechnology, and biology all the time. While humanity is currently on a trajectory to severe climate change, this disaster can be averted if researchers aim for goals that seem nearly impossible.'
Perhaps there will even be disincentive from fixing the problem: http://www.businessinsider.com/russia-is-militarizing-the-arctic-2014-12