I don't think we can assume costs will keeping coming down in a kind of linear fashion. To get to 50% renewable energy it probably will and I think this will h

I don't think we can assume costs will keeping coming down in a kind of linear fashion. To get to 50% renewable energy it probably will and I think this will happen by itself because there's a clear financial benefit to it. For the other 50% this may be difficult, but this is where carbon taxes probably will have to fill the gap, but this could also mean things like biofuels and carbon capture and a whole bunch of unconventional things we haven't even dreamed of yet will be cost competitive to further expansion of renewables.