Moving away from fossil is very hard. Essentially we have two power sources available to us - Sun and nuclear. We are not very good at capturing sun energy directly, and doing it on massive scale requires both huge investment and global size actions that would have very serious consequences on global scale - from trivial cases like dams changing the terrains to more subtle like massive wind/solar installs changing wind/reflection/heat patterns and thus influencing the climate. I don't think we have any good data on how that would work on the scales needed to replace fossil fuels. With fossil fuels we essentially are using solar energy accumulated for millions of years. Very long term there's an obvious problem there, but on shorter term if we want to make do with only solar energy that is incoming right now, we need to become drastically more efficient in capturing it, and I don't think current technologies are there yet, and that we know how to deal with it on scales required to cover all present energy needs.