In what's generally perceived as a radical reversal, the famed skeptical environmentalist Bjorn Lomborg is now calling climate change a major world issue that must be squarely addressed. Though Lomborg himself is claiming he has not switched positions, this is not the general perception; the Lomborg Wiki characterizes his new stance as a u-turn.
In fairness, contrary to a very widely held misperception, Lomborg has never been a climate change denier. His position was that the problem of global warming was exaggerated, that other global problems deserved much more attention and investment, and that to the extent greenhouse gas emissions were a threat, advances in solar technology would take care of the problem. (In a book, I called Lomborg's faith in solar technology remarkably credulous, for somebody who styles himself as a skeptic.)
If Lomborg is now noticing that solar will not actually be able to solve all our problems, and if he's owning up honestly to the implications, he's to be congratulated. One reason I've always defended Lomborg against his detractors is that he writes clearly and accessibly, and says what he really thinks. The evolution of his well-articulated thinking will be a positive service.