“I admit it. I used to be a climate-change skeptic. I was one of those conservatives who thought that the science was inconclusive, that fears of global warming were as overblown as fears of a new ice age in the 1970s, that climate change was natural and cyclical, and that there was no need to incur any economic costs to deal with this speculative threat. I no longer think any of that, because the scientific consensus is so clear and convincing.”