Obama's thesis is, broadly, that clean energy is good for the environment, helps businesses save money and, in the end, benefits everyone. The last eight years have seen the price of renewables fall while the economy has grown, and clean power employs twice as many people as its dirty equivalent.

While Obama's replacement has deep ties to the oil and coal industries, it's likely that their decline is now inexorable. The president explains that as gas-powered electricity generation is so cheap, the market won't simply re-open unprofitable coal plants. Between the lines, he's saying that whatever Trump has promised, following through won't be as easy as saying things.

It's not the first time that the president has used a principally academic publication to outline or defend his policy initiatives. He has previously written in the American Medical Association's journal in support of healthcare reform and the Affordable Care Act. It's a natural fit for the former academic, who lectured in constitutional law at the University of Chicago for 12 years before he became a senator.