The latest evidence that 2015 was a breakout year for clean energy is in, and it's particularly telling.

In a new analysis, Bloomberg New Energy Finance finds that 2015 was a record year for global investment in the clean energy space, with $ 329 billion invested in wind, solar panels, biomass plants and more around the world. (The number does not include investments in large hydroelectric facilities).

That's 3 percent higher than the prior 2011 global investment record of $ 318 billion -- and most striking is that it happened in a year in which key fossil fuels -- oil, coal and natural gas -- were quite cheap.