World leaders have started to generate some real optimism with their efforts to address global climate change. What's troubling, though, is how far we remain from getting carbon emissions under control — and how much wishful thinking is still required to believe we can do so.

The Paris Agreement has garnered the national signatories needed to go into force this Friday. Some economists see the climate change pact as a promising framework for cooperation among many different countries, especially if those not pulling their weight suffer penalties such as trade sanctions. There's even talk of aiming for the more ambitious goal of keeping global temperatures within 1.5 degrees Celsius or less of their pre-industrial level, as opposed to the currently agreed 2 degrees.

Meanwhile, another major international deal has been reached to phase out greenhouse gases used in refrigeration systems, and solar energy technology continues its rapid advance.