Glasgow, Scotland (AP) — The overarching phrase that dominates Glasgow climate talks is simply a number: 1.5. That’s the chief but elusive goal of negotiations. It’s keeping warming to 1.5 degrees Celsius since pre-industrial times. It’s not easy. Scientists say it’s technically possible but politically unlikely. It’s also a relatively new goal that was a last minute add-on during the historic 2015 Paris climate deal. But since then studies have shown that limiting warming to 1.5 degrees which is really only a few tenths of a degree from now can be a matter of life and death.