The world woke yesterday morning to an early Christmas gift. Not a novelty knitted jumper or bottle of tipple, but something more poignant altogether. Unconventionally, the gift in question was not only immaterial, but universal, unquantifiable, and intergenerational: the prospect of a deal on climate change in Paris.

The final agreement includes a commitment to keeping temperature rises ‘significantly below’ 2C, with the aim of 1.5C as a target. Whilst 2 degrees may sound inconsequential, the difference between today’s average global temperature and that during the last ice age is around 5 degrees. Our climate has never changed so rapidly, it’s unequivocally due to human activity, and avoiding the problem could result in temperature rises of 5-6C by the end of this century. Ask a climate scientist to describe what a 5-degree-world would be like, and you might just wish that you hadn’t.

Whilst a UN agreement provides a mandate for action, the thorny issue of how we get there is likely to make the COP21 negotiations look like a doddle. To this end, we must turn to the pillars of reasoned progress: science and politics. Earlier this year, the Tyndall centre (host to some of the world’s leading climate scientists) published an analysis of future climate projections for the 21st century: exploring 400 different possible ‘routes’ to achieving what has since been agreed in Paris. Of those, 86% rely on unproven technology, such as Carbon Capture and Storage (CCS). For the remaining scenarios, emissions would have had to have peaked in the past at around 2010. Assuming technology will solve the climate problem is an aspiration, not a grounded projection. Whilst it’s unlikely that non-existent technologies will fit the bill, it’s even less-likely that Dr. Emmett Brown will be using his DeLorian to help us fix the emissions of the past.