Whilst the COP21 talks were ongoing, what seems to me to be a more important item of news (in terms of dealing with AGW) has been announced. Engineers and scientists in Germany reported what seems to me (as an outsider) to be a potentially exciting development in fusion power.
The previous best bet (IMO) for fusion has been the Tokamak, as being implemented by the European JET (Joint European Torus). The Tokamak being a toroidal (doughnut shaped) magnetic containment field within which hydrogen and deuterium is heated until fusion takes place.
There is an American system using lasers at the National Ignition Facility, this doesn't fit the bill for me as I will explain. Anyway, back to the Tokamak: The German 'Stallarator' is a sort of Tokamak, but it uses a twisting magnetic containment field.
Both JET and the Stellarator are proofs of concept, nobody has yet generated power from such a system (fusion has been achieved for short periods in the JET system). However, if we can crack fusion for power generation then after that point there is a chance we can make fossil fuel burning largely obsolete, if it is played properly.
Fission using Uranium brings the risks of accidents such as Chernobyl and Fukushima, it also brings the risks of nuclear weapons proliferation. Fusion has none of those risks. Thorium would be less subject to resource depletion, but the proven Uranium based fission relies on a limited resource. Fusion relies on hydrogen, which is unlimited in practical terms (if we get properly space-faring Jupiter makes that even more the case).
I'm sorry to say that I remain sceptical of efforts like COP21, what is needed is a technology to undercut fossil fuel burning and bring about a real 'hydrogen economy' with hydrogen replacing oil for transportation. There is however a risk here, even if fusion were taken to the state where it is a proven base-load power generation system. This risk is that the wealthy nations roll out fusion and the developing world embarks on a second Industrial Revolution using fossil fuels made cheaper by declining consumption in the developed world.
To avoid this, and the resultant maintenance of CO2 emissions, fusion power technology would have to be handled properly. The reason I am dubious about the US's National Ignition Facility effort is that using enormous banks of lasers it seems a very costly system in its essentials. This is in comparison to the Tokamak/Stelarator technology, the proof of principle is costly, but I can see the basics of a system that could be manufactured in places like Europe/North America/China and not just rolled out in the developed world, but rolled out across the entire world. Once proof of principle is achieved and experience has been gained with pilot systems the cost should not be prohibitive and could (I would argue should) be subsidised by developed nations as a 'gift' to the world.
'Politics is the art of the possible', so said Otto Von Bismarck. On my bus journey back home yesterday I was reading about COP21 on my phone, then I looked out of the window and saw the masses of cars. People just will not want to give up their cars, fossil fuels (and hydrogen) remain a far better store of energy than batteries can, and that just will not change. The same goes for heating and the overall massive energy consumption of our advanced civilisation. No politician will be voted in on a ticket of energy austerity. So prohibition of fossil fuels is not within the realm of the possible, however we are now at a stage where making the burning of fossil fuels the costly option might be achievable within decades.
Cracking the problem of cheap energy generation from fusion is not a given, it may prove too difficult, but on balance I think it is looking an attainable goal. If we treat this technology as a subsidised gift to all nations then we could turn fossil fuels into chemical resources and turn the problem of global warming and resultant climate change due to increasing atmospheric CO2 from a serious risk to a manageable problem.