The Kyoto Protocol	Contraction and Convergence	Kyoto2	Greenhouse Development Rights
What is it?	Kyoto aimed to give some teeth to the UN Climate Change Convention, agreed back in 1992. Signed in 1997, the protocol committed industrialised countries to making small cuts in their greenhouse-gas emissions. Whether, and how, Kyoto's first "commitment period", which expires in 2012, should be extended is the main topic for discussion in Bali.	C&C has long been the New Statesman's preferred option. It proposes a global cap on emissions, with countries allocated fair shares of the remaining carbon budget in proportion to their population. It is a "constitutional", rights-based approach. Governments would be assigned emissions rights according to their populations, which they could then distribute nationally to individuals through a carbon rationing scheme such as "personal carbon allowances".	Known in the biz as "upstream cap and trade", this framework proposes that carbon permits be auctioned to fossil fuel producers - petroleum and coal companies - with the carbon cost calculated at the point of production (the oil refinery or coal mine) rather than emission (car tailpipe or gas boiler). The resulting revenue would be used to fund adaptation to climate change and a worldwide transition to a low-carbon economy.	This proposal recognises the "right to development" of poorer countries. It establishes a "development threshold" so that those earning under $9,000 are not required to shoulder any burden of cutting emissions. Everyone else has allocations calculated via a formula that takes into account historical emissions and national wealth.
Scientific rigour	Kyoto fails the scientific rigour test because it is inherently short-term. The latest science suggests that the world needs to cut greenhouse-gas emissions by 80 per cent by 2050 at the barest minimum in order to keep global warming rises within the 2°C range. Kyoto seeks only 5 per cent cuts by 2012, and then only from industrialised countries. So it isn't really a framework at all: it is more a guessing game. 2/10	C&C is a flexible framework, so its cap can be set at any level that science deems necessary to stabilise the climate. This can be tightened if climate change proceeds faster than expected, as may prove to be the case. 10/10	As with C&C, the Kyoto2 approach would be to set the cap first, in accordance with the latest science. Only then would carbon credits be sold to fossil fuel bidders, within the context of a rapidly declining greenhouse-gas budget. 10/10	GDR proponents, which include Christian Aid, suggest a very strict emissions-reduction target to try to keep global warming increases within 2°C. 9/10
Political realism	Kyoto scores highly here, because we have it, so it is by definition realistic. The underlying logic is impeccable: if the international community can't agree on long-term goals, at least we can take some incremental first steps and then try to ratchet things up later. But where will this approach take us long term? No one can be sure. 10/10	C&C has some high-profile converts, not least Germany's Angela Merkel. But the idea is making slow progress. The US is unenthusiastic, given its disproportionate share of global emissions. Developing countries stand to gain most, as many have high populations and low emissions, so can gain from selling unused credits. But China's emissions are close to the global average, so this key player has little to gain. C&C is flexible - both the cap and date of convergence are negotiable. And emissions trading may be attractive to big polluters. 6/10	Kyoto2 is a new idea. Its market-based approach might be attractive to many world leaders. Rather than aiming for country-by-country limits, the auctioning of permits takes place at international level, removing responsibility for implementation from individual governments. The money generated could be a big incentive for developing countries, which need cash now to adapt to climate-change impacts. But distributing the revenue could be a source of disagreement. 8/10	This mechanism tries to reconcile the goals of increasing economic development for the poorest while constraining carbon emissions. The emphasis on historical responsibility will appeal to developing countries, but will be a big sticking point for the US and Europe. The US in particular may not be happy about getting the biggest bill (around $212bn). 3/10
Fairness	Kyoto did recognise that industrialised countries - which have historically been responsible for most emissions - needed to make the first move. But the targets different countries signed up to varied from an 8 per cent cut by the EU to a 10 per cent increase for Iceland, the result of horse-trading rather than a fair formula. Whether developing countries with rapidly rising emissions, such as China, should take on targets in the next round is the big unanswered question. 4/10	Fairness is C&C's main selling point - it represents a historic trade-off between developed and developing worlds. Poorer countries have more to gain by opting for per-capita equity, while rich countries need to get everyone on board if their efforts are not to be swamped by rising greenhouse-gas emissions from the likes of China and India. But despite this, many environmental groups - including Friends of the Earth and Greenpeace - have been mysteriously reluctant to endorse C&C, preferring to opt for further phases of Kyoto. 9/10	While C&C addresses the moral question head-on by asserting that each of us has an equal right to the use of the atmosphere (and dividing up usage rights accordingly), Kyoto2 avoids this by selling credits to the highest bidder and funnelling the cash to the most needy. By auctioning credits it does recognise the atmosphere as a shared resource. An analogy might be the auctioning of digital frequencies to mobile-phone companies by governments. But Kyoto2 still uses the price mechanism: anathema for some lefties. 6/10	GDRs aim to go even further than equitable per-person rights to the atmosphere, by recognising a right also to sustainable development. You can't say fairer than that. 10/10
Simplicity	Should credits for REDD be part of the CDM? Should they be counted in ERUs or CERs, or perhaps even AAUs if achieved via LULUCF by an Annex II party? Enough said. Discussing Kyoto is like leaping into an alphabet soup of acronyms. 1/10	Here, C&C wins hands down. There need be none of the messy horse-trading that characterises Kyoto, with each country arguing that it is a special case. C&C offers a straightforward formula to contract emissions down to a sustainable level, while converging to per-person equality within that overall trajectory. 8/10	As an "upstream" system, Kyoto2 has a big advantage: it would be a lot simpler to deal with a couple of hundred fossil-fuel-producing companies than trying to supervise emissions permits for 6.5 billion consumers. Like turning off the tap rather than trying to stop the water coming out of the hosepipe. 9/10	But simple it isn't. The formula for allocating emission rights is complicated and, even after several readings, the proposal is still not clear to me. Try for yourself (along with the other mechanisms), at the links below. 2/10