China



Plans have been announced for emissions trading systems to be rolled out in six regions by 2013 and nationwide by 2015. China's ambitious strategy to see a 40%-45% cut by 2020 in "carbon emissions intensity" - that is, carbon emissions per unit of GDP - has been praised by those who claim the commitment from the world's biggest source of CO 2 emissions shows up the US's indecision on carbon caps. But there are worries that the true impact of China's increasing number of coal-fired power stations is being masked by the cooling effects of these plants' sulphur emissions.

US



Despite being the second biggest CO 2 total emitter after China, the US has no national carbon tax policy. A bill to introduce a carbon cap was abandoned a year ago by Democrats when it met with opposition from both sides.

Europe

The European Union emissions trading scheme (ETS) is the largest multinational emissions trading scheme in the world and obliges large emitters to produce no more than their particular European unit allowance. Otherwise, they must buy surplus units from other emitters or face severe penalties.

Six years after its launch, the ETS faces criticism for failing to reduce carbon emissions in some cases, failing to spur non-EU countries to adopt cap-and-trade systems, and encouraging fraud and profiteering. As EU members debate the parameters of the next phase, from 2013 to 2020, campaigners are calling for fundamental reforms, or for it to be scrapped in favour of potentially more effective measures, such as carbon taxes. But the system has resulted in overall carbon emission reduction, and the EU has been praised for establishing a wide-ranging climate initiative.

India

India sets emission levels for 563 of the country's biggest polluters, such as power and, steel mills and cement plants, allowing businesses who use more energy to buy carbon certificates from those who use less. Trading will start in 2014.

Nationwide, it has a carbon tax (1 July 2010) of 50 rupees/tonne ($1.07/tonne) of coal produced in and imported to India.

In comparison to many other of its Asian counterparts, India's carbon pricing schemes are ambitious. They reflect an urgent need to curb emission rates from a country that – with four times the population of the US, an economy growing 8-9 per cent a year, and surging energy demand – makes it the country with the third highest carbon emissions.

Although it has refused to accept legally binding targets, India has pledged to reduce "carbon emissions intensity" - that is, carbon emissions per unit of GDP - by 20-25% from 2005 levels by 2020. But there are concerns about how both carbon initiatives will evolve because of a lack of data and trained manpower as well as weak penalties for firms that refuse to comply. Nonetheless, India's tax on coal is one of the first carbon taxes enacted at the national level by any major economy in the world.

• This article was amended on 11 August 2011 because the original said China and India have made a commitment to cut their carbon emissions. To clarify: China and India have said they will reduce their "emissions intensity" (carbon emissions per unit of GDP), as opposed to an absolute reduction in emissions.