Emissions are rising by record amounts, and time is running out to avoid catastrophic warming. What is going wrong and how can the problems be solved?
Politics and economics
Getting 194 nations to agree on anything, let alone a re-tooling of the global energy system that drives economies, is fiendish. Yet without an international deal that sets targets for all, no one nation can be certain that others will pull their weight. Outstanding leadership is needed from the big players such as the US and China when talks resume on 28 November.
But with rich nations transfixed by the economic crisis, there's little appetite to really tackle the climate crisis. That is despite the certainty that dealing with global warming after 2020 will cost far more than acting now. Those promoting a "green new deal", investing in clean energy as a way of driving growth and jobs, are not winning the argument in enough places.
Low-carbon energy
Energy not used at all – "negawatts" – will be the most important way of cutting greenhouse gas emissions. But, after decades of dirt-cheap fuels, energy efficiency remains unloved: 10m homes in the UK have unlagged lofts, for example. Smart carrots and sticks are needed to nudge everyone into spending less on energy. Nuclear and hydroelectric power are established, low-carbon technologies, but safety and cost uncertainties hamper the former, while geography limits the latter.
Renewable energy is all but unlimited, but the technologies appear more costly than polluting alternatives, and subsidies are required. However, the fossil fuel industry received $409bn in handouts in 2010, compared with $66bn for clean energy. Reversing that imbalance, as the G20 aims to do, is vital.
Renewables, especially solar power, are also the best and cheapest way to bring electricity to the 1.3 billion people who are without power.
Fossil fuels
Oil is the biggest single energy source and replacements for the energy-dense, easily transported fuel are hard to find. Only more fuel-efficient vehicles, better public transport, and electric cars will get us off the oil hook. Coal is the next biggest and, while more efficient power stations can make a big difference, only capturing and burying the carbon dioxide pumped out will clean up coal. Carbon capture and storage technology (CCS) is still only experimental, but without it the IEA says "an extraordinary burden" will rest on other low-carbon energy sources. Gas is the third of the fossil fuel big three, and the only one predicted to rise in use by 2035. Shale gas, extracted from rock by the controversial process of fracking, will make up a fifth of supplies by that date. But carbon capture must also be applied to gas power plants.