Global climate change experts will this week lay out a detailed plan to save the planet from the catastrophic effects of rising temperatures. Climate change could be stopped in its tracks using existing technology, but only if politicians do more to force businesses and individuals to take action.
The UN study will conclude that mankind has the knowhow to reduce global greenhouse gas emissions by as much as 26bn tonnes by 2030 - more than enough to limit the expected temperature rise across the planet to 2-3C.
Such a move would cost the world economy billions of pounds over the next two decades, but this could be recouped by savings due to the health benefits of lower levels of air pollution.
Cheaper solutions could bring down emissions to 1990 levels, but that would still see average temperatures rise by as much as 4C this century, with devastating consequences for wildlife, agriculture and the availability of water.
The report, from the Intergovernmental Panel on Climate Change (IPCC), will say a range of measures can be introduced across the energy supply, transport, buildings, agriculture and forestry, industry and waste sectors. The best way to limit future emissions is to focus on clean development in developing countries.
The report, the third this year from the IPCC, looks at ways to tackle global warming and is due to be released in Bangkok on Friday. The previous two reports analysed the science of climate change and its likely impacts. Together, the three reports will underpin international negotiations on a new treaty to regulate greenhouse gas emissions to replace the Kyoto protocol.
The summary of the new report, a draft of which has been obtained by the Guardian, says: "It is technically and economically feasible to stabilise greenhouse gas concentrations in the atmosphere ... provided that incentives are in place to further develop and implement a range of mitigation technologies."
It says global emissions need to peak "within the next two decades" and that the problem is now more serious and requires "more stringent mitigation" than when the IPCC last reported in 2001.
Rachel Warren, of the Cambridge University's Centre for Climate Change Mitigation Research who helped to write the report, said: "We have to reduce our emissions, and the technology to do that already exists or can be commercialised in the coming decades. We need governments, businesses and individuals to be pulling together in the same direction."
The final wording of Friday's report will be hammered out during the coming week by scientists and government officials, who must approve it before its release. Publication of the second IPCC report in Brussels earlier this month was delayed after all-night discussions that saw several scientists walk out in protest at what they viewed as political interference.
This week's talks could see similar scenes, particularly as it deals with the political hot potato of how world governments should act together to bring down emissions. The US has lobbied for research into futuristic technology such as giant sunlight-blocking mirrors in space as "insurance", an idea which the draft summary dismisses as "largely speculative, uncosted and with potential for unknown side effects".
The report says that taking "optimal" mitigation measures might by 2030 stabilise greenhouse-gas concentrations in the atmosphere at 445 to 534 parts per million, up from an estimated 430 ppm today.
It indicates that stabilising concentrations relatively quickly at 450 ppm - an unlikely scenario - could still limit the temperature rise to 2C above pre-industrial temperatures, which scientists say could avert severe damage. Achieving the 445-534 ppm range could cost up to 3% of global gross domestic product (GDP) over two decades, the draft says.
Geoffrey Levermore, an expert in housing emissions at Manchester University and another author on the report, said: "With current technology, new technology and new policies, we can do this, but we might not be as prosperous. If someone has to cycle more rather than using the car, perhaps they might not be so productive."
The report says that different technologies will be better suited to different regions, but that energy efficiency will play a key role for all. Greater use of renewable energy, nuclear power and biofuels will be needed to stabilise emissions, while protecting the world's forests could offer a more "cost-effective" solution.
And it calls for the wider use of technology to capture carbon dioxide spewed from power stations and store it underground, known as carbon capture and storage (CCS). The draft says: "A critical issue is how quickly new coal plants are going to be equipped with CCS, because retrofitting power plants with CCS later is economically unattractive." Energy companies in the developing world are building a handful of "capture ready" power stations, which can be adapted when the CCS technology is ready, but hundreds of plants being built throughout China and India are not so advanced and there will be no way to constrain their pollution.
Jim Watson, an energy policy researcher at Sussex University, said: "A lot of the plants that are being built and discussed in China are not up to the highest standards because they are being built by regional governments and utilities, and there isn't much coordination from the centre."
He added: "Generally it's hard to see a lot of concrete moves in the right direction. The technology menu is going to be broadly similar, and the question is are we any further towards getting it deployed?"
One of the most controversial findings of the report is likely to be its discussion of the various strategies international governments could take - the US has refused to adopt binding targets agreed under Kyoto and is resisting attempts to discuss a replacement, preferring voluntary agreements.
The draft report says such voluntary agreements are not effective, but it also raises questions about the success of Kyoto-style treaties based on targets and carbon trading. It says the best approach is to tie development to investment in clean technology.
Catherine Pearce, international climate campaigner with Friends of the Earth, said: "We hope that this report will push governments to take action, by demonstrating that the policies, measures and sustainable energy technologies are readily available. We have no time to lose, and no excuses for further inaction."
Sector by sector
Despite breakthroughs in cleaner options, such as hybrid cars, the sector is the fastest growing source of emissions, the report says. It highlights emerging technologies such as cars powered by hydrogen fuel cells and biofuels. Some campaigners warn that increasing use of biofuels could worsen problems such as food shortages, as farmers scramble to meet demand. The IPCC suggests this could be eased by a switch to biofuels made from waste cellulose. The report says government policies such as mandatory carbon dioxide emission standards are crucial, but that hikes in car tax, fuel duty and moves such as road pricing will be less effective as incomes rise. Better public transport can make a significant contribution.
Potential saving by 2030 (million tonnes carbon dioxide equivalent): 3,200
Industry offers the largest potential savings, although the report acknowledges: "Their implementation requires a stable policy environment that is respecting international competitiveness and includes measures for stimulating technology uptake." The IPCC suggests new controls on industrial pollutants such as methane, nitrous oxide and the chemicals HFCs and PFCs, all potent greenhouse gases. It also says there are big savings for firms who invest in more efficient use of fuels, materials and electricity, combined heat and power systems, and recycling. Heavily polluting industries could benefit from new process technologies that avoid carbon and are expected to come on-stream beyond 2015, it says.
Potential savings: 6,500
More efficient supply, renewable sources, shifts from coal to less polluting gas and nuclear power will play a role in the short to medium term, the IPCC report says. Managing such a transition requires "active policy involvement" such as reducing subsidies for fossil fuels while helping cleaner technology with renewable quotas for power companies and subsidies. The EU has pledged to generate 20% of all energy from renewable sources by 2020. The report says concern over energy security, combined with the development of power infrastructure in the developing world, creates an opportunity to reduce emissions cheaply.
Potential savings: 5,100
Agriculture and forestry
Soils, trees and vegetation provide an important carbon store, and the report says improved land and forestry management offer some of the easiest and cheapest emission savings. "Many options are immediately deployable, do not reduce productivity and have co-benefits," it says. More efficient fertiliser use and better care of crop and grazing land are good too. On forestry, some 65% of the potential carbon savings are in the tropics, and the report says a "combination of afforestation, avoided deforestation and agro-forestry" is the best approach. One major sticking point is whether developing nations such as Brazil and Costa Rica should be paid not to chop down their virgin rainforest.
Potential savings: 6,000
Low-cost measures to improve the energy efficiency of buildings could save greenhouse gas emissions and money, the report says. It recommends countries should follow the examples of Germany and Switzerland and force through policies to cut emissions from housing. Appliance standards, building codes, better labelling and procurement procedures for the private sector have worked to cut pollution. Geoffrey Levermore, buildings expert at Manchester University who helped write the report, said: "There's no blue sky technology to revolutionise this industry by giving us a little matchbox that will provide all the energy for your house, but if the right policies are implemented, there are some real savings to be made."
Potential savings: 4,400
The IPCC says post-consumer waste, such as plastic bags, generates less than 5% of global emissions, but that the rubbish sector can still help to tackle global warming. Recovering methane from landfill sites in the developing world generates more than 15% of carbon credits traded under the Kyoto protocol. Waste management is a key component of wider moves toward sustainable development, it says. Unlike some sectors, the technologies available to reduce emissions from waste are "mature and readily deployable". It adds: "Recycling and waste minimisation provide indirect greenhouse gas mitigation benefits via the conservation of raw materials, and energy from waste offsets fossil fuel consumption."
Potential saving: 1,250