Leaked climate change report: Scientific body warns of 'devastating rise of 4-5C if we carry on as we are'

The Independent on Sunday has seen a draft of the latest IPCC report, which says the world is not doing enough to combat problem. But, with sufficient political will, all is not lost

Without further action, temperatures will increase from about four to five per cent compared with pre-industrial levels

Global greenhouse gas emissions over the past decade were the "highest in human history", according to the world's leading scientific body for the assessment of climate change. Without further action, temperatures will increase by about 4 to 5C, compared with pre-industrial levels, it warns, a level that could reap devastating effects on the planet.

The stark findings are to be revealed in the latest report by the Intergovernmental Panel on Climate Change (IPCC) today, the last in a trilogy written by hundreds of scientists on what is considered the definitive take on climate change.

The experts were working on the report until the early hours of yesterday morning. Although the thrust of the report is dramatic, it does say that it is not too late to limit global warming to less than 2C, which experts regard as the minimum needed to avoid radical global shifts. But its suggested scenarios would mean slashing global emissions by 40 to 70 per cent by 2050 from 2010 levels.

This would include "fundamental changes in energy systems and potentially the land", the draft found, such as a move towards renewable energy, nuclear power and fossil energy whose carbon emissions are captured or stored.

"These reports make it crystal clear what is at stake, and no government can justifiably say the case hasn't been made for strong and urgent action," said Bob Ward, the policy director for the Grantham Research Institute on Climate Change and the Environment at the London School of Economics and Political Science. "It's affordable and, frankly, the benefits are not even just in terms of climate risks. Shutting down coal-fired power stations in China, for example, will improve local air quality. The only thing standing in our way now is political will. The evidence is conclusive: the current pledges made by governments will be insufficient to get us to our targets."

It was in 2010 that hundreds of governments agreed to reduce emissions so as not to breach the 2C warming mark – the point at which it is thought the risk to food and water supplies would be high, as well as a risk of irreversible changes, such as a meltdown of Greenland's ice sheet.

At this level, we could lose 20 to 30 per cent of our wildlife, as well as face more extreme weather, according to Mike Childs, head of science, policy and research at Friends of the Earth. At 4C of warming, there could be a "devastating" impact on agriculture, wildlife and human civilisation, he added.

But despite global attempts to mitigate climate change picking up in recent years, greenhouse gas emissions grew more rapidly between 2000 and 2010 than in each of the previous three decades, according to the final draft of the IPCC report seen by The Independent on Sunday. The main contributors were a "growing energy demand and an increase of the share of coal in the global fuel mix", the draft found.

It estimated that if mitigation efforts are delayed until 2030, it would "substantially increase the difficulty of the transition to low longer-term emission levels".

Almost 80 per cent of the emissions growth between 1970 and 2010 was caused by fossil fuel combustion and industrial processes, according to the report. To reach the 2C target, the experts warned that the global energy supply must dramatically change, with at least a tripling of the use of "zero and low-carbon" energy, such as renewables, nuclear and fossil energy. It added that a growing number of renewable technologies had achieved a level of "technical and economic maturity to enable deployment at significant scale".

The report found that emissions could be "reduced significantly" by replacing coal-fired power plants with more efficient alternatives. It added that the decarbonisation of the electricity system would be a "key component" of cost-effective strategies – but the Government voted down a plan to do this by 2030.

Caroline Flint, the Shadow Secretary of State for Energy and Climate Change, said that the report "provides overwhelming and compelling scientific evidence that climate change will have a devastating impact if urgent action is not taken to reduce our carbon emissions and invest in mitigation". She added: "It highlights the need for a global, legally binding treaty to cut carbon emissions at the Paris conference in 2015. But to have influence abroad we must show leadership at home. That's why the next Labour government will set a decarbonisation target for the power sector for 2030, unshackle the Green Investment Bank and reverse the decline in investment in clean energy we have seen under David Cameron."

Kaisa Kosonen, senior political adviser at Greenpeace International, said the report should encourage a move from "a decade of coal to the century of renewables". She added: "The solutions are clear. Our energy system needs to undergo a fundamental transformation from fossil fuels to renewable and smart energy. In recent years, the transition has already started, but it must scale up and speed up. Dirty energy industries are sure to put up a fight, but it's only a question of time before public pressure and economics dictate that they either change or go out of business."

The report also concludes that the next decade could be a "window of opportunity" for mitigating global warming in cities, through locating residential areas in spaces of high employment, achieving diversity of land uses, increasing accessibility and investing in public transport.

Where there's a will...

The world can reach its global warming targets if it reduces its emissions by 40 to 70 per cent. It is about transforming our energy supply and the way we use our land. After The Independent on Sunday viewed a final draft of the findings, we asked some climate change experts what we can do now to mitigate against global warming, before it is too late.

Mark Lynas, author and environmentalist, said: "It is important to remember that every measure of climate-change reduction is still worth it. This report is a like a climate-change version of a suspended sentence. The 5C rise would be catastrophic, but we still have time to avoid the permanent rise in sea levels, for example, and we could avoid losing large agricultural zones. The important thing for people to understand is that it doesn't mean going back to living in caves; we can make many of these changes without making enormous changes to our lifestyles."

Darren Johnson, the chair of the London Assembly, who has been working in the field for a quarter of a century, is less hopeful. "I'm desperately worried about the timescale we have to turn things around," he said. "I'm appalled by the lack of will of previous governments and the coalition." But he still believes there is a chance to reduce emissions and prevent the "worst-case scenario". He added: "We need politicians to grasp this. We need a massive switch to renewables, a big investment in wind and solar power, and to reduce energy and reduce vehicles. This has to be made an absolute priority."

As for Sian Berry, Green Party member and part of the Campaign for Better Transport, she thought it was more about behavioural change. "People can stand up against the construction of large supermarkets, and out-of-town developments that would require people to drive more. They can vote for people who are going to improve public transport. They should be planning their lives around driving less."

Joe Kavanagh and Sarah Kavacs