Massive cuts to global greenhouse gas emissions needed in the next few decades to avoid "dangerous" climate change, a major international report has warned.
It is still possible to keep global temperature rises to no more than 2C above pre-industrial levels by the end of the century, the level at which it is thought dangerous impacts of climate change will be felt.
But substantial reductions in greenhouse gases will be needed, through large-scale changes to energy supplies and use, as well as curbing deforestation and planting forests.
Emissions need to be reduced by 40% to 70% on 2010 levels by the middle of the century and to near zero by 2100, to make it likely temperatures will not go above 2C, the report said.
Environmental campaigners have reacted to leaked drafts of the latest UN report into climate change, saying they showed "catastrophic" climate change could only be avoided by reducing dependency on fossil fuels.
Friends of the Earth's executive director Andy Atkins said we are already on track for four degrees warming "which will be impossible for human society to adapt to".
We have the technology to prevent dangerous climate change. What we lack is the political will of our leaders to strongly champion renewable power and energy efficiency.
Tim Ratcliffe from campaign group 350.org said that 80% of fossil fuels need to stay underground in order to avoid a climate catastrophe.
Campaigners have demanded the world moves away from using fossil fuels, ahead of a major international report by the UN's Intergovernmental Panel on Climate Change.
The latest report will set out ways to curb rising temperatures by tackling greenhouse gas emissions.
The third of a trilogy, the study comes just two weeks after the second part of the report warned that the effects of rising temperatures were already being felt across the world.
It said that without action climate change would increasingly threaten security, health and food supplies, exacerbate poverty and damage species and habitats.
Responding to the IPCC's influential report on the impact of climate change, Foreign Secretary William Hague said that "Governments everywhere have to act."
It is clear from the IPCC's report that a two-degree increase in the world's temperature would be dangerous, and four degrees would be catastrophic.
But that is the likely trajectory, unless there is unprecedented global co-operation to bring down emissions.
No country would be left unaffected. Governments everywhere have to act.
The world "needs to act fast" if it is to prevent a future dominated by climate catastrophe, the Energy Secretary has warned.
Speaking to Daybreak, Ed Davey defended the Government's record on tackling climate change but said he thought "the world had acted too slowly" on measures designed to combat greenhouse gases.
The chances of 'severe, pervasive and irreversible impacts' from global warming are increasing say experts in an influential new UN report.Read the full story ›
A clean industrial revolution is needed to cut greenhouse gases and spur economic growth, it has been urged in the wake of the publication of a major report on the impacts of climate change.
Mark Kenber, chief executive of the Climate Group, which works with governments, business and organisations to drive action on climate change, said:
"The IPCC report needs to act as a wake-up call. The 'head in the sand' approach is a ticket to failure. Businesses that refuse to adapt are sealing their own fate and putting communities and investors at risk. They're also wantonly squandering the massive opportunities in low carbon growth.
"The only road that leads to both a reduction in carbon emissions and economic growth is one built on a clean industrial revolution.
"Most of the energy and technology solutions needed already exist, but need rapid scaling up today not tomorrow."
Experts have warned that in many cases, people are ill prepared to cope with the risks of a changing climate.
The Intergovernmental Panel on Climate Change report says the world has seen changes in recent decades to water resources as a result of melting glaciers and differences in rainfall, and reductions in wheat and maize yields.
There has been a decrease in the number of people dying from the cold but an increase in heat-related deaths in some areas, such as England and Wales, the report suggested.
Species including fish stocks are shifting their ranges, coral reefs are being damaged and wildfires are becoming more frequent.
The report on the impacts of climate change said rising temperatures are expected to lead to increased risk of flooding, more droughts and heatwaves, drive species extinct and cause forests to die in many regions of the world.
Climate change is already having an impact across the world in areas ranging from human health to agriculture and wildlife, a major international report has found.
Rising temperatures will increasingly threaten security, health and food supplies, and exacerbate poverty and damage species and habitats, the report from the Intergovernmental Panel on Climate Change (IPCC) warned.
The world is in "an era of man-made climate change" and has already seen impacts of global warming on every continent and across the oceans.