London: Scientists are set to issue the starkest warning yet about the mounting dangers of global warming this week.
In a report to be handed to political leaders in Stockholm on Monday, they say that the burning of fossil fuels and deforestation have now led to a warming of the entire globe, including land surfaces, oceans and the atmosphere.
Extreme weather events, including heatwaves and storms, have increased in many regions while ice sheets are dwindling at an alarming rate.
In addition, sea levels are rising while the oceans are being acidified - a development that could see the planet`s coral reefs disappearing before the end of the century.
The fifth assessment report on the physical science of climate change by the Intergovernmental Panel on Climate Change (IPCC) warns that humanity is on course over the next few decades to raise global temperatures by more than 2C compared with pre-industrial levels.
Such a rise could trigger the release of plumes of the greenhouse gas methane from the thawing Arctic tundra, while the polar ice caps, which reflect solar radiation back into space, could disappear.
According to the new report, humanity has emitted about half a trillion tonnes of carbon by burning fossil fuels over the past 250 years, a process that has caused atmospheric carbon dioxide levels to rise by 40 percent.
The world is now on target to release another half trillion tonnes in the next few decades which could trigger a major jump in global temperatures, the report said.