Carbon Dioxide emissions must be reduced by almost half by 2030 or global temperatures will eventually rise by between 2C and 5C, the Intergovernmental Panel on Climate Change will warn today.
In its fifth report on climate change, the IPCC is also expected to say humans must pump no more than a further one trillion tonnes of CO2 into the atmosphere if temperature change is to be kept below 2C.
The body will say it will be clear within six years if the threat of “dangerous” climate change has been averted.
According to Professor Dame Julia Slingo, chief scientist at the Met Office, the report will warn of “extremely serious impacts for both people and ecosystems” if temperatures increase by more than 2C.
“This is not a problem for later in the century; it is a problem for us now,” said Slingo. The report is likely to reignite the fierce debate with those who believe climate change has been exaggerated or is fictitious. […]
The report will say that, to have a 66% chance of preventing temperatures increasing on average by more than 2C, no more than 2,900bn tonnes of carbon dioxide — above pre-industrial levels — should have been released into the atmosphere.
It calculates that 1,900bn tonnes had been released by 2011. At the current annual emission rates of about 36bn tonnes, the remaining 1,000bn tonnes “carbon cap” will be reached by about 2039.
Climatologists say the cap is important because carbon dioxide remains in the atmosphere for hundreds of years, meaning the total accumulated over time is more important than annual levels…
However, Benny Peiser, director of the climate-sceptic Global Warming Policy Foundation, said the impact of CO2 levels on the atmosphere remained “open to question”.
He added that, “mainly for economic reasons”, it was very unlikely big emitters such as India and China would be able to cap their emissions.
He said: “There is a big scientific debate about the lack of global warming over the last 15 years. The question of what happens if we double the level of CO2, will it cause little more warming or much more warming, that remains an open question.”