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IPCC: 30 years to climate calamity if we carry on blowing the carbon budget

 
Icerbergs in Greenland

Calved icebergs in Qaqortoq, Greenland. The IPCC report says the world is on the way to dangerous levels of global warming. Photograph: Joe Raedle/Getty Images

 

Powered by Guardian.co.ukThis article titled “IPCC: 30 years to climate calamity if we carry on blowing the carbon budget” was written by Fiona Harvey in Stockholm, for The Guardian on Friday 27th September 2013 18.36 UTC

The world’s leading climate scientists have set out in detail for the first time how much more carbon dioxide humans can pour into the atmosphere without triggering dangerous levels of climate change – and concluded that more than half of that global allowance has been used up.

If people continue to emit greenhouse gases at current rates, the accumulation of carbon in the atmosphere could mean that within as little as two to three decades the world will face nearly inevitable warming of more than 2C, resulting in rising sea levels, heatwaves, droughts and more extreme weather.

This calculation of the world’s “carbon budget” was one of the most striking findings of the Intergovernmental Panel on Climate Change (IPCC), the expert panel of global scientists who on Friday produced the most comprehensive assessment yet of our knowledge of climate change at the end of their four-day meeting in Stockholm.

The 2,000-plus page report, written by 209 lead authors, also found it was “unequivocal” that global warming was happening as a result of human actions, and that without “substantial and sustained” reductions in greenhouse gas emissions we will breach the symbolic threshold of 2C of warming, which governments around the world have pledged not to do.

Ban Ki-moon, the UN secretary-general, urged world leaders to pay heed to the “world’s authority on climate change” and forge a new global deal on cutting emissions. “The heat is on. Now we must act,” he said.

John Kerry, the US secretary of state, said in a statement: “This is yet another wakeup call: those who deny the science or choose excuses over action are playing with fire.”

Climate Change Graphic

Credit: Guardian graphics

“Once again, the science grows clearer, the case grows more compelling, and the costs of inaction grow beyond anything that anyone with conscience or commonsense should be willing to even contemplate,” he added.

The IPCC also rebuffed the argument made by climate sceptics that a “pause” for the last 10-15 years in the upward climb of global temperatures was evidence of flaws in their computer models. In the summary for policymakers, published on Friday morning after days of deliberations in the Swedish capital, the scientists said: “Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the northern hemisphere, 1983-2012 was likely the warmest 30-year period of the last 1,400 years.”

Thomas Stocker, co-chair of the report working group, said measuring recent years in comparison to 1998, an exceptionally hot year, was misleading and that temperature trends could only be observed over longer periods, of about 30 years.

Natural variability was cited as one of the reasons for warming being less pronounced in the last 15 years, and the role of the oceans in absorbing heat, which is still poorly understood.

“There are not sufficient observations of the uptake of heat, particularly into the deep ocean, that will be one of the possible mechanisms that would explain this warming hiatus,” said Stocker.

 

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