Posted: 3 October 2013
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Global warming ‘unequivocal’ according to IPCC report
Global warming ‘unequivocal’ according to IPCC report

The Intergovernmental Panel on Climate Change has released its latest report on the science of climate change, describing global warming as ‘unequivocal’.

"It is perhaps the biggest and most rigorous process of peer review conducted in any scientific field."

‘The Physical Science Basis Report’ also confirms that there is a 95 per cent probability that most of the warming since 1950 has been caused by human influence.

The increase to ‘unequivocal’ from ‘very likely’ in the 2007 report is due to more and better observations, an improved understanding of the climate system response and improved climate models.

Following nearly seven years of research, the report draws on thousands of peer-reviewed scientific papers and is produced by 209 lead authors from 39 countries. Endorsed by all of the governments of the world, it is perhaps the biggest and most rigorous process of peer review conducted in any scientific field.

The report estimates that warming is likely to exceed 2oC by 2100, the threshold beyond which scientists think global warming will start to wreak serious changes to the planet, including sea level rises, heat waves and changes to rainfall, meaning dry regions get less and already wet areas receive more. Estimates of sea-level rise range from 26-82cm by the end of the century.

Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

Most aspects of climate change will persist for many centuries even if emissions of Co2 are stopped. The odds of many extreme climate and weather events have increased, and are expected to increase further in coming decades.

Arctic sea ice cover in the summer has reduced in area by about 40 per cent since 1979 and it is ‘very likely’ the ice cover will shrink during the 21st century as mean surface temperatures rise.


The report refutes claims that global warming has ‘stopped’ because global temperatures in the past 15 years have not continued the strong upward march of the preceding years. But the IPCC said the longer term trends were clear: “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 [the earliest date for reliable temperature records for the whole hemisphere].”

The Physical Science Basis Report is the first of four reports to be released with ‘Impacts Adaption and Vulnerability’, ‘Mitigation of Climate Change’ and ‘Synthesis Report’ to be released in 2014.

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IPCC website

The report in numbers

Peer-reviewed articles referenced 9,200
Lead authors 209
Level of confidence that climate change is human induced 95%
Surface temperature warming 1880-2012 0.85oC
Best estimate projected temperature increase by 2100 2oC
Projected temperature increase range by 2100 0.3oC to 4.8oC
Projected temperature increase by 2100 with business as usual 3.7oC
Sea level rise 1901-2010 19cm
Projected further sea level rise range by 2100 26-82cm
Projected further sea level increase by 2100 with business as usual 63cm
Pre-industrial age CO2e parts per million 270ppm
2013 CO2e parts per million 400ppm
IPCC scenario RCP 6.0 CO2e parts per million (mean warming of 2.2oC by 2100) 800ppm
Current annual increase in CO2e parts per million (Potentially doubling by 2050) 3ppm
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