A Matter of Degrees
Mike Robinson, RSGS Chief Executive
September 2013 saw the release of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report. The first volume of the report provided a comprehensive analysis of the latest research on the basic science of climate change, prepared by more than 250 scientific experts from a wide range of universities and research institutes in nearly 40 countries, who were commissioned by the world’s governments to review all of the available evidence, including thousands of scientific papers.
The experts’ assessment for the IPCC was subjected to one of the most rigorous audit processes in the history of science, with more than 50,000 comments made on draft versions that were made available to hundreds of reviewers around the world, including many of those who refute the science altogether. The process only allowed inclusion of data which had been separately corroborated by at least two peer-reviewed papers (which invariably means that by the time it is produced it is probably two or three years behind the curve). It was also subject to scrutiny by representatives of the world’s governments.
If anyone has ever tried to seek agreement for even a simple sentence through a committee, you will know how hard it can be to arrive at a clear outcome. Imagine a process as complex and involved as this, and it is a minor miracle that anything cohesive popped out at the end.
Perhaps not surprisingly given the number and extent of people involved, one copy was leaked by a sceptic earlier in 2013. In it, the IPCC indicated a total budget “for greenhouse gas emissions that should not be exceeded if the world is to have a reasonable chance of avoiding global warming of more than 2°C above pre-industrial temperatures”.
Avoiding a 2°C rise in global average temperatures is a good idea, in the same way that you would want to avoid a 2°C rise in your own body temperature. A 2°C rise would mean that temperature variations were more extreme. It would also increase the ‘energy’ in the atmosphere, meaning more precipitation, stronger airflows, and greater storm intensity, although locally some parts of the world could experience much greater increases whilst others remain less affected.
This idea of an overall ‘budget’ is quite logical. Different greenhouse gases remain in the atmosphere for up to 100 years or more, so it is the total cumulative emissions in the atmosphere which will determine whether we ultimately exceed the thresholds for 2°C, 3°C, 4°C or more. The higher the levels of CO2 and other greenhouse gases, the higher the likelihood of exceeding certain temperature levels. The 2009 Stern Report suggested that the probability of exceeding 2°C, if CO2 levels reached 450 parts per million, was 38% to 78%. (At 500 ppm it was between 61% and 96%). We are currently sitting at just over 400ppm, and increasing at 2-3ppm per year. For all but the last 250 years, humankind has only ever known atmospheric CO2 levels of between 180 and 280ppm.
At the UN climate change summit in Cancún, Mexico, in December 2010, the world’s governments agreed to try to limit global warming to less than 2°C. While most countries have made varying commitments and pledges to reduce emissions, none more so than Scotland, the current commitments are collectively inadequate and would still mean that the emissions budget for 2°C will be exceeded within the next 20 years or so. It is heartening that Scotland’s lead has influenced other nations, and many are beginning to bring forward legislation of their own – the Irish Dáil, for example, took evidence from Stewart Stevenson, the Environment Minister in the Scottish Government at the time of the Climate Change (Scotland) Act, in considering their legislation.
Efforts are now building to try to create a new international treaty, to be ratified at the 2015 climate change summit in Paris, to try to ensure that sufficient global emissions reductions are made and the upward trend in emissions is reversed sooner rather than later. The IPCC Fifth Assessment Report will help to inform this process. But the window of opportunity to minimise this risk is closing, and some commentators insist may have already shut. Should we resign ourselves to a 3°C or greater rise? Or should we be doing more to cut back.
Mike Robinson is a Trustee, a Board Member, and a former Chair of Stop Climate Chaos Scotland, and is a Member of Scotland’s 2020 Climate Group. He has chaired, spoken for, and advised a wide range of governmental and non-governmental forums and organisations on climate change and its impacts.
Mike Robinson is a Trustee, a Board Member, and a former Chair of Stop Climate Chaos Scotland and is a member of Scotland’s 2020 Climate Group. He has chaired, spoken for, and advised a wide range of governmental and non-governmental forums and organisations on climate change and its impacts
“Avoiding a 2°C rise in global average temperatures is a good idea, in the same way that you would want to avoid a 2°C rise in your own body temperature.”