As COP21 has progressed it is clear that one of the most contentious issues to be resolved is associated with setting an agreed global temperature limit to which all nations must limit emissions to remain below. The current target for policy makers is to focus efforts on keeping global temperatures below 2°C of warming, although some nations argue that to avoid the worst extremes of climate change a 1.5°C limit is required. But is measuring temperature the most appropriate means of assessing anthropogenic climate change? The history of the 2°C limit stretches back to the 1970s and could be considered an arbitrary figure. It was first introduced by an economist, William Nordhaus, who warned that such a rise would “take the climate outside of the range of observations which have been made over the last several hundred thousand years”. Further work in the 1990s by the Swedish Environment Institute (SEI) suggested that “temperature increases beyond 1.0°C may elicit rapid, unpredictable and non-linear responses that could lead to extensive ecosystem damage”.
But the SEI also suggested a number of other indicators to measure climate change including sea level rise and the concentration of carbon in the atmosphere. Last week Dr James Hansen, a NASA climatologist, suggested that assessing the concentration of carbon dioxide in terms of parts per million (ppm) was a more appropriate means of measurement. NASA and the NOAA have both reported that global average CO2 concentrations are now above 400ppm (350ppm is thought to be the safe limit). This represents a 24% increase since records began in 1958 and the highest concentrations of carbon in the atmosphere for more than a million years, a time when sea levels were significantly higher and modern humans hadn’t even evolved. Yet research by the University of East Anglia recently reported that global carbon emissions are projected to stall for the second year in a row. The fact of the matter is that regardless of whether emissions have stalled, the most we can hope for is a stabilisation of CO2 concentrations; a reduction would take far longer and would rely on a reduction of global emissions.
If this leaves you slightly confused then you’re not alone. Like others, I have struggled to get to grips with the vast amounts of data, the arguments and counter-arguments, what is evidence-based and what is opinion-based. I think the ‘general public’ can be forgiven for being blinded by science. We only have to look at the mixed messages from food-related research: food which was once bad for us is now considered good, or vice versa; and herein lies the problem. Scientists have an inherent responsibility to ensure that any published work is credible and avoids sensationalism. Recently, Berkeley Earth produced a study stating that spending a day outdoors in Beijing was equivalent to smoking 40 cigarettes a day, but in fact the peer-reviewed study made no mention of this. Whilst air pollution in the city far exceeds World Health Organisation (WHO) limits, the only reference to this statistic was in a press release, which they later admitted was based on rough estimations completed on the flight to Beijing; in fact 40 cigarettes a day would be far worse for your health. The problem is that sensationalist and at times alarmist findings will receive far more media attention than solid research that may not quite have the same wow factor.
So perhaps a pinch of salt is required when making up our own minds on research findings. It is inevitable that nations, organisations and lobby groups will utilise the scientific data that best serves their agenda and supports their own arguments. But ultimately we can have great confidence that the estimates of observed global and regional warming in the IPCC 4AR produced using a wide range of scientific research show that observed warming far outstrips any uncertainties in datasets. There is no doubt that an evidence-based system is necessary to ensure each nation’s success in reducing emissions can be measured, but perhaps ministers need to focus less on negotiating what that limit should be and concentrate more on what needs to be done to reduce our carbon emissions. Regardless of whether it is a 1.5°C or 2.0°C limit to warming, the reality is it is the mechanisms to achieve a reduction that should receive the greater focus and priority; prevarication and argument will only serve to increase the challenge at hand.
Authored by Martin Broderick and Luke Strickland