Abstract
“I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind.”
Lord Kelvin 1883
The Copenhagen Accord reiterates the international community’s commitment to “hold the increase in global temperature below 2 degrees Celsius”. Similarly, the EU maintains it ‘must ensure global average temperature increases do not exceed 2°C’ and the UK’s 2009 Low Carbon Transition Plan, states that “to avoid the most dangerous impacts of climate change, average global temperatures must rise no more than 2°C”. Despite such unequivocal statements the accompanying policies or absence of policies demonstrate a pivotal disjuncture between high-level aspirations with regards to 2°C and the policy reality. In part this reflects the continued dominance of ‘end point’ targets rather than scientifically-credible emission budgets and pathways, but even within the UK, where the policy-community and legislation aligns more closely with the science of climate change, the disjuncture nevertheless remains.
In recent years increasing numbers of national and global emissions scenarios have been developed, each with differing carbon budgets and hence with different temperature impacts. Coordinating national with global analyses is evidently a prerequisite of understanding the scale and rate of mitigation and adaptation accompanying differing levels of climate change. However, as it stands, such coordination is rare with little more than perfunctory correlation between national emission pathways and the quantitative scale of the challenge at a global level. By disaggregating selected global emission pathways into Annex 1 and non-Annex 1 nations, this presentation outlines a much improved understanding of the extent of the mitigation challenge specifically and the adaptation challenge more generally.
This analysis offers a stark and unremitting assessment of climate change. There is now little to no chance of maintaining the global mean surface temperature at below 2°C, despite both repeated high-level statements to the contrary and the conclusions of more orthodox analysis (Committee on Climate Change, Stern, ADAM, AVOID, etc). Moreover, the impacts associated with 2°C have been revised upwards, sufficiently so that 2°C now more appropriately represents the threshold between ‘dangerous and extremely dangerous climate change’. Consequently and with tentative signs of global emissions returning to their earlier levels of growth, 2010 represents a political tipping point.
The science of climate change allied with the emission scenarios for Annex1 and non-Annex 1 nations outlined in this paper suggests a very different mitigation and adaption challenge from that we are collectively prepared to countenance. The implications of this are profound for policy. In terms of adaptation, the scale of change and timeframe within which such changes need to be implemented are much more demanding than previously thought. Current commitments to reduce emissions suggest a global temperature rise of 4°C by 2060-70 is increasingly likely; with the rise being greater at more northerly and southerly latitudes, and greater still for the land areas once the relative thermal ‘cooling’ of the oceans is accounted for. Turning to mitigation – two issues arise: firstly, urgent and radical reductions in emissions are essential if 4°C and higher rises are to be avoided; and secondly, widespread and accurate measurement of emissions of all greenhouse gases and aerosols are a prerequisite of achieving such reductions with minimum societal, ethical and economic disruption.
Focusing on the emissions and science with regards to climate change is an increasingly melancholy affair. However, whilst there is now little chance of avoiding significant climate change, harnessing precedents of human will and ingenuity continues to offer real opportunity to build low-carbon and climate-resilient communities. In guiding such a transition, Lord Kelvin’s assertion with regards to measurement has seldom been more appropriate.
Professor Kevin Anderson - Director of the Tyndall Centre for Climate Change Research
Joint appointment:
University of East Anglia (cross faculty Chair)
University of Manchester (School of Mechanical, Aerospace & Civil Engineering)
