The theme of the GHC, organised and hosted by UCL Medsin, was ‘The Bottom Line’ – one particularly relevant for HP’s recent work on fossil fuel divestment, given detractors’ concerns about the impact of taking action on their bottom line. Moreover, climate change itself poses the ultimate bottom line – the boundary of a planet no longer capable of supporting a healthy society.
Nationally and internationally, this boundary has been quantified in terms of the 2C surface warming goal – the bottom line to which all climate mitigation policy is supposed to add up. But the cultural currency of this simple proposition – that global mean surface temperature increase should be constrained to within 2C warming relative to pre-industrial times – belies the complexity of the underlying science, and the health threats posed by climate change. Three questions immediately suggest themselves. Firstly, why – of all temperatures – pick 2C? Secondly, what do we neglect by making this goal the focus on climate mitigation efforts? And lastly, what do we need to do to achieve it?
However, as that diagram also depicts, by the time of 2007’s 4th assessment report (AR4), things were looking more concerning; those global aggregate impacts looked to be quite costly at 2, and at such temperatures we would even be dicing with bypassing some of those major tipping points. Some of the world’s most prominent climate scientists warned that even then, the IPCC was being too optimistic. And by the time of the 5th report (AR5) in 2013-14, they were to some extent vindicated. Nonetheless, 2C became firmly embedded in climate discourse when it was one of the few successes to emerge from the COP15 climate negotiations in Copenhagen.
But, even if one were to find a perfect way of measuring climate change, would setting our targets in terms of climate change alone be adequate? For, as Christina Figueres (secretary of the UNFCCC) has said, climate change is not a disease; rather, it is a symptom, and only by looking at other associated symptoms can one come to an accurate diagnosis. A host of other planetary boundaries – biodiversity loss, ocean acidification, land use change to name a few – are affected by the same social, economic and political processes driving climate change. Many of these are in fact taken into account in international climate negotiations – but to look at surface temperature warming alone neglects some major associated threats to human and planetary health.