What’s Half a Degree Between Friends?

After 21 years of negotiations and a targeted five year work program culminating in a two week conference, of which one week has already passed, you might have thought the overall objective of the process would be settled.  Well, it isn’t.

The UN climate change negotiations take place under a ‘framework convention’ which has the stated objective of “prevent(ing) dangerous anthropogenic interference with the climate system”. What does that even mean? Who decides what is ‘dangerous’?

At this point in the process there are two target limits being discussed: 1.5°C or 2°C above pre-industrial averages. The 2°C target has dominated discussions in recent years. It was used in publicity slogans by the hosts of the UN climate change conferences in Doha and Warsaw, and it graces the walls of the German pavilion in Paris. However this target remains unacceptable to more than half of the world’s countries.

On Monday, leaders of 106 states along with the Executive Secretary of the conferences, Christiana Figueres, signed a statement calling for the target to become 1.5°C. So what difference does half a degree really make? Quite a lot it turns out.

Moving the aim 1.5°C to 2°C substantially increases the risk of reaching major environmental and ecosystem tipping points. Climate related damages are also highly non-linear, meaning that as temperatures rise, damages grow increasingly rapidly. Levees provide a simple of example of why this occurs. Floods of a certain magnitude are contained, but a flood just 5 per cent above the capacity of the levee channel can cause massive damages.

New research by Climate Analytics presented at a side event in Paris suggests increasing global temperature from 1.5°C to 2°C could amplify annual damages from 0.8 per cent to 2.7 per cent of global GDP. In other words, an extra half degree of warming could more than treble damages.

To put these figures into context, the US financial system bailout cost approximately 1 per cent of global GDP. In narrow monetised economic terms, the difference between 1.5 and 2 degrees could be like dealing with one global financial crisis sized bailout per year compared to three.

A recent IPCC report found limiting warming to below 2°C could cost about 0.06 per cent of global GDP per annum – more than an order of magnitude cheaper than the impacts this temperature increase would inflict.

The lead author of the UNEP’s Adaptation Gap Report, Florent Baarsch, warned that these figures are likely to be large underestimates because they ignore non-monetised impacts. No attempts were made to include the impacts of loss of life, territory or culture. If low-lying states like Kiribati or Tuvalu were to be lost to rising seas, the only costs included in most of these assessments would be the loss of productive land, homes and infrastructure – clearly an underestimate of the actual loss incurred.

In essence, small increases in temperature massively increase impacts on the world’s climate – probably to a greater extent than we understand at present. For low lying island states – moving from 1.5°C to 2°C may be the difference between persisting at the end of the century and being functionally destroyed. For climate vulnerable states it could mean the difference between development and poverty.

Unfortunately, the reason 2°C has dominated discussion so far is that it is seen as being more realistic than the 1.5°C target. Conservative estimates suggest that if all the emissions reductions targets submitted before Paris were fully realised, we would be on track for  a 2.5-2.7°C world by the end of the century. If these emissions reductions targets are locked in until 2030, it is likely to become effectively impossible to hold warming below 2°C.

Our targets are being defined not on what would provide the best outcome for everyone – not even on what would cost us the least. They are being decided by our political inability to address the problem of climate change. And though some will lose more than others, the insufficient 2°C target will cost every person in every country unnecessarily over the coming decades unless it is revised downwards in Paris.