What the graphic shows
The graphic above (courtesy of the Global Commons Institute) plots the carbon budgets associated with specific temperature rises, according to the Intergovernmental Panel on Climate Change (IPCC):
50% odds of limiting warming to <1.5C
66% odds <2C
50% odds <2C
50% odds <3C.
Since the budgets are plotted to scale, the graph provides an immediate sense of their relative size and trajectory.
The UN Environment Programme's Emissions Gap Report 2016 estimates that aggregate INDCs leave the world on track for warming of upwards of 3C.
The graphic helps contextualise that assessment. It reveals that meeting the 1.5C target requires immediate decarbonisation to zero by 2030. It reveals that a pathways towards warming in excess of 3C is heading in more or less the opposite direction to that needed to meet the Paris Agreement temperature goal.
3C is the point at which feedback effects threaten runaway climate change and complete loss of control.
UNFCCC Synthesis Report
The UNFCCC has itself published a reportinto the aggregate effect of INDCs which reaches a slightly more optimistic, but broadly consistent conclusion. It states at paragraph 53:
while actions enshrined in the INDCs will deliver sizeable emission reductions compared with the pre-2020 period, global aggregate emission levels in 2025 and 2030 resulting from the INDCs do not fall within 2 °C scenarios.
At paragraph 42 it refers to the impact of INDCs on the available carbon budget:
According to the AR5, the total global cumulative emissions since 2011 that are consistent with a global average temperature rise of less than 2 °C above pre-industrial levels at a likely (>66 per cent) probability is 1,000 Gt CO2. Considering the aggregate effect of the INDCs, global cumulative CO2 emissions are expected to equal 54 (52–56) per cent by 2025 and 75 (72–77) per cent by 2030 of that 1,000 Gt CO2.
Think of that as an empty bath we start running in 2011, which mustn't be allowed to overflow. According to this conclusion of the UNFCCC, by 2025 the bath will be just over half full; by 2030 it will be three quarters full. Even if global emissions stabilise post 2030 (and there is no evidence that they will) the bath will be overflowing by 2035 (with the tap still running for decades to come).
In the press release accompanying publication of the report, Christiana Figueres, Executive Secretary to the UNFCCC, optimistically declared that 'The INDCs have the capability of limiting the forecast temperature rise to around 2.7 degrees Celsius by 2100 ...'. It's notable however that the figure of 2.7 degrees was not in fact backed up in the report itself, which states at para. 39:
However, temperature levels by the end of the century strongly depend on assumptions on socioeconomic drivers, technology development and action undertaken by Parties beyond the time frames stated in their INDCs (e.g. beyond 2025 and 2030). Making such assumptions is beyond the scope of this report.
In summary, it appears the best we can realistically hope for on the basis of INDCs is global warming of something close to 3 degrees Celsius.
29 June 2016, Washington Post
'It is an established fact that with the current emission reduction policy of 20% at most in an EU context (about 17% in the Netherlands) for the year 2020, the State does not meet the standard which according to the latest scientific knowledge and in the international climate policy is required for Annex I countries to meet the 2°C target.'
Urgenda Foundation v Government of the Netherlands
“PRESIDENT TRUMP MAY HAVE HIS ALTERNATIVE FACTS,
BUT ALTERNATIVE FACTS DO NOT WORK IN A COURTROOM”
The terms 'action / goal deficit' or 'emissions gap', and the graphs and statistics used to illustrate it, may appear technical. It is important to emphasise that, in practice, the 'gap' between 1.5 and 3 degrees warming is the difference between:
The Action / Goal Deficit
'Emphasizing with serious concern the urgent need to address the significant gap between the aggregate effect of Parties’ mitigation pledges in terms of global annual emissions of greenhouse gases by 2020 and aggregate emission pathways consistent with holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above pre-industrial levels ...'
Preamble to the COP21 Paris Decision, December 2015
LEGAL ACTION FOR THE CLIMATE GOAL: TOWARDS EQUITY, SURVIVAL AND THE RULE OF LAW
8 November 2016: Climate Summit's Urgent Goal: Cut More Emissions, Faster