Effect of current pledges and policies on global temperature

 

Data underlying the above graph can be downloaded here

High resolution image of the above graph can be viewed by clicking here. 

 

Addressing global warming

In the absence of policies global warming is expected, to reach 4.1 °C – 4.8 °C above pre-industrial by the end of the century. The emissions that drive this warming are often called Baseline scenarios (‘Baselines’ in the above figure) and are taken from the IPCC AR5 Working Group III. Current policies presently in place around the world are projected to reduce baseline emissions and result in about 3.4°C [1] warming above pre-industrial levels. The unconditional pledges or promises that governments have made, including NDCs [2] as of November 2017, would limit warming to about 3.16°C [3] above pre-industrial levels, or in probabilistic terms, likely limit warming below 3.5°C.

There remains a substantial gap between what governments have promised to do and the total level of actions they have undertaken to date. Furthermore, both the current policy and pledge trajectories lie well above emissions pathways consistent with the Paris Agreement long-term temperature goal. 

Evaluating progress towards the Paris Agreement long-term temperature goal

We base our assessment on the emissions scenarios currently available in the scientific literature, mindful of the assumptions and limitations underlying these studies. The scenarios limit warming below 1.5°C by 2100 with ≥50% probability, and below 2°C in the 21st century with about an 80% probability. We use these scenarios as indicative of the Paris Agreement’s long-term temperature goal, but note these scenarios should not be seen as a definitive interpretation of the Paris Agreement.

A new and more diverse set of scenarios that limit warming to 1.5°C or below are now being developed by the scientific community and will become available in the open literature. The CAT will update its Paris Agreement benchmark scenarios in 2018 to reflect the most recent available scientific literature (more details at CAT Rating System Update).

Limiting warming 1.5°C above pre-industrial by 2100 means that the emissions of greenhouse gases need to be reduced rapidly in the coming years and decades, and brought to zero around mid- century.

The CAT evaluates progress towards this global goal by quantifying the aggregate effects of current policies and the pledges (promises) and NDCs put forward by countries, and compares these with the emissions levels consistent over time with the 1.5°C. The CAT also presents results in relation to a pathway consistent with limiting warming to 2°C with likely (≥66%) probability, for comparative purposes.

The CAT Thermometer explained

The temperatures on the CAT thermometer are ‘median’ warming estimates in 2100. It means that there is a 50% chance that the calculated temperature would be exceeded if the given emissions pathway were followed.

For example, our emissions pathway in the pledge scenario (that incorporates NDCs until 01 November 2017) gives a 50% chance of warming being 3.16°C or higher in 2100. 

Using probabilities to provide more information

The ‘median’ is based on the probability distribution generated by the climate model (MAGICC) when it takes into account uncertainties in our knowledge of climate sensitivity, the carbon cycle, and effect of greenhouse gases, aerosols, and other factors that are used to calculate the temperatures. The probability distribution enables us to provide more information for policy makers and stakeholders about the likelihood of goals being met, or specific temperatures being exceeded. 

November 2017 NDCs likely below 3.5°C and over 90% chance exceeding 2°C

The emissions pledge pathway that includes (I)NDCs has over 90% probability of exceeding 2°C. The current policy pathways have a higher than 97% probability of exceeding 2°C. 

What governments need to do to achieve the global goal

Fortunately, as shown by the IPCC AR5, substantially more action, sufficient to hold warming below 2°C (and to below 1.5°C by 2100) with likely probability is technically and economically feasible. According to the IPCC, the costs of reducing emissions to limit warming to below 2°C are modest, even before taking into account co-benefits such as increased energy-security and health improvements due to reduced air pollution. Annualised reductions of consumption growth are estimated at around 0.06 per cent over the century, relative to a baseline of 1.6 to 3% growth per year.[2]

The IPCC AR5 shows that even starting from emission levels implied by INDCs and current policy projections, 1.5°C and 2°C pathways are still technically feasible. However, the resulting emission pathways are increasingly expensive as they are not consistent with the most cost-efficient policies. Slower-than-optimal emission reductions early on need to be followed by faster reductions later on, effectively leading to significantly higher costs for the period 2030–2050 than would otherwise be needed.  While the challenges are significant, limiting warming to below 1.5°C by the end of the century is still feasible from current emissions levels. However, with every decade lost, these challenges and costs rise and will, at some point, become insurmountable with warming locked in to 1.5 or 2°C and above.[4]

Further information

For more information on the global emission pathways and how they are calculated, please see the detailed analysis and methodology pages.

If you use the provided data or any of the graphs provided on this website, please make sure to reference the Climate Action Tracker and the Ecofys / Climate Analytics / New Climate team!

Last temperature update: 1 November 2016. 'Pledges' include all NDCs submitted by November 1st 2016.

[1] 3.4 is the median of the low and high ends of current policy projections (3.1 to 3.7°C). The uncertainty range on the figure (2.5-4.7°C) originates from carbon-cycle and climate modelling around both the low and high current policy projections. Here we give the 68% range; that is the 16th and 84th percentiles of the probability distribution.

[2] In the term NDC we also include, throughout this briefing, the “Intended” Nationally Determined Contributions of governments who have not yet ratified the Paris Agreement. We project the global effects beyond the NDC timeframes assuming policies of similar strength are implemented through to the end of the century.

[3] The uncertainty range for pledges on the CAT thermometer (2.6-4.0°C) originates from carbon-cycle and climate modelling around both the low and high current policy projections. Here we give the 68% range; that is the 16th and 84th percentiles of the probability distribution. If the more ambitious end of pledge ranges were reached, warming could be limited to a median of 2.6°C.  This includes the upper end of country INDCs where a reduction range is specified and mitigation commitments that are conditional on finance.

 [4] Refer to CAT Briefing "The CAT Emissions Gap - How close are INDCs to 1.5 and 2 pathways?", September 2015.