Article 2 of the United Nations Framework on Climate Change requires its 195 parties, all member states of the United Nations, to achieve “stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” As scientists are making clear, this cannot occur without phasing out anthropogenic emissions of greenhouse gases.

In the 2015 Paris Agreement, UNFCCC parties committed to limiting global temperature rise to a maximum of well below 2ºC/1.5ºC above pre-industrial levels.

Staying well below the 2ºC limit and “keeping pathways to 1.5ºC open” means ensuring that global emissions peak by 2020 then decline to net zero around mid century. Although the IPCC has modelled 1.5ºC trajectories, the majority of scientists focus has been on modelling pathways to avoid 2ºC maximum temperature rise. The Paris Agreement aims to address this by creating the mandate for the IPCC to assess more pathways on how to avoid maximum 1.5ºC temperature rise:

COP Decision Para 21 “Invites the Intergovernmental Panel on Climate Change to provide a special report in 2018 on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways; Parties will play different roles in achieving the universal long-term goal, but they are united in their collective direction of travel and in their support for the regime that the Paris Agreement has set up.”

In November 2015 Climate Analytics produced an overview of what emissions reductions pathways would ensure maximum temperature rise of 1.5ºC. They concluded that to return warming below 1.5 °C by 2100 with a more than 50% chance:

  • Global greenhouse gas emissions by 2050 must be 70-95% (65-90%) below 2010 (1990) levels
  • Global greenhouse gas emissions must reach zero by 2060-2080
  • Global energy and industry CO2 emissions must be 95-120% (95-125%) below 2010 (1990) levels by 2050
  • Global energy and industry CO2 emissions must reach zero around 2050 (range 2045-2055)

(The 1.5°C scenarios underlying the pathways above have a more than 50% chance of returning to below 1.5°C by 2100 and simultaneously have a probability of about 85% to hold warming below 2°C during the 21st century.)

As a result of the Intergovernmental Panel on Climate Change (IPCC) fifth assessment report in 2014 and the assessments made by organisations such as Climate Analytics and Climate Action Tracker, many countries also sought a long-term emissions reductions goal in line with the pathways for keeping temperature rise well below 2ºC/1.5ºC. Their argument that a long-term goal of carbon neutrality or net zero should be included in the Paris Agreement to operationalize the agreed temperature limit and send a signal to the real world economy was heard in Paris. The Paris Agreement, as agreed by 195 Parties in December 2015 and signed by 175 Parties in April 2016, sets out a long-term goal of net zero in the second half of this century, in order to achieve the temperature limits of ‘well below 2ºC’ and to keep pathways to maximum 1.5ºC temperature rise open.

The scientific imperative embodied in the Paris Agreement is also recognised as an evolving field that requires flexibility, measurement, reporting and increasing ambitions and financing of Parties as climate change unfolds. An integral compliment to the political processes of countries submitting decarbonisation pledges is the Agreement’s provision for a ‘global stocktake’. The Stocktake will enable the UNFCCC to measure aggregate (total of all countries) progress to date against the trajectory required to stay within the 2ºC/1.5ºC global temperature limits, in order to ‘inform’ Parties Nationally Determined Contributions (NDCs) in an effort to enhance their ambition and stay on track to achieve the long-term goal of net zero GHG emissions in the second half of the century. This is key to the success of the Agreement over time, as current pledged NDCs (currently called ‘intended nationally determined contributions-INDCs’) still result in a gap between what’s on the table and what’s necessary until the Agreement comes into force in 2020, as demonstrated in the graphic below.UNEP and civil society reviews have found current INDCs are consistent with a 2.7ºC pathway, demonstrating the importance of the reviews and global stocktake for keeping the Agreement on track for net zero, in line with the scientific imperative.

indcs graph

Source of Graphic: UNFCCC Updated Synthesis Report on the Aggregate Effects of INDCs

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