Why we need to limit global warming to 1.5°C

Posted in: Comment, News
Date posted: 27 June 2016

In June 2016, the Operation Noah board agreed on a policy position of limiting global temperature rises to 1.5°C above pre-industrial levels, the more ambitious target referred to in the Paris Agreement. Christian Aid, Tearfund and CAFOD are among the other organisations advocating for 1.5°C.

In summary, the reasons for this position are:

  • The difference in impacts between a rise of 1.5°C and a rise of 2°C.
  • The science suggests that it is still possible to keep global temperature rises below 1.5°C, even though there is little time left and rapid action would be required – and research is currently being conducted into this area by UNFCCC and others.

Why we needed to make this decision

The December 2015 Paris Agreement pledged to ‘[hold] the increase in global average temperature to well below 2°C above pre-industrial levels’ and ‘…to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change’.

In light of this, Operation Noah needed to agree whether to advocate for the churches, the UK government and others to develop policies based on limiting global temperatures rise to 1.5 or 2°C.

There were two main considerations: first of all, the difference in impacts between a 1.5 and 2°C rise in global temperatures. The second issue – important to Operation Noah because our work has always been science-informed – is around the feasibility of keeping global temperature rises below 1.5 and 2°C.

Climate impacts

At the Paris climate talks, Tuvalu and Kiribati were among the nations calling for temperature rises to be limited to 1.5°C by 2100. Temperature rises above this level could result in these nations disappearing entirely, forcing their populations to migrate.

The difference between a global temperature rise of 1.5 and 2°C has been outlined in a recent Carbon Brief article. This highlights the impact of an extra 0.5°C:

  • global sea levels rising 10cm more by 2100
  • a doubling of water shortages in the Mediterranean
  • tropical heatwaves lasting up to a month longer.

The difference between 2°C and 1.5°C is ‘likely to be decisive for the future of coral reefs, with virtually all coral reefs at high risk of bleaching with 2°C warming’. Some scientists have warned that the permafrost will begin to melt even at 1.5°C, releasing methane into the atmosphere and thus leading to further warming.

Infographic comparing the effects of a 1.5 degree rise in temperature and a rise of 2 degrees.

Keeping global temperature rises below 1.5°C

There is little time to act if global temperature rises are to be kept below 1.5°C. At the current rate of emissions, the carbon budget for remaining below a 1.5°C rise in global temperatures would be used up within the next 5 years (if we were to have a 66% chance of staying below 1.5°C), according to Carbon Brief.

The 1.5°C target had not previously been considered by UNFCCC. As a result of the Paris Agreement, UNFCCC will provide a special report by 2018 on ‘the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways’.

A number of scientists, including Myles Allen, have suggested that keeping global temperature rises below 1.5°C is likely to involve relying on Negative Emissions Technologies (NETs).

Negative emissions technologies aim to remove greenhouse gases from the atmosphere over their lifecycle and isolate them from the atmosphere for the long term. These technologies include storing CO2 in original biomass (e.g. afforestation), converting it to another form for more permanent storage (e.g. in geological reservoirs) or extracting CO2 directly through Direct Air Capture. All such technologies are as yet unproven for large-scale deployment.

A paper from the University of Oxford’s Smith School of Enterprise and the Environment has stated: ‘While this type of large-scale removal of CO2 may eventually be required…hoping to reach emissions targets via such an overshoot trajectory is a dangerous alternative to timely mitigation.’

The implications for the churches

Operation Noah believes it would be preferable to aim for the lowest possible rise in global temperatures, and the highest possible chance of remaining below 1.5°C. This will have implications for the pace of change required.

This in turn will clearly have implications for the churches regarding the length of time for which they engage with fossil fuel companies (and the measures being advocated) and the speed with which they shift investments to support renewable energy.

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