Feasibility of limiting warming to 1.5 and 2°C

It is technologically and economically feasible to hold warming below 1.5 or 2°C, without compromising sustainable development or undermining food security – this briefing considers the scientific conditions and critical mitigation technologies.

Date2015, December 01
UNFCCC Climate Conference COP 21, 30 November - 11 Deceber 2015, Le Bourget
 

A new briefing by Climate Analytics outlines the scientific conditions under which warming can be limited to well below 2°C over the 21st century, and return to below 1.5°C by 2100. It provides an overview of the science on some critical mitigation technologies, like bioenergy, carbon capture and storage, and their combination – BECCS. It asserts that it is technologically and economically feasible to hold warming below 1.5 or 2°C, without compromising sustainable development or undermining food security. However, limiting warming to below 1.5°C by 2100 does not allow for any further delay in mitigation action. Global emissions must decline rapidly and steadily after 2020.

Key messages:

  • The IPCC Fifth assessment report shows that it is physically and economically feasible to hold warming well below 2°C above pre-industrial during the 21st century, and return to below 1.5°C by 2100, after temporarily exceeding 1.5°C in the 2050s
  • The Report of the Structured Expert Dialogue (SED) finds that pathways limiting warming to below 1.5 °C by the end of the century are similar to those limiting warming to 2 °C, but call for more immediate mitigation action and an additional scaling-up of the challenging features of the 2 °C scenarios
  • Limiting warming to below 1.5°C by 2100 requires similar transformations in the energy system as holding warming to below 2°C during the 21st century, but the decarbonisation of the energy system needs to be faster and more pronounced.
  • 1.5°C scenarios depend on the availability of technologies leading to negative CO2 emissions, like most 2°C scenarios starting from close to projected emissions for 2020, but have virtually no flexibility to “opt out” of such technologies
  • Large-scale bioenergy deployment has a significantly lower effect on aggregate food price by 2050 (around +5%) than the effect of climate change on crop yields (around +25%). Hence, the key priority for food security is to decrease the impacts of climate change. The detrimental effects of higher levels of warming on agricultural yields – and consequently on food security – are more significant than the impacts of large-scale bioenergy deployment.
  • Holding warming to below 1.5°C does not undermine food security by including bioenergy. The argument that bioenergy would require 500 million hectares of land and thus negatively impact on food security is based on the false assumption that bioenergy it is derived solely from arable crops. Bioenergy relies increasingly on second-generation biofuels, which are extracted from woody biomass, or agricultural and forestry waste.

The considerations in this briefing are based on the findings of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5), the 2014 UNEP Emissions Gap Report, the Report of the UNFCCC Structured Expert Dialogue (SED), as well as the recent scientific literature.

Visit our resource page on the 1.5°C temperature limit.