Few realistic scenarios left to limit global warming to 1.5°C

All realistic scenarios pull all five levers

A triple challenge for humanity

“Humanity is facing a triple challenge to stabilize global warming without significantly overshooting the 1.5°C commitment” says co-author Nebojsa Nakicenovic from the International Institute for Applied Systems Analysis, IIASA. “First is to half global emissions every decade requiring a herculean effort and a decarbonization revolution by phasing-out fossil energy, a quantum leap in efficiency and sufficiency, and climate-friendly behaviors and diets; second to pursue nature-friendly carbon removal through afforestation and land-use change; and third to assure safe operating of Earth systems that now remove half of global emissions from the atmosphere.”

Unrealistically optimistic scenarios over-estimate e.g. carbon capture and storage potentials

Those scenarios classified by the analysis as unrealistically optimistic most frequently tend to over-estimate carbon capture and storage potentials, while others over-estimate energy consumption or reduction of non-CO2 greenhouse gases like methane. Still others make all too bold assumptions about dietary changes towards more plant-based food or about limited population growth.

The authors also took a closer look at the scenarios provided by the International Energy Agency (IEA) in 2018 and the one called ‘Sky’ produced by the Shell oil and gas company. Both scenarios foresee net emissions falling to zero globally as late as 2070. The researchers found that they do not lie within the corridor of carbon dioxide emissions over the next century that seems to offer a realistic chance of meeting the 1.5°C target.  The Shell Sky scenario shows emissions levels in 2030 well above other scenarios considered in this study. 

“The Shell Sky scenario has been called a pie in the sky, and that’s indeed what it is,” says co-author Gail Whiteman from the University of Exeter’s Business School. “From a science perspective, this is quite clear. In the business community some still like it because it seems to offer, in comparison to other scenarios, a relatively easy way out of the climate crisis. Our analysis shows, however, that there are no easy ways out.”

Irrespective of the specific climate target rapid emission reductions are key

“The necessary emissions reductions are hard to achieve, technically but also politically. They require unprecedented innovation of lifestyles and international cooperation,” concludes co-author Johan Rockström from PIK. “I understand anyone who thinks we might fail the 1.5°C target. Also, it is clear that irrespective of the specific climate target rapidly implementing strong emission reductions is key now. Yet I think limiting warming at 1.5°C is worth just every effort because this would limit the risk of giving some tipping elements in the Earth system an additional push, such as ice sheets or ecosystems like the Amazon rainforest. As technical as this all might sound, it really is about assuring a safe climate future for all.”