Alternative Fuels Provide the Best Hope to Limit Aviation’s Global Warming Impact, Says IPCC Report

by Christopher Surgenor (GreenAir Online) With global warming already at 1.1°C above pre-industrial levels, limiting it to 1.5°C requires deep, rapid and sustained greenhouse gas emissions reductions in all sectors, with global emissions needing to be cut by almost half by 2030, warns the UN’s Intergovernmental Panel on Climate Change (IPCC) on the publication of its Synthesis Report (AR6). However, it adds, taking the right action now could result in the transformational change essential for a sustainable equitable world. The huge volume of work included in the report also considers aviation’s contribution to global warming and how its climate impacts can be mitigated. As a hard-to-abate sector, there are no easy answers, said Professor David Lee, one of the report’s authors, with alternative fuels providing the best hope of reaching net zero, together with a need for carbon dioxide removal deployment for residual emissions.

“The Synthesis Report is a very clear signal that there are significant challenges ahead for aviation and no easy answers or quick fixes,” said Professor Lee, Lead Author of the transport component of AR6 Working Group III (WGIII), which focused on the mitigation of climate change, and head of the Aviation and Climate Group at Manchester Metropolitan University in the UK.

Since its Fifth Assessment Report was completed in 2014, the IPCC says there has been a growing awareness that to deal with fast-growing emissions from the sector, there is a need for demand management solutions combined with new technologies such as advanced biofuels, hydrogen fuels and hydrogen-derived synthetic fuels.

“The scenarios literature indicated that fuel and technology shifts are crucial in reducing carbon emissions to meet temperature goals,” says the Technical Summary.

While aircraft and propulsion system efficiency improvements can provide some mitigation potential, additional CO₂ emissions mitigation technologies will be required. For aviation, such technologies include high energy density biofuels and low-emission hydrogen and synthetic fuels. Electrification could play a niche role for short-range aviation and can reduce emissions from airport operations.

In addition to deep, rapid and sustained emission reductions, the deployment of carbon dioxide removal (CDR) to counterbalance hard-to-abate residual emissions is unavoidable if net zero CO₂ or GHG emissions are to be achieved, says the report.

It defines CDR as “Anthropogenic activities removing CO₂ from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical CO2 sinks and direct air carbon dioxide capture and storage (DACCS), but excludes natural CO₂ uptake not naturally caused by human activities.”

Professor Lee said the IPCC had been very careful to define what is meant by carbon dioxide removals, which do not include aviation offsets of ‘emissions avoidance’.

The aviation sector will also have to adapt to climate change impacts such as extremely high temperatures, intense rainfall leading to flooding, more intense winds and/or storms, and sea level rise possibly seriously impacting transport infrastructure and operations. Changes to global jet streams could impact flights, extreme weather conditions could affect runways and cause payload restrictions, and moderate-or-greater clear-air turbulence on transatlantic flight routes in winter will likely increase significantly in the future as the climate changes. More research is needed to fully understand climate-induced risks to transportation systems, says the report. READ MORE; includes VIDEO