Interview with Nicolas Bellouin by Sorbonne University

Climaviation, an innovative project to reduce the impact of aviation on the climate

Interview with Nicolas Bellouin, climatologist at the Institut Pierre-Simon Laplace, conducted by Sorbonne University.

The Climaviation project aims to better understand and quantify the climate impacts of aviation. It is led by Nicolas Bellouin, a climatologist in the United Kingdom and holder of the Aviation and Climate Chair at the Institut Pierre-Simon Laplace (IPSL). This contributor to the sixth IPCC report explains the objectives of this ambitious project, which brings together scientists from the IPSL and the French Aerospace Lab (ONERA).

In what context was the Climaviation project born?

Nicolas Bellouin: Faced with global warming and the need to reduce carbon dioxide (CO2) emissions, the aviation industry has embarked on a worldwide decarbonisation strategy. The task is particularly difficult for this economic sector where CO2 remains very present and where each innovation envisaged on aircraft must be tested and approved before being implemented.

In this context, the French Civil Aviation Authority (DGAC) has funded the Climaviation project over five years to explore different solutions to reduce the climate impact of aviation.

What is the objective of this project?

N. B.: Everyone knows that aviation emits CO2 and that these emissions must be reduced. But CO2 is not the only culprit. Aircraft engines emit other compounds: nitrogen oxides, water vapour and particles. Under the right conditions, water vapour and particles form contrails behind the aircraft. Some of these contrails persist and continue to expand, forming large fields of ice clouds that disrupt the Earth’s radiative balance. This is one of the so-called “non-CO2” effects of aviation.

According to recent climate modelling, the impact of these effects could be greater than that of CO2. But it remains uncertain because of the complexity of the mechanisms to be modelled and the scales to be taken into account in the simulations. Many questions arise concerning the size and properties of the cloud cover induced by contrails, their lifetime in the atmosphere, the formation and composition of ice crystals, the impact of a fuel change on the chemistry of the atmosphere, etc.

The aim of the Climaviation project is therefore to understand and quantify these effects in order to take them into account in climate impact reduction strategies.

What solutions are you exploring to reduce the climate impact of aviation?

N. B.: The aviation industry is intensifying its efforts to improve the efficiency of existing engines or to use alternative fuels with a low carbon footprint, or even new decarbonised energy carriers such as hydrogen.

We are also looking at alternative strategies that rely heavily on the existing fleet: changing flight altitudes, using updrafts, adjusting flight times, and so on. While these strategies do not necessarily require technological change, it is necessary to verify their effectiveness and measure their impact in the short and long term.

The DGAC therefore needs our scientific advice to determine which of these solutions not only reduce CO2 emissions but also limit non-CO2 effects.

This is a multidisciplinary research project combining the strengths of Sorbonne University and ONERA. How is this collaboration organised?

N. B.: This project brings together around thirty scientists. They include atmospheric physicists, cloud physicists, chemists, observers, specialists in automatic pattern detection, etc.

ONERA scientists know how to model the impact on the atmosphere of an engine or fuel change on a space-time scale of a few seconds and a few metres behind the aircraft. At IPSL, we model what happens on much larger scales: on a global level and over several hours, years or even centuries. Through our collaboration, we are trying to bridge the gap between these two orders of magnitude.

Our ambition is to connect ONERA’s models to the climate models developed by IPSL in order to build perennial scientific tools that can be used to estimate the climate impact of any new solution proposed in aviation.

This article is republished by Sorbonne University. Read the original article..