Christchurch Airport is taking a closer look at aviation’s climate impact by integrating non-CO₂ effects into its climate strategy.

After years of focusing on its own operational emissions, the airport has increasingly turned its attention to airline emissions and what happens when flights operate at altitude. Through its work with Estuaire, Christchurch Airport is now using detailed flight-level data to better understand these impacts and identify where meaningful reductions could be possible.

We spoke with Claire Waghorn, the Sustainable Transition Leader at Christchurch International Airport about the shift towards more accurate data, the importance of understanding contrails, and the potential role airports can play in addressing aviation’s climate impact.

Integrating non-CO₂ effects into the climate strategy

• ‍Estuaire: Christchurch Airport is integrating non-CO₂ effects into its climate strategy. What motivated the shift?

Claire Waghorn: Christchurch Airport is proud to be integrating non-CO₂ effects into our climate strategy.

We recognise that first off, it's really important that you address your immediate operational climate impacts as an airport, and we've been doing that for 20 years now. And over the past seven years, we've been looking more deeply into our airline partner emissions and the emissions associated with flights, with airlines burning jet fossil fuel and increasingly now, what happens when that activity occurs at altitude.

So we are eager to learn more about this, understanding that the more you measure and the more that you can understand, potentially, you can also have an impact and make decisions differently based on new data and new understanding.

Moving from generic factors to more granular data

• ‍Estuaire: Before working with Estuaire, what were the main challenges in quantifying Scope 3 emissions, especially from aircraft?

Claire Waghorn: One of the main challenges we had was applying a generic-based radiative forcing factor. And that's fine when you're first getting your head around a new activity. You want to put it into your inventory, you want to recognise it, but over time, it's really important that you start moving to a more granular, bespoke factor that is actually based on real-life activities.

Because when you move over from a generic factor, we initially started applying a 1.9 times factor for our radiative forcing factor. There wasn't a great deal of, I say, scientific agreement on that, but we thought it would be conservative and apply the larger end.

By the following year with our inventory, it was a 1.7 That had sort of been settled on a bit more. And then in this last year, we had Estuaire do a full analysis of every flight that came in and out of our airport to understand the true radiative forcing non-CO₂ impacts of our flights.

And it has been materially different. So it's been hugely useful for us to have actual granular data based on real-life activity happening at our airport.

Why contrails matter

• ‍Estuaire: Contrails are a complex and often overlooked part of aviation's climate impact. How important is it for you to better understand and act on them?

Claire Waghorn: Contrails are an often overlooked aspect within an airport and aviation sector emissions.

It's not as deeply understood as some of the other aspects that perhaps folk have been more familiar with and a longer history sort of leading up to understanding. We know burning jet fuel creates  a negative climate impact. We haven't known to what extent those activities at altitude also have a negative impact.

But what we do know now is that it's really material. It can be for us, around a 1.3 factor up to perhaps 1.9 for much busier airports with full airways above them and, depending on the flight and the altitude, a very significant material impact.

To give you a sense of scale, Christchurch Airport's emissions for our own direct operational airport sits now at 173 tonnes of carbon equivalent.

This is relatively very small. We have reduced our footprint by 95% over the last 20 years. In relation to the airline emissions, they sit closer to half a million tonnes, so 173 to half a million.

On that half a million, you then have the fact that it's happening at altitude and that could mean that half a million actually has a warming impact, you know, of a multiplier between 1.3 and 1.9 more. So it's incredibly important that we understand this activity.

What flight-level data can reveal

• ‍Estuaire: Access to detailed flight-level data makes a huge difference. What are you learning through this work?

Claire Waghorn: Access to detailed flight-level data makes a huge difference. We are learning really interesting insights through our work with Estuaire, such as not all flights will have this extra radiative forcing impact. Some of them don't fly at that significant altitude. Some flights are incredibly impactful. It also depends on what time of day a flight leaves.

A morning flight may not have as high a radiative forcing non-CO₂ climate impact as an afternoon flight. So the more granular you get, you can have some very interesting insights, which means your airport could, or airline, could theoretically make quite an impactful climate difference based purely around slots and timing of flights.

So we think it's a really exciting area of science to be understanding further. It's just another of the very important levers we need to be acting upon in order to address aviation's climate impacts.

A message for New Zealand airports

• ‍Estuaire: What message would you share with New Zealand airports to understand and act on their full climate impact?

Claire Waghorn: I would encourage all airports and airline partners to really lean into understanding their full climate impact with the non-CO₂ effects of flights.

It's super fascinating. It's a potential lever to have a meaningful climate reduction in harm based on some of the levers that you might be able to learn about yourselves, and what time flights leave, and what particular flights out of your airport are most harmful from a warming impact.