I'm someone who cares deeply about the environment. I recycle, I avoid single-use plastics, I recently switched to green power — but I also like to travel.
And when I'm walking down the gangway onto a plane, or waiting on the tarmac, I can't help but feel like a giant green phony.
In those moments before take-off, as I try to rationalise my guilt, I also have questions.
Is flying really that bad? Are there other things I can do if I'm not prepared to stay at home for the rest of my life?
To find out the answers, I spoke to two professors of sustainability. Here's what they had to say.
How air travel costs the environment
Let's use the example of a return Melbourne to London flight, with a stopover in Singapore on each leg.
As the trip is about 34,000 kilometres, and roughly 120g of emissions is created for each passenger every kilometre, the trip would create about 4 tonnes of carbon emissions per person.
To put that 4 tonnes in perspective, if the world is to meet the targets set by the Intergovernmental Panel on Climate Change (IPCC) for 2030, that would be more than the yearly quota for each person on the planet.
"At the moment, we are emitting 52 gigatonnes per year around the world. By 2030, the IPCC says, we have to be below 26 gigatonnes," says Manfred Lenzen, professor of sustainability research at the University of Sydney.
"Now if you divide 26 gigatonnes by 7.5 billion or so [people], you get to about 3.5 tonnes per capita. That is a really good reference point."
At this point, you may be wondering what the average Australian is emitting per year. The answer is about 20 tonnes, Professor Lenzen says.
It doesn't mean you should never fly again. There are ways to offset the impact of flights and you might really value travel and decide to reduce emissions elsewhere in your life.
But we can all help the environment by being a bit smarter about when, where and how we travel.
- How to reduce your travel emissions
- What to know about carbon offsets
- What to do if you don't want to give up travel
Three ways to reduce your travel emissions
Be selective and make the most of flights
Susanne Becken is a professor of sustainable tourism at Griffith University and travel is a big part of her job.
She has a simple rule: if she doesn't have three good reasons to get on a plane, she'll stay at home.
"If you think about your carbon footprint as a cost, just like you would with the financial cost of travel, you can think about how you can get the most out of it," Professor Becken says.
"Maybe you can stay longer, or you can add a holiday or a family visit to a business trip.
"If it's a once-in-a-lifetime holiday, or a wedding or it's really important, I'll go. But I personally try to then bundle up several things to make it really worthwhile."
Avoid unnecessary work travel when you can
What you might not know is that, on a per kilometre basis, domestic air travel creates more emissions than flying overseas.
It's because the fuel burned in take-off and landing is a major component of emissions and shorter-haul flights spend less time in the air.
Thankfully, there's a good reason to stay home: internet and modern telecommunications mean it's easier than ever to work remotely and communicate with people in different locations.
"One opportunity is thinking about different ways to participate in meetings and workshops," Professor Lenzen says.
"Essentially, you can be flying a long way only for a day or two.
"Now the videoconferencing technology is so advanced that you almost feel that you're in the room."
If travel is unavoidable, and you have some more time, you might consider taking a bus or train instead of flying.
Take a road trip with friends or family
While cars aren't as good as catching a train or bus, they're better than catching a plane.
The more people in the car, the more efficient it is, which makes the road trip a good option if a group of you are travelling, Professor Lenzen says.
An average passenger vehicle uses about 10.8 litres of fuel per 100 kilometres. For a carload of four, that works out to be 62.5g of emissions each per kilometre, Professor Lenzen says.
It's better than flying, but that doesn't mean we should be driving everywhere. Again, a bus or a train will be a better option.
What you need to know about carbon offsets
When you book a flight online, you might have noticed an option to pay a few extra dollars to offset your carbon emissions.
If you opt to add this to your purchase, the airline will spend it on projects that reduce emissions, like planting trees or improving energy efficiency.
"I always hasten to say that offsets are only the second-best option to not emitting in the first place," Professor Becken says.
"People need to be aware that an offset is a bandaid. It's more important to work on reducing your footprint."
Instead of paying airlines to offset his travel, Professor Lenzen donates money to an organisation that plants trees that can be used as habitat for endangered native birds.
While many offset programs charge less than $15 per tonne of carbon, Professor Lenzen is happy to pay much more to support a cause he cares about.
"I once asked [the tree-planting organisation] to add up all the costs, including labour, and you get to about $90 per tonne of carbon. If I fly, then to offset that, I calculate $90 per tonne because I think that way my money helps with tackling biodiversity loss as well," he says.
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If you love travel, reduce your impact elsewhere
If travel is important to you, there's always the option of looking at other parts of your life to reduce your emissions.
"If some people find it very hard to reduce their travel, they can do something else. What matters in the end is how much carbon dioxide you emit," Professor Lenzen says.
Here are a few ideas to get you started:
- Reduce your car travel by taking public transport or riding a bicycle instead.
- Shop for second-hand clothes rather than buying new.
- Switch to renewable energy or look for ways to improve the energy efficiency of your household.
- Reduce your consumption of meat and dairy. (Tip: Red meat like beef and lamb is particularly emissions-intensive.)
Editor's note (23/12/19): An earlier version of this article misstated the amount of fuel an average passenger vehicle uses — it's about 10.8 litres of fuel per 100 kilometres, not 10.8 litres of fuel per kilometre.