Making aviation green is a huge challenge.
Flying is such a big part of our lives
and we have to balance that with the fact that it contributes hugely
to global warming.
We've left it a long time.
We've now got a very short window within which we need to get
emissions from this sector down to nearly zero.
We need to be throwing everything at this problem that we can think of.
There are two big reasons why aviation presents a unique challenge
in terms of climate change.
The first is that more and more people are flying,
and the second is that flying remains almost totally dependent
on fossil fuels.
We haven't got green technologies available yet
for the aviation sector.
And that's roughly equivalent to the total emissions from the UK
and Germany combined.
In 2019, airlines carried around
4.5 billion passengers on flights,
and we're really expecting that to grow.
Globally, just 1% of the population,
many of whom are frequent flyers,
generate half of all emissions from the aviation sector.
There is no silver bullet to get aviation
to become green, but rather a whole set of different options,
each with pros and cons.
Winglets are vertical-looking extensions
that we've added at the end of the wings.
And what they do is to increase the efficiency of the wings.
These winglets were inspired by birds and we are currently looking
at much more features from bird wings and bird flights
and incorporating them into our aircraft.
The aviation industry is really good at making itself
more efficient through a mixture of improving technology
and learning to fly the aircraft more efficiently.
If you look at history,
we are improving the efficiency of our aircraft
at about 2% per year.
That is definitely very little and it cannot continue forever,
so we definitely need to change our aircraft fuels.
Jet engines at the moment run on fuel
made from fossil fuels, so it's really important that we find ways
to replace that in aircraft.
Biofuels are a form of fuel which is made
from plant-based materials.
The one possible example is vegetable oil,
which exists in very large quantities
and can be transformed into a biofuel.
For instance, if we were to replace the entire jet fuel used in the UK
with biofuels, we would be using about 68% of the land
that we currently use to grow our food.
Another possibility is what we call e-fuels,
which is scrubbing the carbon dioxide from the air
and putting it through chemical processes
that turn it back into jet fuel again.
So it turns into a circular process where it's all going
into the atmosphere and then coming back out again.
One big disadvantage of e-fuels
is that they are very expensive, not only in terms of their cost,
but also in terms of the energy that they use.
Hydrogen is a gas that, if you react it
with the oxygen in the air, can release a lot of energy.
That makes it potentially a really good aviation fuel,
but it's not without its problems.
For a start, we can't store it in the current designs of aeroplanes.
Secondly, at the moment, about 95% of our hydrogen
comes from fossil fuels.
Hydrogen is very explosive,
which poses serious safety considerations.
Designing, manufacturing and licensing hydrogen-powered aircraft
is something that is bound to take decades
and cost in the region of tens of billions of pounds.
Electric airplanes are still incredibly rare.
So, I'm one of the very few people in the world who has had a chance
to pilot an electric airplane.
Whilst it's possible to make an electric car that works well,
if you put those same batteries into an airplane,
it's simply too heavy to fly.
There's no doubt that it's going to take
a lot of resources, particularly energy.
It's going to cost a lot and it's going to require a huge amount
of effort from business and from government working together,
with the cooperation and support of the public.
It would be great if there was one kind of
fix-it-all solution that we could put in place for this sector.
Unfortunately, we're going to have to do everything we can think of,
and it's all probably going to be quite challenging.
A lot of the technologies that we need
for greening aviation are still some decades apart.
They are very expensive, and the electric energy
that would be required from a renewable source
will also be very expensive and time-consuming to set in place.
Alongside that, just as importantly,
we're probably going to have to fly less.
Because we've left it so long, there just isn't time left.
The aircraft coming off the production line today
will probably still be flying in 2050, which is the date
by which we have to be at net zero emissions.
We need to be building the kind of society in which
there are good alternatives to flying.
So if you choose to take holiday domestically in your own country,
that will start to create that kind of demand that will help
make a more sustainable future.
Do you fly?
I last took a flight before my daughter was born
and she's going to be a teenager this summer.