Companies from British Airways to Facebook...

...and pop artists like Billie Eilish and Massive Attack...

...have promised to make changes...

...to bring their greenhouse-gas emissions closer to net zero

They're joining a club of more than 50 countries around the world

This race to zero is a vital step towards managing climate change

But what does net zero really mean...

...and is achieving it even possible?

Net zero has gone viral

But like all simple slogans, the reality of achieving it...

...is far more complicated

Humans burning fossil fuels...

...has resulted in more carbon dioxide in the atmosphere...

...which is warming the planet

To stop the warming...

...the level of greenhouse gases in the atmosphere has to stop rising

The obvious way to do that is to stop emitting them

But that's easier said than done

For some industries such as aviation and manufacturing...

...eliminating emissions is really hard

In the years leading up to the Copenhagen climate conference in 2009...

...scientists realised something...

...it wasn't possible to cut emissions fast and thoroughly enough...

...to meet the temperature targets that policymakers wanted

What was needed...

...was to actively remove greenhouse gases from the atmosphere too

People began to talk about a world in which greenhouse-gas emissions...

...and greenhouse-gas removals balanced each other out

So that the overall effect was net zero

The countries that signed up to the Paris Agreement...

...pledged to turn this idea into reality, by agreeing to balance their...

...emissions and removal of greenhouse gases...

...in the second half of the century

To achieve net-zero emissions, we need to do two things...

...one, which is more obvious...

..is to cut our output of greenhouse-gas emissions...

...from things like burning fossil fuels

But the other is actually to take emissions out of the air

And that's the harder and sometimes more obscure aspect...

...of getting to net zero

This is known as negative emissions

And the scale in which they might be required...

...is one reason that net-zero targets will be hard to achieve

We'll need to go from a world economy that pumps out on the order...

...of 40 billion tonnes of CO2 a year to one that sucks down...

...that is, removes billions of tonnes per year in the future...

...to get to that net-zero future

There's different ways to do this, forests do this naturally...

...through biological processes or sinks

But what we're really looking at now...

...to achieve ambitious climate targets are man-made approaches

Some methods for removing greenhouse gases from the atmosphere...

...are already being used at scale, such as the planting of new forests

And improving soil so it can store more carbon

But there are new technologies at a much earlier stage of development

Among them ways of capturing carbon dioxide...

...and storing it underground

Carbon dioxide could be pulled directly from the air by machines...

...or by growing plants...

...burning them to generate electricity...

...and then capturing the carbon dioxide as they burn

There's a flurry of innovation in negative-emissions technologies

A range of ambitious to wacky, and none of them are proven at scale

And that's what makes them so problematic

The world is counting on innovations...

...that have not yet been demonstrated at scale...

...to achieve targets that we're setting for ourselves

And that's a big question-mark

We're hopeful, but it is still a risky bet

How much greenhouse gas needs to be removed...

...from the atmosphere...

...will depend on how much emissions can be cut

The conundrum that is, we need both...

...massive reductions in emissions...

...as well as a dramatic scale up and proving...

...of the technologies for negative emissions

There is a tension between the two...

...and it's easy for governments and industries...

...to kick the can down the road saying, well...

...let's go a little slower on the cutting of emissions now...

...which will be better for the economy or for our profits...

...because we can always make massive negative-emissions reductions...

...later when innovation makes those technologies...

...cheaper and better

The dirty little secret in that argument...

...is that it may come too late and it may well give permission...

...for polluters to get away with polluting much more than need be...

...rather than innovating ways to reduce emissions now

There's also the question of who takes responsibility...

...for each molecule of greenhouse gas

One of the most difficult challenges...

...is that lots of countries and companies and individuals...

...don't want to own up to their carbon footprint

For example, carbon-intensive countries like...

...India, China or other emerging markets...

...that are producing enormous amounts of emissions today

They point out that the goods they produce, for example...

...may be consumed by Americans or Europeans

So they should do the negative emissions or they may say...

...rich countries got rich putting carbon dioxide into the air

Now it's our turn to lift our people out of poverty...

...so you pay for the negative emissions

As yet, there is no universal policy for accounting for...

...and attributing emissions

Today, governmental net-zero pledges...

...cover over two-thirds of the global economy

America and the EU are working towards a target...

...of net zero by 2050

And President Xi of China, the world's largest emitter...

...has pledged to achieve carbon neutrality before 2060

Some people see ambitious climate targets...

...and say, fantastic, the problem's getting solved

Here's the problem

A target is no guarantee that we're going to get to the goal

It's important to have targets

It binds society together

It gives you a direction in which policy is going to go

It gives investors and markets some idea and some degree...

...of certainty as to what investments to make

However, we often fall short of targets also we should remember

Most government policies focus on cutting emissions...

...rather than how to tackle negative emissions

Embracing, enacting and scaling a negative-emissions plan...

...to get to net zero is a Herculean task

This is something far bigger than, say...

...the moonshot or other initiatives that it's often compared to...

...because this involves really every economy on Earth...

...every government, ultimately, every citizen...

...all of us have to be involved and change the way we live

And it's not just a technological revolution

We need a revolution in our mindsets

I'm Vijay Vaitheeswaran...

The Economist's global energy and climate innovation editor

To keep up to date with all our climate-change coverage...

...please click on the link

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