Net zero: what is it and why does it matter?

Watch: Explainer: What is net zero?

The UK has a target to reach net zero emissions by 2050 and the Government has set out its strategy for how it aims to get there.

But what is “net zero” and why does it matter?

Greenhouse gases in the atmosphere, such as carbon dioxide, trap heat and keep the planet warm.

But the more of these gases we have put into the atmosphere through activities such as burning fossil fuels to heat homes, drive cars and provide electricity for our lives, the more the planet warms.

These rising temperatures drive climate change, the extreme weather, rising sea levels, heatwaves, and floods that we are already seeing increase around us.

So, just as you need to turn off a tap completely to stop the level of water in a bath from continuing to rise, we need to cut emissions to zero to stop the greenhouse gas levels, and therefore temperatures, rising more to prevent more dangerous climate change.

Completely stopping emissions is extremely difficult, but there are some measures, such as planting trees, which can absorb greenhouse gases from the atmosphere, the equivalent of bailing some water out of the bath to keep the water level steady even if the tap is still running slightly.

Global warming and the greenhouse effect (PA Graphics)

So emissions have to be cut as much as possible, and any remaining pollution, from hard-to-tackle sectors such as aviation, needs to be “offset” by action that absorbs carbon to have the net effect of cutting emissions to zero.

To stabilise global temperature at any level, emissions must reach this “net zero” point eventually.

Scientists say that to limit temperature rises to 1.5C above pre-industrial levels, beyond which increasingly dangerous climate impacts will be felt, global carbon emissions must be brought down to net zero by around 2050 with deep cuts to other greenhouse gases.

And the UN’s Intergovernmental Panel on Climate Change (IPCC) has concluded that significant amounts of carbon dioxide removal will not just be needed for mopping up residual emissions, but for creating negative levels of emissions to bring down temperatures again after overshooting the 1.5C level.

In the UK, the Government legislated in June 2019 that the UK must reach net zero greenhouse gas emissions by 2050, by mandating a 100% cut in emissions by that date.

That requires deep cuts in emissions and therefore changes in all sectors, including how we heat our homes, how we travel, our power sector, how industry uses energy and even our diets, and efforts to capture some emissions.

Natural carbon sinks
How landscapes can catch carbon (PA Graphics)

The statutory advisory Climate Change Committee (CCC) has said it expects more than 100 million tonnes of emissions will be captured in 2050 to offset the pollution the UK is still putting out then.

Ways to do that include burning plant matter for energy and capturing and burying the carbon emissions, known as BECCS, technology that captures carbon dioxide directly from the air, expanding woodlands and restoring peatlands.

Delivering net zero is not without controversy, with concerns raised about the cost.

But the CCC has concluded it would cost less than 1% of GDP through the next 30 years to deliver, and would bring benefits such as cleaner air, better health and provide a jobs boost, though there is a need to ensure the costs are spread fairly.

It is also controversial because some environmentalists are concerned some companies and governments think they can continue to pollute while “offsetting” themselves out of the crisis, instead of tackling the emissions at source.

However, the CCC’s chief executive Chris Stark has said setting a net zero target is the right approach, and the goal has galvanised action.

He said it was different from the UK’s old target of 80% emissions cut by 2050 because there was no longer a 20% of residual pollution that organisations or sectors thought they could emit.

“I see real progress having set net zero as a goal, not just in government circles and in policy, but crucially in the commercial sector,” he said.

Watch: The UK's quest for net zero: Can carbon capture finally fulfil its promise?