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A decade ago, the term “net zero” was arcane jargon. Today, it is the key goal of the fight against climate change and a familiar talking point across the world.

The concept is straightforward. In the words of the : “Net zero carbon dioxide (CO₂) emissions are achieved when anthropogenic CO2 emissions are balanced globally by anthropogenic CO₂ removals over a specified period.”

It is also easy to trace the concept’s rise to prominence. Once the need for net-zero emissions to halt rising temperatures was established, it made its policy debut in the 2015 Paris Agreement. It then exploded into public consciousness following a explicitly stating that the world must reach net zero by 2050 to avoid the worst effects of global warming.

The UK soon became the first major economy to come up with a net-zero emissions pledge. Now, most countries, including China, the US and India – the three largest emitters – have made such pledges of some sort.

What is less clear, however, is whether all these targets are strong enough to get us to net zero fast enough – and what happens to the climate once we do reach our goal.

Many , according to the . Often countries’ plans lack achievable interim steps or leave out important sectors of the economy. That suggests most deadlines will be missed. But reaching net zero 50 years from now, for instance, isn’t enough, says at the Natural Resources Defense Council. “You have to make efforts to cut carbon today.”

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What’s more, achieving net-zero emissions is just one of several important goalposts on which the future climate depends. How much we emit before reaching net zero and what happens after we get there are equally important, says Levin.

Another issue lies in how emitters can claim to be making progress by paying for others to avoid emissions – for instance by protecting a forest that would otherwise be cut down – rather than reducing their emissions. While such “carbon offsets” work in theory, in practice they are often difficult to verify, says Levin. “The offset market today is highly unregulated and, honestly, a Wild West.”

Besides, offsetting based on avoided emissions will grow ever scarcer as we run out of emissions to avoid, so it can’t be part of the long-term solution, says at the University of Oxford. “Because it’s been abused, the environmental community is now fed up with it.” As a result, some have called for commitments to “real zero,” as in no emissions whatsoever.

But emissions from long-distance flights or fertiliser use, for instance, are nigh-on impossible to eliminate, says Levin. Hence the push for CO₂ removal through technologies like direct air capture or other, nature-based approaches.

What happens when we hit net zero?

As for what will happen if the world does reach net-zero emissions on time, one recent study found that warming feedbacks could mean temperatures continue rising, depending on how much we emit overall.

In that case, even more carbon removals would be needed to both address the overshoot and maintain net zero as natural sinks begin to bring down the atmospheric concentration of CO₂.”The real balance we need in the long term is between producing carbon dioxide and permanently disposing of it,” says Allen.