Net zero is the only way to stabilise rising temperatures.
As the graphic shows, this means turning the emissions tap down as far as possible, then counterbalancing what’s left with durable carbon removals.
Carbon dioxide accumulates in the atmosphere like water in a bathtub: as long as more goes in than comes out, the level keeps rising and the world keeps heating. When inflows and outflows are brought into balance, excess CO2 stops building up and temperatures are expected to stabilise.
Net zero only works if we also protect the land and ocean sinks shown on the right of the graphic, which already take up about half of the CO2 we emit each year. We must prevent these outflows from slowing or reversing.
That's why reducing emissions is necessary but not sufficient. Atmospheric CO2 is cumulative and incredibly long-lived: about half of what we emit today will still be in the atmosphere in 100 years, and a small fraction will last up to 400,000 years. Even if global emissions fell by, say, 80%, excess CO2 would still build up, and heating would continue – just more slowly.
Net zero stops the accumulation. To keep the Paris Agreement’s temperature goals alive, global CO2 emissions need to be cut by as much as 90%, with removals counterbalancing what cannot be eliminated easily. These are called ‘residual emissions’. In a geological net zero world, any fossil carbon we dig up and burn ultimately has to be put back underground through durable storage – a 'like-for-like' response on similar timescales.
Once net zero CO2 is reached, ocean heat uptake will slow while land and ocean sinks continue drawing down CO2. These effects are expected to largely cancel each other out, meaning temperatures should stabilise. Going further – to net zero greenhouse gases and eventually net negative emissions – would allow temperatures to fall. But net zero CO2 is the first step.
Carbon removals cannot do the heavy lifting. Many approaches are still early-stage, prohibitively expensive and unproven at scale – hence the dotted red line above. Cutting emissions now is easier and cheaper than trying to remove them later. Yet removals are a vital supporting tool, and must be invested in and scaled to industrial levels by mid-century at the latest.
In a nutshell, achieving net zero CO2 in the next three to four decades means:
- replacing fossil fuels with clean energy
- electrifying energy systems as fast as possible
- protecting, restoring and strengthening the land and ocean sinks that underpin the natural carbon cycle
- scaling up durable carbon removal to industrial levels.
Net zero isn’t a political slogan – it’s physics and chemistry. And it’s the only way to stop global heating.
