Net zero

Net zero means that the amount of greenhouse gas released into the atmosphere is matched by the amount removed from it, so the two add up to zero overall. It doesn't mean zero emissions, but it is a strict standard: it requires deep, real cuts to emissions first, with removals used only for whatever can't be cut yet, not as a stand-in for reducing at the source. Removals can come from forests, soil, or newer carbon removal technology.

Why 2050

The IPCC's 2018 Special Report on 1.5°C found that global CO2 emissions need to reach net zero by around 2050 to keep warming close to 1.5°C, the more ambitious goal set out in the Paris Agreement. This is why "net zero by 2050" comes up so often in government and corporate climate pledges: it's the timeline the science points to for staying within that limit.