In 2018's latest IPCC report, the Intergovernmental Panel on Climate Change shows that net emissions must be reduced to zero in order to stabilise global temperatures. And that any scenario that does not include a reduction to zero would not halt climate change. This target has been ratified by Switzerland, the EU and many other countries under the Paris Accord (see: What is the Kyoto Protocol and the Paris Accord?).
Since the earth reacts strongly even to small changes in the proportion of CO₂, methane and other greenhouse gases in the atmosphere, emissions of these gases must be reduced until the whole system is back in balance. Net zero means that all man-made greenhouse gas emissions must be removed from the atmosphere through reduction measures and that the Earth's net climate balance, i.e. after deductions by natural and artificial sinks (see: What are negative emissions?), is zero. This would make mankind climate-neutral and stabilize the global temperature.
However, the following applies: the later this goal is reached, the higher the negative emissions will need to be. You can find out more about this in the article on negative emissions or in the article to the personal CO₂ budget.
Sources: IPCC 2018 Special Report 15