The world is aiming for net-zero emissions by 2050. Here's what that means

Our planet is changing. So is our journalism. This story is part of a CBC News initiative entitled "Our Changing Planet" to show and explain the effects of climate change and what is being done about it.

Canada has committed to reaching net-zero emissions by 2050 to fight climate change. At the upcoming COP26 climate summit, hitting net zero globally by 2050 is a key goal.

But what does that mean? What does it involve? Why is it so important? Here's a closer look.

It means we are no longer adding heat-trapping greenhouse gases to the atmosphere. Some greenhouse gases might still be emitted, but they would be balanced off or "cancelled out" by the removal of an equivalent amount of greenhouse gases. (This is very similar to carbon neutrality, but includes more than just CO2.)

Some experts, including the United Nations, take the definition of net zero one step further. In a video, the UN describes it as cutting emissions as close to zero as possible. "Any remaining emissions must be reabsorbed, including by healthy oceans and forests." (More on that later).

WATCH | A UN video outlining its definition of 'net zero':

The countries that signed the 2015 Paris Agreement on climate change are meeting in Glasgow, Scotland, for the COP26 summit from Oct. 31 to Nov. 12. The meeting's first stated goal is "secure global net zero by mid-century and keep 1.5 degrees within reach."

Under the 2015 Paris Agreement, 196 countries committed to limiting global warming to well below 2 C — and preferably below 1.5 C — compared to pre-industrial times. That means cutting the greenhouse gas emissions that cause global warming.

The Paris Agreement itself doesn't include the term "net zero," but it does say that in order to reach those temperature goals, parties must reduce emissions "so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century."

Some signatories, including Canada, have already submitted or announced new plans with a net-zero target.

It's the only way to stop climate change. As long as greenhouse gases keep being added to the atmosphere, the average global temperature will keep rising.

Jason Dion, mitigation director for the Canadian Institute for Climate Choices, a government-funded think-tank, puts it this way: "When we get to net zero… we're not making climate change any worse."

Because that's required to keep warming below 1.5 C. The Intergovernmental Panel on Climate Change (IPCC) modelled different scenarios for reaching the Paris targets, and all the simplest paths to 1.5 C required the world to cut emissions to 45 per cent below 2010 levels by 2030 and reach net zero around 2050.

That means if we don't hit net zero by 2050, "we'll lose that window [of opportunity] to stay below two or 1.5 degrees by the end of the century," said Jennifer Allan, a lecturer at Cardiff University in the U.K., who is Canadian.