You'll surely hear the term "net-zero emissions" a lot in the coming weeks when government officials and CEOs, under pressure, discuss how their countries' or firms' influence on climate change. Amazon, for example, recently announced that over 200 corporations have joined its Climate Pledge, pledging to achieve net-zero emissions by 2040.

But what exactly does "net-zero emissions" imply?

“Zero emissions” — without the “net” qualifier – signifies no greenhouse gas emissions.

“Net-zero emissions” has more leeway. It's similar to balancing a chequebook. The country or firm reduces the majority of its emissions through efficiency and clean energy, while the remainder is offset by extracting carbon dioxide from the environment or eliminating emissions elsewhere.

What is the significance of net-zero emissions?

Greenhouse gases trap heat close to the Earth's surface. When their concentrations become too high, they contribute to global warming.

Countries throughout the world agreed in 2015 to keep global warming to far under 2 degrees Celsius (3.6 degrees Fahrenheit) over preindustrial levels, with a goal of 1.5 degrees Celsius (3.6 degrees Fahrenheit) (2.7 F). According to the United Nations, in order to limit global warming at 1.5 degrees Celsius with the least amount of damage, the world must be on a path to achieve net-zero emissions by around 2050. To put those temperatures in context, global warming now is slightly over 1 degree Celsius (1.8 degrees Fahrenheit) beyond preindustrial levels, and rising seas and harsh weather are already an issue.