We’re focused on achieving net zero emissions by 2050, which is the stated goal of the Canadian federal government. But it’s also important to consider the cumulative emissions that will be produced between 2020 and 2050, a concept known as a carbon budget.
The 2050 net-zero goal adopted by Canada and many other countries comes from the UN Intergovernmental Panel on Climate Change’s special report on 1.5°C (SR15) released in 2018. In that report, the IPCC outlines the actions needed to avoid global warming of more than 1.5°C by 2100.
The report concluded that the world needs to reduce emissions to net zero by 2050. But it also shows that the cumulative amount of carbon dioxide and other greenhouse gases produced between now and 2050 will determine whether the world will avoid the worst impacts of climate change. The amount of carbon we can safely emit without permanently exceeding the 1.5°C threshold is the carbon budget.
There are a range of climate models that estimate the global carbon budget, all with different results. All these models agree that we will need billions of tonnes of carbon removal before 2100. A closer review of the numbers suggests that the world will need large-scale carbon to start soon, in the next two to three decades.
The average estimate across climate models is that humans can only emit an additional 560 gigatonnes (Gt) of carbon. This means the world needs to cut its emissions in half immediately, and sustain those reductions through 2050.
It is hard to imagine a scenario in which the world can stay within its carbon budget without large-scale deployment of negative emissions technologies.