Canada must leave 83% of its fossil fuel reserves and 84% of its tar sands/oil sands in the ground if the world is to have even a 50% chance of holding average global warming to 1.5°C, according to a paper published this week in the prestigious journal Nature.

The figures are part of a global calculation that calls for oil and gas production across all regions to fall 3% per year through 2050, the paper states. And the authors say the actual cuts will probably have to be faster and deeper.

Even the 3% annual target “implies that most regions must reach peak production now or during the next decade, rendering many operational and planned fossil fuel projects unviable,” write authors Dan Welsby, James Price, Steve Pye, and Paul Ekins of University College London (UCL). But “we probably present an underestimate of the production changes required, because a greater than 50% probability of limiting warming to 1.5°C requires more carbon to stay in the ground, and because of uncertainties around the timely deployment of negative emission technologies at scale.”

The targets in this week’s release are much deeper than the estimates in a 2015 analysis, of which Ekins was a co-author, based on a 2.0°C target for average global warming, the new paper says. They come at a time when “existing fossil fuel infrastructure already places a 1.5°C target at risk owing to implied ‘committed’ future CO2 emissions.”

“The inescapable evidence that hopefully we’ve shown and that successive reports have shown is that if you want to meet 1.5°C, then global production has to start declining,” Welsby told Inside Climate News.

“It is abundantly clear from this and other work that the conversation now is about declining production,” added Greg Muttitt, senior policy advisor at the Winnipeg-based International Institute for Sustainable Development. “It’s about leaving fossil fuel reserves in the ground.”

Overall, the authors say 58% of the world’s oil reserves, 59% of all gas, and 89% of all coal will be “unextractable” in their 1.5°C scenario. Canada faces a faster, deeper cut than most other regions, based on its high production costs for a polluting form of oil and its limited influence over world oil and gas markets. Middle Eastern countries and former Soviet states will see their production decline, but not as steeply, so that they retain an above-average share of the remaining oil and gas production.

The Australian Broadcasting Corporation says Australia will be in a similar position.

“The United States is the only region that would see oil production increase from current levels, to about where it was before the pandemic, before peaking within a few years and then declining steadily,” Inside Climate writes. “U.S. natural gas production, however, would see an immediate and sharp decline in the paper’s scenario as renewable energy sources displace gas for generating electricity.”

Across all countries, “the plateauing of production and subsequent decline will mean that large amounts of fossil fuel reserves, prospects that are seen today as economic, will never be extracted,” the paper states. “This has important implications for producers who may be banking on monetizing those reserves in the future, and current and prospective investors. Investments made today in fossil fuel energy therefore risk being stranded.”

However, “there continues to be a disconnect between the production outlook of different countries and corporate entities and the necessary pathway to limit average temperature increases,” the four authors add. “The extent of fossil fuel decline in the coming decades remains uncertain, influenced by factors such as the rapidity of the rollout of clean technologies and decisions about the retirement of (and new investment in) fossil fuel infrastructure.”

One of those factors is the extent to which carbon dioxide removal (CDR) technologies become practical and affordable, in time to contribute to a 1.5°C future. “The possible extent of CDR further complicates this picture,” the authors write. “At high levels, this may allow for more persistent use of fossil fuels, but such assumptions have attracted considerable controversy.”

This content was originally published here.