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| 08/02/17

World unlikely to stay within 2°C warming limit


The world is highly unlikely to achieve the target of keeping average global temperature increase to a maximum of 1.5 to 2° Celsius above pre-Industrial Revolution levels, as agreed upon by world governments in the 2015 United Nation’s Paris Agreement. This is the finding of two separate papers out this week in a high-profile climate research journal.

Even if all greenhouse gas (GHG) emissions were halted tomorrow, according to the first study appearing in Nature Climate Change, our past emissions have already locked in global temperature increases that would see the mercury stabilizing at about 1.5°C above pre-industrial times by the end of the century. And there is a 13 percent chance that this “committed warming” of the 1.5°C limit has already been breached.

A second paper describes some 100,000 simulations of various outcomes based on current economic trends, emissions intensity and population growth. In only one percent of these simulations was our civilization able to avoid temperature increases above 1.5°C.

In just five percent of simulations were we able to avoid temperatures above 2°C. The likely temperature increase ranges from 2 to 4.9°C by century’s end, with the median at 3.2°C.

To avoid these scenarios, much more rapid emissions mitigation efforts are needed than are outlined in the Paris Agreement. To be fair, the UN and most governments already acknowledge that nations’ emissions reduction pledges are insufficient. This is why the accord includes a ‘ratcheting’ mechanism wherein every five years, governments are expected to increase their carbon mitigation promises.

But just how much does Canada need to ‘ratchet up’ its commitment?

Last year, two researchers at the University of British Columbia and Simon Fraser University crunched the numbers in two ways. Both looked at Canada’s portion of the remaining ‘carbon budget’, or the room left in the atmosphere for additional output of GHGs before blowing the accord’s climate targets. The first calculation was based on Canada’s fraction of the world’s CO2 emissions (1.6-1.8%, so Canada would get 1.6-1.8% of that budget). The study only considered carbon dioxide and not other GHGs such as methane and nitrous oxides

Contrasting this ‘emissions-based’ assessment, the second calculation assumed that Canada’s share of what’s left would be doled out on a per-capita basis. The researchers call this assessment ‘equity-based’, as it is fairer.

Under the emissions-based scenario, to have a likely (66%) chance of avoiding 1.5°C of global warming, Canada’s contribution would require emissions reductions of 90-99 percent below 2005 levels by 2030, and need to effectively reach zero before 2050. Its remaining carbon budget would be equivalent to less than seven years of emissions at 2013 levels, from 2016 onward. Under the equity-based scenario, Canada would have about a year and a half of emissions left.

The current legislated federal target of a 30 percent reduction on 2005 levels by 2030 and aspirational target of 80 percent by 2050 is consistent with a likely chance of avoiding 2°C of warming, but only using the generous emissions-based budget.

The report did however note that use of negative emissions technology and land carbon uptake could extend the life of Canada’s remaining carbon budget


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To stay within 1.5 degrees of warming by 2100, Canada needs to slash emissions by 90-99 percent by 2030

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