Canada's ambitious climate goals: What difference will half a degree make?

Image by Shever | flickr.com

Image by Shever | flickr.com

Of all the stereotypes Canada has managed to acquire throughout the years, putting forth bold environmental goals isn’t necessarily near the top of the list.

The world saw a different side of Canada on Sunday at COP21 in Paris, when Environment Minister Catherine McKenna announced what is finally considered a bold environmental target for Canada and the rest of the world.

We’ve been told many times - namely by the IPCC - that maintaining global temperatures below a 2°C threshold is an absolute necessity. Exceed 2°C, and runaway warming becomes a real threat. Despite the ongoing debate regarding the precise temperature at which catastrophic, irreversible global damage will occur, the effort to keep warming below 2°C has become the standard by which we have become accustomed to evaluating the future of our climate. A status quo, if you will.

Which is why when McKenna announced Canada’s support for a 1.5°C limit on warming, the world - perhaps in a state of shock - finally paid attention to us. If not with the gutsy target then, likely when McKenna added, “Canada supports legally binding provisions, and we are committed to following through.”

How many of us have ever been optimistic enough to imagine a world with half a degree less warming than we’ve been told to aim for all this time? I certainly never have - especially given that we’ve already increased the global temperature by 0.8 degrees Celsius since 1880. The math is simple: under McKenna’s target, we’re only allowed to heat things up by another 0.7 degrees.

But what will half a degree difference actually look like?

The short answer? Not sure, according to Valérie Masson-Delmotte, coordinating lead author for the IPCC Fifth Assessment Report. She notes that a target of 2°C was much more of a political choice than a scientific one, stating that specific information for a 1.5°C warming scenario is sparse.

Despite a lack of precise calculations for the maximum level of warming endorsed by Canada (as well as other nations, such as the United States, Australia, and Germany), we can still look at existing predictions and anticipate differences between a world that is 2°C warmer and Canada’s ideal world.

Here are some expected differences (adapted from the IPCC) as we shift our focus from the 2 degree to the now famous 1.5 degree scenario:

Water: The maximum number of people expected to experience water stress decreases from 2 billion to 1.7 billion as we move from 2 degrees of warming down to 1.5 degrees. This overlapping range of potentially affected individuals makes it fairly difficult to assess what water stress would look like with half a degree less warming. Drought and flooding events expected to be less intense. Potential difference: Low to moderate

Ecosystems: We could potentially avoid an estimated 20% to 30% of species at high risk for extinction, though substantial amphibian extinctions are still expected at 1.5 degrees. Shifts in species ranges still expected to occur. Wildfires and coral bleaching remains a substantial concern. Potential difference: Moderate

Food: Minimal difference reported between these temperature change ranges. May see some decreases and increases in cereal production in low and mid-to-high latitudes, respectively. Potential difference: Low

Coast: Coastal flooding risks could affect up to 3 million people at the 2 degree mark; no flooding risk noted at 1.5 degrees. May also prevent low-lying areas from becoming immersed. Potential difference: Moderate to high

Health: Risks of disease, deaths from extreme precipitation patterns, and malnutrition may be less intense, but still present. Potential difference: Low

Singular Events: Potential decrease of ice retreat in Greenland and West Antarctic. Potential difference: Low

Additionally, the IPCC AR5 identifies more general effects of warming relative to preindustrial temperatures. Though there appear to be no striking differences between 1.5 and 2 degrees, the uneven global distribution of climate impacts transitions from a moderate (1.5 degrees) to higher (2 degrees) risk (though risks are higher when the 2 degree limit is exceeded), and threatened systems and extreme weather events venture further into a high risk zone in a 2 degree warmer world.

As you can see, aiming for a half a degree less warming than the typical 2 degree goal is expected to reduce some ecological and social impacts of climate change. While the greatest improvements may be observed for ecosystem health and coastal environments, few differences may be in store for issues such as human health and food security, and may impact those most vulnerable to a changing planet no differently than with two degrees of warming.

Half a degree less warming will not mitigate all impacts of climate change. Nor will predictions always unfold as expected. The Earth is a dynamic system, and we must still be prepared to invest in adaptation efforts, as well as mitigation measures.

But half a degree less warming would be a very good start.