I arrived at Western nearly five years ago, and for the first time, I feel like we might have a real winter – temperatures well below zero and snow that stays firm for more than two days. I personally like this weather, but judging from the comments on the streets, from the pipes that freeze in some buildings and the astronomical number of too-cold-to-operate days that schools have had in the last three weeks, something tells me we live on the edge of what people have experienced in this region.
Like many others, my intuition is to associate this cold weather with global climate change.
But how cogent is this inference?
Let me be clear, this is not another cheap climate-skeptic trick. The evidence presented by the International Panel on Climate Change (IPCC) is unequivocal: the planet will be most likely warm up by two degrees by the end of the next century; most of the temperature increase so far happened during the last few decades; and the primary cause is us, i.e., greenhouse gas emission in industrialized countries.
So, my question is not: Is it happening? My question is: Can we relate the global anthropogenic climatic change to particular events in this region?
Climate scientists are showing global climate change does not happen everywhere at the same pace, and for the first time, the 2013 IPCC report made predictions for different regions of the globe. We thus know the effects are distributed and heterogeneous and we should expect a greater incidence in extreme weather patterns.
On the other hand, long stretches of colder temperatures do not appear on the list of ‘extreme weather events’ in the recent IPCC document.
The list includes things like: warmer and/or fewer cold days and nights over most land areas; warmer and/or more frequent hot days and nights over most land areas; warm spells/heat waves frequency and/or duration increases over most land areas; increased incidence and/or magnitude of extreme high sea level, etc. But there’s nothing about extreme cold days.
Now, the few tables I consulted do not exhaust all the extreme weather events related to climate change. In fact, some research suggests there might be a relation between a warming Arctic and cold weather on continents.
So, it is not excluded that longer stretch of unusually cold temperatures in southwestern Ontario has something to do with global climate change. Which brings us back to our original question: Can we say that these recent events would have not occurred in the absence of global warming?
A brief web research convinced me climate scientists are becoming increasingly capable to answer this type of question (i.e., whether specific extreme events result from global anthropogenic climate change). Producing such a verdict requires complex modelling and calculations.
But the general reasoning is relatively simple. It rests essentially on the comparison of two probabilities (or risks):
The probability a certain type of extreme weather event (E) occurs in a region given the actual anthropogenically affected climate (A) – Pr(E|A); and
The probability the same type of extreme weather event occurs in the same region (so E again) given a non-anthropogenically affected climate (N) - Pr(E|N).
In order to make the case that some recent events are due to anthropogenic climate change, we need to prove the following inequality: Pr(E|A) > Pr(E|N). Ideally, the difference should be large enough.
Of course, this is a simplified picture. In fact these probabilities are estimated from a variety of models generate a range of values for each scenario. Perhaps more problematic is the issue of trust that comes with modelling a world without anthropogenic climate change.
Leaving aside the fascinating detail of climate modelling, it seems clear that hitherto, no research has supported the generalization all extreme weather events is due to climate change. It depends of the type of events, the specific region and how the phenomena are conceptualized.
I would like to close on two reflective notes.
First, this kind of work is only in its infancy, but it has some potentially interesting and controversial implications.
As we all know, extreme weather events, especially storms, floods or droughts, can have a significant impact on the well-being of people, the environment and the economy. If we can connect some regional events to anthropogenic global warming, can we also climb up the causal chain and establish responsibilities for these events? Is the line straight and clear enough to think that, in the near future, poorer regions affected by extreme weather can take legal actions against richer countries or the oil and car industry for example?
Second, we are starting to have a better idea of the concrete effects of global warming, and it is clear things are changing. This means we will have to take action and adapt. Obviously, overcoming the inaction of our governments and reducing greenhouse gas emission is part of the solution. Yet, even if we achieve this, global warming and the myriad of changes that come along will not stop immediately.
An old precautionary tale comes to mind here: The fact there are still uncertainties about the concrete mode and tempo of climate change and about its consequences should not be a reason for inaction.
Time to talk adaptation.
Eric Desjardins is a professor in the Department of Philosophy, and a member of the Rotman Institute of Philosophy.