A State of Emergency has been declared in British Columbia because of all the forest fires, and the usual suspects have started their usual game of blaming the forest fires on climate change. The problem is, as I will demonstrate in this blog post, the science is pretty clear that climate change cannot be blamed for this two-year uptick in fire activity. This is not to belittle climate change as a long-term threat to our forests. I cannot make this clear enough, climate change will eventually increase our fire danger. But we can’t blame climate change for everything, all the time. There are lots of moving parts in nature and this fire season is likely due to some other natural or anthropogenic feature, one we have to correctly identify if we are to avoid a repeat next year.
Now I can already hear my detractors saying: “but Blair climate change is an existential threat to our nation. We have to take advantage of the public interest to help us fight climate change”. My response is simple:
The argument being made is inconsistent with the state of the science. When you argue against the science you undermine your credibility.
But let’s think of it in a scientific manner: if climate change is not to blame for the two-year increase in forest fire activity then blaming it on climate change will mean we are missing some important other factor. Think of this as the wrongfully convicted murderer theory of environmental policy. When you wrongfully convict someone of murder you may feel better that someone is in jail but since it is the wrong person that means the real murderer is still out there running free. So identifying the actual cause of the forest fires becomes a really important topic. Why is this true? Because when climate change eventually increases our fire risk having it build on whatever is actually causing our current fires would make a bad situation even worse. So let’s look at what the science says about this topic.
The first misconception we have to clear up is the belief that climate change means everywhere in the world will get hotter and drier. This cannot be farther from the truth. Climate change is predicted to affect different areas differently. Most dry areas will get drier and many wet areas are going to get wetter. In B.C. the global climate models (GCMs) indicate that in the early years of climate change we will have wetter winters AND wetter summers. This will have the effect of initially reducing our risk of forest fires. Consider the most highly regarded of the papers on the topic of climate change and wildfires: Climate-induced variations in global wildfire danger from 1979 to 2013. The paper’s abstract reads like it should provide overwhelming support for the premise that climate change will increase our risk of fire. But a careful read of the paper shows that global trends will not always be seen regionally.
Since I want to make it easy just look at Figures 3 and 4 in the paper. Figure 3 displays “Global patterns of fire weather season length changes from 1979 to 2013“. Looking at B.C. on Figure 3a you see that the length of the fire season has significantly shortened between 1979 and 2013. Figure 3b “shows regions that have experienced changes in the frequency of long fire weather seasons (>1σ above historical mean) during the second half of the study period (1996–2013) compared with the number of events observed during the first half (1979–1996)”. Looking at Figure 3b we see that B.C. has experienced a shortening of the fire season between the start and end of the study period. Figure 4, meanwhile, reinforces the fact that the fire season has decreased in British Columbia over time.
The other thing I have heard is: “the paper says that globally fire incidence is expected to increase”. Well that can be true without it meaning that B.C. will get more fires. Rather the GCMs indicate that B.C. will initially have shorter fire seasons. Why is this the case? Well the simple answer is that as we have warmed B.C. has become wetter. Let’s look at a graph of long-term change in precipitation in BC. Virtually every part of B.C. has seen significantly increasing amounts of precipitation in the last 113 years. Moreover, that precipitation has increased across every season. Winter, spring, summer and fall have all been getting wetter. Now I have already had several people on Twitter argue that the time-window ends in 2013? Considering it is a 113 year time-frame this is an incredible minor quibble, but just to satisfy the pedants let’s look at what has happened in the last 5 years. The data shows that the last five years were even wetter than the 5 years before. The data makes it clear, the wet trend continues. So that argument is simply wrong.
The next argument I have repeatedly heard is that because it is warmer (even though it is wetter) we will still get more fires. Well here is a paper that considers that issue: Fuel moisture sensitivity to temperature and precipitation: climate change implications. What does the paper conclude? That the argument will eventually be true but that it is not true right now. Given the current increase in precipitation compared to the current amount of heating, the precipitation exceeds the values necessary to avoid the increase in fire risk associated with warming. This is why Natural Resources Canada (NRC) has concluded:
This complex combination of influences makes it difficult to identify clearly whether any measurable changes in the patterns of wildland fire over the last few decades can be linked directly to climate change. Nevertheless, pattern changes do appear to be underway.
In Canada’s northwestern boreal regions, for example, the annual amount of forest area burned by wildland fires rose steadily over the second half of the 20th century. Some of this increase has been attributed to climate change.
By contrast, in Canada’s southern boreal forest, the annual amount of area burned seems to have decreased during the 20th century. This trend might be the result of climate change causing greater amounts of precipitation over time in these regions.
However, analyses of fire history suggest that it is the effect of climate variability on precipitation regimes that is the primary reason for the decreasing fire activity in southern regions.
In reading the NRC conclusion recognize that none of B.C. is in the “northwestern boreal region”. We are in the part of the country where we have seen decreasing fire activity. What the NRC and the Flannigan et al. paper make clear: in the long-term (by the 2091-2100 fire regimes) climate change, if it continues unabated, should result in increased number and severity of fires. However, what the data says is that right now this signal is not yet evident.
So to conclude this post lets sum the story up: the science is pretty clear, climate change will increase our forest fire danger, but it is NOT responsible for this year’s forest fires. Why is it so important to make this clear? Because in the last two years we have had a significant jump in forest fires and figuring out what is actually causing the increase in area burned is pretty darned important. We need to determine what changes in forest condition, forest management or whatever has resulted in the last two years of fire behaviour. Understanding that the last two years’ fire seasons are due to something other than global warming frees us to figure out what actually has caused the increase. Most importantly, we need to figure this out before the effects of global warming actually start influencing our fire seasons.