Environmental Impact of Extreme Extremes in a Changed Climate
Reagrding extreme weather events, I believe that the case that “it’s just weather” is going to get much weaker. The good news that us climate concerned will have a big “told ya so” moment is greatly outweighed by the bad news. The damage to natural systems due to climate change is going to increase dramatically.
Natural systems are robust to extremes of a stable climate, but vulnerable to excursions outside the norms. It’s those extreme extremes, the abnormal abnormals, that are just starting to emerge.
It’s Not Just Weather
I decided to try to explain this based on a tweet by Brad Johnson.
Brad’s point is that what could easily be written off as “weather” locally looks very different in a global context.
People who are in denial about how we are changing our climate look at the current heatwave in the southwest, and say “look, this isn’t even a record, it’s just weather”.
Brad’s image is a good start toward understanding the fallacy here, but it’s not by itself decisive. In the 1934 case, hot weather in the eastern US was balanced by cool weather elsewhere. In the 2016 case, it’s warm almost everywhere, and hot in quite a few places.
This balance isn’t perfect, but if you look at the older images you’ll find that on the whole there aren’t especially blue ones or especially red ones. (El Niño / La Niña oscillations provide the largest departures from this balance.) You have to look at the whole record to convince yourself that the image above isn’t a cherry pick. The fact of the matter, though, is that it is really quite representative.
This is what kicked off my effort here. I want to explain why ecological impacts are likely to take a rapid turn for the worse.
So in any given place, we’re flirting with record warmth more often. (Getting unusual precipitation as well. In many places very warm years are associated with drought.) As long as this stays within the range of the baseline climate, ecosystems can adapt, and people focused locally can shrug it off as “bad weather”. Even if we haven’t seen it before globally, we’ve seen this before, here.
But as the warming continues, we’ll increasingly see excursions that are outside the range of even “the normal abnormal”. The Texas drought of 2011 was more severe than any previously recorded by a wide margin, for example.
Biomes are adapted not only to a mean climate but also to an interannual variability. Under the current climate regime, very hot years appear which are just at the edge of natural variation. The biome is stressed, but on the whole remains healthy. So people look around and see that nothing much has changed in their surroundings with the changing climate.
It only takes a single highly abnormal year to cause enormous damage to natural biomes, though. In the extraordinary Texas heat and drought of 2011, the relict pine forest of Bastrop County, Texas, the westernmost range of the loblolly pine forest of the southern US, succumbed to an enormous fire, so intense that the soil died over a large region, visible east of Austin, just east of the town of Bastrop on US Highway 290.
It’s not the record-challenging years that will do us in. Biomes by definition have survived record conditions. But we’re going to start seeing conditions that greatly exceed records. And this is where the problems will become especially serious.
Like Texas, Portugal is no stranger to wildfires. And like Texas in 2011, Portugal in 2017 is seeing fires of a new intensity and greater tragic import than it is used to, under the influence of extremely hot weather. Because trees are immobile and long-lived, forest biome damage is going to be increasingly obvious. Damage in other ecosystems may be less obvious, but it’s coming.
My main point here is that it’s sort of a threshhold effect. It doesn’t kick in when the somewhat abnormal year remains in the range that the given biome has seen as an extreme year. These impacts will not be gradual; they occur at threshholds, and the likelihood of hitting those threshholds is going to go up rapidly as climate increasingly departs from baseline, and at an unnatural rate.
It gives me no pleasure to say this. But if you care about nature, things are going to get very much worse.
Yes, there’s still time to avoid the worst of it. But whatever we see at any moment in terms of ecological impact of climate change will be only a small fraction of what we are already committed to at that moment.
It’s not as though there isn’t damage on the ground already. But bigger losses are coming, especially to forests that cannot adapt quickly. These losses will show up as extreme forest mortality, due to fire or disease or invading pests.