After all, how far can it be said that a catastrophe like the one that is plaguing Rio Grande do Sul is linked to the anthropogenic climate crisis (that is, caused by our species)? Could other disasters, recently or yet to come, be attributed to this cause?
The answers are not simple, but I hope this column serves as a guide for the perplexed, clarifying the most important points of the logic linking extreme weather events to the global crisis that humanity has caused.
The first big fallacy that we need to face when talking about this topic is the use of phrases like “Ah, the climate has always changed!” or “But what about that 1941 flood in Porto Alegre, huh? Was it global warming's fault too?” –classic examples of telling lies using truths.
Yes, extreme events have always happened and will always happen. But it is necessary to take into account that the climate, as a complex system, works in a probabilistic way. This means that the anthropogenic climate crisis is altering the LIKELIHOOD of major disasters happening, simply because they become more frequent. The proverbial rain that would only fall once a century now happens every 50 years or 25 years, let's say; the one that would fall once a decade starts to flood the periphery every year.
It is also common for people to be perplexed by the variety of extreme situations – droughts, rains and even, counterintuitively, snowfalls – with the climate crisis. After all, isn't it just the planet's average temperature that is increasing?
Well, it turns out that temperature rise is a key variable in the climate system, capable of influencing a number of other things at the same time. Perhaps the most important of these is the fact that a warmer atmosphere can be compared to a sponge inside which simply “fits” more water vapor.
Depending on the seasonal, continental and local context (pardon the rhymes), this could mean a much greater capacity for the formation of rain clouds, which can return all this water with more violence – the heat is a kind of “foot on the accelerator” of this process.
In fact, the same can be true for blizzards (in places where it still snows, of course). Keep in mind that, although it affects many things, anthropogenic warming is not capable of changing the tilt of the Earth's rotation axis, which is responsible for the existence of winters and summers around the world. The winter in temperate countries may be weaker, but it still comes, and the water vapor that was concentrating in the atmosphere, instead of falling like storms, starts falling like blizzards (in fact, anyone who knows these conditions knows that, in very low temperatures, snowing is less likely).
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Another paradox is that, again, depending on certain conditions, an increase in temperature can dry out an environment more quickly and lastingly, or make it difficult for air masses with humidity to pass through. Result: more inclement droughts.
I repeat: the key is changes in probabilities and frequencies, which come together to create a riskier and more unpredictable world for us and the rest of the biosphere. “Ah, no one imagined that this could happen”: yes, sir. No more burying your head in the sand like an ostrich.
PS – If you want to understand, step by step, the basic concepts about the climate crisis, I highly recommend listening to the brief and educational episodes of the Tortinha de Climão podcast.
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