Bloomberg Green emails us about “Sao Paulo’s climate paradox” of being too dry and too wet at once, naturally enough “its largest climate-induced stress test in more than a decade” rather than just some bad weather. But then they tell us “‘What’s behind all of this is climate change, derived not only from global warming and greenhouse gas emissions, but also from land use change,’ said Marcelo Seluchi, a meteorologist from Brazil’s National Center for Monitoring and Early Warning of Natural Disasters, also known as Cemaden.” Right. Climate change is behind climate change, and behind the climate change behind climate change lurks global warming and greenhouse gas emissions rather than, say, global warming due to GHGs. And land use change just in case all that stuff was word salad.
It’s hard to know where to start not believing it. Perhaps with its worst weather in more than a decade being proof of some unprecedented alteration in the direction of doom.
It seems it was very dry in 2014-15, then it wasn’t, and now it is again. Which might lead the unwary to think Saõ Paulo is prone to periodic drought. Though of course back then the Guardian blamed climate change, noting a politician’s dissent then invoking the scientists who say, as in “Scientists think otherwise” before admitting that urbanization and deforestation might also be involved.
Again the unwary, especially if they accidentally learned that history didn’t start in 2014, might also stumble over the knowledge that that earlier drought, which in some tellings lasted from 2014-17, was the worst in a century not the worst ever, and the summer of 2013-14 “was considered the hottest and driest in Brazil in 71 years” not the hottest and driest ever.
Speaking of “ever”, Wikipedia also claims the “Grand Seca” of 1877-78 “was the largest and most devastating drought in Brazilian history” and killed something like half a million people. But of course Brazilian history only goes back about 500 years, if you mean the kind of history that relies on written records not speculation. But evidence from what is there known as “pre-Cabraline history”, as in “before the arrival of Portuguese navigator Pedro Álvares Cabral in 1500”, indicates that when it comes to changing weather, stuff happens. Always did. Not always nice. Sometimes wet. Sometimes dry. Sometimes hot. Sometimes cold. Why weren’t we told?
Oh, and put it down to our puckish sense of humour. But we did an online search for whether Brazil is warming faster than the global average and you do not win anything for guessing that yes, it supposedly is, like everywhere else.
Now the Bloomberg Green story also says that Cameden’s:
“data shows that precipitation levels have been falling since the 1960s in much of Brazil, coinciding with widespread deforestation in the central area and in the Amazon.”
Which has, of course, nothing to do with warming or GHGs but chainsaws and brushfires. Which isn’t to say deforestation isn’t bad. It’s to say if we cut down a tree then say it wasn’t me it was the climate change that changed the climate, we should not be believed. Not only because it’s clear that doing stuff other than releasing CO2 that makes a place drier isn’t releasing CO2 that makes a place drier, but more fundamentally because climate change can’t cause climate change.
How can it be possible that this point must be made again and again?
Longer periods of drought and humidity result from weakened zonal circulation. This can cause ocean temperatures to rise. I believe that changes in the stratosphere (ozone layer) have the greatest impact on circulation changes and are related to solar activity. A decrease in solar activity causes an increase in pressure at high latitudes. Such changes in circulation have occurred many times in the past and have caused the collapse of many civilizations that were highly advanced in hydrology.