The paper, "Large Contribution from Anthropogenic Warming to an Emerging North American Megadrought," by a team led by A. Park Williams of Columbia University, has an alarming enough title, but when you read the paper itself, you find that "alarming" is kind of the understatement of the century. Here's a sampler:
Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogenic climate change. We use hydrological modeling and new 1200-year tree-ring reconstructions of summer soil moisture to demonstrate that the 2000–2018 SWNA drought was the second driest 19-year period since 800 CE, exceeded only by a late-1500s megadrought. The megadrought-like trajectory of 2000–2018 soil moisture was driven by natural variability superimposed on drying due to anthropogenic warming. Anthropogenic trends in temperature, relative humidity, and precipitation estimated from 31 climate models account for 47% (model interquartiles of 35 to 105%) of the 2000–2018 drought severity, pushing an otherwise moderate drought onto a trajectory comparable to the worst SWNA megadroughts since 800 CE.There's a lot to unpack here. First, not only is the southwestern quarter of the United States heading toward a drought worse than any in recorded history, close to 50% of its severity is directly due to human activity. On top of that is another thing the study uncovered -- that we were misled (as it were) by the fact that the twentieth century was unusually wet, encouraging widespread settlement by humans and huge investments into agriculture in the region. "The twentieth century gave us an overly optimistic view of how much water is potentially available," said study co-author Benjamin Cook, also of Columbia University, in a press release. "It goes to show that studies like this are not just about ancient history. They’re about problems that are already here."
"Earlier studies were largely model projections of the future," added study lead author Williams. "We’re no longer looking at projections, but at where we are now. We now have enough observations of current drought and tree-ring records of past drought to say that we’re on the same trajectory as the worst prehistoric droughts."
[Image courtesy of Science, Williams et al.]
Drought always brings to mind the struggles faced by farmers confronted with the vagaries of weather, but in this case, the problem is orders of magnitude worse than that. The press release from Columbia University (linked above) mentioned that Lake Mead and Lake Powell -- two of the largest reservoirs in the southwestern United States -- are already seeing a dramatic drop in the water levels. These provide a significant proportion of the agricultural and drinking water to a broad swath of the Southwest. What happens when these and others are functionally dry -- too low to allow for withdrawing water for any purpose?
A combination of short-sightedness, Pollyanna-style optimism, and a stretch of unusually wet years in the twentieth century led to coastal California and sun-belt cities like Phoenix and Tucson being some of the most heavily-settled areas in the United States, and now they're in the situation that if there's a true megadrought -- something far worse and longer-lasting than the piece of it we've already seen -- there could be millions of people without adequate drinking water.
I don't think it's an exaggeration to state that the federal and state governments are simply not equipped to face a disaster on that scale.
I hate to focus on negative shit, I really do, but in this case it's too important to ignore. I'm back to the James Burke quote I mentioned in the post two days ago -- about how we pay for insurance for other much less likely eventualities without batting an eyelash, but when it comes to insurance against climate collapse, for some reason this is considered ridiculous. The media hasn't helped, especially disinformation specialists like Fox News who have been hammering on climate change being some kind of evil liberal hoax for at least twenty years. Now, however, we're paying the price, which will only get steeper the longer we pretend it isn't happening.
Consider, for example, the impact of Donald Trump's firing the pandemic response team because he didn't want to spend money on something that hadn't happened yet.
So we need to sound the alarm. Loudly. Studies like this one should be on the desk of every lawmaker in the United States. Yeah, some of them are likely to ignore it -- I don't think a two-by-four to the head would wake up someone as catastrophically dense as James "Snowball" Inhofe, for example -- but the tide has to turn.
Because if you think things are bad now, my sense is you ain't seen nothin' yet.
This week's Skeptophilia book recommendation of the week is brand new -- only published three weeks ago. Neil Shubin, who became famous for his wonderful book on human evolution Your Inner Fish, has a fantastic new book out -- Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA.
Shubin's lucid prose makes for fascinating reading, as he takes you down the four-billion-year path from the first simple cells to the biodiversity of the modern Earth, wrapping in not only what we've discovered from the fossil record but the most recent innovations in DNA analysis that demonstrate our common ancestry with every other life form on the planet. It's a wonderful survey of our current state of knowledge of evolutionary science, and will engage both scientist and layperson alike. Get Shubin's latest -- and fasten your seatbelts for a wild ride through time.
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