Heeding warnings, and proactive responses to climate change: megadroughts

The notion of designing infrastructure around anticipated environmental conditions is not a new one. The easiest example to illustrate this is probably floods – across the world there are dams, levees, and certain areas – often agricultural fields – can be designated and designed as places for water to flow, to reduce its effects elsewhere. Boston, MA is currently working on a plan to redesign the city with sea level rise in mind. While the waters will eventually reach the point where portions of the city are permanently below sea level, long before that point there will be increasingly frequent flooding from storm surges and high tides. To deal with that, low-lying areas are being turned into public parks that will be useful as recreational areas when they’re dry, and that can be safely allowed to flood when the need arises. EDIT: I had originally said they’re not going far enough with their predictions. That is because I misunderstood and didn’t read thoroughly enough. They are planning for 21″ (53.3cm) of sea level rise by 2050. Good for them!

The image shows a drought-stricken corn field. The soil is cracked and parched looking, the sky is cloudy, but empty of rain, with blue showing behind the white clouds. The corn stocks are brown, bent, and dead. The only green is from a couple hardy weeds and grasses nearby. You can almost feel the heat looking at the silent scene.

Photo by Tom Castelazo

Just as sea level rise is now being accepted as an inevitable problem that coastal regions are going to have to deal with, other areas are also facing near-certain changes that they need to plan for. Some regions, like the American northeast, are likely to see a shift in the direction of a monsoon-like pattern, with more annual precipitation in fewer, larger events, with dry spells between.

What the western US is facing is, in some ways, more straightforward – it’s going to dry out.

With the western United States and northern Mexico suffering an ever-lengthening string of dry years starting in 2000, scientists have been warning for some time that climate change may be pushing the region toward an extreme long-term drought worse than any in recorded history. A new study says the time has arrived: a megadrought as bad or worse than anything even from known prehistory is very likely in progress, and warming climate is playing a key role. The study, based on modern weather observations, 1,200 years of tree-ring data and dozens of climate models, appears this week in the leading journal Science.

“Earlier studies were largely model projections of the future,” said lead author Park Williams, a bioclimatologist at Columbia University’s Lamont-Doherty Earth Observatory. “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.”

Reliable modern observations date only to about 1900, but tree rings have allowed scientists to infer yearly soil moisture for centuries before humans began influencing climate. Among other things, previous research has tied catastrophic naturally driven droughts recorded in tree rings to upheavals among indigenous Medieval-era civilizations in the Southwest. The new study is the most up-to-date and comprehensive long-term analysis. It covers an area stretching across nine U.S. states from Oregon and Montana down through California and New Mexico, and part of northern Mexico.

Using rings from many thousands of trees, the researchers charted dozens of droughts across the region, starting in 800 AD. Four stand out as so-called megadroughts, with extreme aridity lasting decades: the late 800s, mid-1100s, the 1200s, and the late 1500s. After 1600, there were other droughts, but none on this scale.

The team then compared the ancient megadroughts to soil moisture records calculated from observed weather in the 19 years from 2000 to 2018. Their conclusion: as measured against the worst 19-year increments within the previous episodes, the current drought is already outdoing the three earliest ones. The fourth, which spanned 1575 to 1603, may have been the worst of all — but the difference is slight enough to be within the range of uncertainty. Furthermore, the current drought is affecting wider areas more consistently than any of the earlier ones — a fingerprint of global warming, say the researchers. All of the ancient droughts lasted longer than 19 years — the one that started in the 1200s ran nearly a century — but all began on a similar path to to what is showing up now, they say.

Nature drove the ancient droughts, and still plays a strong role today. A study last year led by Lamont’s Nathan Steiger showed that among other things, unusually cool periodic conditions over the tropical Pacific Ocean (commonly called La Niña) during the previous megadroughts pushed storm tracks further north, and starved the region of precipitation. Such conditions, and possibly other natural factors, appear to have also cut precipitation in recent years. However, with global warming proceeding, the authors say that average temperatures since 2000 have been pushed 1.2 degrees C (2.2 F) above what they would have been otherwise. Because hotter air tends to hold more moisture, that moisture is being pulled from the ground. This has intensified drying of soils already starved of precipitation.

All told, the researchers say that rising temperatures are responsible for about half the pace and severity of the current drought. If this overall warming were subtracted from the equation, the current drought would rank as the 11th worst detected — bad, but nowhere near what it has developed into.

“It doesn’t matter if this is exactly the worst drought ever,” said coauthor Benjamin Cook, who is affiliated with Lamont and the Goddard Institute for Space Studies. “What matters is that it has been made much worse than it would have been because of climate change.” Since temperatures are projected to keep rising, it is likely the drought will continue for the foreseeable future; or fade briefly only to return, say the researchers.

“Because the background is getting warmer, the dice are increasingly loaded toward longer and more severe droughts,” said Williams. “We may get lucky, and natural variability will bring more precipitation for a while. But going forward, we’ll need more and more good luck to break out of drought, and less and less bad luck to go back into drought.” Williams said it is conceivable the region could stay arid for centuries. “That’s not my prediction right now, but it’s possible,” he said.

Lamont climatologist Richard Seager was one of the first to predict, in a 2007 paper, that climate change might eventually push the region into a more arid climate during the 21st century; he speculated at the time that the process might already be underway. By 2015, when 11 of the past 14 years had seen drought, Benjamin Cook led a followup study projecting that warming climate would cause the catastrophic natural droughts of prehistory to be repeated by the latter 21st century. A 2016 study coauthored by several Lamont scientist reinforced those findings. Now, says Cook, it looks like they may have underestimated. “It’s already happening,” he said.

The effects are palpable. The mighty reservoirs of Lake Mead and Lake Powell along the Colorado River, which supply agriculture around the region, have shrunk dramatically. Insect outbreaks are ravaging dried-out forests. Wildfires in California and across wider areas of the U.S. West are growing in area. While 2019 was a relatively wet year, leading to hope that things might be easing up, early indications show that 2020 is already on a track for resumed aridity.

“There is no reason to believe that the sort of natural variability documented in the paleoclimatic record will not continue into the future, but the difference is that droughts will occur under warmer temperatures,” said Connie Woodhouse, a climate scientist at the University of Arizona who was not involved in the study. “These warmer conditions will exacerbate droughts, making them more severe, longer, and more widespread than they would have been otherwise.”

Angeline Pendergrass, a staff scientist at the U.S. National Center for Atmospheric Research, said that she thinks it is too early to say whether the region is at the cusp of a true megadrought, because the study confirms that natural weather swings are still playing a strong role. That said, “even though natural variability will always play a large role in drought, climate change makes it worse,” she said.

Tucked into the researchers’ data: the 20th century was the wettest century in the entire 1200-year record. It was during that time that population boomed, and that has continued. “The 20th century gave us an overly optimistic view of how much water is potentially available,” said Cook. “It goes to show that studies like this are not just about ancient history. They’re about problems that are already here.”

Because we know this is coming, we have the ability to act on it, and to reduce the impact it will have. Increasing water storage and water conservation measures now will make it easier to cope with future droughts. Lawns can be replaced with drought-tolerant alternatives to grass, and/or with region-appropriate food gardens. Sewer systems can be re-designed to recycle water. Agriculture will have to either change crops, or move indoors to seek shelter from increasingly harsh conditions. And regardless of what approaches are taken, priority has to be given to protecting existing water supplies from contamination. Industrial contamination of all kinds needs to be controlled. It should be no surprise to my readers that I believe the best way to do this is a combination of research, regulation, and replacing the existing corporate model with democratically operated, worker-owned cooperatives, so that the people running operations that might pollute local water supplies are also the people who have to drink from them.

Likewise, many industries use a huge amount of water, and it’s essential that that be made more efficient where possible, and recycled and re-used where necessary.

As with desalination, this will generate a great deal of more concentrated toxic waste that will, in turn, need to be dealt with. This is true for a number of things. It has already been reported many times that the natural gas industry has, in addition beyond the water used, been generating vast quantities of radioactive waste, which is currently being handled with predictable irresponsibility. That needs to change. Fracking needs to stop, and the existing waste needs to be managed responsibly. Likewise, nuclear waste from fission plants needs to be dealt with based on the requirements of its storage and containment, and not based on what’s profitable for corporations generating that waste. It’s likely that in the coming decades, there will be an increase in nuclear power. I have mixed feelings about this, but if it’s going to happen, then plants must be designed to do without water for extended periods of time, ideally indefinitely. Waste needs to be stored in a manner that does not rely on a constantly replenished supply of water, through dry-cask storage, or better yet used in generators designed to run on radioactive waste while containing and consuming it.

The list of challenges that need to be overcome, in facing the conversion of the western US into a desert, is as long as the list of ways in which we use water. Because we have a solid idea of what changes are coming for different regions, we have the ability to plan ahead even as we work to reduce the speed of those changes by cutting back on fossil fuels.

Just as America missed the opportunity to slow and contain COVID-19 before it could spread out of control, the world has missed the opportunity to avoid a devastating, rapid rise in global temperature. We can – and must – slow that rise, and work to reverse it if possible, but in the meantime, every step we take to adapt to the changes we can no longer avoid will both reduce the suffering caused by those changes, and make it easier for us to continue reducing our emissions, and pulling carbon out of the atmosphere.

The more we plan and act in advance, the less time, resources, and life we will waste on disasters that didn’t need to be as big as they became. The logic of capitalism, with its just-in-time production, its profit-obsessed notions of efficiency, and its focus on greed as an engine for society, has never been valid. That said, we’re entering an era in which it will shift from lethal dysfunctionality to insanity. If you look at any society existing in harsh conditions, you will find that its success and resilience depend on its ability to act and plan collectively, for the good of all. We’re facing a new era in which our technology and medicine can no longer shield us from the dangers of the planet we live on as they have done for many of us – we must adapt to our surroundings as they change, and we can no longer afford to hand over most of our resources into to a tiny number of people to do with as they please.

In reality, we could never afford that, and the current environmental crisis is that bill coming due. Now we have to pay up, and if it’s not dealt with through collective action and through socialism, then I fear it will be through mass death, and or even extinction.

There’s a degree to which I feel like I’m repeating myself with these pieces, and that’s because while some of this work is –finally– beginning to be done, the amount that still remains before we can say we’re really dealing with the problem is… a lot. There’s a lot of work to do, and for much of it, we’ve known it needs doing since before I was born. Just as we knew about the dangers of climate change early enough to do something about it, had we taken action, so to have we known a lot about how to mitigate and adapt to those dangers for long enough that we could have been well on our way to building a more resilient society by now, that could ride out the coming chaos while improving life for everyone. It may be too late to stop the planet from warming for the rest of my lifetime, but it’s not too late, at least in theory, to prevent that warming from causing an unimaginable level of death and misery.

I think the transition town movement has it right – each town, and each region is going to have different needs, based on different sub-climates and different starting points. The role of society as a whole is to maintain a global network of distribution and mutual aid that can help those short on resources to meet their needs, so that when drought, flooding, heatwaves, or disease come for other areas, everyone who’s doing better has the resources to help.

A rising tide can lift all boats, if we make sure that no boats are held down by anchor chains that aren’t long enough. Sailors, you have nothing to lengthen but your chains!

Unfortunately, life costs money, and my income from this blog has yet to meet minimum wage for the time I put into it. If you can afford to, please consider pledging a couple dollars per month or so through my Patreon. This will help me continue creating and improving this blog by keeping a roof over my head, and food in my carnivorous pets so they don’t eat me. Crowdfunding requires a crowd, so if you can pitch in a little, it would help a great deal!


  1. StevoR says

    FWIW. Australia is also going to be hit especially hard by megadroughts and then the mega-fires like the Unprecedented Bushfires we had this Summer.

    Another issue as things change faster, they are going to keep on changing ever faster and ever more for the worse. Everywhere.

  2. StevoR says

    Now we have to pay up, and if it’s not dealt with through collective action and through socialism, then I fear it will be through mass death, and or even extinction.

    The Anthropocene. Its not going to be an era but a Mass Extinction Event :


    We’re already in that mass extinction and too many people just don’t realise it or the depth of the trouble we’re all in.

  3. says

    Yeah. There are tough times ahead. It’s one of those things where I think we have the technical capacity to dramatically reduce the harm to ourselves, and to various ecosystems around the planet, but I’m very worried about whether we’ll have the social/political capacity to do so.

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