The Climate in Emergency

A weekly blog on science, news, and ideas related to climate change


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Update on Hurricanes

Some years ago, I wrote that although global warming seems like it should make hurricanes worse, we can’t really say that it has. Until just a few decades ago, if a hurricane happened not to pass over human observers or equipment, we might not know it existed. It’s not that we have no data before that, it’s just not a complete picture. How can we compare “before” and “after” when we don’t have a full “before”? There are other complications, too.

Of course, as I pointed out, all that applies only if “worse” is taken to mean more frequent or with higher wind-speeds. Since the most dangerous part of a hurricane is always its storm-surge, which is unambiguously worsened by sea-level rise, another answer to the question is that yes, global warming does make hurricanes worse and is going to keep doing so as long as the seas keep rising.

In any case, I didn’t expect any of that to change any time soon–but it might have just done so.

The problem of inadequate “before” data is still there, but a team from Stony Brook University has just modeled Hurricane Florence as it would have been without anthropogenic climate change–essentially, they used the models used to forecast hurricane behavior, but altered the model so as to simulate an un-warmed world. Because the same computer system was used to forecast both the real-world hurricane and the counterfactual one, the reliability of the system can be checked simply by comparing the real-world forecast with the actual behavior of Hurricane Florence–the forecast was pretty good, as it turned out.

So, all of you who were under Hurricane Florence? It’s official. Those of you who saw the heaviest rainfall–you saw 50% more of it because of climate change. And if you live on the coast, the storm was about 50 miles wider when it made landfall than it would have been, so at least some of you were hit by a storm surge that would otherwise have passed you by.

Now, when I say “it’s official,” I don’t actually know whether there is any controversy around this approach. I don’t have an inside view of either climatology or meteorology, though I do have friends I may be able to ask. So we may have to wait a while to see how this is received, but so far it seems legit to me.

While we’re discussing new hurricane research, it seems there are two more variables to how “bad” a hurricane can be, and climate change looks to be making them both worse.

One is the speed at which storms travel. The slower a hurricane is moving, the longer it takes to pass over your house and the more hurricane you get. That was part of the problem with Harvey, which simply stayed put over Houston and rained for way too long. A study just published in the journal, Nature suggests that storms are, on average, getting slower, apparently because climate change is causing weakening of the air currents that move hurricanes along.

The other variable is how fast storms intensify. We’re used to tropical systems strengthening gradually over a period of days, so that if a tropical storm (wind speed no greater than 74 mph) is pointed at you and about a day away, you can go ahead and prepare for a tropical storm, or possibly a category 1 hurricane. But occasionally a storm will undergo “rapid intensification” and you can go to bed prepared for that tropical storm and wake up to find a cat 4 bearing down on you. Scary, no?

And while nobody is actually sure yet how rapid intensification works, it does seem to be happening more and more often. A recent computer simulation shows that climate change does indeed result in more of the most severe hurricanes (categories 4 and 5) and does so specifically by making rapid intensification more frequent.

So, there you have it, folks. While I’m sure more research needs to be done (doesn’t it always?) and the picture will get clearer and more sure as we learn more, climate change is making hurricanes worse. That means worse in the future and it means worse already.

So when I say we all need to vote for climate-sane candidates willing to re-instate Paris? This is why.

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How Does This Read?

I have spent the last few days reworking a series of short essays intended as a kind of post-script to a novel I have just about completed. The following is one of those essays. I have covered much of the same ground in this blog before, though with a slightly different focus, but I want to try out this piece and see how it reads. Feel free to comment with any feedback.

The Post-Petroleum World

Ecological Memory depicts a world of both ox-carts and robotic exoskeletons. Some readers might ask why. Yes, this is a world without fossil fuel, but it’s clearly a technologically advanced society, so why are they stuck using ox-carts? Why not use renewable energy?

The short answer is that they can and do, but if they used enough renewable energy to fully replace fossil fuels, they’d just wreck the world again. Where energy comes from is less important than how much is used.

We’re used to telling the story of technological progress in terms of innovation; cars are more advanced than ox-carts, so they go faster. But the other side of the same story is energy. A car than ran on just a few bales of hay couldn’t go much faster than an ox, no matter how advanced it was. Greater technology has allowed us to use more and more energy and that, not innovation alone, gives us our unprecedented power.

Fossil fuel made possible our energy increases. Fossil fuel use has also caused climate change and ocean acidification, and it indirectly causes several other ills, such as biodiversity loss. The mechanisms involved should be roughly familiar to most readers. The surprise is that drawing the same amount of energy from some other source would likely cause similar problems. Only the mechanisms would be different. To understand why, we need to take a dive into complex systems science.

“Complex,” here, has a specific, technical meaning. A system is complex if it has certain properties, such as self-organization and “nestedness,” meaning a system can have smaller complex systems inside it. I am a complex system and so are you. So are cells, ecosystems, and biospheres, among other examples. Whole books have been written on these systems, and those books are worth a read, but the important thing to know is that systems science is all about the flow of energy.

Complex systems can fight entropy and win. Entropy, readers may remember, is the tendency for everything to gradually run down as energy dissipates. Complex systems also lose energy to dissipation, but they don’t run down because they can actively draw more energy in from outside. If a system is drawing in more energy than it loses, it is anti-entropic. Think of a baby, eating and eating, and turning all those calories to growth and development, or a young forest, rapidly increasing in both biomass and biodiversity. Eventually, the system reaches a point of equilibrium where energy inputs equal losses, and growth stops. That’s maturity. From the standpoint of systems science, individual humans remain mature very briefly. Almost as soon as we reach full size, our metabolisms slow and we start losing energy, what’s called the entropic phase. More colloquially, it’s called aging. If something speeds up the entropy, or causes entropy before maturity, that’s illness or injury. A system that stays entropic long enough will cease being complex. That’s death.

All complex systems go through these phases, though not all automatically become entropic at a certain age. Forests, for example, don’t get old. They can become entropic, though. A forest on fire is entropic, for example. If the fire isn’t too severe, the forest will survive and become anti-entropic again for a while as it re-grows. As Andy explains in the story, size, complexity, and stability increase and decrease together. Adults aren’t just bigger than babies, they are also smarter and more resistant to disease. And there’s a reason we sometimes call the latter part of our entropic phase the second childhood.

All this energy has to come from somewhere, and complex systems often draw energy from the larger systems they are nested within. My cells draw energy from me. I draw energy from my society (mostly by working for a living), and my society draws energy from the biosphere. The catch is that if the smaller system draws too much energy, it will force the larger system into the entropic phase.

Think about why cancer kills if it isn’t successfully treated. Think about a forest being logged at an unsustainable rate. Think about the rapid burning of fossil fuel.

The biosphere, too, is a complex system, and it, too, had an anti-entropic phase when it was actively growing and becoming more complex and more stable—we know it was growing because the carbon dioxide concentration in the air was falling. Remember that plants store solar energy in carbon compounds built out of carbon dioxide and water. Free, breathable oxygen is the byproduct. Those carbon compounds then become the biomas and energy source of the entire living world. As the biosphere grew, the supply of carbon in the atmosphere shrank. The carbon dioxide/oxygen ratio eventually stabilized as the biosphere entered maturity. In recent decades, the carbon concentration has been rising again as the Earth entered an entropic phase.

Let me repeat that; the biosphere is currently entropic because of us.

The loss of stability and complexity and size always go with the loss of mass and energy as a complex system starts to die. Erratic weather, a changing climate, and widespread biodiversity loss are simply what these familiar symptoms look like on a large scale.

That burning fossil fuel should trigger an entropic phase isn’t surprising, given that the whole point of fossil fuel use is to access a lot of energy. The biosphere provides us with an annual energy budget of less than the total solar energy we receive, solar energy that builds plant tissue, drives winds, and moves waters. Were we to stay within that energy budget, living on sustainable forestry and agriculture, plus wind, water, and solar, most of the power we take for granted today would simply be out of our reach. Fossil fuel makes it all possible, and does so by giving us energy at a higher rate than what the biosphere actually receives. Biospheric entropy is the inevitable result.

To be clear, if we stop using so much energy, the biosphere will re-enter an anti-entropic phase and recover, though it will take a very long time for full recovery, possibly millions of years. There is hope, though time is getting short.

Giving up fossil fuel entirely is probably a necessary step towards sustainability. What’s the alternative, some complicated global carbon rationing system? Who could administer such a thing? But the end of the Age of Oil alone will not protect us. Should we ever find and use an alternative energy source to again draw more energy from the biosphere than the biosphere actually has to spare, we’ll be back in the same entropic muddle we’re in now. It would be like replacing a cancerous tumor with a six-mile-long tape-worm. The patient would still die, the only difference would be the mechanism.

Energy is energy. Using too much has consequences.

We will return to an energy budget similar to what the world had prior to the Industrial Revolution. One way or another, we will have to. And that change will impose real limitations on what we can do and how we can do it.

But an energy budget is not a time machine. We will not lose the scientific and cultural advances we have made, nor will we cease advancing. We won’t return to pre-Industrial Revolution life. We will build something new. What that something might be, I can’t say. Exoskeletons and oxcarts are simply part of my guess as to one possibility.


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Climate Change and Cancer

Cancer has been on my mind rather more than I’d like, so this week it occurred to me to check out the links between climate change and cancer. I figured there probably would be some. Horsemen of the Apocalypse tend to roam in packs.

It didn’t take me long online to find out that yes, there are links. There’s even a whole chapter on the subject in a report published by the National Institute of Environmental Health Sciences. Except where otherwise noted, this information in this article comes from that chapter.

Climate Change and Cancers

“Cancer” is not a single disease but rather a whole category of diseases. All cancers have some things in common, but causes and effective treatments both vary. It’s even possible to have two different cancers at the same time, in which case the two need to be treated separately, because what works for one won’t necessarily work for the other. So it’s not good enough to ask whether climate change causes or exacerbates “cancer.” We have to look at which (if any) cancers are involved.

We also have to be clear about what we mean by “involved.” I have not found anyone claiming that being too hot, too dry, too wet, or too wind-blown can actually cause any cancer (though these cause plenty of other health problems!), but there are indeed cancers that would be more rare if we weren’t heating the planet.

Some skin cancers are caused by exposure to UV light, and the thinning of the ozone layer caused more exposure. The main ozone-depleting gasses are also greenhouse gasses. Had those gasses not been released, there would be less climate change and less skin cancer. Higher temperatures also tempt people to expose more skin to damaging UV rays.

The other big climate-related cancer is lung cancer, which can be caused by air pollution. Many common air pollutants are also greenhouse gasses. Wood smoke, as in what comes off of all these wildfires we have these days, may also cause lung cancer.

So, it’s official; more climate change means more lung cancer and skin cancer.

A less direct source of risk is that climate change can make it easier for people to contact certain pollutants. For example, floods caused by the more extreme weather we’re getting often sweep up some very serious pollutants. Exposure to floodwater, or drinking water or soil contaminated by floodwater, could therefore involve exposure to various carcinogens. Higher temperatures make some pollutants more volatile, driving them out of soil or water and into the air. When the pollutants in question are carcinogens, that translates into more cancer, or more cancer risk in places that used to be relatively healthy.

Complicating Factors

You knew there would be complicating factors, didn’t you? One source of complication is that there’s a lot we don’t know about what causes various cancers or how the causal connection works. There are a lot of pollutants that might be carcinogenic, but we don’t know, or we know they cause cancer, but not how dosage relates to risk. Will one swim in contaminated flood water do it? We don’t know.

Another major source of complication is that a lot of the processes being advanced to lessen anthropogenic climate change could also carry increased risk of cancer. Nuclear power is one obvious example. Less obvious is that cadmium is used in the manufacture of solar cells, and cadmium is a known carcinogen. Hydrogen fuel cells could pose a problem if the cells leak, since hydrogen is an ozone-thinning gas and thus an indirect skin cancer risk. Even biodiesel could be a threat, since the chemical profile of its exhaust is different than from petrodiesel, and we really don’t know what breathing in that exhaust might do.

It’s not that we’re damned if we do, damned if we don’t–it’s that the picture is complex and we don’t understand it very well, yet.

What we do know is that using less energy from any source is the best bet for reducing anthropogenic climate change without causing secondary problems. But we knew that already. And using less energy isn’t a popular option.

Specific Pros vs. Vague Cons

While cancer is probably not the worst thing that anthropogenic climate change is doing, it’s definitely on the menu. If you have been touched by cancer in some way, you know how awful the malady is. It’s like a war zone breaks out inside your family and no one else can see or hear the bombs going off, the infrastructure breaking. We know, now, that the further anthropogenic climate change goes without somebody doing something about it, the more cancer there will be.

The problem is that not only don’t we know who is going to get cancer, we also have no way of knowing which cancers are climate-change related. That’s what increased risk means. We might know how many more cancer diagnoses there are, but we won’t know which of those people would have gotten cancer anyway. It’s hard to get emotionally involved with a statistic. You can always convince yourself that it applies to somebody else.

Contrast that with the concrete, obvious benefits of using fossil fuel–if you drive to the store for a loaf of bread, you know perfectly well who got that loaf of bread. If you own a petrochemical company, you know perfectly well who made a very comfortable living. You don’t know who got cancer from that same tank of burnt gas.

The same problem occurs with any cost/benefit analysis of fossil fuel use. If we’re going to get ahead of this thing, we’re going to have to make those unpredictable cancer cases seem just as real as that loaf of bread, that comfortable living.

 

 

 


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Tick, Tick, Tick, Tick, Tick

When I was little, the appearance of a tick itself was reason for alarm.

“So-and-so found a tick the other day!” Mom would announce. “Be careful!” I think I had one on me–just one–my entire childhood. I’m not sure whether there were really so few ticks, or if we were simply bad at finding them. I do know that when I moved to Maryland, I didn’t have to be good at finding the little parasites. Huge numbers of them found me.

Seriously, go for a walk in my neighborhood in the summer, and you’re likely to pull off ten or twenty just while you’re walking. When you get back to the house, strip off your clothes and find a dozen more. They won’t have had time to embed, yet, so it’s not a big deal. You just get in the habit of routine regular tick checks.

Incidentally, I don’t find the standard advice of long pants and so forth very useful. Sure, fewer ticks will make it to skin that way, but some will, and they’ll be impossible to find without taking your pants off, which the neighbors tend to frown on. So the ticks get more time in which the crawl into someplace inaccessible and bite.

My advice?

  • Wear as little clothing as possible and then investigate every tickle and itch immediately–it might be a tick.
  • Do a thorough tick check and take a shower immediately upon returning home.
  • If you walk through a tick-hatch and get zillions of the tiny things on you, don’t panic. They can’t give you any diseases because they’re babies and don’t have any diseases yet. Remove them as best you can, stick them on a length of tape so they can’t escape and bite you again, then invest in a large supply of anti-itch cream.
  • Don’t bother learning to identify different species of tick. They can all give you SOMETHING, so just avoid getting bitten by any of them, and if you get sick, go see your doctor.
  • Look up the proper way to remove an embedded tick. NEVER put anything on the tick to make it let go, because that makes the tick vomit into you first and then you’ll definitely have whatever it was was carrying.

I’m not a doctor, this is just my personal approach to the problem.

The reason I bring all this up is to make clear I am personally familiar with the density of the tick population in the mid-Atlantic region of the United States, and I am equally aware that New England has fewer of them. Don’t get me wrong, New England does have ticks–Lyme disease is named after a town in Connecticut, after all–but the problem is simply not on the same scale.

That could be changing.

There are reasons other than climate change. Tick population dynamics and the epidemiology of tick-borne illnesses are complex, inter-related topics with a lot of variables. For example, modern land-use practices, which has converted vast areas of the United States into mosaics of tiny forested patches with houses mixed in, favors white-footed mice, which are the primary hosts of deer ticks–which transmit Lyme disease. The mice, after all, can use tiny habitat patches (and houses) just fine, but their predators can’t. No foxes, no bobcats, no black snakes, no owls, etc., all adds up to oodles of mice and oodles of ticks. So, some kinds of ticks would be a bigger problem than they used to be, even without climate change.

But yes, the climate is helping.

The story is a complex one, because not only do factors other than climate influence tick populations, but the response of ticks to climate is not straight-forward. For example, ticks of the same species may become active at different temperatures in different parts of their range. All these different variables working together mean that predictions of what climate change will do to different species of ticks can disagree with each other widely. But some increases in tick-borne illnesses have been traced to climate change–so we don’t know what’s going to happen in the future, but in the present, the ticks are worse in some places already because of climate.

For example, the two species responsible for infecting people I actually know, deer ticks and lone star ticks, are both expanding their range because of climate change. Both can transmit multiple illnesses. Lone stars, named for the white spot on their backs, can give you a (possibly life-long) allergy to red meat. Without giving away any individual’s medical history, I can say I’ve seen this one, it’s quite real. And lone stars are now in all New England states, though they didn’t used to be.

(By the way, the article that I’ve linked to above describes lone stars as “hunting in packs.” I’ve seen the behavior the article is describing, and the phrase is misleading. The ticks aren’t acting cooperatively, like mini-wolves. But, unlike deer ticks, they can and do walk towards potential hosts. In my neighborhood, population densities are often high enough that half a dozen might be near enough to notice the same person, and if you stay still for a few minutes they’ll converge on you. They’re easy to avoid or remove, but it’s creepy to watch.)

And then there’s the winter ticks, which have always been in New England, but warming climates are letting their numbers surge so high that they’re literally bleeding moose calves to death.

All of which is to say that if you head north in the summer, as we do, and you notice more ticks on yourself and your pets than you used to, as we have, it’s not your imagination.


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A Break for Puffins

“How’ve you been liking the hot weather?”

I turn around and spot the man sitting on the rock at the edge of the parking lot. He works at the restaurant across the way and he comes here to take his smoke breaks. We say hi to each other every time he does. He’s one of those strangers who’s almost a friend.

“I don’t like it, much,” I say, of the weather. I’ve been either under- or over-dressed all day.

“Yeah, it’s funny,” he says, “yesterday it was warm in Bar Harbor, but cold here. Today, it’s hot here, but it’ll be cold in Bar Harbor.”

Bar Harbor, I should add, is not that far away, yet he could be right. I’ve known it to rain in town but stay dry just three miles away.

“You know, I’ve heard the Gulf of Maine is 11 degrees warmer this year than normal?”

“Yeah, I know,” he tells me.

“It’ll be a bad year for puffins,” I add.

“Oh?”

“Yeah, when the warm water comes in, so do warm-water fish, which are a little bigger and rounder. The adult puffins can catch the warm-water fish just fine, but the chicks can’t swallow them. So, in years when warm-water fish species predominate in the Gulf, every puffin chick in Maine starves to death.”

“That’s really sad.”

“Yeah, it is.”

“That’s really sad.” He seems to really feel for these puffin chicks. “But there’s nothing anyone can do about it.”

“Well, stop global warming.”

“Yeah, but we can’t do that,” he protests.

“Yes, we can,” I counter. “Not immediately, because of atmospheric lag, but you know, nothing is so bad that it can’t get worse? By the same token, nothing is so bad that we can’t keep it from getting worse.”

“Yeah. I like puffins. I have paintings of puffins hanging in my bathroom. I tell people, these are real birds. They’re not made-up! I’ve only ever seen a couple of them.”

“I’ve never seen even one,” I admit. “Where did you see them?”

“It was last year. They took us on a cruise—among the islands.”

“Neat.”

“Yeah. You know, I’ve seen another Maine bird? I can’t remember what it’s called, but I can remember the sound it made, at night, in the water….It sounded like a frog, you know—a, a, bullfrog? Where I’m from, we have another frog that makes weird sounds, it’s called something else. It sounded like a frog, but my friend said, no, that’s a bird.”

“Can you imitate the sound?”

“No, but I can hear it in my head. I saw it, and it was a bird. It was dark, and sort of duck-like….”

“A loon?”

“Yes! That’s it! A loon!”

“They winter with us, in Maryland,”I told him. “They’re here in the summer and with us for the winter. They do make lots of sounds.”

“Cool! Well, I gotta go. It’s been nice talking to you.”

“Nice talking to you,” I tell him, and mean it, and I watch him head back into the restaurant through the back door.


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How Quickly Can We Cool?

I could write about lots of horrible things going on in the news this week. Unfortunately, I suspect there will be plenty of horrible news item to write about next week. This week I want to write about global cooling instead.

I’m working on a book set after the end of the age of fossil fuel, which means I need to understand how the climate responds to a falling carbon dioxide level. Obviously, average temperatures would fall, but how quickly? Warming has a lag time of several decades, because it takes time for heat to build up. Logically, cooling should be much faster. In bed, add an extra blanket and you won’t warm up for a few minutes, but kick your blankets off and you’ll cool down right away. But faster and instant are not the same thing, so how long would global cooling take? Since I need to read up on the issue anyway, I figured I’d share my results with you.

My fictional scenario is that a pandemic triggers the end of civilization, the total end of fossil fuel use, and a 90% reduction of the human population. It’s a complex and complicated scenario, because while most carbon dioxide emissions end, some types of methane emissions, such as leaking well-heads or outgassing landfills, would continue or even increase–and methane is a more powerful greenhouse gas than CO2 is. Would a net increase or decrease in climate-forcing power result? A smaller human population would allow widespread reforestation, but the warming that has already occurred would continue to cause forest dieback in some areas. Would there be a net increase or decrease in forest biomass?

Also, the planet would continue adjusting to the greenhouse gas and the heat that is already present. If greenhouse gas levels stabilized where they are now, temperatures would continue to rise for several decades. And even if the planetary temperature stabilized where it is now anyway, glaciers and permafrost would continue to melt. Melting permafrost, remember, releases methane, so the greenhouse gas concentration might continue to rise. Potential feedback loops abound.

I would love to stick all these variables into some giant computer and run a full simulation, but I don’t have that option. The best I can reasonably hope for is a definitive answer to just one question; assuming the greenhouse gas levels do fall, how long until temperatures start falling also?

Unfortunately, since the chance of my scenario occurring any time soon is very small, nobody seems to be studying what a falling greenhouse gas level would look like.

Fortunately, a version of my scenario did happen about five hundred years ago, when diseases killed off 90% of the population of the Americas, allowing widespread reforestation and causing the second, deeper phase of the Little Ice Age. So, how fast did that happen?

According to one estimate, the reforestation of the Americas could have removed anywhere from two to 17 billion tons of carbon dioxide from the atmosphere. That’s somewhere between 10 and 50% of the CO2 reduction recorded in ice core samples from Antarctica, so something else was going on also. There are various possibilities. But carbon dioxide levels do tend to track known European and Asian pandemics, which also allowed reforestation. The first, less severe phase of the Little Ice Age, may have been, in part, related to reforestation after the Black Death.

So, let’s look at the timeline–since researchers at Stanford University must think the timing of the second phase of the cold period is consistent with it being influenced by the American reforestation. Does the timeline suggest a lag exists?

The second phase of the Little Ice Age began around 1600 and lasted until around 1800. The drop in carbon dioxide, as recorded by Antarctic ice cores, that includes the result of American reforestation began in 1525 and lasted until the 1600s. The first smallpox pandemic in what is now Mexico began in 1519. I can’t confirm that was the first of the American contact pandemics, but Europeans handn’t set foot on the mainland much before that, so it must be close to the beginning.

So,

1519: people in the Americas start dying of exotic diseases to which they have no natural immunity.

1525: global carbon dioxide levels dropped by six to 10 parts per million and stayed that way for over 75 years.

1600: temperatures drop globally, though the drop may be most severe in the northern hemisphere and stays that way for two hundred years.

There is a lot about the Little Ice Age that is debatable–why is started, why it stopped, how severe it was, all of that. That significant reforestation could follow the beginning of the pandemic by only six years itself seems questionable. However, regardless of why the carbon dioxide drop occurred, it was followed by a drop in temperature 75 years later. Carbon dioxide levels rose again shortly thereafter. Temperatures rose again about 100 years after carbon dioxide levels–that delay on warming is consistent with the principle of atmospheric lag.

Richard Nevle and his colleagues at Stanford believe that a 75 year delay in cooling is not too much for a causal relationship to exist. So there is a significant lag on cooling also.

In our modern situation, carbon re-sequestration is unlikely to be rapid–even in the best case scenario, reforestation cannot absorb more than a fraction of what burning fossil fuel released. The rest must be accomplished by peat accumulation and slow absorption by ocean water. And whatever drop in carbon levels occurs, whenever it occurs, a human lifetime could pass before the temperature follows.

We’ve got to get started.

 


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Nor’easters

Last week, I spent three days huddled inside because of high winds rattling the house and ripping dead branches off of swaying trees–and I live in Maryland, where the storm (“Winter Storm Riley,” officially) was relatively minor. What we saw was nothing, compared to what the people in coastal Massachusetts experienced.

Now we’re preparing for another one (“Quinn”). And some meteorologists expect another storm after that.

What Are Nor’easters?

This week’s storms are nor’easters. They’re not unusual, although the recent one was an extreme example. Like hurricanes, they are very large low pressure systems that bring wind and rain (or snow) and last for several days. Unlike hurricanes, they draw their power, not from warm water (there wasn’t any under Riley) but from the interaction between warm and cold air masses. They generally form in winter. In the case of Riley, a storm system moved east across the US, then drove the rapid development of a very intense low pressure area just off the coast, which then moved north and gradually east. On satellite images, the thing looks like a hurricane, a massive pinwheel of swirling cloud off the coast. While too far out in the Atlantic now to influence my weather directly, Riley still exists. It’s busy causing damaging surf on Puerto Rico from thousands of miles away.

Nor’easters seldom approach hurricane force winds. Typically, these storms are gusty, not windy, a serious inconvenience, but not a danger, unless you have bad luck (such as an unusually weak tree limb right above your car). Rily was the most intense I’ve seen, and around here it was only in the high tropical storm-force range.

The lesser winds do not make these storms mild.

For one thing, nor’easters have much larger peak wind fields than hurricanes do. While a hurricane might have sustained winds of 90 miles an hour near its center, most of the area the storm passes over will get much weaker winds, say 50 or 60 miles per hour. A strong nor’easter will blast the same 50 or 60 miles per hour over the same large area, it just lacks the 90 mph core.

Second, wind is not the most destructive aspect of a hurricane, it’s just the easiest way to compare storms to each other. The size of the wind field, the speed the storm travels (and hence how long it spends in any one place), the size of its storm surge, and how much it rains are all much more important in terms of its destructive power–and above all, there is the question of what it hits. A low-lying, heavily populated area where the people lack both money and political power is where the disaster happens. And nor’easters have large wind-fields, heavy precipitation, sometimes heavy coastal flooding, and can persist for days.

And, as with hurricanes, when we get a bad one (or several) people start asking about climate change.

Nor’easters and Climate Change

Meteorologists can be quick to point out that individual storms can’t be linked to climate change, which both is and is not true. One recently referred to efforts to draw the link as “witch-craft.” That’s at best disingenuous.

We can absolutely prove that climate change is making nor’easters worse, for the same reason that climate change is making hurricanes worse. First, the single most dangerous aspect of either storm is coastal flooding, which is unquestionably worse now that the sea level is several inches higher than it was when most existing infrastructure was built and when the data used to define flood zones for insurance purposes were gathered. The apparent sea-level rise varies from place to place, because geological forces are also in play making the ground rise in some places and fall in others, but climate change can claim about eight inches of it world wide, due to a combination of thermal expansion (things, including oceans, expand when they heat up) and glacier melt. That means every coastal flood event, including all hurricanes and all nor’easters, are  eight inches worse than they would otherwise have been.

Eight inches doesn’t sound like much, until you imagine them inside your living room.

Also, a warmer planet means more humid air, which means wetter storms. In the winter, as long as the air temperature is below freezing (which isn’t really very cold), that means more snow–more closed roads, more fallen trees and snapped power lines, more collapsed roofs, more car accidents, more missed days of school. All of this should sound very familiar to some readers right about now. All that white stuff? Yup, it’s a symptom of climate change, not a negation of it. In warmer weather, wet storms means rain which means flooding. That’s ruined houses, damaged roads, washed-out bridges, soaked earth–leading to toppled trees and snapped power lines–and drownings.

We’ve been through this already with hurricanes; climate change does not have to cause individual storms, or even make a certain type of storm more likely or more intense, in order to directly cause more storm damage.

But can climate change cause nor’easters? Yeah, it kind of looks like they can.

Connecting the Dots

To tell this story, we have to cover a bit of atmospheric anatomy.

Remember the polar vortex? It was all over the news a few years ago, but I haven’t heard of it of late. It still exists, though. Actually, there’s two of them. Or sometimes three.

The polar vortex is not a type of storm, but rather either of two long-term atmospheric features–this sounds a little different than the last time I explained it, because the two features tend to get mixed up in public discussion, and I only recently learned that they are distinct.

Originally, “polar vortex” meant a circular pattern of winds that forms in the stratosphere around the pole in winter. It’s also called the polar night jet, because the sun does not rise in the winter at its latitude. The winds blow from west to east and divide cold polar air from warmer air at lower latitudes–the stratosphere is a layer that begins several miles up, above where weather happens. But in recent years, the term has also been applied to the jet stream, a circular pattern of winds in the troposphere–a much lower layer–also at a boundary between warm and cold air, but much farther south. The jet stream meanders, across the latitudes covered by the United States and southern Canada. The jet stream exists winter or summer, and its shape and location help determine whether any given area gets warm, tropical air or cold, arctic air this particular week.

Ok, so, definitions taken care of, what does either polar vortex have to do with climate change or Winter Storm Riley?

A lot of the strange weather we’ve had in recent years has been caused by extreme waviness in the jet stream. Because the jet marks the boundary between warm air and cold air, an extreme meander means that warm air flows much farther north than normal over here, while cold air flows much farther south than normal over there. At the same time, weather systems tend to persist longer and move slower than normal. Rainy weather becomes catastrophic floods. Dry, hot weather becomes killer heat waves and droughts. The extra waviness is likely caused by global warming, especially the loss of Arctic sea ice. As the planet warms, the polar regions warm faster than the rest of the planet, decreasing the contrast between the warm and cold regions and weakening the jet stream that lies at their boundary. Weak jets are slow and wavy.

So climate change doesn’t cause snowstorms in Florida by some magical method of “global weirding,” but instead through a fairly straight-forward form of atmospheric messiness, a weakened and wobbly boundary between warm and cold caused directly by the warming Arctic.

The next bit is less certain, as in not all scientists agree, but a weak and waving jet stream could be one of the mechanisms able to put pressure on the polar vortex and cause it to temporarily break down and allow warm air in over the pole. Such an event is, sensibly enough, called a Sudden Stratospheric Warming, or SSW. Although the stratosphere itself doesn’t have weather in the normal sense of the word, it can influence the weather of the troposphere, resulting in odd weather several weeks later–such as cold snaps, warm periods, or violent storms. SSWs appear to be natural (we have only been measuring stratospheric temperatures for a few decades, now, so it is hard to be sure), and their frequency has not increased, but some computer models suggest an increase could happen, and the extra-wavy jet stream could make it happen–or could already be making it happen. It takes a while to gather enough data to document a change in events that don’t happen every year.

Riley (and presumably its sibling-storms, to some extent) was triggered by a particularly severe SSW, one which ripped the polar vortex in two and triggered a bizarre winter heat wave in which parts of the Arctic rose above freezing for days on end. There’s no sun up there, remember, yet the ice started melting instead of growing–a bad sign. That triggering is not in doubt. And the SSW could have been triggered by a weak and wavy jet stream, which is itself caused by melting sea ice (notice the ominous cycle implied there?). Melting sea ice is, rather unambiguously, a symptom of global warming.

That “maybe” in the middle of the causal chain remains, but this is very close to a linkage between climate change and a single storm. Anyone who claims differently is going to have to marshal a much better argument than claiming “witchcraft” to convince me otherwise.