The Climate in Emergency

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


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Climate Fiction: In Lullaby and Warning

Obviously, this is not three-minute fiction. It’s a longer piece I wrote for a different contest. I did not win, so I’m debuting the story here, instead. Much sympathy to the victims of the flooding in West Virginia; it’s been a bad week for extreme weather. –C.

 

“Where is my jet-pack?” demanded Andy Cote, the eminent scientist.

“Your what?” asked his nine-year-old daughter, Jordyn, from the living room floor. She was busy doing his portrait with crayons.

“He’s joking, honey,” explained her mother.  Alejandra Garcia came up behind her husband in his recliner and rested her hands on his shoulders. “If you had a jet-pack you’d just incinerate your feet,” she told him. She brushed his hair off his forehead and kissed him there.

“I would not!” he protested. Theirs was a marriage of professors (he of ecology, she of literature), but he was the absent-minded one and she would not let him forget it. “We’re halfway through the 21st century now,” he continued. “You’d think we’d have jet-packs. Or at least flying cars, like in ‘Back to the Future?’ Remember?”

“That was a little before my time,” confessed Ale. She was fifteen years his junior.

“You had to have seen ‘Back to the Future,’ though.”

“Nope.”

“Daddy, are you turning into a grumpy old man?”

“What? No, why?” Even as he spoke, Andy noticed that his daughter had selected the grey crayon for his hair and was scribbling away with it. She didn’t bother with the admixture of light brown he swore was still there.

“Because grumpy old people always talk about the past,” Jordyn explained, simply. Then she pitched her voice down as far as it would go and waved her arms around pompously. “When I was your age, it snowed on Christmas! And the snow would stay on the ground for weeks! There were no hailstorms or hurricanes and it was never too hot and if it was we just turned on the air-conditioner!”

“Ok, but it did used to be colder.”

“Da-ad!”

“I’m headed off to class,” Ale announced. “Don’t forget to feed our daughter lunch.”

“I wouldn’t!” He feigned hurt. “I get too hungry to skip meals.” His self-deprecation made her laugh, that lovely russet laughter. When she tried to walk away he grabbed her arm and held her, his gaze dark and urgent. “I love you,” he told her, just in case. He always said that before they parted, even if she’d only be gone a few hours.

“I know,” she said him, and kissed his mouth. Her fingertips lingered just under his jaw for a moment and then she was gone. He glanced at his daughter, wondering if she were old enough yet to find parental displays of affection embarrassing. She looked up at him.

“Ok, Dad, what’s actually wrong?”

He sighed. She was as direct as her mother. He wasn’t sure he could explain this to a child, or that he even wanted to try, but he didn’t want her to think him unwilling to answer questions, either.

“When I was your age,” he began, and stopped. Hadn’t she just said that’s how old men talked? But he was not going to let himself be cowed by a nine-year-old. “When I was your age, tablet computers, autonomous drones, and a lot of the other technology we take for granted was science fiction. Now, I’ve just read online, on my tablet, that my friend, Diana Cartwright—do you remember her?—has launched three hundred drones to help her collect climatological data. It’s like I’m living inside one of those movies I used to watch. And whenever I have that thought about living in a movie, I remember being a little boy and then a young man, with all the expectations I had for the future.

“But those movies never covered climate change. The one thing we actually knew about the future–and we ignored it. Intellectually, of course, I knew that the way we lived was unsustainable and would have to change somehow, but emotionally I believed the movies. I don’t mean jet-packs. I mean that I expected the life I knew to basically continue. And when those expectations didn’t pan out, I felt like I had lost something. Sometimes I still feel that way. Does that make sense?”

He was unprepared for Jordyn’s aggrieved shock.

He had told her before, briefly, about how the old civilization finally collapsed and about his other family, the wife and children who had died. He knew she had probably guessed that those losses still haunted him. But he had not stopped to consider how these pieces of knowledge would fit together inside the child’s mind. He had a blind spot where others’ perception of him was concerned and he realized too late how Jordyn would feel seeing him grieve a world and a family that hadn’t included her.

“But Daddy,” she exclaimed, “I’m here!”

I am the worst parent in the world, he thought. How was he to explain that yes, he wished he had never been widowed and he was grateful every minute of his life for his new wife and child? Just like he was overjoyed that the age of fossil fuel had ended at last, even though it had taken a stupid and preventable catastrophe to accomplish the change, and he missed air conditioners, passenger airplanes, and his motorcycle? None of it made any more sense than his fantasy of using a jet-pack.

Andy Cote had written and published three books and co-authored 47 papers and two monographs. He made most of his living by talking to people, either in class or in public lecture halls. And yet at that moment he had no words at all to comfort his daughter. He opened his arms to her instead and she climbed into his lap, which she was really too big to do anymore, and he held her tightly as though someone or something might try to steal her away.

And he sang, just like he had sung over her cradle when she was a baby, a James Taylor song about a young cowboy.

He had meant the old song simply as a lullaby, a way to evoke a point in their relationship when fatherhood was simpler and love more obviously expressed. But as he sang, a new meaning welled up in the words and he realized he wasn’t singing about a fantasy figure alone on the range–Andy was singing about himself. Like the cowboy, he had no real companions outside of work and he, too, had organized his career around travel. He had a solitary streak and a wanderlust no love could root out and over which he had no control. He taught classes in the winter and spring, but with the next academic season he would be off again, walking across the country, meeting with colleagues, teaching where he could, and exploring the world. His next departure was only weeks away.

And so he sang in lullaby and in warning. He would leave again, and someday he would die. And the world would continue to change—the greenhouse gas emissions already up in the sky had not yet finished their work. It still snowed sometimes, where he lived in Pennsylvania, and sometimes it snowed a lot. It didn’t have to be very cold for snow, after all. But there might come a day when even that respite from the heat would be lost to them. He’d given his life, his intellect, his labor, and his heart to learn how to repair the world, but he understood it might not have been enough.

In his singing and his embrace were the only legacy, the only love, he could be sure of leaving his daughter; his acknowledgement of the truth of her world.

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If We Stopped Tomorrow

What would happen* if we stopped causing climate change tomorrow?

It’s a fantasy, obviously, though an appealing one. It’s also food for a lot of interesting thought. What would life be like? What kind of climate would we be left with? Would climate change stop right away, or would there be residual change? Here, I’m going to explore the climate part of the question; if humans stopped producing greenhouse gas emissions right now, how would the climate respond?

For simplicity, our scenario is that all humans everywhere simply vanish and that all our machinery shuts itself down safely at once–I’ll ignore complications caused by unattended machinery blowing itself up and so forth. I want to be clear that I do not actually think my whole species should go extinct, I just don’t want to get pulled off topic by an overly complex scenario.

When do greenhouse gas emissions stop?

Emissions of different greenhouse gases stop at different times in our scenario. These gases are carbon dioxide, methane, nitrous oxide, and two groups of related gases, the chlorofluorocarbons and the hydrofluorocarbons (CFCs/HCFs), plus water vapor. I’m going to ignore water vapor here because the primary way its atmospheric concentration varies is not from emissions but from changes in the hydrologic cycle.

So, in our scenario, fossil fuel use and its carbon dioxide emissions stop immediately–but that’s only 57% of total greenhouse gas emissions worldwide by weight. Another 20% of the total is carbon dioxide from other sources, such as forest fires or aerobic decomposition. 14% is methane, 8% is nitrous oxide, and 1% is CFCs/HCFs. These gases come from different processes and some of these processes would continue a while.

Nitrous oxide comes largely from the production and use of nitrogen fertilizer. Its emissions should therefore drop off pretty quickly in our scenario. CFC/HCFC comes from industry and refrigeration and would therefore drop off much more slowly as abandoned refrigeration units slowly broke down and leaked. But the real issue would be methane and non-fossil-fuel-related carbon dioxide.

If the world were simple, then after our piles of wood and paper and other biomas finished burning or rotting (that might take a few years), atmospheric carbon oxide levels should stabilize. The only remaining emissions would be from natural wildfire or decay and that carbon would be taken up again as other plants grew. But the world is not simple. One of the things climate change is doing is shifting some places from forest to savanna. It’s unclear how much of that shift has happened yet, but it’s quite possible that some of our forests are essentially dead trees walking, so to speak. They won’t get the rain they need to survive and when they die they will be replaced by grass, shrubs, and the occasional tree, not forest. In that case, their carbon won’t be recovered, driving the atmospheric concentration up. One of the nightmare scenarios we’re looking at is if climate change caused by forest dieback becomes enough to cause further dieback–a runaway positive feedback cycle in which the planet starts warming itself.

If that nightmare feedback loop has not started yet, I doubt it would under our scenario, given the substantial emission cuts from the end of fossil fuel use. But elevated CO2 emissions will persist at least as long as it takes those forests doomed by climate change to die and rot or burn.

Methane levels might actually not drop in our scenario. Methane occurs as a fossil fuel and is also produced by anaerobic decomposition at the surface. Agriculture is a major source, mostly from rice cultivation and animal husbandry, and these emissions would probably taper off pretty quickly. Our vast herds of cattle are not going to survive us for very long. But landfills and leaky fossil fuel facilities will keep producing methane for a long time–only we won’t be here to capture and burn off those emissions (burning converts methane to carbon dioxide, which is actually a good thing because methane is a much more powerful greenhouse gas). So those emissions could actually increase without us. I do not have enough information to calculate what the net result would be. And the nightmare scenario is that melting permafrost liberates enough methane to warm the planet enough to melt more permafrost and release more methane….

So, what we’re looking at is that if humans vanished and neither nightmare cycle has begun yet, total greenhouse gas emissions would drop immediately by somewhere around 60% and then probably decrease further over a period of years. When the system would reach equilibrium seems unclear. The relative contributions of each gas would change dramatically as well, with methane becoming co-dominant with CO2 by weight. Since methane is both more powerful and less persistent in the atmosphere, this shift would be very important to anyone running climate models of our scenario.

How long will the climate keep warming after emissions stop?

Even if the atmospheric concentrations of all the greenhouse gases stabilized today (which under our scenario they would not), the global climate would continue to warm for a period of years. This lag between cause and effect is actually a very familiar principle; if physics didn’t work this way, cooks would not have to use timers because food would become fully cooked the instant it went on the stove or into the oven. Earth’s climate has a longer lag than it might otherwise because we have oceans and water can swallow a huge amount of energy before changing temperature, but basically things just take a while to warm. The experts aren’t sure, but Earth’s lag is probably around 40 years–which means we are now experiencing the consequences of the greenhouse gas emissions of the 1970’s.

In our scenario, then, the loss of humans does not start to show on our climate for another couple of decades. Only then will the planet start responding to the dramatic decreases in emissions.

How long will sea level keep rising after the warming stops?

Here is another familiar principle: ice takes time to melt.Glacial dynamics are a bit more complicated, since they receive new snow as well as lose meltwater and they move, but when scientists say a certain amount of melting is “locked in,” that basically means that a certain amount of ice already has the conditions necessary to melt. It’s like an ice cube set out on the table at room temperature; that ice cube is going to melt away to nothing even if the air in the room does not get any warmer. Because glaciers are very big, some of the melting now locked in might take thousands of years–or it might go faster. Scientists aren’t sure, and of course the rate of melt is likely to increase because the temperature will keep rising (for at least 40 years!), but however long the process takes, the melting we have already triggered will cause at least three feet of sea level rise, probably more.

How long will greenhouse gas levels stay elevated?

Under our scenario, and assuming those cycles of viciousness aren’t in operation yet, greenhouse gas levels would level off as soon as emissions stopped and then eventually start falling. How long would it take for the atmosphere to return to something close to what it was before? The answer depends on which gas you’re looking at.

CFCs/HCFs and their kin vary a lot. Some can stay in the atmosphere for thousands of years, some for less than a year. I do not know how many of each kind we have up there and in what proportions, but we’re looking at a process that begins immediately and lasts for a very long time. Nitrous oxide breaks down in the stratosphere and takes just over a century to do it. Methane is quick, lasting only about 12 years (my source does not say what any of these chemicals becomes afterwards–I am suspicious that methane may become carbon dioxide, a complicating factor!).

Carbon dioxide is the tricky part, since it can leave the atmosphere by several different means. Much of it is absorbed into the ocean pretty quickly, where it no longer causes the greenhouse effect but instead causes ocean acidification. Also, this mechanism only works if there is more CO2 in the air than what the water near the surface can absorb. The upper layers of the sea are getting “full” now, meaning that not much more CO2 will go into the water until ocean mixing brings new water up to the surface. Chemical weathering of rocks also absorbs CO2, as does, of course, photosynthesis. And that last is the complicated one.

If the distribution of plants across the globe is roughly stable, then carbon sequestration by photosynthesis will be roughly matched by carbon emissions from fire and decay. But reforestation–and the re-establishment of wetlands–could become a powerful force for carbon sequestration with humans out of the way. Unless environmental damage has in some way precluded regrowth, which is possible, and unless the nightmare cycle has begun.

Without factoring in regrowth, somewhere above 65% of our carbon dioxide will be absorbed by the oceans in the next 20 to 200 years and the rest will drop very gradually, finally reaching equilibrium after a few thousand years. If plant regrowth proves significant, the process could go faster, maybe much faster–there is evidence that reforestation following the conquest of the Americas caused the Little Ice Age. In our scenario, it would be the entire world regrowing.

So what’s the scenario?

Bringing all of this information together, we can fill out the details of this scenario.

Humans either vanish or somehow become ecologically negligible in November of 2015. Right away, that very month, greenhouse gas emissions drop by about 60% and then continue dropping gradually over a period of years. Atmospheric concentrations of these gases also start to drop right away, though more gradually. Within a few years, meaningful reforestation begins in some areas, possibly balancing out climate-related deforestation elsewhere.

But the global average temperature keeps climbing–and it’s climbing faster than ever because the oceans have absorbed enough energy that now they’re warming rapidly, too. Extreme weather gets more so. If there are any humans left, they are having a very rough time of it. Somewhere around 2055, the climate begins to stabilize, although what it looks like by that point is anybody’s guess.

But by that point the atmospheric concentration of methane has fallen and leveled off at whatever its new normal is. Carbon dioxide levels are starting to fall meaningfully. I don’t know whether there is the same lag on cooling as there is on warming, but by sometime around the turn of the century I’m guessing the planet has started cooling again–and the cooling gradually accelerates over the following century as nitrous oxide starts to break down and as more and more carbon dioxide is absorbed by the oceans and by growing plants.

All this time, the sea level is rising. Water creeps gradually across the hurricane-ravaged ruins of many of the world’s major cities and upstream into previously fresh areas of the world’s rivers. Oysters grow on the streets of Manhattan.

I’m guessing that the cooling will take much longer than the warming, because greenhouse gas levels will stay somewhat elevated for thousands of years. The  planet would also see a lot of delayed effects of the warming–along the lines of changing plant growth patterns or changing ocean salinity triggering various feedback loops. I don’t know what those loops would be or when they might occur. At some point the pace of change would slow enough that the biosphere will start to recover–but recovery from a mass extinction takes about ten million years.

Feeling depressed?

I don’t mean this as an exercise in pessimism. I mean it as an illustration of what optimism looks like at this point, what we can look forward to in the best possible scenario we can anticipate. If being limited to this as optimism bothers you, consider how the next generation will feel if we do not get our butts in gear right now.

 

  • Note: After writing this, I’ve thought of a bunch more complications that might change the details of the picture I’ve given. I stand by my factual statements, but my suppositions might be muddy. Creating a detailed, accurate climate projection is not my intention, though–that requires a supercomputer I don’t have. The point is to draw attention to the questions, to the issues of lag and lingering emissions–to provide food for thought.


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Your Tuesday Update on Wednesday: For a Little Boy

I first posted “A Family Expecting” shortly after the birth of my nephew. I have re-posted it occasionally since then, but he’s getting old enough now that I figured the piece was due for  a major re-write. So, here it is, edited for length and clarity, and with a new ending. Please check out the original for the research links posted at the bottom.

Yesterday, my first nephew was born. He is small and wrinkled and has acne on his nose. He has wispy black hair and silvery-blue eyes. He knows the voices of his family and the scents and sounds of the hospital. He does not know about his home, going to school, or getting a job. He doesn’t know about casual friends, mean people, or birthday cake. He doesn’t know what the world will be like for him.

Neither do we, obviously, but if he lives to see his 89th birthday then his life will touch the end of the century, spanning the same period of time across which many climate models dare to predict. He comes from farming people in the Peidmont of the Mid-Atlantic. If he stays here and inherits his parents’ farm, as he might, then his life will also be the life of this landscape. What will he see?

This child will go home soon, and become the son of the land. He’ll rest in a cradle on the floor of a barn, his mother rocking him with one bare foot as she directs customers picking up vegetables in June. In two or three years, he’ll carry handfuls of squash guts as gifts for the chickens and a rooster as tall as he is will look him in the eye and decide he’s ok. He’ll listen to his parents worry about droughts. He’ll learn to hope the heavy rains don’t rot the tomatoes and that rising gas prices don’t break the bank. There will likely be more such worries as he gets older. Summers will be hotter. His mother will say it didn’t used to be like this, but grown-ups always say that.

According to the IPCC, by the time he’s a teenager, temperatures in the Mid-Atlantic will average maybe two degrees higher than they did during his mother’s childhood. That does not sound like much, but averages rarely do. One degree can turn a pretty snow into a destructive ice storm.

Warming, in and of itself, will be good for the crops; only a local rise of about five degrees Fahrenheit or more hurts productivity. That’s unlikely to happen here until my nephew is a very old man. But the Great Plains may warm faster, enough to cause a problem; he could study the shifting agricultural economics in college. Or, he might prefer the shifting flights of birds, since many migrants head south based on conditions in Canada, and Canada will warm faster yet. Should be interesting.

Our area could either get wetter or drier. Parts of northern and central Mexico will almost certainly get drier, maybe dramatically so. These areas are dry already, so I imagine a lot more people will start heading north. My nephew will discuss the refugee problem with his friends, lean on his shovel in the morning sun, and wonder if the United States has a responsibility to keep Mexicans from dying when Congress is already deadlocked over how to pay for the flooding in New England. Seems you can’t keep a bridge built in Vermont, anymore. He takes off his sun hat and scratches his thinning hair.

Years pass. My nephew thinks about his upcoming fiftieth, and also about New York City, where three of his grandparents grew up. It’s turning into a ghetto. It’s not under water, exactly, though the highest tides creep slowly across abandoned parking lots in some neighborhoods, spilling over the older seawalls. The problem is this is the second time it’s been stricken by a hurricane, and now no one can get the insurance money to rebuild. The same thing has happened to New Orleans and Miami. Boston may be next. Those who can get out, do. Those who can’t, riot. They have a right to be angry. His daughter is pregnant with his first grandchild. My nephew cannot keep his family safe indefinitely, but he’s glad his parents taught him how to grow food.

My nephew turns sixty-five. He proud of his skill as a farmer, especially with the way the rules keep changing. The farm seems to be in Zone 8, these days. He’s got new crops and new weeds. He’s got friends in southern Maryland who haven’t had a hard frost in two years. Maybe this year they will; Farmer’s Almanac says it’ll be cold. Last year he and his wife took a trip through New England and let his kids take care of the harvest for once. They stayed at romantic little bed-and-breakfasts and took long walks in the woods, holding hands. There was white, papery birch-bark on the ground, here and there, the stuff takes a long time to rot, but he knew he’d have to go to Canada if he wanted to see one alive. It’s sad.

My nephew lives long enough to see more change than any prior human generation has, and that’s saying something. A lot of the change is environmental, but not all of it. Major technological shifts rework the country yet again, and the entire political and economic center of gravity pulls away from the coasts. He is aware of this upheaval intellectually, but viscerally he is used to the world he lives in. He lives well. He is loved and he is useful. No dramatic disasters befall him, the worst-case scenarios do not play out, but plenty of disasters do happen to other people. My nephew is sympathetic. He writes his Congress-people and gives generously through his church whenever he can.

But a lot of good that could have been done decades ago wasn’t.

I saw my nephew tonight. He’s at home now, wrapped in a blue blanket like an animate dumpling, slowly fretting against the swaddling. His wrists and ankles are as thin as my thumbs. He’s too young for baby fat. He doesn’t know what his future holds. And neither, really, do we.

——————–

I wrote the above fantasy several years ago and many of my predictions have already come true. My little nephew has indeed learned about birthday cake (I hope he does not yet know about mean people) and does indeed share his farm with chickens, though he prefers the company of the goats and can imitate their voices. More darkly, Manhattan was hit by a major storm-surge (Superstorm Sandy) and Miami Beach now floods regularly due to sea-level rise. I don’t think he knows it, but the years of his  life thus far have seen consecutive global heat records broken, two successive record-breaking tropical cyclones (Haiyan and Patricia), rumors of “jellyfish seas,” a major climate-related refugee crisis, the possible California Megadrought, and dramatic, unprecedented fires in Canada, the United States, and Indonesia. Among other deeply worrying developments.

Come on, people, put your backs into it, whatever we make of the future, my nephew will have to live there.


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Your Tuesday Update: Prosecute ExxonMobile

As some of you will have heard, Exxon knew that climate change was real and largely caused by fossil fuel use back in the eighties. The company then publicly denied climate change for decades, working through many of the same PR experts who had previously worked for the tobacco industry.

In a way, this should not be news. After all, I knew about climate change in the eighties. And I was a little kid at the time, not one of the leaders of a major corporation. Of course Exxon’s leadership knew.

But for Exxon to use climate research to plot corporate strategy (such as deciding to pursue drilling in the Arctic because the warmer climate would make doing so cheaper) while simultaneously insisting to the public that these same studies were unreliable…it’s just insulting, is what it is.

And, as it turns out, the whole strategy may be illegal under the RICO statutes–the Racketeer Influenced and Corrupt Organizations Act, a law originally passed in order to tackle organized crime. The tobacco industry was successfully sued under RICO for exactly the same strategy of willful disinformation–so why not EXXON? The settlement could be big enough to fund some serious climate adaptation and mitigation and could discourage other professional deniers. This could be big.

I don’t suggest specific actions very often, but this seems important; please click here to sign a petition asking President Obama to sue ExxonMobile under RICO for climate denial.


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Your Tuesday Update: The State of the State

So, being in Maine at present, I decided to do an online search for “climate change Maine” and see what happened. What I got was a report on the state’s present and future climate, an update on a more extensive report on the same topic conducted several years earlier. It’s dry but quite readable–and it’s shorter than it looks, since many of the pages don’t actually have a lot of text on them. You can get an overview of the state of the state, as it were, in just a few minutes.

To read the report, click here.

I won’t try to summarize the whole thing, but here are a few highlights:

  • Air temperatures have increased, especially in the winter. The warm season is about two weeks longer, now.
  • Overall precipitation has increased.
  • The number of extreme precipitation events has increased (including extreme snow).
  • Ocean temperatures in the Gulf of Maine are rising faster than in the ocean as a whole.
  • The Gulf of Maine is more vulnerable to ocean acidification than is the ocean as a whole.
  • Practical impacts of these changes include increased risk of heat stroke, Lyme disease, and flooding, as well as disruption to fisheries, agriculture, and winter tourism.

The report concludes with a list of information resources.

I haven’t checked every state, but it looks like at least most of them have commissioned similar reports and they’re easy to find online. What is the outlook for your state?


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Your Tuesday Update on Wednesday

Hi, all,

Looks like I did not post on Tuesday as I meant to! As noted, for the time being I’m only doing mini posts on Tuesdays and doing a full post on Thursday. This, then, is your mini-post.

Last night, I heard on the news a story about extreme weather all over the US–flooding, hail, a dust storm, all within the same few days, though widely separated in space. I also heard my husband exclaim that California is rather seriously on fire right now. He’s a firefighter, and reads national fire reports regularly. There have been two fatalities this year associated with wildfire, and a huge amount of money invested in getting the fires contained. But he doesn’t know whether any of this is actually unusual in an objective sense.

ARE we in a spot of climate-change-induced bad weather? Certainly we could be, as climate change makes both droughts and floods more likely, but I do not know whether this week is actually unusual, or if the newscasters just wanted to talk about the weather for whatever reason. I did not do a thorough search for information. But I did hop online and poke around and I found an interesting article about different kinds of extreme weather. What struck me is that while heavy rain events are getting more frequent, there’s no evidence that tornadoes and severe thunderstorms are–because we do not actually know how many such storms are normal. Up until the last few decades, most supercell storms must simply have gone unrecorded. Now we have a lot of weather radar capable of spotting most of them, but there’s a lot we don’t know. For example, most tornadoes never have their windspeed measured, so their severity is measured strictly by how much damage they cause. That means there is no way to compare tornadoes to each other independent of what they happen to pass over. The whole thing is similar to the situation with hurricanes, only worse, because we have even fewer data to work from.

So when they say there’s no evidence that tornadoes are increasing, there’s also no evidence that they are not.

Here is the article I read, if you want to check it out.


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What Scientists Don’t Know

So, sea level rise has been in the news, recently, in part  because of recent warnings from Dr. James Hansen that we could see as much as ten feet of rise in the coming decades. The story is a little more complicated than that and has caused significant controversy. In the interests of clarity, I’ll summarize what I’ve been able to learn about Dr. Hansen’s announcement and also explore the overall topic of sea level rise.

According to Ars Technica, Dr. Hansen and his colleagues have completed a research project that involved using a computer model to explore how ocean currents would respond to various speeds of sea level rise. They could set the model to “ten feet in fifty years,” and the computer would show them ocean currents for that scenario. The study did not look at how much the sea will actually rise how quickly, only at the consequences of different rise scenarios. Then, the team submitted a paper on their research to a peer-reviewed journal, but the review process can take a long time. The team evidently wanted their results to support meaningful climate action at the Paris conference in December, and worried that the paper might not be published in time. So, they chose a journal that has an unusual public peer-review process, enabling the researchers to speak publicly about their results before the review is complete. As part of getting the word out, they also released a short summary of their research, which included speculation that the sea could in fact rise ten feet in the next several decades–something this particular research project did not address, but Dr. Hansen is entitled to make educated guesses in his area of expertise.

The problem is that the wording of the summary leaves it unclear that he is speculating, and the public media have generally reported that the study actually predicted a rapid ten-foot rise–something that is well beyond scientific consensus at this point. To be clear, that doesn’t mean the rapid rise won’t happen. It probably could, because Dr. Hansen is very much an expert on the subject, and he could turn out to be right. He is not in any way misrepresenting his research, he is just talking about something else besides his research and doing it in a way that leaves the distinction between the two unclear.

Here is an analogy:

Say that an auto-safety researcher conducts a series of crash-tests and concludes that a given model of car has a design flaw such that a particular type of crash is lethal at an unusually low speed. She then calls a press conference, presents her findings, and says “given my results, I am especially concerned about young drivers–the traffic mortality of drivers in the 16-to-21 age group may sky-rocket if the manufacturer does not correct the flaw.” The media then respond by saying that safety test predicts teen driver mortality to sky-rocket, even though that isn’t at all what the test was about.

It is possible that Dr. Hansen created the current media buzz deliberately in order to get attention for his cause–but if he’s being alarmist, it’s only because we are in an emergency that deserves the sounding of alarms. It’s not wrong to shout “FIRE!” if the crowded theater is, in fact on fire.

I expect climate denialists will pounce on this one and paint it as an episode of deliberate dishonesty, but they would probably find a way to do that no matter what Dr. Hansen decided to say.

So, here is the overall situation with sea-level rise as we know it so far:

The world is warming, and has been for some time, now. That’s not a prediction, it’s simply historical fact. It can be difficult to measure the rise in any one location because not only does the sea go up and down, but so does the land. In much of New England, for example, the land is very gradually rising because it is still rebounding from the weight of the glaciers of the last ice-age. That makes it harder to notice sea-level rise on New England coasts. In contrast, my home area, in Maryland, is sinking, making sea-level rise seem faster than it really is. But by comparing multiple sites, measuring from satellites, and other techniques, scientists can work out how fast the seas are actually getting bigger; the water has risen about eight inches since the Industrial Revolution. Most of that rise is due to thermal expansion–warm water takes up more space than cold water. The rest is due to meltwater from glaciers.

Glaciers anywhere in the world, even those that are nowhere near the sea, raise the sea level as they melt because the meltwater eventually flows into the sea. We know how much ice is currently locked up in glaciers, so we know how much the sea could rise if all of it melted. And because all that ice takes a long time to melt, we know that even if the global temperature stabilized tomorrow, the ice would continue to melt and the sea would continue to rise until the world caught up to its new temperature. What we don’t know is how fast the ice will melt or exactly how much melting we have already committed itself to.

Not all ice has an effect on sea level, however. Floating ice–either sea ice, which forms when the ocean surface freezes, or icebergs, which form when chunks of glacier break off and land in the sea, can melt without changing the sea level at all. To demonstrate this, fill a glass with tap-water, drop a few ice cubes in, and carefully mark the water level. Allow the ice cubes to melt, and you’ll see that the water level remains unchanged. This is because when ice melts it shrinks and the volume it displaces when it floats is precisely equal to the volume of water it turns into. The melting of the arctic sea ice is a terrible catastrophe, but it’s irrelevant to sea level rise. The fact that sea ice around Antarctica is growing (remember that warmed-up ice remains ice until it reaches 32 degrees, and Antarctica is very cold) is also irrelevant.

What does matter is how much ice is floating in the sea, so if a glacier starts calving off icebergs faster (as many glaciers are), that raises the sea-level, even if those floating icebergs don’t melt. Also, much of the ice surrounding Antarctica is actually sitting on the sea-bed. That is, the glaciers rest on solid rock, and that rock is below sea level. If those glaciers thin to the point that they begin to float, then not only does the water that melted off them raise the sea, so does the fact that they are floating. One of the scary things about the science here is that it’s not always obvious from the surface which ice has begun to float–there are tests scientists can do, but those tests sometimes give surprisingly bad news.

We’ve had a lot of bad news from glaciers recently, some of which have moved very quickly, broken apart, or melted away quite unexpectedly because of reactions below the surface that scientists did not anticipate. We’ve never seen the world warm this quickly before, so we don’t know what ice does in situations like this. That is one reason why Dr. Hansen could be right–although the speeded-up melting he warns about has not happened yet, and nothing we know about ice suggests it is going to happen, there is a lot we still don’t know about ice.

Dr. Hansen is guessing that what we don’t know will hurt us.