The Climate in Emergency

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

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High Tides Higher

Dorchester County, Maryland, sits on the eastern edge of the Chesapeake Bay. It’s the fourth-largest of the 23 counties in the state. By century’s end, it could drop down to the 14th-largest, thanks to some of the fastest sea-level rise in the world.

High Tide in Dorchester is a lovely and frightening documentary on the impacts, current and potential, of sea-level rise in this salty, marshy, and deeply historic part of my state. Except where otherwise noted, the information in this post comes from that documentary, which I heartily recommend.

The What and the How of Local Sea-Level Rise

A human, possibly a white man, stands facing away from the camera looking over the water to the horizon. He is wearing a red baseball cap and mostly dark, casual clothing. The water is very calm, barely a ripple, and the sea and sky are both lovely shades of blue and pink. It is apparently either sunset or sunrise. The man stands on what appears to be a wet, concrete platform, possibly a dock or a jetty. The end of the platform is underwater, suggesting sea-level rise.

Photo by Nicholas Barbaros on Unsplash

 Most of us know the sea is rising, and we know the basics of why, but of course there is more to the story than the basics. I’ve discussed some of this in other posts (for example, here and here and here), but Dorchester is a good place to see all of it come together in a worst-case scenario already well underway.

Besides glacial melting and thermal expansion, which are more or less global in their impact, there are several other, more local or regional causes of sea-level change, and by a weird coincidence they all come together in Maryland. These are:

  • A redistribution of water formerly held near the poles by gravitational attraction to the masses of ice on Antarctica and Greenland. As the glaciers lighten, this water sloshes back away from the poles, raising sea levels in other places. Maryland is one of those places.

  • The Gulf Stream runs along the surface of the ocean, like a river in the sea, until it gets near northern Europe. By then it has gotten a lot salter through evaporation, and so it sinks and continues on as a deep-water current, part of a global cycle of moving water. But the fresh water melting off of Greenland’s glaciers is diluting that salty water, making it slower to sink, causing the entire Gulf Stream to back up a bit—and that backed-up water also raises the sea-level in Maryland and parts nearby.

  • At the same time that the water rises, the land in the Mid-Atlantic region is sinking. This one, for once, isn’t caused by humans. Instead, it’s North America slowly readjusting itself to the melting of our glaciers some 12,000 years ago. The weight of the glaciers pushed the northern part of the continent down, creating a bulge just to the south. So with that weight off, northern areas are gradually rebounding (partially offsetting sea-level rise) while we just as gradually subside (adding to sea-level rise).

  • Erosion isn’t sea-level rise, but the faster the sea rises, the more quickly the lands erode.

It all adds up. Near the beginning of the documentary, the host—a white-haired, though still spry, gentleman—stands on what was the baseball diamond where he played as a boy. He’s standing in three feet of water.

Three feet of water on what was dry land within living memory—and the average rise globally is only about eight or nine inches so far.

The speed of sea-level rise is increasing. Global average rise is likely to hit two feet within the next 30 years. Depending on how much greenhouse gas ends up being pumped into the sky, it could top five feet by century’s end. What is that going to mean for Dorchester?

And Dorchester County is so flat that every one foot of vertical rise translates into five horizontal miles of land lost to the sea.

The Human Side of Things

A human (gender is unclear) with long dirty-blond hair is walking a medium-sized dog along a footpath through a vast yellow and gray grassland, possibly a big saltmarsh. The human is wearing a red sweater and long, dark pants and is carring a camera on a shoulder strap. The dog is on a short leash, is all black, and appears to be either a Lab puppy or a Lab/terrier mix. The color palatte of the photo is drab but restful, and the human appears casual and candid, not posed.

Photo by Patrick Hendry on Unsplash

Holland Island was once a well-to-do community, but is now just marsh with scattered dead trees. Its last house washed away in 2010. On Hooper’s Island, graves are falling into the water—the eroding shoreline is scattered with pieces of coffins and human bone. Farm Creek Marsh, as the name implies, was once farmland and still has the visible remnants of a settlement. The families of people who owned businesses there still live nearby. These are radical changes happening quickly enough that worlds change noticeably in a generation—or less.

Islands that once supported thriving communities have been reduced to marsh dotted with ruins and old graves. Towns shrink. Farmland reverts to swamp. Schools open late or close early as high tides creep across roads, obstructing buses. Snowplows are called into service any month of the year to sweep flood debris off low-lying roads.

If you live in Dorchester County, especially if your family if from the area, you already know all of this. You cope with the tidal flooding, the salt-water intrusion, the public events rescheduled in deference to the tide. You, or someone you know, has lost land, lost familiar landmarks, lost property value, lost a community, to the incoming salt water.

You may or may not attribute all of the above to climate change.

Many people living in the area attribute the losses to erosion, which is indeed part of the problem. And it’s true that there would be erosion in at least in parts of Chesapeake Bay even if sea level were stable (I have just confirmed this with my mother, a retired geologist). And while sea-level rise unquestionably makes erosion worse, it’s difficult to say which erosion is climate-related and which is not.

But as the documentary points out, the flooding and the salt-water intrusion (which is basically flooding that comes up inside the soil, rather than flowing along on top of it) are distinct from erosion and are wholly climate-related.

In some contexts, such as the conversion of marsh to open water, it can indeed be difficult to disambiguate erosion from rising seas. Did the water come up, or did the land go away? But where the land has not gone away, where it has just become wetter or saltier or both, that is not erosion.

“Nuisance flooding,” or “sunny day flooding” refers to saltwater flooding not associated with storms—no rain, no storm surge, just water coming up where it shouldn’t. Tides naturally vary, both over the month and over the course of a year. Winds can push water towards or away from shore even in good weather, too, adding a few inches to tidal extremes on occasion. Even were sea level not changing, we might expect to see an abnormally high tide wet a waterfront property now and then.

But, ask yourself, is such flooding getting more common?

When the abnormal high tide that once happened every year or so becomes a monthly or a twice-monthly occurrence, that’s not erosion. Something is changing.

Dorchester County is not the only sea-level rise hot-spot in the region. To a lesser extent, it’s happening all through the Mid-Atlantic. I’ve seen water creeping up into the streets in St. Michaels. I’ve seen fishing piers entirely underwater near Berlin. Nobody builds roads or fishing piers where they’re likely to flood semi-regularly—these structures are older than the current sea level is. Sunny-day flooding is becoming common in parts of Virginia, due to rapid land subsidence caused by unsustainable groundwater removal, plus the regionally-intensified effects of climate change.

There are other regions with their own hot spots. For example, though much of coastal Florida, sea-level rise is complicated by the porous limestone bedrock; build a sea wall to keep the rising tide out, and the water just flows through the bedrock and rises up on the other side to the exact same level as that of the sea. Lots of places have their own issues. Lots of people are facing much faster sea-level rise than the global average.

The future is not going to look like the past.

Looking Ahead

Sea-level rise, and the other symptoms of climate change, are not politics. Politicians may argue and disagree about how to respond to climate change, but the water itself doesn’t care whom you vote for, it just flows across your lawn.

The question is, what to do about it?

The people in Dorchester, and in Delmarva more generally, have a long tradition of connection to place, of attachment to the waters, marshes and forests that make up their home, and to the people, the human communities rooted in these places. These are inter-generational connections, and they don’t just wash away. Nor do they need to.

If emissions can be lowered, sea-level rise can be slowed, perhaps enough to allow the communities of low-lying areas to adapt. Buildings can be raised. Shorelines can be stabilized against erosion. Infrastructure can be moved back away from the water so that marshland can expand inland even as its outer edges are drowned by rising water. We need marshes to protect us from hurricanes and nor’easters and to provide breeding grounds for marine life, including the animals that go into the region’s famous seafood. We have a lot of options.

But to save communities in sea-level rise hot-spots will require partnerships between these communities and the wider world. Climate change is a problem no one can solve alone.

But we can solve it together.

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Dead Zones?

In previous years I have written New Years’ retrospectives, recapping notable climate-related news stories from over the past twelve months.

This year, a retrospective of the past few weeks might be in order.

While I’ve been occupied writing holiday posts–for Yule, for Christmas, for New Years’ Day–and generally being distracted by family obligations, we’ve seen California’s worst wildfire ever (followed by a deadly mudslide just today, which is not unrelated), a rather startling case of Extreme Winter, and a new and really frightening report on marine dead zones. And there have been various political issues. Let’s pick one of these stories and catch ourselves up, shall we?

Please note that where I make statements of fact without linking to a source, it’s because I’m using a source I already linked to.

Dead Zone

The term, “dead zone” is, unfortunately, not a metaphor. These are areas, usually along the coast, but sometimes out at sea, where there is so little oxygen in the water that animals can’t live. It’s a horrifying idea. Imagine minding your own business, living as you usually do, and all of a sudden breathing does no good. Dead zones aren’t spontaneous. They are caused when flushes of nutrients (usually runoff from over-fertilized farm fields or lawns, or from sewage treatment plants) trigger massive algae blooms in the water. Although algae itself make oxygen, when the supply of fertilizer is exhausted, the algae die off and decompose and bacteria go through a population explosion. While not all bacteria breathe oxygen, these do, and there are so many of them that they use up the local supply, causing a dead zone.

In some circumstances, a dead zone can also be caused by algae directly, since algae, too, must breathe (I mean “breathe” loosely here, since all this happens under water)–it is a misconception that plant breathing is the reverse of animal breathing, that plants breathe in carbon dioxide and breathe out oxygen. Instead, plants breathe in oxygen just as we do, and for the same reason–to “burn” sugars for energy. The difference is that we get our sugars by eating, whereas plants make sugars by photosynthesis. Free oxygen is a byproduct of photosynthesis, and fortunately for us, plants make more of it than they need. But in warm, shallow water, a super-abundance of algae can sometimes run short of oxygen at night, when of course photosynthesis stops but breathing doesn’t. In Mobile Bay, in the summer, if the wind and tide are just right, this type of dead zone can move towards the shore, driving anything capable of fleeing before it. Long about dawn, anyone on the right stretch of shoreline can scoop up as much seafood as they want. Before the reason for this influx was discovered, it seemed like magic, an unearned gift from the sea. It’s called the jubilee.

Jubilees occur, less predictably, in other areas, too, such as the Chesapeake Bay, anywhere a dead zone can develop and then move towards shore. The size, shape, and duration of a dead zone depends on many factors, including, temperature, salinity, and wind direction. Dead zones are often low-down in the water column, leaving oxygenated water near the surface, which is why jubilees involve bottom-dwelling species, such as flounder or crab.

Dead zones occur in certain areas every summer, but their shape and size vary from year to year. Evidence of dead zones has been found in sediments going back at least to the late 1800’s, but the same study shows a worsening of the problem since 1950. It may be possible for a dead zone to form without human help, but humans unquestionably cause most of them.

In any case, the problem is less that individual animals die in the short-term, and more an issue of habitat loss. Because of dead zones, the places where marine life can exist are now smaller.

It’s worth noting that there are parts of the ocean where very little lives, and very little has ever lived because there is not much in the way of nutrients for various reasons. These are not dead zones. By definition, a dead zone is a place where life would occur if something had not used up so much of the oxygen.

Ok, Where Does Climate Change Come In?

Dead zones are mostly a story about pollution and land use–the factors that send excess nutrients downstream and into the sea. As such, the problem is sort of a cousin to climate change; the two have causes in common. But climate change also has a direct influence, most obviously because the warmer the water is, the less oxygen it can carry–and the less oxygen must be used up before a dead zone occurs. Also, warmer water raises the metabolisms of the animals that live in it, meaning that they need more oxygen, using the precious stuff up faster–and possibly also making dead zones occur at higher oxygen saturation levels.

Also, remember that salinity and wind direction are also factors in dead zones–and climate change can alter both.

The mechanisms here are a little complex, and I’m not going to describe all of them. Fresher water is lighter than saltier water, which means the two tend to resist mixing. River water flowing into the Chesapeake Bay, for example, or raining onto it, tends to float on top of saltwater flowing in  from the ocean. This resistance to mixing is not absolute–the surface waters of the Bay get brackish pretty quickly–but it is enough that the water on the bottom has trouble getting oxygen from the air. If the algae and sea grass in the water can’t produce enough of their own oxygen, a dead zone develops. The salty water is effectively under an air-tight lid, unless wind blows and stirs the layers.

Well, as sea level rises, more saltwater flows into the Bay. As the deeper waters get saltier, the resistance to mixing gets stronger, and dead zones get more likely.

In fact, although the dead zones of the Chesapeake Bay are now shrinking (thanks to concerted efforts in the Chesapeake watershed to limit nutrient run off), the amount of excess nutrient in the Bay water is shrinking faster. That is, the Bay has been dying more easily now than it used to, and the problem is getting worse. No one is exactly sure why, and various feedback loops and long-term ecological changes  (water dies easier if it’s been sick for a while?) could be in play, but sea level rise could be part of the answer, as could rising temperatures. Changes in wind direction may also play a role, as winds from the south have become less common since the early 1980’s, in favor of winds from the west. Since the Chesapeake is large, north to south, and skinny east to west, the change in wind direction has meant less wave action, and thus less mixing in Bay waters. I don’t know that the change in wind direction has anything to do with climate change–but I don’t know that it doesn’t, either.

As often happens, there are other factors that could be involved, some of which could actually mean climate change reduces the size of dead zones, long term. No one knows for sure.

But so far, as climate change progresses, dead zones have been getting worse. I suppose that could be a coincidence….

What’s the Story?

The reason I’m bringing all of this up now is that a study has just come out showing that although the Chesapeake dead zones are shrinking, dead zones elsewhere are getting much worse–and dead zones are even occurring and worsening in the open ocean, which is generally much more resilient.

Each area’s dead zone has its own history and its own context. How long has the zone been occurring, which industries cause it, who gets hurt by it, what is the relative political power of each, what details of local geography and ecology make the situation worse or better, what stresses other than low oxygen levels might be bothering marine life…. I’m reluctant to make generalized statements without first looking into the rabbit hole of information on each zone. Climate change may be a factor in some zones but not others.

But these zones are worth watching. Is there one near you? Does something you do, or don’t do, help cause a dead zone down stream? Are your state, local, and Federal representatives aware of the problem and concerned about it?

There are zones in the water that kill fish and many of them are growing.



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Seeing Patterns

Last week, I had the distinct pleasure of a hike on Mount Desert Island with my friend and teacher, Tom Wessels–the same man who lead the hike in the White Mountains described in my post, The Ghost of White Birches. Only, then he was leading an organized group activity associated with the school I’d just graduated. This time, for the first time, we were just friends going hiking together.

Myself, my husband, our elderly but still spry dogs, and him.

Switching contexts can have an unpredictable effect on relationships, and I can be slow on the uptake when the rules change. I had left it to Tom to suggest a hike, rather than saying so myself, because I did not want him to think I was expecting him to work on his day off. But as it happened, I need not have worried. Nothing had really changed between us. And while he had no planned lectures, no educational objectives, and had not previously hiked our whole route (as a professor, he appears to meticulously plan everything), he still kept us appraised of the cultural and natural history around us, knowing and sharing our interest. Tom is not one of those people who wears radically different hats for changing circumstance. He is always and exactly himself.

He told us that part of the trail we followed ran along the bed of the first road on the island. He pointed out a big-toothed aspen so furrowed with age that it looked like an ancient cottonwood, and how two other trees of the same size and species nearby must be much younger, having smoother bark.* He commented that the rhodora was coming into bloom. He answered questions, asked and unasked.

“Sap,” he said, spotting me examining a mass of white stuff at the base of a tree. I had thought it was either sap or bird urine and that either way it indicated some story. “These spruces are not doing well. Fungus comes in, then ants, then woodpeckers. Carpenter ants can’t excavate healthy wood.” The sap had flowed from the work of a pileated woodpecker, going after carpenter ants.

I knew from previous conversations that one of the reasons the spruces are becoming more vulnerable is climate change.

Much of Mount Desert Island is dominated by spruces, a cold-tolerant genus of tree that is rare at this latitude. The island–and the coast of Maine generally–is different because the frigid Humbolt Current bathes the land in cool sea breezes and cold sea fogs. According to rangers at Acadia National Park, which includes much of the island, the Gulf of Maine is now warming faster than almost any other water body in the world. Lobsters are moving north, to the detriment of lobstermen in southern New England. Southern fish species are moving in. In warm years, every puffin chick in the state starves to death, unable to swallow the larger, southern fish their parents bring.

I was right to think the white stuff at the base of the tree held a story.

Tom sees patterns. In a somewhat different and still less-developed way, so do I. A hiker without this kind of knowledge would see a pristine wilderness, protected in perpetuity by the US Park Service. Tom sees spruces not doing well (and paper birches dying off, lobsters moving, puffins starving) and is saddened.

There is a certain comfort to be had by sharing your reality with another. We chat about our home, mine and my husband’s, in Maryland, and how our forested lot prevents our having a garden, or a solar panel, or a wind turbine, but does protect us from the damaging effects of winds. In the ten years I’ve been there, I say, we’ve survived two hurricanes (Sandy and Irene) and a derecho, and the wind mostly flows over the tops of the trees.

“Those will happen more frequently, because of climate change,” comments Tom. We know. My husband talks about the changes he’s seen in Assateague Island in the forty years he’s been watching the place. Casual visitors don’t see that, either, only an unspoiled, wild beach, but we have friends who were married in a house on that beach and the house is not there anymore. The place where it stood is now several yards off shore. Maryland is slowly sinking, a natural subsidence triggered by the retreat of the glaciers tens of thousands of years ago, but sea level rise from climate change is real, too.

Last month, in St. Michaels, a town on the Chesapeake Bay, I saw water quietly lapping over the edge of the town dock, standing a few inches deep on pavement. Nobody else said anything. Nobody acknowledged it was happening, let alone extraordinary. Tidal height can vary. There is the influence of the moon’s phase, of course, since full moons and new moons produce extreme tides, and an onshore wind can pile up water on the coast. If both occur at the same time, tides can become extraordinary quite naturally.

But the town dock would not have been built where it was if flooding were normal at the time of its construction.

Last night I dreamed that nothing I did turned out right, that I was driving down winding country roads, lost, that the roads became dangerously, fantastically steep so I pulled over, only to watch my parked car roll down hill into the back of another. The metaphor of my subconscious is clear; I don’t know what to do about any of these patterns.

My mother and I discuss politics over breakfast. We are both worried about the survival of democracy. I go to bed with a hard knot of anxiety, the same nauseous fear that has plagued me since the election. I attend marches, write political letters, sign petitions, keep this blog, but there is something else that must be done, some stronger, more effective way to fight, but through the fog of anxiety, I don’t see it. Other than to acknowledge the truth, share my reality, I don’t know what to do.


  • The rate at which wood grows varies, as many people know, but the bark of each species grows at a nearly constant rate. Thus, an individual growing more slowly than normal for its species will have thicker, more textured bark. With some few exceptions, trunk size plus bark texture gives a better indication of tree age than either does alone.


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When the Sky Does Not Make Sense

As I explained on Tuesday, the East Coast of the US has been pummeled recently by horrible weather. The worse of the flooding struck South Carolina, but the storm caused flooding every state from Georgia north to Maine and inland as far as Ohio. The storm was remarkable for many reasons, not least because of its vast size and the shear amount of water that fell out of it:

  • In Maine, Caribou, Millinocket, Houlton, and Portland all broke daily rainfall records–Portland’s new record is double the previous record, which was set in 1922. One area, Searsport, received more than ten inches in total from the storm.
  • In Massachusetts, Boston almost doubled its daily rainfall record, previously set in 1899. The worst of the rain had not get moved through the state at that point.
  • In Rhode Island, Provincetown set a new daily record and New Bedford had to shut down Route 18 for two hours due to flooding.
  • Some parts of South Carolina got one or two feet of water out of the storm in total. Dams breached, highways flooded, and caskets literally floated up and out of their graves.

Coastal flooding–a storm surge driven by wind–was just as bad and, in some areas, worse. Just as unprecedented as the flooding was the storm’s structure–record-breaking floods in this part of the world are categorically hurricanes or tropical storms, but this was neither. There is simply nothing in the record-books remotely comparable.

There was a hurricane involved, though.

Hurricane Joaquin was an extremely strong Category 4 storm–its strongest sustained winds were just 2 mph shy of qualifying as a Cat 5. Hurricanes of this intensity are extremely rare–the last one in the Atlantic was five years ago. It hammered the Bahamas and sank a cargo ship with all hands. It never made landfall in the US, but its influence sent high surf along the length of the Eastern Seaboard (in Maine I heard surf about a mile inland–and the closest water is a protected cove that typically has no waves) and contributed to the huge storm surge in the South. The hurricane and the un-named storm were close enough to influence each other, with the monster un-named stormed steering Joaquin and the hurricane funneling moisture into its extratropical partner. This relationship between two storms was also highly unusual and was one of the reasons that meteorologists had trouble developing forecasts for Joaquin.

Detractors sometimes complain that any time the weather gets weird, somebody cries “climate change.” The reason for that is that an altered climate means weird weather. A climate is essentially the normal pattern of weather in a given area–or across the entire planet. When the pattern of typical weather changes, that is, by definition, climate change.

But what are the links between this particular weather event and the greenhouse effect?

Most directly, the sea is higher. Any time you get a storm surge, that surge is worse than it would have been because the sea starts out higher. The difference is only about eight inches (some areas see much greater effective rise because the land is also subsiding), but that is enough to have a huge effect. Anyone who doubts that should imagine the difference between zero and eight inches of water in their living room. Or, for that matter, the difference between zero inches and one inch! Last week’s storm pushed seawater up onto the land in South Carolina, North Carolina, Virginia, Maryland, Delaware, New Jersey, and Massachusetts. Today I saw, posted on Facebook, a video of a shark cruising down a flooded street in West Ocean City less than ten miles from my house. People who live in the affected areas can now go out and see exactly what climate change looks like simply by holding a ruler up to the high water marks. That’s about as unambiguous as it gets.

Secondarily, the sea over which Joaquin intensified was unusually warm–at least as of August, that area actually had record-breaking warmth. Warm water feeds hurricanes, so this pool of warm water explains Joaquin’s unusual strength. And Joaquin helps explain the huge amount of moisture in the un-named storm. Pools of warm water, like pools of warm air (heat waves) come and go, but global warming means they are more intense and more frequent now.

Third, a warmer planet means more extreme weather, including more extreme rain events. Again, the issue is frequency. This past week’s event was a thousand-year storm–that’s not a schedule but an expression of probability. The chance of such a storm occurring in any given year is about one in a thousand or 0.1%. Yes, it was certainly possible to get more than one per millennium, just as it’s possible to flip a coin and get heads seventeen times in a row, but you wouldn’t expect it. With extreme rain events happening more often, now we can expect these more often. I doubt this past week’s records will be broken any time soon, these things are still going to be pretty rare, but what isn’t going to be rare is the breaking of some record somewhere, especially those that involve precipitation (including snow!) or drought, or heat.

“We’ve never seen anything like this before!” is what climate change sounds like.

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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.


Bigger Floods in Texas, Reprise

Texas is flooding again, unfortunately.

Tropical Storm Bill formed in the Gulf of Mexico overnight and is–right now, as I write this–coming ashore between Houston and Corpus Christi. Bill is “only” a tropical storm, not a hurricane, but that ranking depends on wind speed, not on overall severity. Tropical storms, by definition, have sustained wind speeds somewhere between 40 and 74 miles per hour–any more, and they become hurricanes, which Bill will not do because these storms can generally only strengthen over water. Bill is not a very windy storm; its highest gusts are likely to be around 50 MPH. But the real problem is flooding.

Historically, most of the people who die in hurricanes and tropical storms drown.

The flooding is from two sources, rain and storm-surge, although the two interact in coastal areas if the storm surge makes it harder for rainwater to drain away. How much rain falls is not just a factor of how much moisture is in the clouds (typically a lot, but it can very) but also how big the storm is and how fast it moves. A large, slow storm takes longer to move over any given area and therefor rains more. Bill is about as wide as the Gulf Coast of Texas–big, but not monstrous. I have not learned whether it is slow-moving.  An old frontal boundary across Arkansas and North Texas will likely merge with Bill, adding more moisture to the system. A sickle-shaped area across parts of Texas, Oklahoma, Arkansas, Kansas, and Illinois is now under a flash flood watch. A much larger sickle of less severe rain reaches all the way to Maryland (which is ok, we need it).

Storm surges are caused by winds and pressure changes pushing along a dome of sea water. The surge looks something like a very rapid, unusually high tide–it can roll in within a few minutes. Before the modern era of accurate storm tracking, people sometimes went down to the beach to watch dramatic surf and then died as unexpected storm surges came in faster than they could run. Tropical Storm Bill’s winds are fairly modest, so its surge is only about four feet at the most, but the storm is rolling in at high tide–and we’re close to the New Moon right now, so this is one of the highest tides of the month. So, while we’re not looking at a monster surge by any means, Bill’s timing makes it worse than it might otherwise have been.

Again, this is weather, not climate. While human-caused climate change underlies all weather, just as a rising tide underlies all waves, this tropical storm is not, all by itself, a climate change story. So far, Bill looks like the same kind of storm the Southern US has always been vulnerable to. But what is a climate-change story is the context into which this storm is now moving.

First and foremost, Texas and Oklahoma are already soaked from weeks of intense, sometimes disastrous rain (following years of horrible drought). When the ground is already wet and rivers are already high, it doesn’t take much more rain to cause a major flood all over again. And while some flooding has always been a fact of life, the rapid swing from drought to weeks of torrential rain has all the hallmarks of the new, globally-warmed normal of extreme weather. It is because of this recent history of saturated ground that I am frankly worried about my friends and family in Texas right now.

Of course, Bill’s storm surge is also eight inches higher than it would have been were it not for sea-level rise–both from seawater expanding as it warms up and from the melting of glaciers. Eight inches might not seem like a lot, but imagine the difference between zero and eight inches of salt water inside your house.

Finally, according to a Alan Weisman, whose really neat book, The World Without Us, I have just read, the Gulf Coast of Texas is now uniquely vulnerable to storm surges because of the oil industry:

When oil, gas, or groundwater is pumped from beneath the surface, land settles into the space it occupied. Subsidence has lowered parts of Galveston 10 feet. An upscale subdivision in Baytown, north of Texas City, dropped so low that it drowned during Hurricane Alicia in 1983 and is now a wetlands nature preserve. Little of the Gulf Coast is more than three feet above sea level, and parts of Houston actually dip below it. –p. 143

So, a storm surge coming ashore near Galveston of “only” two to four feet is really serious business. Petrochemical extraction is not itself climate change, but it’s obviously intimately related.

This is not the first Tropical Storm Bill, nor will it be the last. Meteorologists reuse storm names, only retiring those that, like Katrina, become particularly note-worthy. None of the previous Bills has earned that distinction, and this one probably won’t, either. But we live in a world where even modest storms are more destructive than they might otherwise have been.

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Hot News from Down South

The latest climate news to light up social media is that Antarctica has hit a new, all-time record high of 63° F.

According to CNBC,

A single temperature event doesn’t make a trend, but it’s a situation worth watching, said Jordan Gerth, a researcher at the Cooperative Institute for Meteorological Satellite Studies. “One rare temperature doesn’t tell us a whole lot,” Gerth said. “But if we see these events happening more frequently over the next decade or so, it could be a larger story to tell.”

This comment is a strange one. I’m going to give Dr. Gerth the benefit of the doubt and assume he is being misrepresented or misunderstood, somehow, but the implications of the quote are worth discussing.

It is quite true that one event does not make a trend. Without context, an extreme weather event is not evidence of anything because even if our climate were not changing, the occasional hot day would still occur. To find the footprint of climate change, you need to look at weather records over time. But then, why can’t we just look at Antarctica’s weather records over time and determine if there is a trend? Dr. Gerth appears to think we can’t do that for some reason, but must look to the future instead. Either that, or his words might be taken to mean global warming has not been conclusively spotted in Antarctica yet.

And that is rather patently not true.

I am inclined to think Dr. Gerth meant that there isn’t enough data on Antarctic weather to draw conclusions. Frankly, I don’t see how there could be much weather data on the frozen continent, given how sparsely populated it is and how recent the human presence is there. There are, indeed, weather stations on Antarctica, some of them the better part of a century old, though their records are not necessarily continuous–but there aren’t very many of them. Until the age of weather satellites, there must have been huge swaths of the continent where any weather could have been happening at all and no one would know. The signal of climate only emerges from the noise of weather once you have about thirty years of data to look at and the satellite temperature record is only 37 years old.

Antarctica is also fairly big and some of its associated islands (including the sites of the recent temperature records) are actually well outside the Antarctic Circle. The emotional punch of the headline (“Antarctica tops 60°!”) is a bit misleading, given the tendency of the outside world to equate all of Antarctica with the South Pole.

And yet we do have a fairly simple way to tell that Antarctica’s temperatures are indeed going up; the sea level is rising. About half of the observed rise is due to melting ice, as opposed to thermal expansion and other factors, and much of that ice was in Antarctica. Even if we had no weather data for that continent at all, we would know its climate is warming.

We also do have long-term climate data for the south of the world,quite apart from weather stations. The glacial ice records evidence of temperature, along with other important information, such as atmospheric composition, in layers, for thousands of years. A British team drilled in and got a sample some years back:

What the scientists discovered, however, removed any doubt. “We found that the peninsula has been warming for the past 600 years,” said lead author Robert Mulvaney, of the British Antarctic Survey, in an interview. “But the rate of warming has been much faster during the past century, and fastest over the past 50 years.”

From this and other studies, we know that Antarctica is warming, and is in fact warming faster than anywhere else in the world. Also, Antarctica is not the only place that has set a new heat record recently: Equatorial Guinea, Ghana, Samoa, and the Wallis and Futuna Territory have all either set or tied their high temperature records in 2015. Five national or territorial heat records in a year not quite four months old yet is remarkable, especially as exactly zero have set cold records (sorry, Boston).

So why did CNBC quote Dr. Gerth as saying there is no larger story to tell?

There is, in fact, a regional story here as well as a global one, and it’s an oddly familiar story for those of us in the United States since it involves the polar vortex.

Polar vortexes are not some unusual type of winter storm, popular media representations to the contrary. Instead, they are simply the cold air masses around the poles. The boundaries between these air masses and more temperate air are quite abrupt and marked by currents of upper-air winds–the jet streams. The location of the boundary changes, sometimes developing huge meanders that bring unusual temperatures to unusual places. Over the past few years, we in the United States have seen several such events in which the Southeast of our country froze while Alaska (and many other places) saw record warmth.

The recent unusual warmth in parts of Antarctica is also due to a wavy polar boundary and was also associated with unusually cold temperatures (even for Antarctica) elsewhere on the continent. The same wind pattern was also responsible for the other major climate-related news story, the flooding of the Atacama Desert, in Chile. While the rainstorms only brought about an inch of water, that is as much as the area usually gets in fourteen years. And with little vegetation to absorb water or stabilize the ground, the floods were dramatic.

Now, I’ve written before about the link between melting Arctic sea ice and the recently wavy polar boundary, but I do not know if an equivalent process is at work in the south. It may well not be, since Antarctic sea ice is actually expanding. The sea and air are both steadily warming, but both are still cold enough to allow ice to form in the Southern Sea–meanwhile, wind and water currents that previously limited sea ice are changing, allowing more ice to form (sea ice has no effect on lea level; the land-based ice that does influence sea level is melting rapidly).

So, is this particular extreme weather event related to global warming in an clear, causal way? I do not know. But when an entire system changes, it is unrealistic to expect any corner of that system to remain untouched.

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Conversation with a Skeptic

This is a rewritten version of a piece I wrote in college–it is a fictional representation of mt attempt to play “devil’s advocate” with what I knew about climate change at the time. The character of Skeptico is entirely fictional. The information in the piece came largely from the book, Global Warming: The Complete Briefing, by John Houghton, from Cambridge University Press. It’s an excellent book, but it was written in 1997, so if you read it, remember the case for climate change being real has grown even stronger in the past seventeen years.

I remember posting this piece here, but cannot find it in the archive, so I’m posting it again.

Let us say that I sit down on the edge of the dock next to my friend, the climate skeptic, whom we will call Skeptico. The tide is up, so I can swish my bare feet in the water, as my companion is already doing. We admire the view in silence together for a few minutes before either of us speaks.

“I don’t get why you environmentalists have to be so negative,” he says. “Look at this! It’s beautiful. If you had your way, no one would ever see this, no one would fish here, no one would get to enjoy this…all these things take fossil fuels. I don’t think we should consider getting rid of all the modern conveniences that let so many people enjoy the environment in the first place.”

“Is that a rhetorical statement or a real question?” I ask. “Do you want to talk about why I do the things I do?”

“Yeah, I do, actually.”

“Ok,” I begin, “you mentioned fossil fuels. It sounds as though you don’t think their use should be limited. That implies that you don’t think global warming is a problem. Is that true?”

“Yes, that’s true. I don’t think we should give up things we want and need and worked hard to get just because of some unproven theory.”

“Why do you call it an unproven theory?”

“Well, that’s what it is, right? It’s just a theory, it’s not fact.” Skeptico seems almost angry, saying this, and fidgets a bit. I think for a minute.

“Sounds like you’re saying that theories are ideas that are not yet proven, that when it is proven, it graduates to fact-hood.”


“Ok, that’s not what a theory is, not the way scientists use the term, anyway. Theories are attempts to organize and explain the things you know so you can make educated guesses about the things you don’t know. Like if I know why the water is warm today I can get a good idea whether the water will be warm tomorrow. Makes sense so far?”

“Yeah, I know what a theory is,” replied Skeptico, irritably, “but theories do change. They say one thing this year, another thing the next. You can’t tell me that a theory is the same thing as a fact.”

“No, I’m saying a theory is a completely different thing than a fact. You’re right, theories do change, and sometimes they are abandoned altogether and replaced. But that doesn’t mean that theories are just guesses; theories are the ideas with which we make guesses. The more consistently right the guesses are, the more reliable the theory is. When high tide was yesterday is a fact. We can use a theory about tides to predict when high tide will be today—and that’s reliable enough that you’ll plan your day around it so you can go fishing. I’ve seen you do it.”

“You know it like a poet,” Skeptico replies, but seems slightly embarrassed and lapses into thought for a moment before speaking again. “Oh, so when they say ‘theoretically, such and such is true,’ they’re guessing, but the guess isn’t a theory–it’s theoretical because a theory generated it?” My friend seems pleased by this insight, but frowns again a moment later. “But why is global warming a reliable theory? I don’t see the sea level rising.”

“You don’t? This island was wider ten years ago,” I point out.

“That’s erosion from storms. That’s different.”

“I’m not so sure about that,” I respond, “but in any case, global warming isn’t a theory, it’s data. The greenhouse effect is a theory.”

“That’s just rhetorical,” Skeptico protests. “It’s not my fault if I don’t use exactly the right terms. You know what I mean!”

“No, it isn’t rhetorical. Global warming isn’t a theory because ‘global warming’ just means the globe is getting warmer—which it is. It’s been measured. That’s data, not an explanation of data. The theories are about why the globe is warming and what is going to happen next.”

“Ok, well, either way, how do we know the theory is reliable?”

“Because it’s the same set of theories they use to predict the weather.”

“The weather! Weather predictions are completely unreliable!” Skeptico scoffs.

“Really?” I challenge. “It’s not exact, but in the last few years they’ve gotten pretty good. I’ve seen you decide not to go out on the water when they’re predicting thunderstorms. Weekly outlooks are usually right, and they can predict the track of hurricanes within a few hundred miles a week ahead of time.”

“Ok, that’s a few days. That’s different than the decades you’re talking about with climate change.”

“There are longer-term predictions as well, like for El Niño-related events. It all depends on what kind of simulation the computers run. But there is a lot of overlap in both theory and data for climate vs. weather. And the weather reports are accurate enough to act on, so the climate predictions should be, too.”

“Ok, that makes some sense. But I’m still not going to just take some weatherman’s word for it.”

“Nor should you,” I say. “Listen, at their most basic, these theories are pretty simple. The idea is that several of the gases modern human activity produces trap heat. As the atmospheric concentration of these gases rise, so does the global temperature, creating all sorts of problems. That’s the idea on the table here. Where do you see weaknesses?”

“How do we know the planet as a whole is getting warmer? Couldn’t it just be some kind of sampling error? Or some kind of natural cycle?”

“They compile measurements from all over the planet and take an average. They can also chemically analyze the air bubbles in glaciers to see what temperature the air was when the snow originally fell—that’s not enough to get a global average from, but it does go back many thousands of years, and ice cores can be taken at many locations all over the planet and compared. According to that record, the warming over the recent few decades is not normal.”

“How do we know these gasses trap heat? Has that been proven?”

“Basically, yes, it has. For example, was identified as a greenhouse gas back in the eighteen hundreds. I can look up the names of the people who made the discovery if you like, when we get back to the computer lab. The Earth doesn’t actually receive enough sunlight to account for the planet being as warm as it is, unless something in the atmosphere were trapping heat. When CO2 was first identified as a greenhouse gas, they calculated out what would happen if carbon dioxide concentrations increased, and they came very close to predicting the actual warming we’ve experienced. Wouldn’t it be strange if their theories were wrong but something else heated up the planet exactly as if they were right?”

“Ok, but what if carbon dioxide levels aren’t rising? Is that possible?”

“If carbon dioxide levels aren’t rising, where else is all the carbon dioxide released by modern industry going?”


“Yeah. Anyway, changing carbon dioxide levels have been measured, too. I suppose—theoretically—that data could be wrong, but there’s so much data involved from so many different sources that would have to be an awfully big foul-up or a ridiculously vast conspiracy. If we’re going to go there, we might as well say nothing is reliable ever, which is not particularly realistic.”

“Ok, but we’ve been talking about a simple version of these theories, right? It’s not really simple. I’ve read articles about these things, how increased cloud cover could block a lot of sunlight, or how melting ice in the North Atlantic could change ocean currents and cause another ice age…even if in the simple version the Earth would continue to warm, how do we know what will happen in real life where things aren’t simple?”

“Well, most of that detail, is accounted for in those computer programs. That’s why climate predictions require so much computer power to calculate. Yes, it’s possible some undiscovered something will fix the problem or buy us more time, but it’s equally possible that some surprise will make things much worse. There have been a couple of nasty surprises already, like Antarctic and Greenland ice melting much faster than expected.”

“I heard about that, but I don’t really know who to believe. You don’t even think scientists are always right–you take vitamins with no established daily value, you’d rather take unproven herbal things than medicine….”

Ooh, touché! I chuckle a bit before speaking.

“I question mainstream science; I don’t reject it wholesale. I question everything, as do you, which is why we get along. Look, if modern science was completely out to lunch, modern technology wouldn’t work as well as it does, and it clearly does work. One aspect of science is an extended community of people who share data and check each others’ conclusions. Sure, sometimes they still make mistakes, but the system works well enough that we’ve created the modern world. So, when the top scientists of almost every country in the world say an issue is important, I pay attention.”

The tide has ebbed while we talked; I can’t reach the water with my feet now. The swallows that darted over the water after insects by day have been replaced by bats as night comes on. We watch the bay turn pink and silvery under the reflected light of the fading sunset and then Skeptico speaks again.

“Ok, so we know the temperature is rising because it’s been measured. We know the atmospheric concentration of greenhouse gases is rising because that’s been measured, and anyway, where else are the gases we produce going besides the sky? We know they are greenhouse gases because they have been studied by chemists whose predictions proved reliable, and we know rising temperatures are going to cause problems because weather forecasters say so and they’re usually at least partly right. We know all this isn’t the product of some wild-haired maverick because many well-respected scientists agree with it, and we can’t just assume that all of them are crazy together because if they weren’t right most of the time modern technology wouldn’t work. That’s an answer for everything…but I still don’t know. I don’t know if I trust mainstream science.”

“Look, I’m not saying to trust them. I’m saying think about what is most likely. Do you really want to bet the future of life on Earth that thousands of the most intelligent and well-educated people on the planet are all wrong at the same time in the same way?  And that their “mistake” actually conforms to common sense in most respects? I mean, you read the news. Does it look like the weather has been normal for the past decade or so?”

“Do you want to bet the economy that they’re right?”

“Who said the economy is really on the line here? Isn’t using less petroleum and wasting less energy a good idea anyway?”

“That’s another conversation.”

“Yes, probably for another time. I’m getting bit up. But think about it. When you do arithmetic, how do you check your answers? You do the problem again, right? Maybe you even do it two different ways. If you get the same answer, that means you’re right, right? If your only remaining argument against anthropogenic climate change is to suggest that thousands of scientists all made the same mistake over and over again for decades on end, that really doesn’t sound too convincing.”

“No, I suppose not. I still want to think about this, though.

“Good. Thinking things through is good,” I say.

Skeptico gets up, stretches a bit, and fumbles for shoes. Neither of us thought to bring a flashlight, although the moon is almost full and should make additional light unnecessary. I fish a bottle of bug spray out of my pack, explaining that I plan to stay out a bit longer. Before going, Skeptico turns to me and thanks me for our conversation.

“I didn’t think you’d actually talk to me about this stuff, but you really took my questions seriously.”

“And neither of us died!” I laugh. “Good night!”

“Good night. See you tomorrow.” And my friend walks off.