The Climate in Emergency

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


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The President’s Plan, Part 1

Early in June of this year, President Obama announced, to great fanfare and controversy, his new plan to fight climate change. As he had promised, the plan depends not on Congressional action (which is not forthcoming) but on direct administrative action.

The White House website describes the plan, but not in very reader-friendly terms. Although the page is full of lots of charts and graphics and links, it is hard to see just what, exactly, Mr. Obama has done.

Rather than summarizing the plan as a plan, the website is a lecture on the problem of climate change and the progress the Administration has made towards its goals. Some of this progress includes the steps of the President’s new plan. Other progress bulletins involve events that are several years old or not directly Mr. Obama’s doing.

For example, since he took office, the United States has tripled its wind generation of electricity and increased its use of solar ten times over. That is worth celebrating, and President Obama’s policies may have helped, but he could hardly have ordered it.

As a public service, I’ve waded through the morass.

The cornerstone of the plan, and the only component actually announced in June, is a new set of proposed rules through the Environmental Protection Agency (EPA) regulating and limiting carbon dioxide emissions from existing coal-fired power plants. This proposal builds on earlier proposed rules to regulate and limit emissions from any future coal-fired plants.

More on these rules shortly.

But the President has referred to executive actions (plural) in discussing his plan. The White House website does, indeed, boast of several other points to the plan, but these took place earlier this year or late last year.

These other actions address vehicle fuel efficiency and energy infrastructure, electrical efficiency, electricity from renewable sources, national resiliency in the face of climate changes already occurring, and plans to work with other countries to reduce emissions abroad.

Here is my summary of the Administration’s domestic action steps over the past year towards combating climate change, organized chronologically:

  • September, 2013, the EPA proposed carbon dioxide regulations for new coal-fired power plants.
  • December, 2013, the President signed a memorandum directing the Federal government to buy a certain minimum of its electricity from renewable sources by 2020.
  • December, 2013, the Department of Agriculture (DOA) committed money to improve energy efficiency and renewable energy use in rural areas.
  • January, 2014, the President signed a memorandum creating a Quadrenniel Energy Review (QER) process. This means that a group of high-level officials will communicate with various experts and stakeholders about energy and submit a report to the President every four years.
  • February, 2014, the President told the EPA and the Department of Transportation (DOT) to develop higher fuel efficiency standards for heavy-duty vehicles. This follows on earlier fuel efficiency increases.
  • March, 2014, the Administration announced a Strategy to Reduce Methane Emissions, largely through preventing leaks and unnecessary venting from pipelines, wells, and landfills.
  • May, 2014, the Department of Energy (DOE) said it will support training programs through community colleges for future solar industry worker
  • June, 2014, the EPA proposed carbon dioxide regulations for existing coal-fired power plants.
  • Since June, 2014, the DOE has raised a number of standards relating to the efficiency of electrical appliances and equipment.

It’s hard to avoid being underwhelmed with a few of these steps. The new QER process sounds fancy, after all, but it’s only a report. Don’t we have enough reports? Likewise, virtually none of these steps will go into full effect immediately. They aim to cut emissions in various ways by some future date. The EPA’s new rules are only in the proposal stage.

However, this is the President acting on his own without Congress, a condition that, by design, renders the American president almost powerless. Further, even these minimal steps–chiefly the new EPA rules–are being fought, tooth and nail, by the fossil fuel industry. This may be all we can get right now, and it is far from certain we will even get this.

On the other hand, the President’s plan, if it is allowed to stand, could do a lot of good.

The EPA’s new rules should reduce carbon dioxide emissions from existing coal-fired power plants by 30%, compared to 2005 levels. That does not count reduction due to regulation of new plants–a complication I won’t touch either, though it is probably significant.

What does this 30% mean?

According to the Washington Post, existing power plants contribute 38% of US carbon dioxide production and are therefor the single largest source of American CO2 (transportation comes in second). Carbon dioxide, in turn, accounts for 82% of the country’s total greenhouse gas emissions–some of the others, such as methane and CFCs have a more powerful greenhouse effect, but there is so much less of them that carbon dioxide is still the dominant problem.

So, we’re looking at removing 30% of 38% of 82%. Roughly speaking, that works out to almost one tenth of the United States’ total greenhouse gas emissions which Mr. Obama has turned off with the stroke of a pen.

I don’t have the numbers to calculate the results of his other actions, but most of them involve reducing demand for electricity and gasoline, thus hitting the first and second largest sources of domestic carbon dioxide again. The Strategy to Reduce Methane Emissions could also be very significant, given how powerful that methane’s greenhouse effect is.

The United States is one of the most serious global-warmers in the world, so a major reduction in its greenhouse gas emissions is significant on the global scale.

Perhaps just as important, for the US to reduce its emissions gives it the moral credibility to ask China and India to do the same–countries that are just now industrializing and are understandably reluctant to give up their turn at the wealth that using fossil fuel brings.

Could the United States do more to reduce its greenhouse gas emissions? Yes–and indeed, it must do more, and soon. But there is a huge amount of political and economic weight being thrown into the US doing nothing at all.

Do not forget that one of the reasons the President is about to be sued by Congress is his action on climate change (more particularly, his attempt to use his own authority to get around Congress’ inaction on the subject).

Climate change mitigation is a dead issue in some Congressional districts, especially those where the coal industry is economically important. It’s to the point that, in some races, supporting carbon dioxide regulation is something mudslinging candidates can accuse each other of.

(Yes, regulating coal plants could cost some communities money they can’t afford to lose, but doing nothing about climate change would be far worse for far more people)

Congressional Republicans are currently trying  to stop the EPA’s regulation of carbon dioxide, both through an appropriations bill and through additional legislation.

The regulations themselves are still only proposals. The EPA must go through an internal review process before finalizing the rules. The public comment period for the regulation of new power plants has closed. The comment period for the newer rule, the one regulating emissions from existing power plants, is still open.

This means that there are multiple fronts along which the coal industry–or politicians who simply dislike anything Mr. Obama does on principle–can attempt to defeat the regulations.

They can comment, as members of the public.

They can lobby for passage of bills to undermine the rules, or, more broadly, the whole EPA.

They can attempt to ensure that no climate-friendly politician ever gets elected again, so that when Mr. Obama leaves office, his successors can undo his work.

But, the American people can respond by the same means.

Comment on the proposal. Contact your Congresspeople. Support environmentalist candidates and VOTE.

If President Obama’s plan sticks–and if it receives widespread public support–there might be more good progress on the way later. If not…this might be our last chance to get started.

 

 

 

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The Time Has Come

“The time has come, the Walrus said, to talk of many things.

Of shoes and ships and sealing-wax, of cabbages and kings.”

That’s Lewis Carrol, of course. I’m not the first person to use those lines of his to try to open a dialogue, and I doubt I’ll be the last. What I want to dialogue about is the future of this blog.

While future plans aren’t by any means set, I’d like to expand the project. I want to get the message out to more readers, and I’d like to develop a platform to bring people together around solutions, some kind of project-incubator,if you will.

To expand, I’ll need an expanded budget. Right now,I do get a stipend to cover my own time, but to take the project to the next level I’ll need to be able to hire assistants, use publicizing tools that are not free, and so forth.

I have some ideas, but before I do anything I want to check in with readers.

So, what suits you? I cover a lot of topics here on these posts–what do you like? What do you want to see more of? More science,more current events, more suggested solutions? More profiles of scientists and activists?

Are there any services I could add that would make this blog more useful to you? Like an ask-an-expert feature (I’m not an expert,but I do know several) or a page of useful links?

What fundraising methods would appeal to you? I could just ask for donations,or I could set up page where you could buy artwork or donated writing,or I could do raffles or organized fundraisers….What seems best to you?

I’m asking what you want because, after all, you’re the readers. You make this project work. Without you, I’d just be a voice in the wilderness, as it were, crying a warning to no effect. With you–maybe, just maybe, we can do something about this emergency.

 

 

 


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Meanwhile, Not in the News

Droughts, fires, tropical storms, tornadoes, they all make the news, but news is a fickle thing and it never stays in one place very long. What follows is a brief–and not intended to be exhaustive–summary of extreme weather around the world.

Droughts

About a third of the United States is in some form of drought as of this writing, but many of those droughts are mild or short-term. Monsoonal rains have eased severe drought conditions in some parts of the Southwest. “Monsoon,” by the way, does not mean “heavy rain” but is instead a season. During monsoon, the prevailing wind direction shifts, bringing a different, wetter, weather pattern. The Southwest is in monsoon now, but that does not mean all of it is getting rain and almost the entire region is still in some form of drought.

California does not get the Southwest monsoon because it is too far west. It is currently in its dry season, so its severe drought is simply getting worse and will until the fall at the earliest. This is the same drought I’ve discussed in these posts several times before, and it is almost certainly global warming-related.

Droughts mean fire danger (which also has connections to global warming), and indeed there are several large fires currently, mostly in Washington and Oregon, which are also in drought. However, despite the unseasonably severe fire activity early in the year, current fire activity for the US overall is about normal for July.

California is hardly alone. There are splotches of severe drought scattered all over the world right now. The largest such splotch is in Africa, mostly in the Democratic Republic of Congo, where an area the size of the Eastern US is entirely in one giant severe drought. A couple of minutes’ search online does not, however, yield any articles on current conditions in the impacted countries, though there was a lot of media attention about ecological and humanitarian problems there earlier in the year.

Heat Waves

Britain is having a hot summer. So far I haven’t found any indication that the heat is causing a disaster, but it is unusual; this summer could end up being their hottest in over 20 years. Asia had severe heatwaves this past May, which shifted East over Japan in June. I haven’t found detailed figures for July, yet, but June was abnormally hot for many countries, including New Zealand, Australia, Greenland, and Iceland (remember that Australia and New Zealand are in winter right now, so these are warm temperatures for June). Globally, this June had the seventh-hottest land temperatures on record. The other seven hot Junes were all in the past ten years, by the way. And this was right after the warmest May ever recorded.

Tropical Cyclones

Everything is quiet on the tropical cyclone front right now, with only two systems in existence, an unnamed tropical depression in the Atlantic and, in the Pacific, a tropical storm called Matmo that was once a Category 1 typhoon but is now falling apart over China. However, Matmo caused extensive damage in Taiwan and it is the second typhoon this month to hit China. Ramussun, before it, was China’s strongest typhoon in 40 years.

Floods

Parts of the United States and Canada have been badly flooded this month. A major pulse of floodwater is making its way down the Mississippi after flooding in June that closed some of St. Paul’s docks and parts of both Saskatchewan and Manitoba are under states of emergency. The Assiniboine, a tributary of the Red River, ran so so high that officials planned to deliberately allowed some areas to flood, inundating some 150 houses, in order to reduce pressure on the levies that protect Manitoba City. The reports I found are over a week old, so I do not know whether they went ahead with the flood diversion plan.  More modestly, my own part of the US sustained some road damage last week because of flooding from a series of rainstorms, culminating in a dump of 3 inches in a couple of hours over night.

Parts of England received flash floods during the same time period. Floods in parts of Western and Central Africa are causing serious humanitarian problems. Severe flooding in parts of Argentina are beginning to recede, allowing evacuees to start returning home.

Climate Change?

Does all of this extreme weather mean climate change? Some of it does and some of it probably doesn’t. Some extreme weather is normal, and our planet is very big, so if there wasn’t a problem somewhere that itself would be freakish. The heat waves are, of course, a bad sign, and both floods and droughts are predicted to increase as climate change progresses. But to say whether a given week of world weather is really extreme in a way that shows global warming’s thumbprint would take very careful analysis, which I did not do.

My point is not that this July has especially extreme weather, although it may. My point is that today, as I type this, the weather around me is beautiful and mild and when I turned on the news this morning, freakish, dangerous weather didn’t make the deadlines. Perhaps you, as you read this, are similarly blessed.

That doesn’t mean crazy weather isn’t happening.


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A Climate for Wine

A tried and true way to bring home the reality of global warming is to focus on its impact on beloved agricultural products, such as Durham wheat (for pasta), cacao (for chocolate), and barley (for beer).  Grapes follow in this tradition, with recent articles on how shifts in climate are shifting where wine grapes can grow.

But wine grapes have also been used by climate deniers to argue that humans are not causing global warming. Those arguments are not especially sound, but they fall apart for interesting reasons. The long and short of it is that these vines tell an interesting climate tale.

The premise is that grapes are dependent on a specific temperature range, so that where grapes grow reflects where that temperature range occurs.

And indeed, grape-growing regions are shifting. Traditional areas in Australia, France, and California are running up against the upper temperature limits. In coming decades, if no one does anything about climate change, growers will have to shift to other grape varieties or give up viticulture altogether. In France, shifting to new varieties would be problematic because specific types of wine, and therefore specific varieties of grape, are tied to particular regions by law.

Meanwhile, new wine regions in China and other areas are opening up. Parts of England and Nova Scotia, which have been quietly growing white grapes for years, are starting to grow reds.

Obviously, the possibility of new wine regions means economic opportunity for some. This is not entirely a story of doom and gloom. But creating new vineyards necessarily means destroying something else, because there is no land that isn’t already occupied doing something. In China, for example, planting new vineyards means destroying giant panda habitat. In the United States, it could mean destroying the habitat corridors that the wildlife of our western parks depends on.

It’s also important to recognize that even if total annual wine production does not change much in coming decades, the relocation of wine would hurt a lot of people. Industry tends to relocate much faster than population and culture do–consider the economic blight left behind when manufacturing jobs move overseas. The success of wineries in China and Washington State will be small comfort to the owners of bed-and-breakfasts in Napa Valley, California or the Bordeaux region of France.

But if changing climate drives changes in viticulture, does it follow that historical changes in the wine industry can be used to infer climate?

Researchers have made the attempt, and depending on their study designs it is possible they succeeded. Most likely, historical records of wine production could work to augment other sources of climate data, such as records of blooming and harvest times, records of weather, and studies of tree rings and lake sediments.

But the connection between climate and grape vines is a lot more tenuous than it might at first appear.

Grapes make a poor indicator of temperature because they are also dependent on other factors besides temperature for their growth. Rainfall, for example, is important to grapes. Perhaps more to the point, grapes are dependent on humans wanting to grow grapes.

It is possible to grow grapes in Great Britain, just as it is possible to grow them in Nova Scotia, the Pacific Northwest of the United States, and even Alaska. It’s not that you couldn’t make wine in those places until recently–it’s that you couldn’t make good wine. A certain inertia of reputation is probably in play, too, since the British wine industry has actually been growing in both production and quality since the 1950’s.

The many English vineyards of the early Middle Ages might have been a sign that temperatures were warmer then than in more recent historical periods. Climate deniers sometimes use this as evidence for their cause, the idea being that the Industrial Revolution isn’t a precondition for warm temperatures (although there are more English vineyards now, so if grapes did work as a proxy, they’d be evidence of unprecedented heat).

The problem with this line of reasoning is we don’t know how good the Medieval English wine was. It might have been terrible. At the time, the English used much of their wine for celebrating Mass, so pleasure at table wasn’t the point. Economic changes, such as easier importation of quality French wines and the closing of the English monasteries, probably did more to hurt the English vineyards than the climate did.

In any case, grapes are not a good indicator of climate past, but they are a good indication of climate present. Because the wine industry isn’t indulging in climate denial–when scientists predict where wine grape growing weather is likely to move, they find wine grape growers already there. The vineyards opening in new places or shifting to new varieties are well-aware and willing to admit that the climate is changing.

 

 


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Whispers of Hurricanes Yet to Come

This is the fourth in a four-part series on tropical cyclones, beginning with Windy Changes, on last year’s Typhoon Haiyan and continuing with Data of Hurricanes Past  and Problems with Hurricanes Present. Note that “tropical cyclone” is a catchall term that includes tropical storms, hurricanes, and typhoons. I have not repeated reference links from the previous post.

The Atlantic Ocean is quiet at present. So is the Eastern Pacific. The National Hurricane Center (NHC) does not expect any tropical cyclone activity in either basin within the next 48 hours.

The Western Pacific is different, currently sporting two storms, the as-yet-unnamed Tropical Depression Ten and Typhoon Rammasun. TD Ten is predicted to become a tropical storm (and receive a name) sometime today or tomorrow and to become at least a Category 1 typhoon sometime next week. Typhoon Rammasun has already hit the Philippines and is currently intensifying. It could become a Category 4 storm later today and is expected to hit Vietnam and China Friday and Saturday (since the Philippines have their own system of naming storms, the typhoon was called Glenda there. I have been unable to find a reliable damage report yet).

The Atlantic hurricane season was predicted to be mild. The Western Pacific Typhoon Season was predicted to be just above normal, but with more intense typhoons because of a developing El Niño. Although the characteristic atmospheric pattern hasn’t formed yet, so there is no El Niño yet, the Pacific is unusually warm, consistent with El Niño formation. So, this season is shaping up as predicted so far.

But what about tropical cyclones farther out? Next year or the year beyond? Or ten or twenty years out?

Common sense dictates that because these storms feed on warm water, global warming should make them worse. Indeed, with every monster storm that roars into the news, global warming gets easier to believe.

However, problems with historical storm data make it very hard to tell whether tropical cyclones have been getting worse because of climate change so far. Because “bad” storms are not necessarily the most intense meteorologically, it’s even hard to say what “getting worse” means. Looking into the future is similarly difficult.

The climate system as a whole is very complex. Besides warm water, tropical cyclones also require reduced wind shear and other atmospheric patterns. If wind shear  increases due to climate change, then there will be fewer tropical cyclones even as the weather warms. Other possibilities are that the number of storms could stay about the same but the intensity could increase, or that the storm tracks could change and bring typical storms into atypical areas.

Different storm basins can respond in different ways, too.

Scientists make predictions about what is going to happen using computer models. The basic idea is that a computer simulation capable of recreating changes in the past can also show what will happen under certain conditions in the future.

But no computer simulation can represent the full complexity of the real world; The Matrix is still very much fiction. Computer models posit a simplified version of the world and they therefore have limitations. When scientists use a model, they generally understand those limitations fairly well. Models are useful because scientists know how to ask questions the model can handle and they know how to put the results in context. But we aren’t at the point where a computer can tell us what will happen.

Computer can give us pictures of the range of possibility.

I have read a number of different predictions, including the summary by the IPCC, and I have not yet found one that predicts a dramatic increase in both frequency and wind intensity of tropical cyclones all over the world.

Instead, many show the total number of tropical cyclones not changing very much, but the proportion of Category 4 and 5 storms increasing, all over the world. NOAA’s version of this prediction warns that there is so much variation from year to year that the difference might not be evident for many decades–the old problem of finding the signal within the noise.

NOAA does not point out that this doesn’t mean there has been no change yet. Indeed, another study shows that there has been a significant increase in storm power in some ocean basins already.

NOAA’s prediction adds that tropical cyclones are going to get rainier, and this is very bad news. We already know that the sea is rising, making storm surges worse. With storms also getting rainier, freshwater flooding is set to get worse, too. Since most people who die in tropical cyclones die of water, not wind, this means we’re looking at the deadly parts of the storm getting worse.

A separate NOAA study shows storm tracks have been changing, moving further into the temperate zones more often. This means more storm surges and more flooding in areas not prepared for big storms, worldwide. How many times can the bridges in Vermont be rebuilt? How long till Boston and Portland join the list of cities filled with FEMA trailers?

The question is, what greenhouse gas emissions were these predictions based on? Do we still have time to not create these scenarios?

The present is the future’s past.


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Problems With Hurricanes Present

This is the third in a four-part series on tropical cyclones, beginning with Windy Changes, on last year’s Typhoon Haiyan and continuing with Data of Hurricanes Past. Note that “tropical cyclone” is a catchall term that includes tropical storms, hurricanes, and typhoons. I have not repeated reference links from the previous post.

Last week I went over how “are hurricanes getting worse (because of global warming or any other reason)?” is tough to answer. Basically, there are problems in the data. But even if we did have a lot of great data and could compare storms easily and precisely it would still be hard to say whether one storm is “worse” than another because “worse” is hard to define.

Does getting worse mean more Category 4 and 5 storms? Lower air pressure in the eye? Such metrics are the easiest way to compare tropical cyclones, but that’s not really what most people want to know. We want to know if we can expect another Katrina, another Irene, another Sandy. We want to know if there will be more catastrophes, but catastrophe is more complicated than just violent weather.

Hurricane Katrina, for example, was briefly a Category 5 storm, but it weakened before making landfall as a strong Category 3. Now, that’s still an insanely powerful storm, but it’s hardly unprecedented. Katrina became the catastrophe it did, not because of the hurricane’s own characteristics, but because it passed over a major city that had been built more or less under a lake–I remember that morning, watching on the news as all the weather people expressed relief that, miraculously, New Orleans had dodged a bullet and would be basically ok. And then the levee broke.

Hurricane Irene downgraded to a tropical storm the night it made landfall (and passed right over my house). Our area sustained no real damage, but as the tropical storm headed north over New England its associated flooding destroyed critical roads and bridges, temporarily isolating some towns. Because the storm produced so much rain, and possibly because it hit an area that rarely gets hurricanes, Irene was a truly catastrophic storm, even though it wasn’t even a hurricane anymore.

Katrina and Irene were the first and seventh most costly storms in US history respectively, but a scientist looking at how often Cat 4 and 5 storms hit us would miss both of them.

Sandy and Haiyan were both powerful and genuinely unusual storms, but both were catastrophic for not strictly meteorological reasons–both hit densely populated areas that were unusually vulnerable to storm surges for various reasons (Tacloban sits at the back of a bay that funneled and intensified the surge and New York City’s electrical system wasn’t protected against salt water flooding). Of course, the power of those storms was very much part of the problem, too, but what a storm passes over is at least as important t as how it behaves.

So, even if global warming doesn’t make tropical cyclones more powerful or more frequent (which seems unlikely), if they hit vulnerable places more often they’ll seem worse. Conversely, if we make our infrastructure less vulnerable to storms and deal with the racism and poverty that makes so many storms worse, intensification due to global warming might be less noticeable.

If we want to know whether climate change will make tropical cyclones worse, as opposed to simply more powerful in a strictly meteorological sense, we would probably do best to look at storm surge, rain potential, storm track, and storm frequency, not wind speed.

Flooding is the major killer in tropical cyclones, so whether rain and storm surge increase is important (and, of course, storm surges are getting worse because of sea level rise). If typical storm tracks change, them more storms will hit places that aren’t prepared for them. And if we get catastrophic storms by whatever definition more often, it is possible our capacity to respond will be exhausted.

Repairs from Superstorm Sandy continue. Hurricane Irene hit in August of 2011 and destroyed a lot of roads and bridges in New Hampshire and Vermont. While almost all of the initial repairs were completed within three months, that just meant the roads were functional again. Three years later, the repair work continues. Some repair projects from Katrina were still underway as of last year, eight years after the storm. The United States is one of the richest countries on Earth and we’ve been able to absorb these costs, as well as providing disaster relief abroad. But sooner or later we’ll reach our limits.

As ever, getting a useful answer depends on asking the right questions.

 


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The Data of Hurricanes Past

Japan is being pummeled today by Tropical Storm Neoguri, which was briefly a super typhoon (meaning winds in excess of 150 miles per hour) before. Last week, the Atlantic hurricane season produced its first named storm, Arthur, which intensified to an unusually early Category 2 hurricane and struck North Carolina before weakening and moving to the northeast, dropping huge amounts of rain on parts of New England and Eastern Canada on the way.  While both storms are atypical in some ways, neither has been catastrophic.

But with big storms so much in the news, this seems like a great time to address the role of climate change. Is global warming making hurricanes worse? That question is actually a whole swarm of questions, each of which is difficult to answer for its own particular reasons. Because are are, as yet, no simple soundbite answers, it is important to understand the science in order to be able to put the sometimes conflicting press releases we hear into perspective.

Today we’ll start by exploring just one of the swarm of questions; has climate change made hurricanes and related storms worse so far. We’ll save the other questions for subsequent posts.

A Note on Terminology

Tropical cyclone” is the generic term that covers tropical storms, hurricanes, typhoons, and clones. All these storms have a distinct eye and draw their energy from the evaporation of water, rather than from temperature differences between adjacent air masses as extra-tropical cyclones do.

“Tropical storm” refers to a tropical cyclone with sustained winds of anywhere from 39 MPH to 74 MPH. Once a storm intensifies to 75 MPH or beyond, it is called a typhoon in the Northwest Pacific, a cyclone in the South Pacific or the Indian Ocean, and a hurricane everywhere else. I have not found any explanation for this diversity of names for the same kind of storm. Perhaps it is a relic from a time before we knew they were all the same.

Has Global Warming Make These Storms Worse?

The short answer is yes. Whether or not climate change has intensified the storms themselves, sea level rise is unquestionably making them more destructive.

Since the 1880’s, global sea level has gone up eight inches, so that storm surges, the dome of high water that tropical cyclones push ahead of them, are eight inches higher than they otherwise would have been.

Nine feet, the total height of Superstorm Sandy’s surge, might not seem that different from eight feet, four inches, which is what it would have been without sea level rise. For the people who got all nine feet, it probably isn’t that different. But for the people on the edge of the flood who got eight inches, the extra height mattered a lot. For Sandy, each extra inch meant roughly 6000 more people were inundated.

But Have Tropical Cyclones Changed?

This one is harder. You’d think that all a scientist would have to do would be to count up the number of tropical cyclones in each wind speed category per year, crunch the numbers, and see whether there is a trend.

Tropical cyclone records are being studied, but the problem is the data are “noisy.” That is, there are so many variations that are not related to the greenhouse effect that it’s hard to spot the variations that are.

A further complicating factor is that wind speed is only one aspect of a tropical cyclone. From a human perspective, it isn’t even the most important, because most people who die in these storms don’t die of wind. They die of water, either in storm surges along the coast or in freshwater floods from so much rain. The size of the storm surge, the amount of rainfall, the diameter of the storm, and how long it sits on top of any one area can all vary independently of wind speed and of each other. Wind speed category is only a rough approximation of how “bad” a storm is.

What’s All That Noise?

Some of the noise in tropical cyclone data is the natural variability in storminess from year to year. Normally scientists can tune out such noise by looking at a large enough dataset. The basic procedure is to let random variations cancel themselves out–years with a lot of hurricanes are balanced by years with very few, if you look at enough years. What variation doesn’t get cancelled out is actually the climate changing.

But with tropical cyclones that standard procedure doesn’t work very well because there are problems with the data:

  • We don’t have good records of tropical cyclones before the Industrial Revolution. Scientists only started realizing that some large storms are spirals around 1820. Modern weather forecasting based on networks of weather stations didn’t begin until the 1860’s and most of the technology used to monitor hurricanes was only invented in the 20th century.  It’s hard to do a before-and-after comparison if you have no “before” shot.
  • The United States has been conducting aerial reconnaissance on hurricanes for decades, but since similar flights into typhoons have stopped, the data on storms in different parts of the world are not directly comparable.  That makes it hard to really get a global picture.
  • A lot of research on tropical cyclones is done by satellite, especially in the Pacific, but satellites are a relatively new technology so, again, we don’t have a good picture of how storms change over time.
  • Which information we get about which storm is a little random. For example, getting a measurement of a storm’s highest winds at landfall depends on getting the right instrumentation into the right part of the storm at the right time. For obvious reasons, that doesn’t always happen.
  • The conventions on how researchers analyze data and how they make estimates can change, subtly but definitely changing the numbers they record.

Scientists can and do work around these limitations, but they can’t make the limitations vanish. The bottom line is that just because scientists have trouble saying whether global warming has already changed tropical storm behavior doesn’t mean it hasn’t.

What We Do Know

At least one study has shown a trend towards more tropical cyclone intensity, at least for some ocean basins. That is, these storms are not getting more numerous, but they are getting stronger. A greater proportion of them reach Category 4 or 5. Another recent study suggests the storm tracks are changing, carrying more tropical cyclones into subtropical and temperate areas.

We know, as already mentioned, that the sea level is rising. We also know that the sea is getting warmer and that sea surface temperature and the total energy in tropical cyclones per year track each other pretty closely. Both have been trending up, at least in the Pacific.

Sea temperature at depth is also going up and that might matter even more.

When a large tropical cyclone passes across warm surface water, the storm grows, but it also stirs up the water, allowing cooler water from below to come up. This cooler water acts as a break, not only on the storm doing the churning, but also on any second storm that might be following behind. If the water at depth is also warm, though, there is no break.

Both Hurricane Katrina (which was a Category 5 storm before it weakened just before landfall) and Typhoon Haiyan intensified to catastrophic proportions right as they passed over very deep pools of unusually warm water. In fact, beneath Haiyan, possibly the most powerful storm ever to make landfall, the sea was hot enough to feed a typhoon—about 80 F.—even three hundred feet down.

No word yet on what the deep water is like under Neoguri.