## Adobe Lightroom for scientific photos

As some readers may know, now I’m retired, I am deeply invested in a multiyear longitudinal study of (primarily) mosses (Bryophyta) at 25 plots near my home. This has been running since end of November 2020, with the first month spent deciding what to do and where.

I have also spend much of the first half of 2021 learning field work and tooling up with equipment and techniques for doing this project, and starting a couple of side projects, some because of suggestions from university bryologists. More about those some other day.

My primary dataset are photos, principally using macrophotography. I do have specimens and they are stored in the conventional way for bryology, as dried pieces of moss in paper envelopes documented with collection information. But because this survey entails getting one or more photos of each of my plots each week, as well as supporting photographs and videos, I now have 5200 high resolution photographs.

I had been storing these in Google Photos, but it offers no capability for mass tagging or editing EXIF data associated with photos, even as collected in albums. So there is no way to tag all photos in an album declaring, say, these or a bunch are Climacium americanum. I have struggled the last two months to find a way around this, including trying to write code to manage photos in Google Photos from R, and shopping for packages and utilities.

After asking at talkphotography.co.uk, Jonathan Ryan suggested Adobe Lightroom. At first I did not realize that it backs up its photos on Adobe Cloud rather than locally, so I was hesitant, since I cannot trust putting this painstakingly collected data entirely on a local disk. But it does, and I have now migrated entirely onto Lightroom. And I am beginning the tagging I wanted to do at Google but could not. And I am learning to use LR with facility.

## Stranded Assets Nightmare

Yeah, a lot of people are going to be hurt. Should they have known better? Very probably. Were they led to their conclusion by misrepresentation on the part of companies they invested in? Definitely. (Will that lead to class action suits against such companies? I hope so.) Still, these are people, perhaps too unsophisticated to invest in this market but nonetheless.

Alas, the financial markets system touts such resolution in markets as canonical, and they have nothing to do with resolving it. People choose and the outcomes reflect the wisdom of their choice or they don’t.

## Botkin’s Discordant Harmonies, a comment

The 1990 book Discordant Harmonies by Daniel B Botkin, professor of Biology and Environmental Studies, is a wonderful treatment of Ecology, the subject, and Ecology, the policy, as it should be seen. Professor Botkin is first and foremost a teacher, and in doing so he brings the reader to see how ecosystems work, how interactions among coexisting species is complicated and nonlinear, and how human interventions based upon ironclad policies unresponsive to feedback and monitoring data inevitably fail.

Professor Botkin also gives the reader an education about various quasi-biological and quasi-botanical ideas, like those which attend notions of invasive species. That oughtn’t be a strange critique to readers of this blog, because I’ve noted it elsewhere. (I’ve noted it twice in fact.)

I promised to read it, and I did, and I took copious notes. This, however, is not a review, for any such review would need to be detailed and would have overwhelmingly positive things to say. This, instead, is a comment about a point which I believe Professor Botkin got wrong in the book, and I’m only qualified to say something because it concerns something squarely within my wheelhouse: The world of quantitative modeling. Note I have done a minimal review elsewhere.

I also need to note that Professor Botkin wrote an update to this book, one called The Moon in the Nautilus Shell, written a decade later, which may have other views about the opinions expressed in Discordant Harmonies. I cannot say yet. I am reading The Moon. I have not yet finished. I may update this comment if I find something which revises or clarifies.

The point I believe Professor Botkin got wrong in Discordant Harmonies was his interpretation of what the Lotka-Volterra differential equations model means, how it is to be used, and its implications. This is a major concern of the third chapter of Part I (“The Current Dilemma”). It’s possible for anyone to get something wrong. I do, often, but then I learn and correct. In the case of Professor Botkin, unfortunately, while, per The Moon he might eventually get it right, in Discordant Harmonies the critique of the Lotka-Volterra model is seized as a paradigm for what is wrong about a computationally based, “machine”-oriented approach to managing ecosystems. Such approaches to natural management may well have severe imperfections, but Professor Botkin’s interpretation of Lotka-Volterra cannot be their basis. Because his interpretation is, well, just wrong.

I should say my own prejudices come from an interest in sessile, botanical communities, most recently, mosses, and to the degree that may or may not have a bearing upon my view, I feel readers should know. My own first introduction to Lotka-Volterra came in the text:

Peter Yodzis, Competition for Space and the Structure of Ecological Communities, Lecture Notes in Biomathematics, 25, Springer-Verlag, 1978.

These equations are a set of coupled linear differential equations which offer a simple model to describe aspects of real ecological communities. They are not a complete description, nor were they ever proposed to be a complete description. But to the degree to which they successfully capture features of actual biological systems, notably ecological systems, their presence gives powerful ideas for biologists and people to think about such systems. Professor Raymond Pierrehumbert, a geophysicist, has a dedication in his textbook Principles of Planetary Climate which captures this idea:

For Arnold E Ross, who taught us to think deeply of simple things

R. Pierrehumbert, Principles of Planetary Climate (2010), Cambridge University Press, frontspiece.

Lotka-Volterra equations have been used in many successful ways to describe many such systems, not all biological. They are an idea, that powerful idea. They are not a complete vision, nor are they, in themselves, the basis for policy.

The critical flaw in Botkin’s treatment is he took from Lotka-Volterra the limit or extreme cases as being the only contribution they had, and he has, in his text, no understanding that these are dynamical systems with complexity and nuance, describing a whole range of behaviors and interactions beyond and besides these canonical limit cases. Indeed, Lotka-Volterra systems come in many orders. The standard presentation and introduction to them is the predator-prey model with a single predator and a single prey, but these can be made endlessly more complicated, introducing a forage for the prey which grows at a fixed rate per unit time, or a forage which grows at such a rate and then is impacted by a drought, or a predator which preys on the previous predator as well as the prey, or many other complications, all within a quantitative framework.

Botkin’s key failure is a statement

Lacking the understanding to analyze and thereby criticize these equations, they accepted them on the basis of authority.

D. Botkin, Discordant Harmonies, page 41

Botkin then goes on to recapitulate what “they” took away from “these equations”, notions of stability. In fact, it’s clear the lack “of understanding” he cites not only failed “field ecologists” in their criticism of the equations, if Botkin is correct, it also failed them in the conclusions which the equations presented. For Lotka-Volterra systems, like many dynamical systems, are anything but stable, and anyone who concludes otherwise has grossly misunderstood not only Lotka-Volterra equations, but the whole significance of dynamical systems theory of which they are a small part.

This might be a small piece of a dark corner of biological, but names like Lorenz and Mandelbrot and Smale were out there, investigating chaos theory which is all about these kinds of systems. Indeed, they appear in a major way in the 1974 textbook by Hirsch and Smale Differential Equations, Dynamical Systems, and Linear Algebra as Chapter 12.

My conclusion is that both for Botkin and his “field ecologists” the problem is and was not the Lotka-Volterra paradigm, but their failure to learn enough mathematics to appreciate what Lotka-Volterra and differential equations meant. And that’s not the fault of Lotka, Volterra, differential equations, or mathematics. That’s Botkin’s fault. That’s the ecologists’ fault.

And that is another reason why I, a retired statistician and quantitative engineer, am trying with the kind help of a few erudite and experienced bryologists and ecologists to bring mathematics back into biology in a practical way, if only in bryology.

## ‘Keystone Pipeline Developers Seek \$15 Billion From U.S. for Cancellation’

“We’re not doing this for symbolic or political purposes. This is a business decision,” Prior said in an interview. “We had all the permits and requirements in place to start construction on the line, and did so, and we worked with federal and state regulators in both countries for a very long period of time. This is just about recovering that destroyed value of investment.”

Bloomberg By Jennifer A Dlouhy, November 22, 2021, 4:30 PM EST

The thing is, if this suit were awarded, could fossil fuel companies in future seek to recover costs and damages for assets stranded by a hypothetical future U.S. law which prohibits emissions from burning of fossil fuels?

The American legal system and its Constitution are a mess, at least in terms of environmental legislation.

## My favorite presentation on climate disruption these days

Corinne Le Quéré | TEDxWarwick

Speaking of showing oscillations …

Feliks, Yizhak, Justin Small, and Michael Ghil. "Global oscillatory modes in high-end climate modeling and reanalyses." Climate Dynamics 57, no. 11 (2021): 3385-3411.

## Photo of the week: Repeatedly distressed Mnium hornum

This Mnium hornum community is located near a brook which occasionally overflows its banks and at a relative elevation lower than the brook floor. Because of unusual big rains in Dover, Massachusetts in 2021, this hornum community has been inundated by water and mud several times since early June 2021. The withered or dark stems and leaves show the aftereffects of these. The good structured and colored leaves show recovering stems.

This photographic result and, in fact, a series of them come from my ongoing longitudinal study of mosses at four sites in Westwood and Dover, Massachusetts, having a protocol of weekly visits and surveys. There are 33 plots involved. Two of the sites are brooks like the one having the Mnium hornum above.

## “Aggregating the harms of fossil fuels”

From Dan Farber at Legal Planet, the post.

## Awesome.

You can have a Carbon Tax, or a Carbon Dividend scheme. Or, instead, you can price entry into a zone of a city, sometimes called a congestion tax, or an emissions tax. Or you can price travel on the roads.

Options for doing this are now incredibly flexible. Vehicles need to be registered with their state. Technology for reading license plates at times is now awesomely reliable. Registrations give the type of car associated with the registration, so, the authority knows how many emissions per mile it typically exudes.

These pricings used to be called tolls, as on the Massachusetts Turnpike in the United States. All ICE cars pay a toll in their gasoline tax which helps to pay for highway and road repairs, but EVs don’t, because EVs don’t buy gasoline.

There has been discussion about charging some kind of annual premium to cars atop their town surcharge to compensate for this. But that’s a flat fee, not a usage-based fee, and so it has drawbacks. This modern technology and modern needs associated with low emissions or low congestion zones gives the idea. Price road use. When any vehicle uses a road, there should be a small charge imposed on the vehicle, to an account associated with that vehicle. (It wouldn’t be difficult to demand a credit card or checking account be set to justify that.) That fee can be flexible, varying by the road, by the type of vehicle, even by the time. The latter sophistication would deflect the avoidance tactics some use to fail to pay for road use, such as some silly drivers who refuse to use the Massachusetts Turnpike.

Out of state drivers could be warned, if they are occasional visitors, or expected to enroll, if they are regular ones. After all, their vehicles use and harm the roads, too. The occasional visitor might be tagged a flat fee, payable at their first encounter with a public service, whether a toll booth (via the EZ Pass system) or a parking meter or an EV charging station or a gasoline station.

EVs ought to pay their way. But so should ICE vehicles, on all roads they use, not just designated highways. This can be used to reduce emissions, too, by discriminating upon vehicle type and model, and favoring EVs over emissions intensive ICE vehicles.

## Fecklessness

This is from The New Yorker‘s 7th November 2021 issue. It features an article by staff writer Elizabeth Kolbert titled “Running out of time at the U.N. climate conference” which is subtitled “To really appreciate America’s fecklessness, you have to go back to the meeting that preceded all the bad COPs—the so-called Earth Summit, in 1992.” That article reports (excerpts):

To really appreciate America’s fecklessness, however, you have to go all the way back to the conference that preceded all these bad cops—the so-called Earth Summit, in 1992. At that meeting, in Rio de Janeiro, President George H. W. Bush signed the United Nations Framework Convention on Climate Change, which committed the world to preventing “dangerous anthropogenic interference with the climate system.” At the United States’ insistence, the convention included no timetable or specific targets for action … The sad fact is that, when it comes to climate change, there’s no making up for lost time. Every month that carbon emissions remain at current levels—they’re running at about forty billion tons a year—adds to the eventual misery. Had the U.S. started to lead by example three decades ago, the situation today would be very different.

Elizabeth Kolbert, November 7, 2021, The New Yorker

Professor Katharine Hayhoe quoted via Twitter via Peter Sinclair’s Climate Denial Crock of the Week argues we just need to keep going. But I think governments aren’t up to this, and business and corporations need to take the lead (paywall at link, Financial Times).

## David Wallace Wells …The Uninhabitable Earth and its implications

Think of this in the context of whatever investments you have.

## Don’t like high or volatile petrol prices? Get an EV to replace your gas-guzzling thang

Volatility in prices is inherent in fossil fuels, and fuels for internal combustion vehicles. This variation can be detrimental or even nasty to households.

One solution is to switch to EVs, which do not have this volatility in their price lines.

If you don’t, you are throwing money away.

## Clearly not consumption based … but, well …

To see a clearer more detailed ersion of the above image, right-click and choose “open in new tab.”

## We are living through the closing door of climate targets

Where we are now, and what we have to do to limit to +2C:

And, as far as +1.5C goes, it’s gone. Or at least that target can no longer met without invoking the fantasyland of negative emissions. There isn’t enough time.

## Sunday’s Storms Made Gas More Expensive, Thanks To Yet More East Bay Refinery Flare-Ups

Petrol too expensive? Replace your cars with EVs! There are plenty of choices. And, better still, replace your heating/cooling with electric heat pumps, and your appliances. Install PV solar on your roof and property. Get batteries, and almost leave your local grid. You can take back control of your energy supply from your utility.

It’s more about the zero than the net.

From Climate Adam. I support Climate Adam through Patreon. You should, too. At least see, listen to, and like his vids. They’re great.

I like the part about making a definitive plan, and acting upon it.

This isn’t only for companies. It’s for people and families, churches and schools and towns. Y’can’t really help the climate problem by just doing a couple of easy things. Everything needs to change. It’s going there anyway. If you do it yourself, you’ll be ready for the time you’ll economically have to do it.

## Words from Mother Jones

Mother Jones is rich this Autumn.

## Well, brevity in argument is not something to be expected from training at new, Palantir-supported University of Austin

Or maybe it’s just Niall Ferguson.

I’m sure the educational institution will succeed, if only because of student sifting, being located in Texas.

I’m surprised they call themselves a “university.” They had choices. MIT doesn’t.

## ‘Will Ford do away with the dealer model?’

Now there’s a question of the moment!

## Ford’s CEO Says Tesla Needs To Be Taken Seriously As The Dominant Player In The EV Market

That’s an article by Johnna Crider at CleanTechnica.

## Hydrogen production from curtailed generation

Why is it necessary that wind+solar+storage systems be “sized to meet peak demand”? That’s particularly true if capital costs per kWh for constructing them are very low, fractions of operating costs of fossil fuel installations. Why not build them to be multiples of peak demand, thereby protecting generation from lack of wind or insolation on a portion of the generating footprint.

This assumes, of course, that adequate land is available to site these, which is why constraints upon land use is effectively a subsidy to fossil fuel generation.

There has been a lot of talk about making electrolytic “Green Hydrogen” using electricity from wind and solar power that would otherwise be curtailed. Less climatically helpful, there is also potential to use electricity from natural gas generators that would otherwise be idled.

Tyler Ruggles set out to answer the questions:

1. How much additional flexible load could we put on electricity systems before we would need to add more generating capacity?
2. In an economically efficient system, how would the fixed generation costs be allocated across fixed and flexible loads?

This study was published in Advances in Applied Energy under the title, “Opportunities for flexible electricity loads such as hydrogen production from curtailed generation”.

Tyler H. Ruggles, Jacqueline A. Dowling, Nathan S. Lewis, Ken Caldeira, Opportunities for flexible electricity loads such as hydrogen productionfrom curtailed…

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## Losing sight of the big picture

When chasing political solutions to mitigating climate disruption, it’s long been tempting to go after relatively easy quick wins in the short term rather than facing up to the real problem: Emissions of Carbon Dioxide. So, in a world where lack of progress in the UNFCCC as evidenced in the recent COP26 seems a failure of international and national politics, the idea of focusing upon reducing Methane emissions and other short-lived climate pollutants is an easy branch to grasp as we are falling from the horse. John Broder at The New York Times reports on how the United States is doing just that.

Another Times journalist, Andrew Revkin, summarized the scientific consensus on why this focus is misplaced, even bad in his “Scientist’s View: In Climate Action, No Shortcuts Around CO2.” His article quoted James Hansen, Susan Solomon, Ken Caldeira, and Ray Pierrehumbert, linking to Professor Pierrehumbert’s piece at RealClimate (“Losing time, not buying time”), one which included the following figure:

And this one:

Yes, this is a long game, one where Methane is a bit player.

What’s also concerning is measures to curtail some short-lived climate pollutants, notably the hydrofluorocarbons, will result in more Carbon Dioxide emissions in the long run. While there are substitutes available for hydrofluorocarbons, at present none are as effective as the originals and, in an example of the engineering trade-offs (*) which riddle through all solutions to climate disruption, they are key components of geothermal and air source heat pumps, devices which replace natural gas and oil furnaces, particularly in northern climes. Zero CO2 emissions there, and no emissions of hydrofluorocarbons when the units are properly maintained.

I’ve blogged about Methane before, quoting some of the same sources. Professor Pierrehumbert has a more detailed technical review article presenting the arguments why the focus should and must be Carbon Dioxide, as politically and economically difficult as that might seem (**). And he keeps trying to make that point.

Quoting Professor Pierrehumbert’s RealClimate article:

Let’s suppose, however, that we decide to go all-out on methane, and not do anything serious about CO2 for another 30 years. To keep the example simple, we’ll think of a world in which methane and CO2 are the only anthropogenic climate forcing agents. Suppose we are outrageously successful, and knock down anthropogenic methane emissions to zero, which would knock back atmospheric methane to a pre-industrial concentration of around 0.8 ppm. This yields a one-time reduction of radiative forcing of about 0.9W/m2. Because we’re dealing with fairly short-term influences which haven’t had time to involve the deep ocean, we translate this into a cooling using the median transient climate sensitivity from Table 3.1 in the NRC Climate Stabilization Targets report, rather than the higher equilibrium sensitivity. This gives us a one-time cooling of 0.4ºC. The notion of “buying time” comes from the idea that by taking out this increment of warming, you can go on emitting CO2 for longer before hitting a 2 degree danger threshold. The problem is that, once you hit that threshold with CO2, you are stuck there essentially forever, since you can’t “unemit” the CO2 with any known scalable economically feasible technology.

While we are “buying” (or frittering away) time dealing with methane, fossil-fuel CO2 emission rate, and hence cumulative emissions, continue rising at the rate of 3% per year, as they have done since 1900. By 2040, we have put another 573 gigatonnes of carbon into the atmosphere, bringing the cumulative fossil fuel total up to 965 gigatonnes. By controlling methane you have indeed kept the warming in 2040 from broaching the 2C limit, but what happens then? In order to keep the cumulative emissions below the 1 trillion tonne limit, you are faced with the daunting task of bringing the emissions rate (which by 2040 has grown to 22 gigatonnes per year) all the way to zero almost immediately. That wasn’t very helpful, was it? At that point, you’d probably like to return the time you bought and get a refund (but sorry, no refunds on sale items). More realistically, by the time you managed to halt emissions growth and bring it down to nearly zero, another half trillion tonnes or so would have accumulated in the atmosphere, committing the Earth to a yet higher level of long-term warming.

(Some emphasis added in the above.)

Accordingly, all the United States position on Methane and other gases means is that leadership has been lost, and if that’s all there is, the COP26 is indeed a failure. Without more political and economic ambition on the part of developed countries to reduce their CO2 emissions, it can’t be anything else.

I’m not suggesting sackcloth and ashes here, and I’m not even suggesting reducing consumption. I am suggesting that those with means, who consume the most, need to rejigger their kit, switching to EVs on their own dime, putting PV panels everywhere they can, installing home batteries, and demanding their suburbs generate sufficiently electricity on the lands they have and control to supply all their needs. They have the wealth to do this, comparatively speaking, without hardship. The tools to do this are here, now, and they do not require some unproven future technology to achieve. In my opinion, there is no need for degrowth.

## Update, 2021-11-15

There was a lot of back in forth in the comments of another forum to which I contributed (***). This concerned whether or not the so-called Global Warming Potential (GWP) in particular with respect to Methane was meaningful for policy purposes. I got a bit wrong, because I did not realize infrared absorption spectra were built into the definition of GWP. With help from an expert advisor (****), I discovered that the GWP of a substance is the warming contributed by a one tonne pulse of the substance contributed to atmosphere over a hundred year interval relative to the effect of a one tonne pulse of Carbon Dioxide. This seemed to be widely accepted, even if it has some dark corners which I won’t get into here.

However, while doing some reading on this I discovered:

Allen, Myles R., Jan S. Fuglestvedt, Keith P. Shine, Andy Reisinger, Raymond T. Pierrehumbert, and Piers M. Forster. "New use of global warming potentials to compare cumulative and short-lived climate pollutants." Nature Climate Change 6, no. 8 (2016): 773-776.

Allen, et al point out there are shortcomings to using GWP and, in fact, there are alternatives, including one called Global Temperature Potential or GTP. What this means for methane and black Carbon (soot) is illustrated by the following figure:

I strongly recommend the article to see what some of the problems are with GWP.

$\noindent\rule{16.1cm}{2.1pt}$

(*) Land use for solar and wind farms versus aesthetics and appearance, even though the forests are unhealthy. Land use for traditional agriculture versus land use for agrivoltaics. Sea areas for wind farms versus preserving traditional fishing and shrimping spots. Fossil fuel industry jobs despite impact upon health, the climate, and its economic inefficiency versus wind+solar+storage+electrolyzed Hydrogen. Highly reliable EVs versus ICEs which support employment at gas stations, auto repair jobs, and the auto assembly lines. Discounting the harms to future generations in OECD countries and harm which is occuring to the non-OECD versus taking the moral responsibility to effectively pay for the harms done to the climate. There are many others.

(**) The fault, in my opinion, isn’t Republican versus Democrat, since parties have historically done nothing substantial to fix greenhouse gas emissions, as reported by James Gustave Speth in They Knew: The Us Federal Governments Fifty-Year Role in Causing the Climate Crisis (2021). The fault is to a great degree Western culture and a collective refusal to acknowledge how our quality of life is do primarily to our exploitation of the resources of the planet.

(***) Alas, despite searching, I could not locate this discussion. I think it was at Peter Sinclair’s Climate Denial Crock of the Week.

## Stuart Stevens: Covid a Stress Test, and So Far We’re Failing

Apart from divergence from political principles which a polity might have thought they held for a long time, the key question is what would be the actual, realized long term costs of an extended dalliance with an anti-intellectual, anti-realist movement to the country whose majority swings that way? Are there any?

Failures to prepare for consequences of climate disruption and works to eliminate behaviors and choices involving greenhouse gas emissions are not limited to people who are anti-intellectual. There’s a lot of practical denial of climate disruption simply in people continuing to do and buy as they’ve always have done, even — and some evidence says especially — among the well educated, at least in the United States. So climate may not be a good test at all.

There may be more urgent challenges. A contest with a rising world power may offer one. As world hegemon, the United States prides itself on its military, and upon the technological successes of its recent past. It naturally assumes its military continues to be dominant, and that its technical capacity is unrivaled, and, so, tends to believe up-and-comers cannot seriously threaten it. Improvements in military capability are explained as happening as a result of espionage rather than inherent capability. The trouble with this story is that it leaves the hegemon underestimating the capability of the new power. For as long as technological capability and military prowess merely follows the path with which the hegemon is familiar, all remains predictable, and responses possible. But if a new power knows how to create new technology, hidden in its military establishment, the hegemon no longer has the ability to predict or even counter something which hitherto hasn’t been seen.

When such advances have been brought to military contest in times past, the militaries on both sides adapt only slowly. And measnwhile the casualty counts rise.

That’s a military threat. What about an economic threat?

There is some acknowledgement, for example, that the United States needs to transition its energy supply to zero Carbon sources. This might be seen as a government perspective, associated with Democrats, but there is substantial realization among businesses and business leaders that this is how it needs to happen. (In fact, I can’t seen how Senator Manchin can claim he’s listening to business in his various flavors of opposition. The people who have his ear do not represent anything like a typical cross section of business interests, weighted by wealth.) There are two ways this could be done. One is to purchase the needed technology on open markets, and a good number of those sales might go to China. The other is to build the capability to make them in the United States, despite the acknowledged gap between U.S. manufacturing capability here and that available in the international marketplace. So, does the U.S. wait until it has such manufacturing capability before it rolls anything out to address climate? How does the nascent manufacturing sector get supported and funded? Government grants? That’s not really an open market, and it’s an approach that offers many opportunities for mistakes by government.

So, an anti-China stance may well hurt the United States economically, because it can no longer rely upon international sources for parts, specifically China, for it cannot be seen as cooperating with its new arch rival. The build up of capability can result in delays, products of inferior quality, setbacks in the marketplace.

What would make sense is to buy now, transitioning to domestic sourcing once the industry masters its products and its market. But superpower rivalry seldom results in paths which make sense.

## The Truth about Sea Level Rise

Nice post. Using different techniques, but an update of what I wrote about in 2014, better and more comprehensive.

It’s easy to see that sea level rise has not been steady. It has accelerated.

In fact it has accelerated a lot, especially recently. For most of the 20th century, it rose sometimes faster, sometimes slower, but for the last few decades its rise has picked up speed. The clearest demonstration is the change in global mean sea level. There are several different estimates of that based on historical data from tide gauges around the world, which differ on how much and how fast sea level has risen, but they all show — without a doubt — that the rise has not been steady.

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