Author: Iowa Climate Science Education

Learning About The AMO

Guest Post by Willis Eschenbach

I must admit to being greatly bemused by Michael Mann’s new (and sadly, paywalled) opus magnum about the Atlantic Multidecadal Oscillation (AMO), sometimes called Atlantic Multidecadal Variability (AMV). Here are a couple of quotes from our boy on the subject, emphasis mine:

Mann 2011:

“The AMO, defined as a 40-60 year timescale oscillation originating in coupled North Atlantic ocean-atmosphere processes, is almost certainly real

and

“This is a key finding of Knight et al (2005) (of which I was a co-author) as well as Delworth and Mann (2000) [the origin of the term ‘Atlantic Multidecadal Oscillation’ (AMO) which I coined in a 2000 interview about Delworth and Mann w/ Dick Kerr of Science].”

followed by Mann 2021

“Two decades ago, in an interview with science journalist Richard Kerr for the journal Science, I coined the term the “Atlantic Multidecadal Oscillation” (AMO) to describe an internal oscillation in the climate system resulting from interactions between North Atlantic ocean currents and wind patterns.  … Today, in a research article published in the same journal Science, my colleagues and I have provided what we consider to be the most definitive evidence yet that the AMO doesn’t actually exist.

I do enjoy Mann’s implication that he was the discoverer of the AMO phenomenon, when in fact it had been described in detail in 1994 by Schlesinger and Ramankutty, six years before the publication of Delworth and Mann. Also, in the linked Kerr article in Science that Mann refers to above, despite discussing the name “Atlantic Multidecadal Oscillation” in detail, Kerr never says that Mann named the phenomenon … but I digress.

First, what is the AMO? It is a slow temperature swing of the Atlantic, most visible in the North Atlantic. Here’s a graphic of the oscillation.

Figure 1. Long AMO, from NOAA. This shows a period of about 65 years. There are various instrumental versions of the AMO data. This is the longest instrumental version of the AMO held by NOAA, starting in 1856.

Since the first description of the AMO in 1994, the phenomenon has been extensively studied by any number of scientists. A search on Google Scholar shows 31,300 web pages discussing the AMO. So why does Michael Mann now claim it’s not a natural variation of the Atlantic?

Because “state-of-the-art” climate models say so … his study starts like this:

An analysis of state-of-the-art climate model simulations spanning the past millennium provides no evidence for an internally generated, multidecadal oscillatory Atlantic Multidecadal Oscillation (AMO) signal in the climate system and instead suggests the presence of a 50- to 70-year “AMO-like” signal driven by episodes of high-amplitude explosive volcanism with multidecadal pacing

(Protip—any time someone starts out by talking about “state-of-the-art climate models” you can safely ignore their claims … but again I digress.)

Mann’s claim in his new paper, Multidecadal climate oscillations during the past millennium driven by volcanic forcing (paywalled), is that in preindustrial times what people have been calling the “AMO” was actually a stable Atlantic that was being forced by sporadic volcanic eruptions that just happen to have the same frequency as the AMO. But then that volcanic forcing has died out in modern times, and just in the nick of time volcanic forcing has been replaced by anthropogenic forcing … funny how that works. In M. Mann’s world, it’s always the humans who are to blame.

In any case, I thought I’d see what I could learn from the data in both the instrumental and proxy AMO records, along with the volcanic records discussed by Mann. To start with, here’s the Amman et al. dataset that Mann et al. used of 61 tropical eruptions that they say drove the AMO before modern times. I’ve shown the eruptions as vertical lines. On top of these volcano lines, I’ve overlaid several of the empirical modes of a Complete Ensemble Empirical Mode Decomposition (CEEMD) analysis of the eruptions, showing the various longer-term cycles in the data.

Figure 2. Tropical volcanic eruptions, and various CEEMD modes.

Here’s the thing about signals. As the brilliant mathematician Joe Fourier showed way back a couple of centuries ago, any signal can be decomposed as the sum of underlying signals of various periods. CEEMD is like Fourier analysis, except it doesn’t break a signal down into regular sine waves. It breaks a signal down into underlying signals that can change over time, as you can see above.

Now, is there a cycle in the eruption data similar to the ~ 65 year period of the AMO? Well … kinda. But since each and every signal can be broken down into underlying signals, it may just be by chance. The underlying signals have to have some period, and it might just be fifty to sixty years, as in the volcanos.

So that’s the volcanos. How about the proxy records of the AMO? The main one that is discussed by Mann is the Wang et al study, “Internal and external forcing of multidecadal Atlantic climate variability over the past 1,200 years“. The data is available here. It’s based on “a network of annually resolved terrestrial proxy records from the circum-North Atlantic region.” In that study, Wang et al. distinguished between what they called “AMV”, Atlantic Multidecadal Variability”, and the AMO. They said that something like 30% of the variability of the AMV was from volcanoes, and when that’s taken out we’re left with the AMO. Me, I doubt that, because modern volcanoes show little effect on the AMO. I also wanted to see how well the eruptions matched up with their data, so I’ve used their raw “AMV” data.

First I looked at how well the Wang proxy records matched the instrumental records shown in Figure 1. I’ve also added in the 50-60 year empirical mode of the CEEMD analysis of the Amman eruption records shown above in Figure 2.

Figure 3. Two AMO records and one eruption record, 1856 to present.

We see a couple of things in Figure 3. First, the Wang paleo proxy AMV (red) is very close to the modern instrumental AMO (blue).

However, the Amman eruption data is a quite poor match to the modern AMO data. This is no surprise. Look at Figure 1. If you don’t know which year the huge Pinatubo eruption occurred, you couldn’t tell it from Figure 1.

Next, I looked at the longer term view of that same data. Figure 4 shows that result.

Figure 4. Two AMO records and one eruption record, 800 to present.

Again, some interesting things in Figure 4. First, the average length of the cycles in the Wang paleo AMV is 65 years, which matches the modern data.

However, as in the modern period, there’s a very poor fit between the Amman eruption data and Wang paleo data. Among other things, the period of the eruption data averages 55 years, not the 65 years of either the Wang paleo data or the modern instrumental data. So although at times it matches up with the Wang data, it goes into and out of sync with both the instrumental AMO and the Wang AMV data.

So … how did Mann et al. come to their conclusions? As mentioned above, computer models …

The CMIP5 Last Millennium multimodel experiments provide a pseudo-ensemble of N = 16 simulations driven with estimated natural forcing (volcanic and solar, with minor additional contributions from astronomical, greenhouse gases, and land-use change) over the preindustrial period (the interval 1000 to 1835 CE is common to all simulations). We estimate the forced-only component of temperature variation by averaging over the ensemble, based on the principle that independent noise realizations cancel in an ensemble mean.

(In passing, let me note that it is certainly not always true that averaging a number of model outputs means that the “noise realizations cancel”. But again I digress …)

I rather did like the idea of a “pseudo-ensemble”, however … is that a bunch of random computer models hanging out on a street corner smoking cigarettes and pretending to be an ensemble? But I digress …

And what were their conclusions (emphasis mine)?

The collective available evidence from instrumental and proxy observations and control and forced historical and Last Millennium climate model simulations points toward the existence of externally forced multidecadal oscillations that are a consequence of competing anthropogenic forcings during the historical era and the coincidental multidecadal pacing of explosive tropical volcanic activity in past centuries. There is no compelling evidence for a purely internal multidecadal AMO-like cycle.

His claim is that for about eleven centuries, “explosive tropical volcanic activity” made it look like there is an AMO. And coincidentally, just when the volcanic forces left off, a competition between CO2 and sulfate forcings caused the AMO swings.

You’ll forgive me if, given what I see in the Figures above, I don’t find that argument even slightly compelling.

Finally, this is what I love about studying the climate. The science is far from settled, and that gives me the opportunity to learn something new from every paper that comes out.

Here on our dry northern California coastal hillside, rain is forecast starting tomorrow morning and lasting two days. However, around here, rain forecasts even twelve hours out are sometimes way wrong, and it’s generally true for rain forecasts three or four days out. Funny thing about chaotic systems. They tend to be … well … chaotic.

[NOTE: It’s now “tomorrow morning” when the rain was supposed to start … bright sunlight and not a cloud in the sky. Gotta love chaotic systems.]

Seems like out here in the real world, the modelers don’t have that whole “noise realizations cancel” deal completely worked out … but I digress.

My best regards to all, skeptics and mainstream folks alike,

w.

PS—I sign everything I write with my initial, “w.”, and for the same reason I choose my words very carefully—because I wrote them, I take ownership of them, and I know that it is always possible I will be called upon to defend them. However, I can’t defend your interpretation of my words. So when you comment, please quote the exact words that you are discussing. This avoids endless misunderstandings.

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March 8, 2021 at 01:01PM

Let them eat bugs! The latest from the UN biodiversity conference

“Let them eat bugs!”

That seems to be the rallying cry for environmental organizations of late, as many groups called for the international community to restrict both meat consumption and pesticide use at a recent UN Biodiversity virtual meeting.

Specifically, the UN meeting centered on agricultural practices pertaining to the Convention on Biological Diversity (CBD). The general goal of these meetings is to achieve what the UN calls living in “harmony with nature” by 2050.

But to the participating NGOs, that goal should be achieved no matter the cost to humans.

Many groups condemned what they called the negative environmental impact of meat-eating, and specifically, raising livestock.

The CBD Alliance didn’t mince words, saying: “A recent report by UNEP and others make it clear that feeding the world’s population without destroying biodiversity is not possible without a significant reduction in the consumption of meat and dairy from intensive livestock production systems, because animal farming occupies 78% of agricultural land while providing only 18% of global calorie supply and 37% of global protein supply.”

But meat is a product only wealthier nations and families can afford. To imply that meat is somehow bad because it only supplies 37% of the world’s protein doesn’t prove meat is bad, it only shows how many more people need access to meat.

Overconsumption should always be a concern when it comes to obesity, but meat-eating brings many important nutrients to a healthy human diet. Leaner red meat contains protein, B12 vitamins, iron, and more nutrients essential to human health. Chicken contains important amino acids.

And thanks to modern farming methods, more people are being fed than ever before in history. In the United States alone, conventional farm production per acre tripled over the last 70 years. Corn production increased 500% while using 20% less land.

Yet even modern farming practices were the target of NGOs during this UN meeting.

A group called ProNatura, in collaboration with Friends of the Earth Europe called for minimizing the use of all pesticides and asked the UN to begin targeting fertilizers as well.

The African Center for Biodiversity (ACB) said that “Industrial agriculture in Africa is built upon gross inequalities and social exclusion and has benefitted primarily the corporate sector, while hunger and malnutrition are continuously on the rise.”

To be certain, freedom of entrepreneurship and human rights issues need to be addressed in many parts of Africa and the world. Yet according to the Global Hunger Index, hunger severity in many parts of Africa has fallen significantly over the last two decades.

In the Democratic Republic of Congo, the “Global Hunger Index Severity Scale” (GHI), a grading scale for evaluating a country’s hunger problem, showed marked improvement for the nation over the last 20 years. The GHI scale fell from 33.8 in 2000 to 26.0 in 2020. Similar numbers can be seen in Chad, where the index went from 50.9 to 44.7. Sierra Leone has also seen significant improvement, going from an “extremely alarming” rating of 58.3 in 2000 to a “serious” problem of 30.9 in 2020.

Of course, all these numbers are still too high. But eliminating pesticides and telling Africans they need to eat less meat isn’t just bad policy, it is inhumane.

Only time will tell if these environmental NGOs will have their say over UN policy, or if the miracles of modern agriculture will be preserved.

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March 8, 2021 at 01:01PM

Modeling shows the true cost of heat on solar PV system performance

Solar power complex in California [USA. Gov – BLM – Bureau of Land Management]

It was already known that PV systems dislike high heat, which is clearly awkward when they depend on the biggest heat source in the *solar* system in order to be of any use. This study tries to quantify the problem in more detail. On the face of it, carpeting desert regions with solar panels looks less than ideal.
– – –
Lowering the operating temperature of solar panels by just a few degrees can dramatically increase the electricity they generate over their lifetime, KAUST researchers have shown.

The hotter a panel gets, the lower its solar power conversion efficiency (PCE) and the faster it will degrade and fail, says TechXplore.

Finding ways to keep solar panels cool could significantly improve the return on investment of solar-power systems.

The long-standing focus of photovoltaics (PV) research has been to improve solar modules’ PCE and make solar power more cost-competitive than nonrenewable power generation. The higher the PCE, the better the PV system’s financial payback over its lifetime or the lower its “levelized cost of energy” (LCOE).

Other factors can skew these LCOE values. Capturing sunlight is inherently hot work. “All solar cells generate heat, which can lower the electrical output and shorten the module lifetime,” says Lujia Xu, a postdoc in Stefaan De Wolf’s team.

Panels can regularly reach 60-65 degrees Celsius, but heat’s impact on LCOE rarely receives much consideration.

Now, Xu, De Wolf and their colleagues have developed a metric that directly compares the LCOE gains by reducing the module temperature with the LCOE gains for improving module efficiency.

Under typical operating conditions, the same improvement in LCOE by finding a hard-won one percent gain in PCE could be achieved by lowering the module temperature by as little as 3 degrees Celsius, they showed.

The key factor was that hotter panels fail far more rapidly.

“A 4 degrees Celsius decrease in module temperature would improve the module time to failure by more than 50 percent, and this improvement increases to over 100 percent with a 7 degrees Celsius reduction,” says Xu.

Full article here.

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March 8, 2021 at 12:42PM

Coal India approves 32 coal mining projects worth $6.4 billion

Coal India Ltd. approved an investment of about 473 billion rupees ($6.4 billion) on mining projects as the company seeks to boost output to replace imports of the fuel, the Kolkata-based miner said in an emailed statement.

The approvals include eight new projects as well as expansion plans for 24 existing mines, Coal India said. The 32 sites will have a combined peak output of 193 million tons a year, the highest capacity approved during a fiscal year, it said. The projects will produce 81 million tons annually from the financial year starting April 2023, by when the miner targets reaching 1 billion tons of annual production.

The world’s biggest miner is counting on a revival in demand for the fuel as the Indian economy emerges from a pandemic-induced slump. Besides industrial consumption, the approaching summer is expected to boost demand for electricity and spur power generators to replenish their declining coal inventories, Coal India’s Chairman Pramod Agrawal said last month.

Full story

The post Coal India approves 32 coal mining projects worth $6.4 billion appeared first on The Global Warming Policy Forum.

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March 8, 2021 at 11:25AM