First, the esoteric question. Simply put, over the last two million years or so, the Earth has gone through a couple of dozen cycles that have ice ages at one end and very warm periods (such as the one we were in in the 19th century) at the other end. The first several cycles were modest, but the most recent have been extreme, with the cold periods involving the growth of major continental glaciers big enough, for example, to cover most of Canada and a chunk of the US. The current warm period, enhanced by anthropogenic global warming, is probably already warmer than the previous really warm periods, and over the next couple of decades will certainly be what has been called a “super-interglacial” with temperatures consistently being above anything during this entire glacial-interglacial cycle.

This cycling of climate is linked to a cycle of how much of the Sun’s energy falls on the earth, when, and where. The simple version of this arises from the fact that land masses, where continental glaciers can form, are concentrated in the Northern Hemisphere. Continental glaciers have their own cooling system (by being bright and reflecting away sunlight, mainly) so once they form they tend to be self sustaining. But it is difficult for then to form to begin with because, well, the Earth is usually too warm. But, if Northern Hemisphere summers are chilled down sufficiently several years in a row, these glaciers can start to form, and this can be part of the onset of a new glacier.

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Current and recommended books on climate change.
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The Earth wobbles as it rotates. The elliptical orbit of the Earth around the Sun varies in how elongated it is. The location of the Earth on this elliptical orbit during a particular moment in the seasonal round changes over time (so every now and then the solstice, for instance, happens when the Earth is maximally distant from the sun). These three factors change in a regular cycle over different time periods. Every now and then all three factors cause the following thing to be true: late June, the longest and thus sunniest period of the year in the Northern Hemisphere, is also the time when the Earth is farthest from the sun on an elliptical orbit that is as elongated as it ever gets, but the Earth has wobbled up so that the Northern Hemisphere is not as pointed towards the Sun as it could be. When this happens, Northern Hemisphere summers have a minimal amount of the Sun’s energy.

But that difference is probably not enough to start an ice age, and the opposite times, when the Northern Hemisphere’s summers are maximally sunlight, are probably not enough warmer than other periods to kill off an ice age.

During the 1970s and early 80s, the cycles of Sun’s energy variation caused by these orbital quirks were reconsidered (it was a 19th century observation) and correlated with recently obtained isotope data from sea cores indicating glacial cycles. They matched. More NH summer extra sunlight happened during interglacials pinned down by the isotopic data, and NH summer reduced sunlight matched in time with the glacial periods. But, over subsequent years, research tended to show that the changes in sunlight and glacial activity did not correlate exactly. Rather, other causes of the onset or melting of glaciers seemed to be other things.

Over time we have come to realize that the orbital effects, known as Milankovitch Cycles, probably determine the potential for the Earth to be in a glacial period vs. an interglacial period, but other factors actually push the climate system into these new states.

This is like so many other things in nature. You have the right genes to develop perfect pitch, but that does not make you a musician. Growing up in an environment that would encourage one to be a musician is not sufficient to make you a great musician. Having perfect pitch and a music-friendly environment and a few other things, all together in for the same person, might create a David Bowie. Or not. But given millions of people, there will be hundreds of great musicians, and most of them will have most of these factors in place.

The current research is a study that relates atmospheric CO2 changes and Milankovitch changes, and it may be an important contribution to understanding this complex system. I’ve not thought about the paper enough to say this (or not say it), but that is what the paper is about.

Meanwhile, years ago, back in the late 1960s and through the 1970s, paleoclimate experts like John Imbrie and JM Mitchell and others pointed out that greenhouse gasses would likely bring on a “super interglacial” that would obviate an ice age that might otherwise occur very soon. They also noted that after thousands of years following the burning of the last available fossil fuel, or the curtailment of this insane practice, the CO2 added to the atmosphere would likely cycle back into solid form, and the next time orbital geometry matched up with other stuff, we could have our ice age again.

More recently, Bill Ruddiman looked at human activities in recent history and suggested that land clearing practices associated with agriculture, and the early burning of fossil fuels, was sufficient to put off an ice age.

Today we know that the cycling in and out of Ice Ages over the last million years or so is associated with atmospheric CO2 levels well within the range of 200ppm to 300ppm. So, I would guess that once we passed around 300ppm we left the likelihood of an ice age behind. Indeed, it is possible that had we not done that, we might have eventually figured out that we should do it, to avoid an ice age.

But enough is enough. The fact that you like your hamburger cooked does not mean that therefore you should cook it at 10,000 degrees C for a year. You cook it the right amount. More than that ruins it. We might benefit from “cooking” the Earth just a little bit to avoid an ice age (and yes, we do want to avoid an ice age), but we don’t want to overcook the Earth. We passed annual an average CO2 concentration of 400ppm a few months ago. The hamburger, and our goose, is being overcooked.

One outcome of the new research is to suggest that without human perturbation of the climate, we would have skipped this ice age anyway. This assertion is the reason I’m reserving judgement on this paper. I wonder if all the appropriate factors have been taken into account, because I find this assertion difficult to believe. But, I’m not going to make an argument based on incredulity. I’ll just note my incredulity, as someone who has studied Pleistocene climate change, and consider getting back to you on this at a later time.

The paper further suggests that current burning of CO2 will extend that period of time to the next Ice age by double, and that “Our simulations demonstrate that under natural conditions alone the Earth system would be expected to remain in the present delicately balanced interglacial climate state, steering clear of both large-scale glaciation of the Northern Hemisphere and its complete deglaciation, for an unusually long time.”

So, when media report that this study suggests that anthropogenic global warming has put off an ice age, they are talking about shifting a 50,000 year delay to the next ice age (without human effects) to a 100,000 year delay. This would be a new idea, because we were thinking that we had put off an ice age that was just about to happen (over the next centuries). So, the paper actually says nearly the exact opposite of what the press says it says. How could this happen? Can’t imagine…

The Paper:

Ganopolski, A. R. Winkelmann,& H. J. Schellnhuber. 2016. Critical insolation–CO2 relation for diagnosing past and future glacial inception. Nature 529, 200–203 (14 January 2016) doi:10.1038/nature16494.

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h3>The 1970s Ice Age Myth and Time Magazine Covers
– by David Kirtley

A few days ago a facebook friend of mine posted the following image:

From the 1977 cover we can see that apparently a new ice age was supposed to arrive. Only 30 years later, according to the 2006 cover, global warming is supposed to be the problem. But the cover on the left isn’t from 1977. It actually is this Time cover from April 9, 2007:

As you can see, the cover title has nothing to do with an imminent ice age, it’s about global warming, as we might expect from a 2007 Time magazine.

The faked image illustrates one of the fake-skeptics’ favorite myths: The 1970s Ice Age Scare. It goes something like this:

• In the 1970s the scientists were all predicting global cooling and a future ice age.
• The media served as the scientists’ lapdog parroting the alarming news.
• The ice age never came—the scientists were dead wrong.
• Now those same scientists are predicting global warming (or is it “climate change” now?)

The entire purpose of this myth is to suggest that scientists can’t be trusted, that they will say/claim/predict whatever to get their names in the newspapers, and that the media falls for it all the time. They were wrong about ice ages in the 1970s, they are wrong now about global warming.

But why fake the 1977 cover? Since, according to the fake-skeptics, there was so much news coverage of the imminent ice age why not just use a real 1970s cover?

I searched around on Time’s website and looked through all of the covers from the 1970s. I was shocked (shocked!) to find not a single cover with the promise of an in-depth, special report on the Coming Ice Age. What about this cover from December 1973 with Archie Bunker shivering in his chair entitled “The Big Freeze”? Nope, that’s about the Energy Crisis. Maybe this cover from January 1977, again entitled “The Big Freeze”? Nope, that’s about the weather. How about this one from December 1979, “The Cooling of America”? Again with the Energy Crisis.

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Now, there really were news articles in the 1970s about scientists predicting a coming ice age. Time had a piece called “Another Ice Age?” in 1974. Time’s competition, Newsweek, joined in with “The Cooling World” in 1975. People have collected lists and lists of “Coming Ice Age” stories from newspapers, magazines, books, tv shows, etc. throughout the 1970s.

But if it was such a big news story why did it never make the cover of America’s flagship news magazine like the faked image implies? Perhaps there is more to the story.

In the 1970s there were a few developments in climate science:

• Scientists were finding answers to the puzzle of what caused ice ages in the past: variations in earth’s orbit.
• Scientists were gathering data from around the world to come up with global average temperatures, and they found that temperatures had been cooling since about the 1940s.
• Scientists were realizing that some of this cooling was due to increasing air pollution (soot and aerosols, tiny particles suspended in the air) which was decreasing the amount of solar energy entering the atmosphere.
• Scientists were also quantifying the “greenhouse effect” of another part of our increasing pollution: carbon dioxide (CO2), which should cause the climate to warm.

The realization that very long cycles in earth’s orbit could cause the waxing and waning of ice ages, coupled with the fact that our soot and aerosols were already causing cooling, led some scientists to conclude that we may be headed for another ice age. Exactly when was still a little unclear. However, the warming effects of CO2 had been known for over a century, and new research in the 1970s was showing that CO2 warming would more than compensate for the cooling caused by aerosols, resulting in net warming.

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This, in a very brief nutshell, was the state of climate science in the 1970s. And so the media of the time published many stories about a coming ice age, which made for timely reading during some very cold winters. But many news stories also mentioned that other important detail about CO2: that our climate might soon change due to global warming. In 1976 Time published “The World’s Climate: Unpredictable” which is a very good summary of the then current scientific thinking: some scientists emphasized aerosols and cooling, some scientists emphasized CO2 and warming. There was no consensus either way. Many other 1970s articles which mention a Coming Ice Age also mention the possibility of increased warming due to CO2. For instance, here, here and here.

Fake-skeptics read these stories and only focus on the Coming Ice Age angle, and they enlarge the importance of those scientists who focused on that angle. They totally ignore the rest of the picture of 1970s climate science: that increasing CO2 would cause global warming.

The purpose of the image of the two Time magazine covers, and of the Coming Ice Age Myth, is not to show the real history of climate science, but to obscure that history and to cause confusion. It seems to be working. Because today, when there really is a consensus about climate science and 97% of climatologists agree that adding CO2 to the atmosphere is leading to climate change, only 45% of the public know about that consensus. The other 55% must think we’re still in the 1970s when scientists were still debating the issue. Seems newsworthy to me, maybe Time will run another cover story on it.

To learn more see:

• The Discovery of Global Warming: Revised and Expanded Edition (New Histories of Science, Technology, and Medicine), Spencer R. Weart. The author has an online expanded version of this book.
• Ice Ages: Solving the Mystery, John Imbrie and Katherine Palmer Imbrie.
• “The Myth of the 1970s Global Cooling Scientific Consensus,” Peterson, Thomas C., William M. Connolley, John Fleck, 2008: Bull. Amer. Meteor. Soc., 89, 1325–1337.

Then the ice went away, but the effects of the ice having been there are still being felt. A paper coming out next week in Nature explores the effects of deglaciation on the oceans. We can see the effects of the ice in the flooding going on right now in the Red River Valley on the North Dakota-Minnesota border. The lack of native worms in the northern regions of North America, and the survival of a number of rare plants is related to the deglaciation process. The effects of the great ice sheet and it’s subsequent melting have shaped the landscapes and cityscapes of many regions.

South Minneapolis is the largest part of the city in terms of both land area and population size. Minneapolis is called the City of Lakes (and thus, our basketball team is “The Lakers” ( … or did they move somewhere else, can’t remember … ), because of the lakes in west side of the city. If you look at a map of Minneapolis and surrounding areas, you’ll see that you can connect these lakes together between two roughly parallel lines, and that these lines indicate the outer limits of an ancient river channel. The river channel is still very much in place, and if you get down on the ground you can see where the sides of this channel are even where there are no lakes. The lakes are simply spots within the channel that were filled with more ice than sediment as the glaciers melted away. When the ice melted, a depression was left behind, and that depression is now a lake.

This explains why most of the lakes around here, most of which were formed from ice melted in the glacial ’till’ (as the stuff is called) are round. Imagine a concentration of big chunks of ice of any shape in one area below the ground. Maybe they are 30 feet to 200 feet below the present surface. It takes them forever to melt, but eventually they do and even if the void left behind is filled with water, the sediment collapses into the void. Now, think of this void as the lower part of an hour glass. as the sediment from above sifts and pours down into the void, the space that is above the passage way into the void is more or less unformly empties of its sediment, which means that an odd shaped void down deep is displaced and becomes a globular (round, from the top) shaped void above. A rounded circular depression in the landscape, which in turn becomes a lake.

If you take a broader view of the region, you can see that there are segments of ancient river channels all over the place, and if you start connecting them together, you will see that there is no way that these channels can be matched up to be the single channel of some ancient river. Rather there is a web-like network of channels everywhere. At any given time in prehistory, one or two rivers meandered across this region using some subset of channels.

If you remove all the glacial sediment and leave only the channels, what you would actually get is a landscape consisting of buttes and mesas separated by u-shaped valleys. It would look roughly like the badlands of the Dakotas.

One of these ancient channels (as discussed here) is the large recent course of the Warren River, and it is the nature of this valley’s formation that contributes to the modern day flooding we see in the Red River Valley, which occupies part of this ancient water route.

Getting back to the peer reviewed paper at hand.

This is the abstract from the paper, and I’d like this abstract to serve two purposes:

Rivers are the dominant source of many elements and isotopes to the ocean. But this input from the continents is not balanced by the loss of the elements and isotopes through hydrothermal and sedimentary exchange with the oceanic crust, or by temporal changes in the marine inventory for elements that are demonstrably not in steady state. To resolve the problem of the observed imbalance in marine geochemical budgets, attention has been focused on uncertainties in the hydrothermal and sedimentary fluxes. In recent Earth history, temporally dynamic chemical weathering fluxes from the continents are an inevitable consequence of periodic glaciations. Chemical weathering rates on modern Earth are likely to remain far from equilibrium owing to the physical production of finely ground material at glacial terminations that acts as a fertile substrate for chemical weathering. Here we explore the implications of temporal changes in the riverine chemical weathering flux for oceanic geochemical budgets. We contend that the riverine flux obtained from observations of modern rivers is broadly accurate, but not representative of timescales appropriate for elements with oceanic residence longer than Quaternary glacial-interglacial cycles. We suggest that the pulse of rapid chemical weathering initiated at the last deglaciation has not yet decayed away and that weathering rates remain about two to three times the average for an entire late Quaternary glacial cycle. Taking into account the effect of the suggested non-steady-state process on the silicate weathering flux helps to reconcile the modelled marine strontium isotope budget with available data. Overall, we conclude that consideration of the temporal variability in riverine fluxes largely ameliorates long-standing problems with chemical and isotopic mass balances in the ocean.

If you read that, your head probably hurts because it is a typical scientific abstract written to not be understood by the average person. First, I want to tell you briefly what it means, then I want to pick out a few sentences and hold them up as reasons that that authors who wrote this and the editors who let it pass should be flogged. (Flogging is British, right? This is Nature. So, right, flogged.)

What it means is this: The elements that are dissolved in the ocean change over time more than we would expect if this was simply a matter of the hard parts of the continents slowly eroding into the ocean, and the ocean getting rid of some of these elements when they settle to the bottom of the ocean or go somewhere else. It turns out that after a glacial period is over and the ice goes away, there is extra chemical stuff eroding into the ocean because the glaciers ground up more of the rock than would normally be eroded to contribute chemicals to the ocean. Interesting. Simple. Important. Not hard to understand.

But this is hard to understand:

In recent Earth history, temporally dynamic chemical weathering fluxes from the continents are an inevitable consequence of periodic glaciations.

Let’s break it down.

“In recent Earth History..”

This is a paper about the earth. And history. That this is Earth history and recent tells us nothing but adds mystery. This is nota mystery paper. Give dates. Such as, “During the last two to five million years” ..

“temporally dynamic chemical weathering fluxes”

OMG give me a break. Temporally = over time. Dynamic = changing, variable. Fluxes = changes. The word “chemical” in a paper about “elements and isotopes” means nothing. Oh, and by the way, isotopes are elements… no need to use the extra words.

Try: “Over time, changes in weathering”

“are an inevitable consequence of periodic glaciations.”

That’s OK, but it is really just hoiti toiti language. So, this:

In recent Earth history, temporally dynamic chemical weathering fluxes from the continents are an inevitable consequence of periodic glaciations.

… would be readable and more literate if it was dynamically fluxuated into this:

During the last 2-5 million years, changes in weathering from the continents happened because of periodic glaciations.

Is that so hard?

Here’s a half dozen more bits of the abstract.

… To resolve the problem of the observed imbalance in marine geochemical budgets, attention has been focused on uncertainties in the hydrothermal and sedimentary fluxes.

… the physical production of finely ground material at glacial terminations that acts as a fertile substrate for chemical weathering.

… we explore the implications of temporal changes in the riverine chemical weathering flux for oceanic geochemical budgets.

We contend that the riverine flux obtained from observations of modern rivers is broadly accurate, but not representative of timescales appropriate for elements with oceanic residence longer than Quaternary glacial-interglacial cycles.

… Taking into account the effect of the suggested non-steady-state process on the silicate weathering flux
…

…we conclude that consideration of the temporal variability in riverine fluxes largely ameliorates long-standing problems with chemical and isotopic mass balances in the ocean.

How would you rewrite these?

Vance, D., Teagle, D., & Foster, G. (2009). Variable Quaternary chemical weathering fluxes and imbalances in marine geochemical budgets Nature, 458 (7237), 493-496 DOI: 10.1038/nature07828