Wednesday, January 25, 2012

Migration 13: Climate Changes, A Human Timetable, and The Canyon

William Ruddiman has been a scientist of climate (see over most of the recent span of a tremendous growth in the study of that subject, a growth that continues a two-century surge in earth/life sciences, marked by the work of Hutton, Darwin, Wegener, as well as in the study of humanity's story. His most recent effort -- which I am attempting to extract from here (and any re-statings and errors in this entry are, be assured, mine) -- resulted in Plows, Plagues, and Petroleum: How Humans Took Control of Climate (Princeton 2005). His work does not directly deal with the Grand Canyon, of course, yet his thesis is an important element in understanding the Canyon's human context, its politics. His thesis also impacts heavily on the idea of wilderness and what it can mean if we properly comprehend humanity's history. 

Briefly stated, Ruddiman argues that human activities arising from the Neolithic Revolution have already had the not-to-be-understated result of preventing the start of a period of increasing glaciation. To show this, he summarizes the current picture of ice ages, emphasizing their periodicity. That periodicity indicated that a glacial was due and yet is not happening. In investigating why, he could find no convincing natural cause, and so studied human activities that might have increased the greenhouse gases of carbon dioxide and methane over the relevant period of the past 10+ millennia. 


I am not going to go into his presentation in detail; his book is readable and less than 200 pages. Here I want to summarize enough to set humanity's latest stage. For what I have found valuable in his book is his presentation of a timetable of human history set against the timetable of natural climate cycles. For the latter, his authority must be great, with a vita of work at the Lamont-Doherty Earth Observatory (Columbia Univ.) followed by a professorship (emeritus now) of environmental sciences at the University of Virginia. For the former timetable, however, he is, like me I hope, an informed, inquiring lay reader of the work of others, anthropologists, etc. Since the human timetable he presents fits what I have been able to glean, it seems an appropriate corroboration of my understanding. I should add that whatever our agreement on the human timetable that I present below, he still approaches this subject as a scientist, I as an activist. So our thoughts about what this all means are not necessarily in agreement.

So first, some climate science. In recent geological time, the Earth has been gradually cooling, enough to introduce a series of ice ages, times of glacial advance and then retreat. More exactly, 2.75 million years ago (mya) cooling reached a threshold such that ice sheets appeared and spread in the Northern Hemisphere. These glacials were followed by interglacials during which the northern ice sheets retreated. After considerable scientific labor, and taking more than a century, the theory was confirmed that these ice ages of glacial/interglacial periods were periodic, and due to three astronomical factors that affect how much solar radiation we get (see Ruddiman, pp. 24-54):

1. The angle of at which the Earth's axis tilts is not constant at the current 23.5º, but varies from 22.2º to 24.5º over a period of 41 millennia.
2. Our distance from the sun changes, with the orbital eccentricity changing over 100 millennia, though somewhat irregularly. 
3. Precession --wobble of the axis-- has the effect of causing a change in the direction in which Earth leans on its tilted axis--so there is change in the amount of tilt and the direction of tilt. This cycles over 22 millennia. Eccentricity changes act as a multiplier on precessional changes.
The combined effect is that the periodicity from 2.75 to .9 mya was in 41-millennia cycles, and since .9 mya has been in 100-millennia cycles. Overall, there have been 40-50 cycles. These cycles are a phenomenon of the Northern Hemisphere; the Antarctic sheet stays in place. Also, the increase in global cooling has continued with the ocean getting cooler. The longer cycles now are the result of ice sheets not melting all the way, in between 100 ky peaks.

During glacials (nine in the past million years), there would be no forest about the Alps, but a deep tundra. To the south and east, Europe was grassy steppe, similar to Siberia now. In America, the jet stream was forced by the ice to flow more southerly, dropping more moisture in, for example, the Great Basin (and the Colorado River Basin?). Deserts expanded farther south. The windy, dry, dusty conditions picked up dirt and blew it around, leaving evidence so we can now trace history. After glacial peaks, the southern Sahara was wetter & greener, as from 10-5 millennia ago. This is traceable to monsoon strength, which is directly related to solar radiation strength in the summer. Also, methane increased due to vegetation flooding. Ruddiman doubts this overall history of these climate changes had direct impacts on our evolution. However, I think it fair to say that this part is all argumentative, based on his view that before 8 millennia ago, nature was in control with those ~3 million years of glacial/warming cycles. 

The most recent glacial took over 10 millennia to melt, from 20  to 6 millennia ago, with the finish of the melting of ice sheets. A melting period is a contention between ice sheets keeping cold and warming from the sun plus greenhouse gases. So 11 millennia ago, the ice sheet was being melted, aided by high natural values of CO2 and methane. The gases reached a maximum, then started to decline toward the next glacial threshold. The maximum temperature occurred ~8 millennia ago. Or in summary, the significant markers were at 20 --> 11 -->  8 --> 6  millennia ago.


Now we get to the fun part, dealing with Ruddiman's timetable for the most recent human times (pp 169ff). Earlier, p23, he had set up human evolution over a few million years with increasing brain size, improving communication skills, and spreading out, but still being deep in the Stone Age. By the way, he offers an interesting claim of child spacing at four years or more, which helped keep population down. However, his bibliography does not suggest a definitive source for this notion, which might or might not be relevant to the question of the organization of human bands.

So, 150-100 millennia ago there is us, "fully modern humans", few in number and moving about for food, with an increasing sophistication in (stone) tools, fire, burials. He ponders how they are like us, but with "primitive" lives. However, as I have found in other ponderers of early humanity, there is NO MENTION OF LANGUAGE, only his earlier note of an increase in communication skills. 

50 millennia ago, human creative potential became evident, p55, in artifacts, painting, statues, jewelry, burial goods, bone for clothes-making & tent-making tools, rope, nets, hooks, spears.  Also, by that time, we had managed the crossing into Australia. Again, I would argue the realization of this potential, along with so much else, was dependent on language and the type of sociality it encouraged.

12.5 millennia ago, (and probably before, I would add), humans were migrating into the Americas, and quite possibly employing our skill as hunters to push a number of large fauna toward disappearance. Ruddiman, speaking as an expert on climate change, does not accept an alternate explanation of the die-outs as being caused by the climate change; there had been too many previous cycles without such mass die-offs.

12 millennia ago, agriculture was "discovered", p4. I prefer the formulation that we invented domestication, first of plants, later animals. Ruddiman also uses the phrase "development" of cultivated cereals at this time, p10.
11.5 millennia ago, people in Mesopotamia "created" agriculture, p63. 
Whatever the term, agriculture led to settlement and an increase in population.
On p65, he ruminates on the problematic advantages of agriculture for a culture of such botanically sophisticated gatherers, since nutritional balance would be sacrificed and energy expenditure in procuring food would increase. Perhaps, he suggests, there was enough bounty of gathered food that cultivation provided an add-on, not the only, source. Compared to forest or desert, the area was well-provided with food, and farming only enriched the bounty. 

10 millennia ago, south Sahara was wetter and greener, due to the stronger monsoon. Then came a drying out, p50ff
Before 10 millennia ago, animal domestication began: dogs, then goats & sheep; pigs & cattle by 9 millennia ago.
10.5 millennia ago, permanent farm villages existed with hundreds of inhabitants. In Ruddiman's view, the increase in the numbers of children was connected to no longer being  migratory. However, would not any problems with soil or water supply lead these (genetically migratory) humans to shift about? Could the impulse to migrate just have been lost? Indeed, it hasnt, ten millennia later. That is, I suggest, more children were desirable as labor supply, just as marriage and religio-legal bonding would develop as adjuncts to labor needs, and still later as defender/warriors.
9-8 millennia ago, agriculture was spreading into India.
8 - 5.7 millennia ago, it was spreading into Europe.
In this interval, irrigation was begun in Mesopotamia. 

At 8 millennia ago, humans began to clear forests for farming in southern Europe & northern China. Deforestation spread over the following millennia. Burning over the land also added CO2. (Would there have been a contribution from more wood used as fuel for that increasing population, too?) 
This deforestation, Ruddiman hypothesizes, is the source of the reversal of natural CO2 decline. Not sudden & dramatic, the action here was low level but continued and gradually increased.
7+ millennia ago, rice is being grown in China.
7 millennia ago, agriculture came into north Africa and southern Europe. (That is, around the Mediterranean; were there boats, and trade?)
6 millennia ago, metallurgy arose, and the Bronze Age started in north China, p71. The wheel was invented in southeast Europe. There were, perhaps, upward of tens of millions of us. 
5 millennia ago, civilization, as we call it, began with Sumeria .
At 5 millennia ago, irrigating, flooding lowlands for rice, in southeast Asia, added increases in the other main greenhouse gas, methane, along with less powerful activities, p82.
4± millennia ago, in China, fortified towns arose, and then states. India too. Also pastoralism in central Asia contributed another strong move away from our natural, evolved huntiing-gathering economy. 
3 millennia ago, iron production started in south China (71). Much of China was deforested by this time.
2 millennia ago, our population had reached 200 million.

Horses, oxen, and metal plows meant that "most" arable land in south Eurasia had been cleared and most lowland delta land of Asia was in rice. So CO2 & CH4 (carbon dioxide and methane) had by then increased above the natural trend, and were near the top of the range of variation, high enough to cancel the cyclic natural cooling, i.e., our effect was nearly equal to that of nature up to 200 years ago, when industrialization got underway, bringing faster deforestation for industrial fuel, as well as more farming as population rapidly increased.

~100+ years ago, use of coal, oil, and gas rapidly increased replacing deforestation as the primary human source of CO2. CH4 also increased from human activity: irrigation, landfills, releases from wells, etc. Our impact on the climate moved into an exponential increase, above anything in the last several hundred millennia, i.e., way above the natural cycles of past climate history over millions of years.
   There are counters to that increase: solar radiation continues going down, there are lags in the climate system, and sulfate discharge is an anti-warmer. These will be overcome, Ruddiman argues, as greenhouse gases continue to increase over the next decades and centuries, to levels, and thus temperatures, unprecedented in the last several million years (p. 173).


One conclusion that seems easy to draw is that anthropogenetic climate change will happen. Period. That has been proven by the fact of it's already having happened. We have already prevented a glacial period from starting, if unwittingly. Now, perhaps anti-wittingly, we are pushing change even harder. But we cannot escape the possibility that since we are shaping what is going to happen, we can make choices to bring about certain results. We are not the victims here; we are the perpetrators. The biggest problem, as in so much policy debate, is not in choosing this or that path, but in pretending that there is an inevitable path, one we have no control over. As always, that is, it is the stand-patters versus the alternative-seekers. And while what we do will affect the biosphere, the Earth, primarily we need to pull up our socks so we do not stumble into a future we would hate to live in.

Ruddiman's thesis might appear to be anti-wilderness. After all that we have done, in detail and in the largest Earth-wide terms, since the Neolithic Revolution occurred, there can be no non-human affected land-, sea-, or climate-scapes. Not the only influence, obviously, nor even always the most powerful. But what we have to accept is that wilderness is not apart from us, but is a concept out of us, something we needed so much that we invented it in order to help us make choices about what kind of world we want to live in. 

There is a great range of -scapes -- from classic wilderness, to intense exploitation of the world's wood and metal and dirt etc., to every-square-centimeter urban development. We have to decide how heavily our hand will fall. We have to prove our capacity to continue by showing our respect for that which supports us. The choice to protect wilderness, wildness, wild things, is, just as the Grand Canyon is, an indicator that we do not intend to walk off the edge into the valley of the shadow we ourselves have conjured up. 

From his 1954 collection, As I See, I have long treasured this warning, titled "The Triumph of Wit" by the artist Boris Artzybasheff:

The explosion, as Ruddiman makes clear, does not have to be immediate. It can gather force over thousands of years, and still be a destroyer. Except now it is counted in hundreds of years.

The Canyon's climate is going to change, just like for the rest of us. The climate will affect the flows into the reservoir behind Glen Canyon dam, and the qualities of the water that is released directly impact the Canyon. It will affect how far back into the Canyon Hoover dam's reservoir intrudes, and thus the fact of ¾-century's accumulation of debris. We can decide to do more damage or less; it may not be the primary motivator for some, but everyone needs to recognize the damage, how it is caused, and what might be done if it is deemed undesirable. Had those ice sheets returned in their natural cycle, and the jet stream brought storms of the magnitude that filled old Lake Bonneville, waterflow and life in the Canyon would change. If we have, as Ruddiman argues, altered that natural recurrence, then we will be contending with another species of change, perhaps an ultra-dry future. The Canyon offers us the chance to ponder the past, yes, and prompts us to recognize the future is heavily our creation. 

Furthermore, in asking what we do with respect to the Canyon, we are asking not just what we do IN the place, like a dam or a skywalk or motoring-for-profits, but also seeing the Canyon as an icon existing WITHIN an even larger environment, emblematic of the condition we want our global home to be in, like powerplant pollution and endless noise from the sky. If we are careless about the Canyon and its environment, how likely is it that we will curb our carelessness and callousness for any other element undergirding our future? That is what having language, and being a social creature thereby, is all about. We are not the victims, and the Canyon reminds us that there are choices for us perpetrators to discuss and make. 

We started on a fraught road 10 millennia ago. On the one hand, Ruddiman points with clarity at a most far-reaching of the changes we have brought about. On the other, the Canyon points at the choices we have yet to make, provoking us to think about the detailed results of what we do, wittingly or with foolishness. 

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