September 18, 2010
Climate Change – then and now
Points of Reference
Earth
formed 4.5 billion years ago.
The first single-celled organisms appeared 3.5 billion years ago.
Cyanobacteria began producing oxygen 2.3 billion years ago.
Most of today’s basic animal body plans (phyla) had evolved by 488 million years ago.1
Homo sapiens appeared 160,000 years ago.
The
Climate
Plate Tectonics
Over millions of years, as continents ride on plate tectonics around the globe,
They change the flow of air and ocean currents, thereby changing the
Climate. Continents move at an average rate of 5 centimeters per year. This
Means that over the course of the average life span of a mammalian species,
Which is 2.1 million years, continents will be displaced by some 400 kilometers.
To date, the fastest change of climate due to continental drift has been 4 degrees
Celsius per
1.5 million years – just more than 0.000,001 degree per year.2
That is a rate with which evolution can easily keep up. The average rate of
Mutations is one per 500 generations. For mammals, reptiles and amphibians,
Therefore, the derivation of a new species requires about 2.2 million years.
The match is good. The changing climate increases the selection pressure, and
Stimulates evolution. Indeed, tectonic-scale climate changes have been accompanied By bursts of speciation. [Not included in the one-per-500-generations mutations, which,
In
sequence, lead to speciation, is the very rare (one per 44 million years) mutation
Which leads to a complete innovation, such as a new
basic body plan (phylum)].1
The Milankovic
Oscillations
Superimposed on the tectonic scale climate changes, are the Milankovic cycles,
Driven by astronomical events – the shape of Earth’s orbit around the sun (a 413,000 Year cycle), the angle of Earth’s axial tilt (a 41,000 year cycle), and both the change
In the direction of Earth’s axis of rotation (Earth’s wobble), and the change in the Direction of its orbit’s axis of rotation (the orbit’s wobble) (a 22,000 year cycle).
These cycles are too fast for evolution to keep up. Best known are
Those occurring during the last ice age, the Pleistocene Period, which
Lasted from 2.6 million years ago to 11,430 years ago. Milankovic
Fluctuations produced 39 oscillations from glacial to inter-glacial ages,
And extinctions occurred in all of them, sometimes of major proportion.
For instance, during the transition, beginning 14,000 years ago, from the last glacial
To the present inter-glacial interval, the warming rate was 5 degrees per 5,000 years – 0.001 degree per year. Suddenly, within one decade, a large influx of fresh glacial
Water into the North Atlantic shut down the thermohaline circulation, plunging Northern Europe and the globe into a climate several degrees colder, for 1,300 years.
This event, the Younger Dryas stade, lasted from 12,800 to 11,500 years ago
(10,800 to 9,500 B.C.E.). In central North America, where Paleo-Indians had just
Established themselves, the combination of hunting and cold brought extinction
To all of the species weighing more than 1,000 kilograms, 50 percent of the
Species weighing 32-1,000 kg, and 20 percent of the species weighing 10-32 kg.3
The Medieval Warm Period
The Medieval Warm Period was a warm spell from about 1,150 to 750
Years ago (950-1,350 C.E.). Causes are unclear. The planet warmed by one
Degree in 100 years – 0.01 degree per year. While the warming had major Consequences for many civilizations, surprisingly, in Yellowstone Park,
Protected from human influences, 39 of the 40 mammal species survived.4
The way they survived was not through genetic changes, which,
Of course, could not keep up. The species survived through the process
Of recombination – novel combinations of the same genes, one set
From each parent. Recombination provides variations upon which
Natural selection can act, enhancing or diminishing reproduction rates.
In the Yukon, for instance, within 10 years (1989-1998), recombination and
Selection helped red squirrels advance their breeding date by 18 days. However, Recombination without sufficient mutation is only a temporary solution to changes
In climate. It is limited to the specific species in which it occurs, it sometimes
Introduces a deleterious trait, and eventually, it runs out of primary genetic variations.
The Present
By the year 2000, Earth was about the same temperature as it was during
The Medieval Warm Period. By 2007, Earth was 0.4 degrees warmer than then.
The rate of warming predicted, in 2007, was, 1.1 to 5 degrees in one century –
0.01 to 0.05 degree per year. This rate is 10 to 500 percent faster than that
Of the Warm
Period (and, by 2009, was considered a severe under-estimate).5
Should the warming be on the low side, 1.1 degrees during the present century,
Then, by 2050, Earth will be warmer than it has been in at least 400,000 years, well Before Homo sapiens appeared, 160,000 years ago. Should the warming be on the
High side, 5 degrees, then, by 2100, Earth will be warmer than it has been in 3 million Years, when not one mammal or bird species existing today had yet appeared.
The only way for animals to adapt to such a high rate of warming is through
Recombination, and the only animals able to use this mechanism sufficiently quickly
Are those which have extremely abundant populations (hence, a high level of
Genetic variation), have generations times measured in days, not months or
Years, and produce hundreds or thousands of offspring at each generation.
We call those animals vermin – flies, mosquitoes, cockroaches, rats . . .
In terms of substantial change at the genetic (DNA) level, the only species
With evolutionary rates which are keeping up with the present rate of
Global warming, are fruit flies (Drosophila), and possibly mosquitoes.
This is why, after life’s five greatest extinctions, 439, 364, 251, 210 and 66
Million years ago, when 90, 80, 95, 80 and 75 percent of species became extinct,
It took from 20 to 100 million years for diversity to recover to its prior level.6
There was just no genetic material for evolution to act upon.
The scenery was all pests, vermin, and in the ocean, noxious slime . . .
Notes
1. Phylum: In the classification of organisms, a phylum is the rank below kingdom and above class. (It is the equivalent of a division in the plant kingdom). The most common phyla in the kingdom Animalia are the Mollusca, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Echinodermata, and Chordata (of which humans are a part).
2. Conversion: 1 degree Celsius = 5/9th of a degree Fahrenheit.
3. Stade: A stade refers to glacial conditions less severe than those during a full glaciation. A stadial interval is of lesser amplitude than a glacial interval.
4. The Medieval Warm Period, Effect on Civilizations:
In Europe:
On the Continent, between 1,100 and 1,300 C.E., bountiful harvests encouraged the clearing of forests in order to increase farmland. While, in 500 C.E., forests and swamps covered 4/5th of temperate western and central Europe, by 1,300 C.E., half of this cover had been cleared.
In Scandinavia, between 1,100 and 1,300 C.E., longer summers, milder winters, and remarkable climate stability provided the opportunity for Norse explorers to settle in Greenland and Labrador. By 1,450 C.E., the Norse colonies had been abandoned.
In the Americas:
In western North America, epochal droughts lasted from 900 to 1,250 C.E. , extending into east-central Oregon, the Rockies, and the adjacent Great Plains. In the Sierra Nevada mountains, in present-day eastern California, the droughts were among the most severe in 4,000 to 7,000 years. The four driest periods centered around 935, 1,034, 1,150 and 1,253 C.E., all of them within a 400-year interval of overall aridity. After 1,300, persistently wetter conditions abruptly appeared, and continued for 600 years.
In central America, the Maya civilization was at its apogee, in 900 C.E., when the droughts of the Medieval Warm Period made themselves felt. The period following 900 C.E. was one of rapid decline, and many of the major cities were abandoned. By around 1,100 C.E., most major centers in the lowland Maya empire had been abandoned.
In Asia:
In central Asia, droughts may have wreaked havoc on steppe pastures, perhaps motivating the Mongol king, Genghis Khan (1,162-1,227 C.E.) to send his armies westward. From 1,218 to 1,224, Khan conquered Turkistan, Tansoxania and Afghanistan, and also raided Persia and eastern Europe to the Dnieper River.
In present-day Cambodia, around 1,150 C.E., the Khmer Empire began its decline, as it fell into internal strife. A precipitous decrease in crop yields may have been a decisive factor. In 1,431 C.E., the Empire ended, when it was sacked and looted by Ayutthaya invaders.
In northern China, beginning around 1,000 C.E., the Medieval Warm Period brought not only a warmer climate, but also one characterized by extreme, violent swings. Years of aridity alternated with years of torrential rainfall, during which thousands of acres in the Huang He river basin were inundated.
In the South Pacific, weakened trade winds provided the opportunity for Polynesian voyagers to sail eastward, and around 1,200 C.E., reach Rapa Nui (Easter Island), the most remote of all inhabited Pacific Islands (Fagan 2008. Grimes 2008. Columbia Encyclopedia).
5. Warming Predictions: Anthony Barnosky relies on data from the Inter-governmental Panel on Climate Change (IPCC), 2007. “Summary for Policymakers,” in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Inter-governmental Panel of Climate Change. New York, N. Y.: Cambridge University.
For 1990-2100, this IPCC estimate is a warming of between 1.1 degree Celsius (2 degrees Fahrenheit) and 6.4 degrees C (10.5 degrees F). The most likely scenario is between 1.8 degrees C (3.2 degrees F) and 4.0 degrees C (7.2 degrees F) (Barnosky 2009, pp. 23, 27 and 217n8).
By 2009, many scientists considered the IPCC 2007 predictions as being considerable under-estimates. For instance, a study by the Massachusetts Institute of Technology, Joint Program on the Science and Policy of Climate Change, published in the Journal of Climate (American Meteorological Society), May 2009, concludes as follows:
“The MIT Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100 . . . The median surface warming [projected for 2095] is 5.2 degrees Celsius . . .” (p. 1. Emphasis mine).
Co-author Ronald Prinn explained that the amplifying feedbacks are greater than previously thought, and that hence, this projected temperature rise is almost certainly an underestimate:
“The odds indicated by this modeling may actually understate the problem because the model does not fully incorporate other positive feedbacks that can occur – for example, if increased temperatures caused a large-scale melting of permafrost in Arctic regions, [with a] subsequent release of large quantities of methane, a very potent greenhouse gas. Including that feedback is just going to make it worse” (p. 2).
In this study, the predicted median atmospheric concentration of carbon dioxide, by 2095, was 866 (range: 500-1,000) parts per million – reflecting the increasing saturation of carbon sinks (pp. 2-3).
At an atmospheric CO2 concentration of 866 ppm, the warming would be 5.2 degrees C (9.4 degrees F). This is the median projection, not the upper end of the projection (Climate Progress, 2009).
6. Extinction 66 million years ago: This is the extinction which killed the dinosaurs. An asteroid hit the planet. It was previously thought that this was the only cause for the mass extinction. It is thought now, however, that the asteroid hit at a time when the atmospheric carbon dioxide was 1,000 parts per million, global temperature was, therefore, relatively high, and, as expected, biodiversity was depressed. Many redundant species and perhaps some keystone species had already been lost at the time of the impact (Barnosky 2009, pp. 163-164).
References
Principal Reference:
Barnosky, Anthony. 2009. Heatstroke – nature in an age of global warming. Washington, D.C.: IslandPress/Shearwater.
Pp. 9 and 195 (Earth warmer than 400,00 years ago); P. 19 (Cyanobacteria enriching the air with oxygen); P. 22 (Average life span of mammals); Pp. 23, 27 and 31 (Climate change due to continental drift); Pp. 26-28, 31, 106, 109 and 238n8 (Milankovic cycles); P. 28 (Appearance of Homo sapiens); Pp. 28, 31, 92, 96-101, 235n15 and 236n23 (Medieval Warm Period); Pp. 47-49, 51-53 (Noxious slime in the ocean); Pp. 60, 68-69, 71, 190 and 201 (Extinctions 50,000-11,500 years ago); Pp. 63-64 and 228n10 (Younger Dryas); Pp. 163-164 (Big Five mass extinctions); P. 166 (Most of the animal phyla common today had evolved by the Cambrian Period, 542-488 million years ago); P. 167 (First single-celled organisms, 3.5 billion years ago); Pp. 169-173, 177-180 and 249n29 (Mutations; recombination); Pp. 176-177 (Genetic diversity); P. 195 (Earth warmer than during the Cambrian Period, 542-488 million years ago).
Other References:
Answers.com. Undated. “Stadial.”
http://www.answers.com/topic/stadial-1. Accessed September 19, 2010.
Climate Progress, 2009. “M. I. T. doubles its 2095 Warming Projection to 10 Degrees Fahrenheit – with 866 ppm, and Arctic Warming of 20 Degrees Fahrenheit.” (Center for American Progress Action Fund). May 20.
http://climateprogress.org/2009/05/20. Accessed May 30, 2010.
Summarized in Francoise Hall, 2010. “Oil: changing the Course of Evolution.” (Poem) May 28 (14 pages, unpublished).
Columbia Encyclopedia. 2000. 6th edition. New York, N.Y.: Columbia University/Gale Group.
Fagan, Brian. 2008. The great warming – climate change and the rise and fall of civilizations. New York, N. Y: Bloomsbury Press.
Grimes, William. 2008. “Climate Change? Been there, done that.” The New York Times. March 21.
http://www.nytimes.com/2008/03/21/books/21book.html. Accessed September 20, 2010.
Hall, Francoise,
2005. “Ask the Mosquitoes.” (Poem). March 19 (13 pages, unpublished). (See Wilson 1992/1999).
2010. “Oil: changing the Course of Evolution.” (Poem) May 28 (14 pages, unpublished).
2010. “History poised to repeat itself.” (Poem). August 25 (9 pages, unpublished). (See Ward 2010).
Hirst, Kris, undated. “The (pre) History of Clovis – Clovis were the first well-established People in the Americas.” About.com guide.
http://archaeology.about.com/od/clovispreclovis/qt/clovis_people. Accessed September 20, 2010.
Rozell, Ned, 2003. “Red Squirrels show Signs of adapting to Climate Change.” Alaska Science Forum. Article 1637. March 13.
http://www.gi.alaska.edu/ScienceForum/ASF16/1637.html. Accessed September 21, 2010.
Ward, Peter. 2010. The flooded Earth – our future in a world without ice caps. New York, N.Y.: Basic Books.
Summarized in Francoise Hall, 2010. “History poised to repeat itself.” (Poem). August 25 (9 pages, unpublished).
Wikipedia, 2010.
“Agriculture.”
http://en.wikipedia.org/wiki. September 19. Accessed September 19, 2010.
“Angkor.”
http://en.wikipedia.org/wiki. September 20. Accessed September 22, 2010.
“Earth.”
http://en.wikipedia.org/wiki. September 15. Accessed September 18, 2010.
“Extinction Event.”
http://en.wikipedia.org/wiki. September 14. Accessed September 18, 2010.
“Genghis Kahn.”
http://en.wikipedia.org/wiki. September 22. Accessed September 22, 2010.
“Genotype-Phenotype Distinction.”
http://en.wikipedia.org/wiki. September 7. Accessed September 18, 2010.
“Geologic Time Scale.”
http://en.wikipedia.org/wiki. August 23. Accessed August 24, 2010.
“Medieval Warm Period.”
http://en.wikipedia.org/wiki. September 15. Accessed September 19, 2010.
“Milankovitch Cycles.”
http://en.wikipedia.org/wiki. September 18. Accessed September 18, 2010.
“Phylum.”
http://en.wikipedia.org/wiki. September 13. Accessed September 19, 2010.
“Pleistocene.”
http://en.wikipedia.org/wiki. September 13. Accessed September 18, 2010.
“Younger Dryas.”
http://en.wikipedia.org/wiki. September 19. Accessed September 19, 2010.
Wiktionary, 2010. “Phylum.”
http://en.wiktionary.org/wiki. Accessed September 21, 2010.
Wilson, Edward. 1992/1999, The diversity of life. New York, N.Y.: W. W. Norton.
Summarized in Francoise Hall, 2005. “Ask the Mosquitoes.” (Poem). March 19 (13 pages, unpublished).
Wordiq.com. undated. “Phylum.”
http://www.wordiq.com/definition. Accessed September 21, 2010.
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