New Climate Paradigm.
Scientist : William F. Ruddiman , a professional climate scientist ( Professor of Environmental Sciences at University of Virginia ) . He is a well-regarded university scientist not connected to any pressure groups .
Publications : Various peer-reviewed journals .
Popular book :
“ Plows , Plagues & Petroleum”
Published by Princeton University Press in 2005
ISBN 10: 0 691 12164 8
A very balanced , clear-headed view of the whole climate-change history .
Large scale agriculture has since circa 8 000 ago counteracted natural climate cooling (which was caused by Milankovitch cycles) through land clearing (ie deforestation -CO2 release) and rice paddies ( flooding - methane release) . This was gradual until about 200 years ago , when the Industrial Revolution started .
Evidence used includes quantitive calculations on how humans could have released the required masses of green-house gasses – a very convincing argument .
The inverse ( the abandonment and subsequent reforestation of agricultural areas on a large scale due to pandemics ) and the reversal to the natural cooling is covered .(ie Little Ice Age circa 1400 AD to 1800 AD mainly due to Black Death and American pandemic depopulation of extensive agricultural areas throughout Mississippi-valley , Middle-America and Amazon-riverbank after Columbus ) .
1 . The New-Paradigm
The previous assumption was that the climate changed and humans adapted to it . But if the alteration in human numbers or practices is of sufficient magnitude to alter the climate past certain critical thresholds , then a lot of history has to be re-written .
The cause of green-house gases fluctuation may be local , but the climatic effect is global .
2 .Feedback processes :
The effects of even small climate-fluctuations on marginal or overpopulated areas are severe . For example , the Little Ice Age . The extinction of the Norse colony in Greenland and the famine deaths in Europe can be shown to be causally linked to the bubonic plagues in Europe and the massive depopulation in the Americas .
The fate of the Roman Empire is also about to be redelved . Middle-East , etc .
Some completely unexpected things occur .
Globalization means cheap trade .
Agricultural products like wheat or corn can be imported cheaper from more favourable areas than they can be produced locally . Local agricultural land is then abandoned and reforested , while the population usually relocates to a city . The effect is the same as a pandemic in the country-side and swollen cities . The imports are produced more efficiently than a subsistence farming set-up , so the net global effect is a reduction of the human agricultural foot-print .
Even a subsistence farmer cannot survive , since he cannot trade a surplus for certain really , really essential things he cannot produce (eg salt , agricultural implements ) . His surplus is valueless for trading , since it can be imported cheaper than he can produce it . He might store it , but one or two years of drought and he literally starves . Of course , minor things like education or health is simply unaffordable
A good example of this is Africa today .
( A personal observation : in the area from Port Elizabeth to East London in South Africa ( about 400 km on the national route) there are no commercial farmers and vwery few subsitence farmers ( I counted 3) . The formerly commercial farmers converted to zero-maintenance game-farms and the subsistence farmers moved en-masse to Cape Town . The whole reach was reverting to thickets of thorn trees .)
The same thing happens with logging : it is more cost-efficient to log virgin tropical forests and ship them thousands of miles than growing and logging cultivated forests .The net global effect is a reduction of the human forest destruction .
The net effect of both is cooling effect , even though populations have increased . (The effect of industrialization is stripped out ) .
Local effects are severely asymmetric . Intensively cultivated prairies in North America means abandonment of farms or factory animal feedlot-farms in Europe or Asia . Clear-cutting in Indonesia means forests in Japan ,Europe or North America . Climatic disturbances in the short term ( 50 years) will occur .
But if the trading system breaks down , (ie collapse of the civilization) , the survivors usually restart subsistence farming , with the consequent deforestation . A warmer period follows . Examples: Warming after fall of Roman Empire , Collapse of Bronze Age civilization circa 1200 BC . (But not the Mayans – why?)
But there is another joker in the pack : ecological disturbance . The original deforestation/land clearing selected as survivors the toughest pests ( like rats) . Disease-prone areas were also left to the last . When abandonment occurs , these pests and their diseases explode into the vacant niches . The humans have by then packaged themselves into nice , concentrated parcels in the cities. Cycles of pandemics occur .
The wild comes to the city .
The broad pattern then seems to be :
Agriculture -> deforestation ->warming ->surpluses -> trade ->cities -> globalization ->farm abandonment -> reforestation -> cooling , severe ecodisturbances -> wars , pandemics -> collapse -> trade ceases -> subsistence farming restarts -> deforestation and the cycle repeats .
4 . An intriguing speculation about the Roman Empire.
Did the trade of cheap Egyptian corn through the Roman empire cause a switch from cereal growing to vines or olives (which is reforestation ) , causing a cooling which reduced the rainfall on the steppes , bringing the volkewanderung of steppe-dwellers down on their heads ?
Note that the very large central water wheat-mills in Gaul makes more economic sense if the wheat is imported , ground and the flour then distributed , rather than the wheat being collected , milled and then redistributed .
Reforestation crops (like vines , olives or fruits ) take years to yield a return . They are value-added crops , that can only afforded growers with deep pockets . The net result is the destruction of the small landowner . Even large latifundia were vulnerable . Even large pieces of ground are abandoned as they cannot produce any crop that cannot be produced cheaper elsewhere in the empire . As noted above , not even subsistence farmers can survive in this environment .
The citizen-farmer , once the backbone of the old Republic , has now become a client of a patron in a Roman city . The patron can afford it because of his large landholdings , worked by slaves and maintained by other armed slaves .
The only exception is on the frontiers , where retired soldiers are subsidized onto subsistence farms . But as already noted , subsistence farms are not viable in an empire . So the empire had to keep on subsidizing them . Eventually , this cost beggared the Roman Empire . It wasn’t just a soldier : it was his wife , children ,parents , uncles , cousins , etc. . If the state tried to refuse , they threatened to rebel or join the invaders ( who were family in any case) . The state by this time had only slaves or clients ( who were semi-slaves to the patron ) – not good soldier material .
The exception was the Christians , which had become more militant . (The meeker ones had been killed off in the pogroms) . Constantine realized this . He reorganized the army around loyal Christian cadres , concentrated them in the cities and cut the frontiers and the latifundia loose . This was a much bigger betrayal than the Roman retreat out of Britain . At first , only the relations of the frontier-troops burst through . Still , there were centuries-worth of scores to settle . But then came the steppe-dwellers , ferociously hungry because of the cooling and lower rainfall caused by the Roman Empire .
The age of the independent castle and armoured cavalry had arrived .
One of the largest land-reformation exercises ever unfolded . All the latifundia in Europe were parceled up as farms to the invading tribes . Vines , olivetrees , etc were uprooted and burnt (only fuel available) .
Trade crashed . Food transport ceased . A terrible time ensued .
Cities not having hinterlands protected by Christian troops , were looted and most of the inhabitants killed .
During the first winter , superfluous slaves on the latifundia (or cities) died of starvation , as the invader’s crops were not in yet , and they had none to spare .
Bitter triangular warfare between the newly invading (farmer) tribes , the steppe nomads and the fortified Christian Roman cities raged . The steppe nomads lost and were expelled . The tribes remained on the land outside of the Roman fortified cities .
This learning episode is the main reason why a Mongol invasion of Europe would have failed .
Constantine’s gamble salvaged something , but at a terrible price .
All this burning , looting and farming over the whole of Europe sharply raised the CO2 levels . The time-sensitivity of the climate to mild changes to CO2 levels is about 50 years (from Ruddiman) . So , by about 600 AD the climate in Europe got warmer , rain increased on the steppes and the steppe-dwellers’ pressure ceased .
5 Do the Steppe-Dwellers have a stable population size ?
The answer seems to be yes . (See Atlas of World Population History by McEvedy and Jones ) . The Mongolian steppe area’s population has remained steady at about 700 000 for millennia ( even during Genghis Khan).
The reason seems to be the low wealth multiplier : a herder can get only one calf a year , no matter how good it is . A farmer can get 30 – 100 fold increase in a good year . He can also store this . The herder has to have at least 30 years of good years in succession to equal one good farmer’s year . Now you see why nomads are just about extinct .
A farmer can survive 3 bad years in succession , because of this multiplier . A herder cannot . Every bad year might kill say half his stock , leaving him with about 10 % of what he started with at the end . The succeeding good year will leave him with at best 20% of his starting stock .
So , nomads cannot overpopulate easily , but is very sensitive to long-term downward trends in climate .
Which leads to the interesting speculation that the collapse of the middle-American civilizations (Maya , etc) triggered the initial cooling that led to the Mongolian excursions .
Another anomaly is the collapse of Chinese innovation in the 1400 –1500 ‘s . The Little Ice age decreased temperatures over Mongolia and Manchuria . Barbarian pressures on the Northern Frontiers increased and the disasterous central decision was made to concentrate resources on repelling this threat . The exploration fleets were burnt .
One can go on and on.