mardi 29 mai 2012
vendredi 25 mai 2012
(Ce n'est pas un jeu vidéo)
Four decades ago, a Massachusetts Institute of Technology computer model called World3 warned that the global industrial system has so much inertia that it cannot readily correct course in response to signals of planetary stress. But unless economic growth skidded to a halt before reaching the edge, they warned, society was headed for overshoot— that could kill billions.
Jorgen Randers of the BI Norwegian Business School in Oslo, and one of the original World3 modelers, argues that the second half of the 21st century will bring us near apocalypse in the form of severe global warming.
Dennis Meadows, professor emeritus of systems policy at the University of New Hampshire who headed the original M.I.T. team and revisited World3 in 1994 and 2004, has an even darker view. The 1970s program had yielded a variety of scenarios, in some of which humanity manages to control production and population to live within planetary limits. Meadows contends that the model's sustainable pathways are no longer within reach because humanity has failed to act accordingly.
"I see collapse happening already," he says. "Food per capita is going down, energy is becoming more scarce, groundwater is being depleted."
Most worrisome, Randers notes, greenhouse gases are being emitted twice as fast as oceans and forests can absorb them. Whereas in 1972 humans were using 85 percent of the regenerative capacity of the biosphere to support economic activities such as growing food, producing goods and assimilating pollutants, the figure is now at 150 percent—and growing. For the coming few decades, Randers predicts, life on Earth will carry on more or less as before. Wealthy economies will continue to grow, albeit more slowly as investment will need to be diverted to deal with resource constraints and environmental problems, which thereby will leave less capital for creating goods for consumption. Food production will improve: increased carbon dioxide in the atmosphere will cause plants to grow faster, and warming will open up new areas such as Siberia to cultivation. Population will increase, albeit slowly, to a maximum of about eight billion near 2040. Eventually, however, floods and desertification will start reducing farmland and therefore the availability of grain. Despite humanity's efforts to ameliorate climate change, Randers predicts that its effects will become devastating sometime after mid-century, when global warming will reinforce itself by, for instance, igniting fires that turn forests into net emitters rather than absorbers of carbon. "Very likely, we will have war long before we get there," Randers adds grimly. He expects that mass migration from lands rendered unlivable will lead to localized armed conflicts.
Graham Turner of Australia's Commonwealth Scientific and Industrial Research Organization fears that collapse could come even earlier, but due to peak oil rather than climate change. After comparing the various scenarios generated by World3 against recent data on population, industrial output and other variables, Turner and, separately, the PBL Netherlands Environmental Assessmeng Agency, conclude that the global system is closely following a business-as-usual output curve. In this model run the economy continues to grow as expected until about 2015, but then falters because nonrenewable resources such as oil become ever more expensive to extract. "Not that we're running out of any of these resources," Turner explains. "It's that as you try to get to unconventional sources such as under deep oceans, it takes a lot more energy to extract each unit of energy."To keep up oil supply, the model predicts that society will divert investment from agriculture, causing a drop in food production. In this scenario, population peaks around 2030 at between seven and eight billion and then decreases sharply, evening out at about four billion in 2100.
But there are the optimists.
Most of the Earth’s surface is covered by water. Water shortage should not therefore be a problem if an efficient and ecologically-sound way of desalinating it can be found. (They say it has.) And there are also developments in water purification which permit the re-use of dirty water. Food production can be increased through genetically-engineered plants, artificial meat (grown from stem cells) and vertical farming (employing hydroponic techniques). The obvious alternative to burning fossil fuels as a source of energy for industry, transport and households is the sun. Until now a major problem has been how to store electricity. Diamandis and Kotler say this is in the process of being solved. Appropriate biomass can also provide a substitute for mineral oil.
Yet things are not looking good. The goals of economic activity are profit and accumulation. All other values must be sacrificed to them. The market system unfortunately doesn't care about sustainable development.
Apprenez que la version anglaise deWikipedia sur World 3 comporte un chapitre qui comme par hasard ne figure pas dans la version française, c'est celui de la critique du programme, y compris par ses auteurs. Lisez-là bien et vous comprendrez pourquoi je la trouve brillante !
Lisez aussi cet article que j'ai rédigé en mai 2021 :
mercredi 23 mai 2012
dimanche 20 mai 2012
(Petite fable sans morale à la fin, qui parle de la sincérité des opinions)