By David Holmgren,
Four Energy Descent scenarios are considered, each emerging from a combination of either fast of slow oil decline and either mild or severe climate change over the next 10-30 years.
Brown Tech Scenario (Slow energy decline rates, severe climate change symptoms)
The Brown Tech world is one in which the production of oil declines after a peak 2005-2010 at about 2% per annum and the subsequent peak and decline of natural gas is also relatively gentle, but the severity of global warming symptoms is at the extreme end of current mainstream scientific predictions. The tendency in existing systems for massive centralised investment by corporations and governments, give priority to getting more energy out of lower grade non-renewable resources (eg. tar sands, coal and uranium) and biofuels from industrial agriculture and forestry. At the same time the cost of defending or replacing urban infrastructure threatened by storms and future sea level rise consumes more resources. Rapid onset of climate change tends to support centralised nationalist systems.
Green Tech Scenario: Distributed Power down (Slow energy decline rates, mild climate change symptoms)
The Green Tech scenario is the most benign, in that adverse climate changes are at the low end of projections. Oil and gas production declines slowly as in the Brown Tech future, so the sense of chaos and crisis is more muted without major economic collapse or conflict. However higher commodity prices allows some poorer producer economies to escape their debt cycle. As in the Brown Tech scenario, electrification is a key element in the energy transition but the renewable energy sources of wind, biomass, solar, hydro, tidal, wave etc. grow rapidly developing a more diverse and distributed mix.
Earth Steward Scenario: Bottom Up Rebuild (Rapid energy decline rates, mild climate change symptoms)
In this scenario the decline in oil production after a peak in total liquids production before 2010 is at the extreme end of authoritative predictions (about 10%) and is followed by an even faster decline in gas production plus a simultaneous peak in coal production. The shock to the world’s fragile financial systems is overwhelming, resulting in severe economic depression and perhaps some further short, sharp resource wars. This economic collapse and these political stresses, more than the actual shortage of resources, prevents the development of more expensive and large scale non-renewable resources that characterise the Brown Tech scenario or the renewable resources and infrastructure of the Green Tech. International and national communications networks break down.
Lifeboats Scenario: Civilization Triage (Rapid energy decline rates, severe climate change symptoms)
In this scenario, supplies of high quality fossil fuels decline rapidly, the economy fails and human contributions to global warming collapse but lag effects and positive feedbacks in the climate system continue to drive an acceleration of global warming. As of 2007, an increasing number of scientists believe it may already be too late to avoid catastrophic climate change. In the Lifeboat scenario the adverse symptoms of the Brown Tech and Earth Steward scenarios combine to force a progressive collapse in most forms of economy and social organisation. Local wars, including use of nuclear weapons accelerate collapse in some areas but the failure of national systems of power prevents global warfare. Successive waves of famine and disease breakdown social and economic capacity on a larger scale than the Black Death in medieval Europe leading to a halving of global population in a few decades.
