Extinction of all life on Earth scheduled for 2031-2051

[kurt_cagle]

64. Feedback loops

I think the following is more likely -

1) Decline from peak civilization (which I think we've already hit - put it at 2007) will cause the petrochemical based economy to collapse by 2045. Civilization drops back to about the latter part of the 18th century in many respects. The mega-nations, such as the US, Russia, China, India, Mexico - break up into smaller bioregional states. Pockets of electrified civilization remain, but they become smaller and more disconnected. Population begins its first major plunge, going from 8 billion people in 2025 to 2.5 billion people by 2070.
2) By this same time, most coastal cities are below sea-level. As technology fails, one by one, these cities succumb to increasingly powerful storms that make any kind of pumping or dike arrangement possible. Princeton, NJ becomes beach-front property.
3) Buildup of hydrocarbons and CO2 in the atmosphere slows about then, as the pump that had been pushing these into the atmosphere declines due to far lower emissions. There's a period in there where things look like they may have stabilized, but instead what will have happened is that without the carbon heat pump the atmospheric carbon cycle will start a positive feedback loop.
4) Between 2090 and 2120 or so we will see horrific storms - hurricanes in excess of 300 miles per hour that will cover much of the planetary surface as energy stored in the seas and the atmosphere bleed out very quickly. Human population will drop precipitously, to the extent that by the time 2140 rolls around, the global human population will be maybe one million people, and technologically we will be at perhaps the late bronze age (say, c. 1000 BC).
5) Once that energy leaves the planet or gets otherwise sequestered, then we move back into the solar cooling period that we've been keeping artificially at bay for the past four thousand years. Glaciation begins in earnest, and by 2200, much of North America to perhaps Northern Florida and most of Europe to the Mediterranean will be under thickening layers of snow and ice. By 2250, ocean levels will have dropped dramatically, but the remnants of the cities will be uninhabitable. Mankind will exist in roving bands along the southern coasts, and will likely have dropped to perhaps a few tens of thousands of people globally.
6) After 1500-2500 years of this, the sun will kick back into a warming phase again. If humanity hasn't been completely wiped out a this point, ethnographic differences will likely make for the beginning of speciation, with two or perhaps three new hominid species emerging from the remaining stock. Civilization may very well rebuild at that point, but having tapped out our petrochemical heritage, having mined the easily accessible high grade ores (and with most of what had been produced in terms of metals now rusting at the bottom of the sea), with foodstocks sorely diminished, and having to wait while glaciers retreat enough to take advantage of new topsoil, such a civilization will likely never get much beyond the neolithic, then each of these dim lights will fade away. It's really hard to see how humanity will be around 5,000 years from now.

Seem extreme? We've never experienced a global civilization collapsing before. The largest civilization to have collapsed was the Romans, and it can be argued that what happened there was more of a case of a single very large empire fissioning into several smaller empires - Constantinople in the east and the Franco-Germanic empires to the West, even while the city of Rome itself collapsed into a primarily agrarian backwater. We've also always been on the upside of the resource curve - discovering more resources as we needed them. That trend changed in the late 20th century.