It is only natural that we humans see ourselves as the ultimate species and stage of either Earth's or its biosphere's progression. Yet to the sphere itself, if it could analyze the matter, we may be no more or less significant and interesting than you and I might regard a mold mat or a colony of bacteria spreading across an opportune resource, in the process altering its habitat. Most recently, this opportune resource in our case has been the store of fossil fuels, derived from many millions of years of previous life forms, that we, in a twinkling of geological time, are reducing to excess carbon dioxide in Earth's atmosphere, thereby assuring the next chapter in our planet's story.

It turns out the coming chapter is but the latest version of a warm world from before. One future scenario which gives climatologists pause involves an average increase in global temperature of 9-11 degrees F. In only a few decades since the first concerns about global warming, evidence is mounting of predicted changes occurring even sooner than had been anticipated. Without dramatic alterations in the ways we generate power - and there is no indication we are prepared to make such changes - it appears we or our descendants shall see a version of Earth similar to one prevalent 56 million years ago, when an as yet unexplained release of vast quantities of carbon assured a world totally without ice. Ocean temperatures in Earth's polar regions were in the 70s (F). Arctic and Antarctic latitude land masses had environments similar to South Carolina swamps today. Regions north and south which we currently consider temperate were proportionately hotter still. And it took Earth 150,000 years to sufficiently reabsorb the excess carbon that lower temperatures and a new cycle became possible once more. Considering that this duration is longer than our species is thought to have been in existence, the figure may be relevant if we are now entering a new and similar thermal maximum. Another way of looking at it is that 150 years, give or take, of our species' immoderate use of fossil fuels could radically alter the climate, geography, flora, fauna, and economic prospects for a 1000 times as long.

I have assumed for awhile now that such radical changes, were they to occur in our near future, would lead to such massive die-offs that mostly just simple varieties of life could then survive, one-celled plants and animals, funguses, more complex but still invertebrate creatures, etc. In that future world's oceans, for instance, I anticipated that the highest forms might be jellyfish.

Artist's depiction of a primitive whale species (Wikipedia)

However, what is new to me and highly intriguing is that scientists have discovered that 56 million years ago, when such a surge in temperatures occurred, there was a profusion of new living things, not just low level creatures but highly evolved plants and animals. This was a time, in fact, when the hoofed forerunners of modern horses, antelope, camels, and cattle plus the lineage of primates, which eventually would lead to we ourselves, were coming into dominance within the natural order of things. So it causes me to wonder, once many of the life forms alive now but adapted to a cooler, lower sea level world have ceased to be, what marvelous new beings will be ushered in who in time may replace the likes of us and of most of the animals with whom we feel a kinship?

Paleontologists tell us that in the hothouse world of 56 million years ago, the Paleocene-Eocene Thermal Maximum (PETM), there was a huge explosion in the numbers and varieties of life forms. These included: disease causing viruses and bacteria; insects; turtles; chicken-sized horses; the rodent- and rabbit-sized precursors of modern monkeys and apes; creatures who later would evolve into rhinos, others who would become deer; plants with smaller than modern leaves; bean trees; etc. It was also a time of major evolution among early shark and marine mammal species.

While the hotter world caused greater average rainfall in some regions, others became far drier than before, as some think is occurring now in the American southwest, parts of Australia, and in sub-Saharan regions of Africa. The ranges of plants tended to move north and south, closer to the poles, in some cases by 1000 miles.

This was evidently also a time not merely of catastrophic droughts but also of disastrous flooding and of ocean storms the like of which we can hardly imagine. Displaced boulders give evidence of the scope of such cataclysms. Ocean currents also were shifted from their prior patterns. Were this to occur again, the Gulfstream, for instance, might cease, flow in a new direction, or dump hot surface waters onto the sea depths, accelerating and sustaining warming trends.

If we continue in the way we are headed, using up Earth's store of fossil fuels as rapidly as we can, then our future is in many ways like that of the PETM. According to climate modelers, not merely in Texas but throughout much of the United States as well as in China, India, and southern Europe, summer temperature lows would be in the 100s (F), night after night, for years at a time. Scientists typically avoid providing much information of this sort, fearing to be labeled alarmists, but say that even their mid-range forecasts are for much worse conditions than people generally expect.

While during the PETM life mushroomed despite large numbers of extinctions, there is no guarantee this will occur if we restore similar weather and climate patterns through our own ongoing carbon releases. Life on our planet is already under stress from other causes, i.e. deforestation, over fishing, pollution of streams and ground water, etc. My own nightmare scenario, in which, besides Homo sapiens, only simpler forms of animal life can prevail, may yet prove to be accurate.

Whichever turns out to be the case, we are playing Russian roulette with the world's environment, and our own kind will not be unscathed. Earth's future likely holds a biosphere enormously different than if we had more cautiously affected things in pursuit of our energy needs.

Primary Source: World Without Ice. Robert Kunzig (photos by Ira Block) in National Geographic; pages 90-109, October, 2011.