Global climate change is a process that takes much more than a single lifetime to play out – or to see the worst effects. On a long-term scale, the scope of the change is so great that geologists have proposed that we are currently living through the dawn of a new geologic era: the Anthropocene, also known as the Age of Humanity.
It was only a few thousand years ago that much of North America was covered in kilometer-thick layers of ice. The ices ebbed and flowed across the continent over the course of millenia due to natural warming caused by the Earth’s wobbly orbit around the sun. Our current place in the complex ‘wobble’ would ordinarily put us at the beginning of another period of giant ice sheets scraping across the continents. But we’re not only stopping this ice age, we’re going much further: The forecast for the Anthropocene is that it’s to be an age of extreme warming.
In the best case scenario: we collectively dump only a half-trillion ton slug of carbon dioxide equivalent gasses, and the world becomes two degrees Celsius warmer. What does a world that is two degrees warmer actually look like? We need only look 130 thousand years back in time to see a world that was about that much warmer – the Eemian Interglacial period.
Based on what we know about the Eemian , we can very likely expect a shifting of natural ecological ranges in the next few thousand years. It is unlikely that today’s animals will be able to move with these ranges, because humans are in the way of any migration. We are currently living in the beginning of a massive, planet-wide extinction event that could rob our descendants of 50 to 90 per cent of the biodiversity that exists today. The Eemian Arctic was likely seasonally ice-free, which is an ignoble milestone we will see again in our lives. However, the Eemian interglacial period cooled off when the wobbly orbit of the planet caused enough of a temperature drop to allow glaciers to flow once again, which won’t happen this time, as the warming is happening due to humans and not a wobble.
To get an idea of the worst case scenario, we must look much farther back, to 55 million years ago, to the Eocene. This was the last time the planet experienced what paleoclimatologists call a “super-greenhouse”. A super-greenhouse is caused by an quick, enormous dump of greenhouse gases into the atmosphere, on the order of one to five trillion tons of CO2 equivalent gas. Much of this may have come from methane-ice known as clathrates, which are very sensitive to oceanic temperature. Whatever the initial cause, this gigantic mass of extra carbon caused a global warming event that involved extreme changes that would be reflected in the climate for millions of years. If our industrialized society continues business as usual – and we do indeed have sufficient reserves to do so – burning gas, oil, and coal reserves could potentially release trillions of tons of CO2 in the next few hundred years.
Today, around 60 per cent of the carbon we emit annually is absorbed into the oceans, which makes them much more acidic. The acidification during the Eocene global warming period was so severe that it actually burned a red mark in the global sea sedimentary deposits. About half of all coral species, but particularly the deep-water variety, disappeared from the fossil record. Modern day species that may be vulnerable to any future acidification of the oceans include the global coral reefs (themselves the base of a staggering amount of biodiversity), lobsters, crabs, oysters, and many deep-sea microscopic life forms that form the root of the oceanic food chain.
The excess CO2 in the Eocene was sufficient to raise the global average temperature by as much as ten to twelve degrees Celsius, warmer at the poles than the tropics. Fossil evidence from the time indicates that even the northernmost point in the Arctic Circle was warm enough to support tropical species of plants and animals, suggesting a polar heating change of over twelve degrees Celsius.
From the point of view of a human lifespan, the extra carbon that we are putting in the atmosphere will be there essentially forever, as will the effects on the climate and biodiversity. The outcomes of pollution might seem apocalyptic and outlandish, but the reality of the situation is that extreme greenhouse gas emissions have caused large changes to the environment in the past. It is irresponsible of us to refuse to understand the very long-term implications of our actions today. So, on behalf of those without the benefit of having the choice, who will come long after we’re gone, we ought to decarbonize our economy now. Welcome to the Anthropocene: let’s make this next geological era a good one.