Cast your mind back 65 million years, to when Tyrannosaurus Rex ruled the land and Plesiosaurs and Mosasaurs hunted the seas. The world was warm and tropical, with a cosy blanket of volcanic carbon dioxide covering the Earth. Glaciers were banished to the highest mountains. All appeared perfect, but for the dinosaurs, the terrible menace of climate change loomed.
For millions of years, careless dinosaurs and hapless plants had been falling into peat bogs and, trapped, sinking to their dooms. Instead of decomposing on the surface and returning their nutrients to the biosphere as all environmentally responsible dinosaurs should do, the precious carbon that made up nearly a fifth of their body weight was trapped. Each peat bog death trapped enough carbon to remove from the atmosphere almost half the creature's body weight in carbon dioxide.
For a time, volcanoes continued to release vast quantities of carbon dioxide into the atmosphere, and balance was preserved. Eventually, though, among the lush overgrowth, the peat bogs began to win their eternal war against the greenhouse effect. As the carbon dioxide levels dropped in the atmosphere, the Earth began to cool.
The dinosaurs were now in terrible danger - if they'd had the same computer modelling tools that we humans have now, they'd have known that our Earth is very vulnerable to the so-called Snowball Earth scenario. As the climate cools, more of the Earth's surface is covered in highly reflective snow and ice. This increases the Earth's albedo, sending much-needed solar warmth back into space and further cooling the planet. The resulting positive feedback cycle sends the temperature spiralling downwards, and soon the entire globe is covered in ice and the equator is as cold as Antarctica.
Eventually a massive meteor strike tipped the balance, and the Earth entered an ice age. After millions of years of warmth, the dinosaurs could not adapt to the snow and ice, and began to die out, leaving the world to the birds, the fish, and us annoyingly cute fuzzy warm things. We shivered and grew our fur ever longer to keep warm, and waited for the patient volcanoes to finally spew forth enough carbon dioxide to trap some scant warmth from the sun, and melt the ice again.
Now jump forward to the present day. It looks like we're about to repeat the dinosaurs' fatal mistake, doesn't it? We're releasing all that sequestered carbon that they stored over so many years, carelessly tampering with our environment, and we're sure to cause certain doom... right?
Consider the following points:
- The carbon balance got messed around in the opposite, much more dangerous, direction while dinosaurs roamed the Earth. We're still here and the world is quite alright.
- It wasn't actually carbon sequestration that caused the last ice age anyway, it was a stonkin' great meteorite that blew up a 600km wide chunk of the Indian ocean near Mumbai.
- Earth is slowly heading into an ice age, right now. Over the last 3 million years, the cycles of glacial growth have been intensifying. Every 40k - 100k years, the glaciers grow and then retreat, and each time they grow a little further.
- The carbon dioxide that we're releasing by burning fossil fuels was taken out of the atmosphere when prehistoric plants and animals fell into peat bogs instead of decaying in the atmosphere. We're not introducing it into the atmosphere... we're just putting it back.
- We're fuzzy mammals with big brains. We can build things like fur coats and air conditioners to allow us to live in a far wider range of environments than big slow dumb lizards can handle.
There are things that can dramatically alter our planet's environment, this is true. These things can mess up our ecosystem and probably kill most of us, although I'm a firm believer in humanity's ability as a species to survive pretty much anything - we beat cockroaches hands down.
Things that can destroy our planet's environment:
- The sun. If the sun changes its output significantly in any way, we're fucked.
- Meteorites. If we get hit by a supermassive meteorite, we're fucked.
- Stars. If a star goes supernova within 20 light years, we're probably fucked.
- Volcanoes. These things made virtually all of the carbon dioxide in the atmosphere. They can always make more, and in fact they're constantly doing so, a fact which saves us from a permanent 'snowball earth' scenario.
- Continental drift. This seems to be a major factor in long-term (millions-of-years scale) climate changes.
We'll be fine. Or if we're not, it'll be because of something that we can't do jack about, so there's no real point worrying. Carbon limits are fun (I intend to make my millions off 'em :). Renewable resources are wonderful because in future they'll become cheaper and more convenient than burning tonnes and tonnes of coal a day to keep the trains running on time. But really, people - stop worrying that we'll destroy the world. We're not that big.