The Great Filter Discovered

We have never discovered extraterrestrial life. Why not? Something must be stopping life from getting sufficiently advanced. This something, mysterious as it is, has been called The Great Filter.

What is The Great Filter? It could be as banal a idea that intelligent life like ourselves is just a very rare thing. So many conditions have to be just so, that in fact it arises only once per trillion stars say. But more ominously, The Great Filter could be the inescapable tendency for intelligent civilizations to wipe themselves out.

As for the first possibility: We are finding a lot of planets orbiting stars already. Clearly there are many, many planets out there. Organic chemicals are quite common, we know from comets. Are planets like ours really that scarce? Admittedly they have to be watery, far from big clusters of stars and associated frequent gamma ray bursts, and in a system with some outer gas giants to shield them from collisions. But I doubt such conditions are all that rare.

So we're left with that sticky little second possibility: that civilizations invariably wipe themselves out before getting to the technological state to spread through the galaxy.

Sounds nutty that we can observe no little green men and conclude therefore that we are likely doomed to be wiped out soon. Yet there are 100 billion stars in our galaxy, and they have had billions of years of time to colonize the galaxy (or to build space probes called "Von Neuman Probes"). It would only take about 20 million years to reach every star in the galaxy, assuming probes could reach 1 percent of the speed of light. So little green colonists or Von Neuman Probes should have been here for billions of years. Yet they are not. Why not?

Well I think that recent events have provided us with a likely answer. The Great Filter is... climate change. Here is my reasoning.

Over the millions of years required to develop intelligent life, planets tend to accumulate carbon. This carbon gets sequestered in various places around the planet, such as gaseous carbon in cold places (methane trapped in permafrost, methane stores in the ocean floor) as well as liquid and solid forms, stored in warmer, more accessable places (oil fields, coal deposits). Such carbon is too easy a fuel source, and an intelligent civilization will invariably learn to burn the warmer sources of carbon, achieving rapid growth in population.

Every planet has a limit at which it will be overwhelmed with the greenhouse effect achieved from burning carbon (i.e. from CO2), to the point that a warming trend eventually releases the trapped gaseous carbon, sealing the planet's fate. It so happens that planets can hit the released carbon tipping point much sooner than they can learn to build intragalactic rockets or Von Neumann Probes. They hit the tipping point before they can develop technologies to reverse it (carbon sequestration). Even before they have time to convert to carbon neutral energy sources (wind, nuclear).

It turns out that our gaseous carbon tipping point will likely occur very soon, like within a decade, according to climate scientists who build predictive models. Our planet will likely be a very hostile place, mostly desert by the end of this century. One climatologist predicts Earth's population to be just 1 billion by 2099.

It's fashionable at this point in the discussion to put a positive spin on things and say we can solve our problems. I see no reason to do this. Positive spins just promote complacency and inaction. There is no reason for positive spin here. We can pretty much be certain that 6.76 billion Earthlings are not going to come together and stop burning fuels. We are not even going to come together and slow the rate at which we increase burning fuels any time soon. Carbon sequestration technologies are not going to happen on a large enough scale.

Our planet, like the 10 to the x ones before it, will wipe itself out due to climate change. And that will probably occur over just the next couple centuries. Even today's child is likely to experience major hardship or early demise because of this problem. Sorry folks.

That said, I do not believe in fatalism. I intend to do all I can to delay this. The more generations we can eek through our post-industrial Fools Paradise the better.

Q: How many vicious cycles does it take to kill a planet?

Answer: 1

But my occasional read of the popular science magazines finds 5.

(1) Warming planet melts polar ice caps, which reduces polar reflectivity, which increases absorption of sunlight, which warms planet, ...

(2) CO2 acidifies the oceans to the point that calcium carbonate dissolves, killing the organisms that have been sequestering carbon, which increases CO2, ...

(3) Melting permafrost releases methane, which has ~23X the global warming potential of CO2, which causes warming, which melts permafrost, ...

(4) Warming oceans release methane trapped near the bottom, which warms oceans, ...

(5) Human technology (a) invariably through history increases human consumption and (b) increases human technology, which ...

See this alarming article. It says that many climatologists' models predict that the world will be mostly uninhabitable just 90 years from now.
http://www.newscientist.com/article/mg20126971.700-how-to-survive-the-coming-century.html

We humans need to wake up and get our heads around the very real likelihood that we will destroy our world in but a century.