A tipping point isn't that instant when water begins pouring over the canoe's gunwale. The tipping point is actually before that, when the canoe is heeling over and can't be stopped. It's summer time. Get in a canoe and try it. There's a brief moment, perhaps not more than a second or two, when the outcome is both obvious and inescapable - the center of gravity has shifted and your momentum is going to carry you over. At that point you're just along for a rather wet ride.
Climate change, anthropogenic global warming tipping points are very similar to what happens in a canoe. The environment begins to heel over until it reaches a critical point at which there's no turning back.
The international community has set 2 degrees Celsius as the point at which we still have a reasonable chance of not rolling over. No guarantees, just a reasonable chance. That's based on a best guess from what we knew of climate change many years ago. Many scientists are now telling us that 2C target is way, way too high. That's discouraging because we've already loaded the atmosphere with enough greenhouse gases that we have locked in at least 1.5C of warming over the course of this century.
We need to remember, very clearly, what these targets are all about. They're an attempt to reach a goal for arresting warming before all those emissions from our smoke stacks and our tail pipes and our cow farts trip natural feedback mechanisms that we cannot control and that will drive runaway global warming.
What do these natural feedback mechanisms look like? We have a pretty good idea, a list, but it's not necessarily exhaustive. One example is the pine beetle infestation that has devastated hundreds of thousands of square miles of forest across the west, turning those once verdant pine forests into rust-coloured, high-resin kindling, all dried out and waiting for a careless hiker or a lightning strike. When it comes to wildfire fuel, it just doesn't come any better than that.
In case you haven't heard, the West is on fire from northern Alaska all the way down into Mexico. Step outside and you can't see the CO2 emissions but you sure can see and smell the heat absorbing soot in the air. It builds up on your window sills, it gets all over your furniture and your floors. Suddenly forests that, while alive, were powerful carbon sinks sucking CO2 out of the atmosphere for photosynthesis have now become carbon bombs. There's a natural feedback mechanism for you right there. Come out this way, you can't miss it. Although, from what I've read this is one time the West has come to you. Sort of like that Mount St. Helen's thing.
Arctic sea ice is vanishing and quite rapidly to boot. The ice cover that once reflected solar radiation, heat, back into space has walked off the job. No brilliant white ice means dark green ocean that is a heat sink. That warming Arctic ocean warms the atmosphere that causes the tundra to dry out and catch fire. As the tundra burns it creates black soot that winds up turning the Greenland Ice Sheet a dirty colour and that accelerates the melting of the ice sheet and sea level rise.
The thawing, burning tundra also exposes the permafrost underneath that, as it thaws, releases massive amounts of once safely sequestered, formerly frozen methane, a very powerful greenhouse gas. As the Arctic ocean warms it also triggers the thawing of ancient, frozen seabed methane clathrates - methane ice if you like - that bubbles to the surface and then onward to the atmosphere.
From rampaging wildfires to tundra fires to ice caps covered in black soot to the release of ancient stores of methane from the permafrost and seabed clathrates these are all the feedback mechanisms
Have we passed the point of no return. The good news is that's a conversation we're not really having right now. We're still proceeding - although not very quickly and not very well - with talks that assume we're not there yet and can, if we just try hard enough dammit, avoid the worst - maybe.
Today we're at just 0.8 degrees Celsius above pre-industrial levels. We're not at the 1.5C mark yet because that persistent atmospheric greenhouse gas needs time to work its magic. It will and as it does our children and grandchildren will experience the changes in creates.
There are two things that we must understand, and that includes you.
First off. That 1.5C is something we've already bequeathed our kids and theirs. What we need to realize is that emissions are cumulative which means our greenhouse gas emissions from today onward add to that 1.5C. Every tonne of CO2 we emit goes on top of that 1.5C pile. We're experiencing the impacts of barely 0.8C of warming (and it's a real bitch). As today's warming keeps getting hotter, those who follow us will endure a variety of impacts that are even greater, more dangerous, and demanding of new adaptation responses.
Second. These numbers don't include the natural feedback mechanisms we already seem to have triggered. The greenhouse gas emissions they create - CO2 from forest fires, methane released from the permafrost and seabed clathrates - also go atop that 1.5C we have already locked in.
What more incentive do we need to rapidly decarbonize our economies and our societies? What conceivable justification do we have to continue to dither and squabble? This is a moral imperative, a fundamental obligation we owe not just our kids and theirs but to the very future of our country. It's time to sweep denialism and those behind it out of our path for they are immensely more dangerous than any terrorist group or tinpot tyrant that has ever beset our world.
Oh yeah, one other thing. While we're decarbonizing and sorting out the climate change business, we have to realize that any real solution also must address two related challenges without which we don't stand a chance - over-consumption and overpopulation. They're all tied up together and you have to solve them all if you're to solve any of them. Bear in mind that if we don't come up with solutions that address all three of these existential challenges, they'll come up with their own solutions and we won't be very happy when they arrive.