Tipping points

Everybody’s heard about greenhouse gases, and the rainforests being destroyed and the icecaps and glaciers melting, but how about the permafrost melting? How about plankton die-offs? Albedo?

The big problem with climate change isn’t any of these things in isolation. The problem is that the whole is more than the sum of its parts. There are many feedback loops that have already been started in motion, and that’s what I’m going to be talking about here.

But first, a bit of vocabulary. A “negative feedback loop” has nothing to do with a subjective analysis of its quality, but rather is one that negates itself, that is self-correcting, returning to equilibrium. There are many of these in normal body functioning, for instance blood sugar regulation, body temperature regulation, and water and salt conservation. On the other hand, a “positive feedback loop” increases its own output, rather than cancelling; population growth is an example.

The industrial revolution started dumping greenhouse gases into the atmosphere in radical excess of previous levels. There were various buffering mechanisms in place which prevented the effects from being felt for much of the past 150 years. One such mechanism is the oceans.

As the concentration of atmospheric CO₂ increases, some of it gets absorbed into the oceans. The reaction looks like this:

CO₂ + H₂O = H₂CO₃ = H⁺ + HCO₃^-

The middle section is carbonic acid, which is what gives soda its fizz, and why old soda tastes watered-down – the reaction moves from the center to the left, giving off CO₂ and leaving water behind.

But that “acid” in the name should trigger an alarm bell. As more CO₂ get pushed in from the left, more hydrogen atoms (H⁺’s) get pushed out the right side. Which means that the more CO₂ we put into the atmosphere, the more acidic the oceans get. That’s a bit of a problem.

First of all, it’s only a buffer. It won’t continue to absorb CO₂ indefinitely.

Second, the acidification has other effects. If you drop acid on limestone, (formula CaCO₃, notice how similar that is above), it bubbles off CO₂ too. Limestone is made of the compressed and crushed shells of plankton, the little floating photosynthetic things that make up the base of the marine food chain. So if we follow this chain, it means that the acid in the water starts breaking down the shells of the living plankton, which understandably would have some detrimental effects on their survival.

So the plankton start dying off, which causes the higher levels of the marine food chain to starve. As if we’re not already having enough problems with collapsing fisheries. They are also a very large carbon sink, and their mass death releases even more CO₂ into the atmosphere, and the greenhouse effect continues to spiral and escalate.

Furthermore, since they’re not photosynthesizing anymore, they’re not producing oxygen anymore. And phytoplankton produce fully half of the oxygen we breathe.

So next we turn to the arctic permafrost. Or what’s left of it, anyway. All of the organic matter buried in the frozen peat bogs in Siberia and Canada has been fermenting (because of a lack of oxygen), and the resulting methane has been building up. The bubbles haven’t been able to move and escape, because the ground has been frozen. Until recently. Now that the permafrost is thawing, the methane is being released, and the bitch of it is that each molecule of methane contributes to the greenhouse effect 20 times as much as CO₂ does.

Another quick chemistry lesson: If a gas molecule in the atmosphere is composed of three or more atoms, it contributes to the greenhouse effect. Nitrogen and oxygen gases, which compose over 98% of the atmosphere, are composed of two atoms each (N₂ and O₂), and are not greenhouse gases. CO₂ consists of two oxygen atoms and a carbon, and is a greenhouse gas. Methane is composed of five atoms, a carbon and four hydrogens (CH₄).

And now trending into a meteorology lesson: Water vapor is also a greenhouse gas (H₂O), and the amount of water the air can hold is only going to increase as temperature does. That’s why they always talk about relative humidity, because it’s a sliding scale based on the air temperature at the time. That’s also where “dewpoint” comes from – given so much (total) water in the air, how cold does it have to get before the air is saturated, and starts condensing on the ground as dew? So there’s another positive feedback loop.

Now let’s go to another methane source – the deep oceans. Just like in the frozen peat bogs, methane is accumulating, some dissolved in the water, some frozen in pockets buried deep below the ocean floor, and some frozen in the superficial sediments along the edge of the continental shelf. As the oceans warm, the ice gets slushy and starts shifting under the weight of the sediments on top of it. Along the edge of the continental shelf, especially, it can trigger mudslides which will then release that methane into the atmosphere.

This isn’t just what-if thinking, either. It’s happened before, which means it can happen again. This kind of methane release now appears to be the major (immediate) cause of the Permian extinctions around 251 million years ago.

And as that methane oxidized to CO₂ (absorbing oxygen in the process), it may have dropped the ambient oxygen concentration from its previous high of 35% down to 12%. Add to that the absence of photosynthetic plankton, and we're in serious trouble. According to that linked Science Daily article above, 16% atmospheric oxygen is like being at 14,000 feet above sea level, and will seriously impede your athletic program. Humans will suffocate at 15%.

So now we come to albedo. Ice reflects up to 90% of incident sunlight, only absorbing 10%. Water, on the other hand, absorbs over 90%, and bare soil and rock aren’t much better. As the ice melts, leaving water and glacier-scoured land behind, less sunlight will be reflected back up into space and more will be absorbed, thus heating the surface more.

And it’s not like stopping global warming today will stop these problems, either. If you drop an ice cube in a room-temperature glass of water, it doesn’t disappear immediately. It takes a while for it to melt completely, even if the glass itself is insulated completely from its surroundings. The melting in Antarctica, Greenland, and the few remaining glaciers around the rest of the world won’t stop immediately; we've heated the glass too much.

But once again, the problem isn’t any one of these alone, it’s all of them in combination. The more ice melts, the more albedo increases, which causes more ice to melt. The more air temperature increases, the more methane is released, which makes more ice melt. The more CO₂ we dump into the air, the weaker plankton get, and the more CO₂ they release, further increasing the greenhouse effect.

These positive feedback loops, once they get going, are very difficult to stop, because they continually feed themselves until they eventually hit some critical mass or run out of resources and are forcibly shut down. The environmental geeks who know more about this than I do have been talking about “tipping points”, that invisible transition where we’ve pushed things too far and they take off on their own, without any further input from us, and all we can do is watch. Apparently, we’ve already passed it, sooner than most predictions had placed it. And note that these articles are now nearly two years old. Here’s another article, only a little over a year old, that talks about all of the various identified tipping points.

I’ve been believing that it was still possible to stop that kind of runaway-train climate change. Not necessarily feasible, but possible. I thought we had more time before we passed the tipping point. It really wasn’t until finding all the links for this post that I discovered that we passed it two years ago. I really can’t describe how that makes me feel, aside from being a further kick in the ass to get my act together and get the hell out while I still can.