So far, I’ve been talking about climate changes that might be quit gradual and predictable based on what we know about physics. But in this topic, I want to talk about some different sorts of changes, those that might be quit sudden and surprising.
There are some aspects of the climate system that can best be described by imagining you are sitting in a kayak.
A kayak basically has two stable states, upright and completely upside down.
If you’re sitting upright in the kayak, you can move from side to side and pop back to the centre.
It’s still stable.
But if you move too far, the kayak will completely flip over.
We think the climate system has some of these sort of rapid tipping points as well.
But the problem is we don’t know precisely where they are.
And we don’t know how far the climate system can be perturbed before we tip right over.
These tipping points occur because of something called positive feedbacks.
And this is a topic I’m going to come back to and talk about in more detail later on.
But for now, let me give you just one example.
Up in the frozen north of the northern Hemisphere, the soil is called permafrost, basically because it’s frozen.
This soil contains a lot of carbon in the form of both solid carbon and also methane.
As the world warms up, permafrost is melting.
And as it melts, a lot of this carbon is being released into the atmosphere.
This is a positive feedback because of course it amplifies the warming.
The more methane and carbon dioxide released into the atmosphere, the more warming we get, the more the permafrost melts, and so on.
And while we’re on scary subjects, here’s another one.
Deep in the ocean, there’s actually quite a lot of methane stored.
But it’s stored in little tiny cages of ice.
And in this form, it’s called methane clathrate or methane hydrate.
The methane is very safe in this form, as long as it stays very cold and under a lot of pressure.
But if the ocean warms up too much and the ice melts, the methane in the clathrates could be released.
It could be released right through the ocean and then into atmosphere.
If this happened on a large enough scale, we could get what’s called a runaway greenhouse effect.
And that’s a very scary prospect in deed.
So the really critical point for our future is where these tipping points might be and what would trigger them?
Well, we can’t be totally certain, but the most recent analyses point to the idea that if global average temperatures get to about 2 degrees above pre-industrial levels, the chance of the kayak flipping is greatly increased.
This 2 degree level is sometimes called the guardrail.
We need to stay beneath this guardrail to be on the safer side.