Climate change: have we tipped the balance?

The concept of a ‘tipping point’ is something that is mentioned often with regards to climate change - the idea that after a certain point there’s NO going back, and things are only going to keep getting worse. Kat Arney spoke to James Dyke from Southampton University to discuss what this might mean for us as humans...

James - First off it’s important to point out, or at least remember that the Earth’s climate has always changed. If you go back far enough into Earth’s history we’ll see massive changes, so perhaps the biggest changes that we would observe over the 10,000 year timescales would be the ice ages. About 10 to 100,000 years ago, the Earth was about five degrees cooler than it is, sea levels were about 120 metres lower, and much of Northern Europe and Northern America were under hundreds of metres of ice.

Since the last ice age, the Earth’s system has been slowly warming up and sea levels have been increasing. But what we’ve witnessed over the last couple of hundred years has been really quite unprecedented rates of change of surface temperatures and other indicators that there is a significant warming pulse happening largely as a consequence of human emissions of greenhouse gases.

Kat - What do we mean by this concept of the tipping point? What does it look like and what are we tipping towards?

James - Many people think that climate change is a progressive and gradual thing. If it takes hundreds or thousands of years for the Earth’s climate to reach a new equilibrium, then we may think that the climate and the Earth’s system will respond smoothly and linearly. So if look at something like sea level rise, we’re looking currently about 3mm a year, which doesn’t seem very much but, unfortunately, the Earth’s system seems to be full of these tipping elements.

So when people talk about tipping elements or tipping points in the Earth’s climate, they're often referring to what’s proved to be a very influential study in the Proceedings of the National Academy of Sciences back in 2008, where they identified nine elements of the Earth’s system. So things like the Arctic sea ice or the Greenland ice sheet, the Boreal forests or the Amazon forests or some large functioning of oceanic currents.

What they’re worried about now, and what we’re increasingly worried about is that you can drive the Earth’s systems so much and these systems respond sort of sluggishly, but then you go beyond a point and they suddenly flip. They may flip into positive feedback states where once they begin to change it will be effectively impossible for those things to be arrested.

Kat - So I guess it’s a bit like you imagine all water just trickling slowly out of a bucket that’s tilting but then, at some point, it’s just going to overbalance and the whole lot comes out?

James - Yeah. You’ve got this metaphor that you’re rolling a great big boulder up to the top of the hill and it takes an awful lot of energy to get there. When it’s right at the top it might be precariously balanced and a slight nudge is just enough to push it down to the other side, and as soon as it starts rolling, it’s going to have tremendous amounts of momentum and you’re not going to be able to stop it. So when you’re thinking about the collapse of the Antarctic ice sheet, it looks as if certain regions of western Antarctica are melting, they’re falling off into the ocean. Once that process begins, it’s practically impossible for it to stop.

Kat - Is this really a point of no return? Are there things that we can get back? We can’t rebuild icebergs but is there anything we can slow, or stop, or reverse?

James - There are some wacky ideas at the moment about putting in machines up in the Arctic to try and refreeze the Arctic. These things will cost hundreds and hundreds of billions of dollars and they most probably won’t work, and we most probably won’t be able to deploy them in time. It sounds obvious, but the best thing that we can do to avoid these tipping points, or at least to reduce some of their impacts, is to significantly reduce our forcing on the Earth’s climate, which means making significant reductions in greenhouse gas emissions.

Kat - If we don’t, if the worst happens. If we hit these tipping points and all this climate change massively accelerates, release of carbon dioxide into the atmosphere massively accelerates, temperature goes up. What is going to happen and on what kind of timescale? Are we going to wake up in ten years time and it’s just an apocalypse out there?

James - Wherever we do end up, we want to be hopeful that we go there very slowly. Because, if the Earth’s climate changes slowly, then humans will be able to adapt but then also other species too. So you may be able to find species that will be able to go up higher mountains or find climate refugia.

The worry about tipping points is that then can engender very rapid change. At the moment, when you look at the current predictions of the total amount of warming that we seem to be locked into, it seems to be at least about three degrees celsius. We can visualise impacts in terms of the Earth’s climate through things that we care about, so our ability to get access to water, the impact on ecosystems, our ability to grow food, coastal communities, impacts on human health. And as they increase beyond the already established one degrees celsius of warming, those things increase in terms of impacts.

If we really do end up going beyond three degrees celsius, we’re currently going beyond three degrees and maybe even five degrees within a couple of hundred years, many people would argue that that is a recipe for the collapse of human civilisation as we know it.

Kat - So very, very briefly, we’ve got a few seconds left. There are some people who go “la la la, I can’t hear you, the Earth has always changed, the climates always changed. This is all just basically made up by the Chinese,”  mentioning no names. If you had a sentence to say to them to make them realise that this is a big problem, what would you say?

James - Climate change is happening right now. If you’re in Australia in Sydney you would have been experiencing 47 degrees celsius of temperatures over the last week. You can’t live your life like that and that’s important. That’s an omen of future changes that are happening. Just off the eastern coast of Australia you have the ongoing collapse of one of the World’s marvellous natural resources, The Great Barrier Reef, because of high temperatures. So climate change is happening right now and it’s going to be impacting much much more over the following years.