Why It’s Misleading To Say We Only Have 12 Years To Avert Dangerous Climate Change

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How late can we leave it and still stop the planet getting too hot?

We have 12 years to limit climate change catastrophe“. “Planet has only until 2030 to stem catastrophic climate change“. “We have 12 years to act on climate change before the world as we know it is lost“. “The world has just over a decade to get climate change under control“.

So say the headlines today. They are certainly correct to emphasise that climate change is an extreme threat to our civilisation and that we need to take urgent action. But the claim that there are 12 years until the point of no return is at best questionable, and at worst actively confusing. The reality is that there is no such cut-off: just a problem that gets worse and worse the later we leave it.

The Intergovernmental Panel on Climate Change (IPCC) has today published a special report looking at the impacts that are likely if the world warms by 1.5°C. This is a crucial question, because 1.5°C was the target that almost all the world’s governments agreed to in 2015. In that year’s Paris Agreement, nations promised to “keep a global temperature rise this century well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius“. So it would be good to know what 1.5°C would look like, and what it would take to ensure the planet warms no further.

Since we have already caused about 1°C of warming, we only have 0.5°C of breathing room. To put a lid on warming, the report says, we need to start cutting global greenhouse gas emissions rapidly. By 2030, emissions need to be about 45% below what they were in 2010, and by 2050 we should not emit anything overall.

This should come as no surprise to anyone who follows the news. 20 years ago climate scientists were calling for rapid emissions cuts and warning that if we waited we would have to cut faster. We waited, and here we are.

However, there are two problems with the much-repeated claim that we have just 12 years to take action.

The first is that we have heard similar things before, many times. “Only five years left before 1.5C carbon budget is blown“, said one 2016 headline. “Researchers say we have three years to act on climate change before it’s too late“, said Popular Science just last year.

Indeed, the jokes are being made. “Deja Vu – the Rio Climate Summit was in 1992. Back then 26 years ago activists said that we only had ten years to get climate change under control“, grumbled one Twitter user. I doubt that this new deadline, coming after so many others, is going to sway anyone that wasn’t already convinced of the significance of climate change.

The second problem is that the figure of 12 years gives the wrong impression. Let’s unpick this, because understanding why there isn’t a single hard deadline for this will clarify many things. A study published in August in Earth System Dynamics takes a close look at the idea of a point of no return, and it is revealing.

The researchers examined what it would take to limit global warming to either 1.5°C or 2°C. They first ask how certain we want to be: we could either have a 67% probability of meeting our target, or a 95% probability. In other words, we could give ourselves a two-to-one chance of limiting warming to a desired amount, or a twenty-to-one chance.

Next they ask how rapidly we can increase renewable energy’s share of the market: 2% per year, or a more ambitious 5% per year. And finally they ask whether we will use lots of “negative emissions technologies” later this century, to remove carbon dioxide from the air on an industrial scale and thus limit the temperature rise.

Depending on which combination of factors the researchers plugged in, they got a different point of no return. In the most exacting case, where we try to limit warming to 1.5°C with a 95% probability of success, without relying on carbon dioxide removal later in the century, they found that we might well be too late. On the other hand, if we’re prepared to accept 2°C, with a larger probability of going over and a heavy reliance on carbon dioxide removal, the point of no return looks to be way off in the 2040s.

The point is that the climate is not so simple as to give us a neat cutoff date for action. (Well, unless the climate passes a tipping point and begins changing uncontrollably, which is a definite possibility – but we don’t know where such a tipping point would be) Indeed, there is an argument that putting it in terms of deadlines just creates a feeling of hopelessness when we inevitably miss them.

So, forget about deadlines. The simple truth is that stopping climate change gets harder if we leave it later.

It’s like putting off paying your credit card bill. The interest just keeps mounting and the total bill gets ever worse. There is no cutoff point, except bankruptcy – which is best avoided.

Climate change is our bill coming due, and we would do better to pay up now before the interest starts spiking.

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