Extra information about irreversible climate change

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My first ever blog post! I aim to do lots of these in the future on topics which don't suit the video format, but for now this will be a quick extra thing related to my video on irreversible climate change. In writing the script for this video there were several bits of information which I wanted to include but in the end got in the way of the flow of the video, so are presented here.

Originally I was going to include a few rebuttals of common climate change misconceptions in the video, but to be honest these are freely available in lots of places, and the people watching will be almost certainly on board with, you know, science. So there didn't seem much point. And so not much point in repeating them here either. It is just exhausting to, every time you want to discuss climate change or geoengineering, have to preface the relevant discussion with anything more than the basic facts of the situation. When discussing something like structural engineering you don't need to include a long rebuttal of populist reasons why gravity isn't real. Anyway.

In this post I want to add detail to two things to the video: EMICs and timescales.

As discussed in the video, an EMIC is an Earth System Model of Intermediate Complexity. A computer model of the Earth system can be very simple or incredibly complex, depending on what its creator wanted it to do. Models which predict the weather for example are immensely complex, replicating the effects of hundreds of processes like cloud formation and the 3D motion of air parcels at hundreds of thousands of locations in the atmosphere over tens or hundreds of thousands of lines of code. By contrast a model predicting how the global average temperature of the Earth will change with changes in CO2 concentration might evaluate just one equation, averaging temperatures over the whole Earth, and be less than a hundred lines long.

As the name suggests, EMICs are somewhere between these two extremes.

One way to create an EMIC is to take a comprehensive model, similar to that used for weather prediction, and dial back the resolution, reducing the number of locations that equations are evaluated at in the model from hundreds of thousands to maybe a few thousand. This means that the physics in the model is just as complex, but the scale of behaviour described by the model increases. So the smallest feature in the atmosphere that the model captures will be hundreds of kilometres across rather than maybe tens of kilometres across.

But this makes the model worse! Why would you ever choose to do this, if you already have a model that accurately describes the Earth? Well there are three reasons:

  • Firstly, accurate weather prediction models are incredibly expensive and time-consuming to run! We don’t have the time to run them thousands of years into the future

  • Secondly, weather prediction models often don’t include processes which aren’t important in predicting the weather next week, but are very important on long timescales, for example the deep circulation in the ocean. These processes are absolutely crucial to understand how, for example, carbon is taken up by oceans. So EMICs add these longer timescale processes and remove shorter timescale processes.

  • Thirdly, we’re not trying to predict the weather! We don’t need an answer accurate on spatial scales of kilometres, we’re interested in the way the planet as a whole reacts. So we use a different tool specialised for the job.

Lastly, I say in the video that 40% of anthropogenic carbon is going to be in the atmosphere forever... as far as humans are concerned. Of course the carbon isn't going to be there forever. Forever is a long, long time. Given a few million years, the planet will adjust and get itself back to a point similar to a pre-industrial climate, modulated by other factors such as solar variability and a small anthropogenic perturbation. Opponents of climate change point out that the climate has changed plenty before, and they're quite right - if we were never here the climate would still look slightly different than it did before the industrial revolution. But the key issue is the timescale of change.

On human timescales, that is to say hundreds of years, we've enacted changes that the environment has seen before but over hundreds of thousands or millions of years. We are changing things in the blink of an eye as far as the planet is concerned. To the planet itself this is no real biggie. It will simply wait us out - wait for us to go extinct or leave for pastures new - and then re-equilibrate. For life on Earth though it's a different story. On the timescales of living creatures the changes we've inflicted are forever.

The planet doesn't care, and isn't going to swoop in to preserve the environment we evolved into. Equally, as I stress in the video, we can't trust in some new technology to do so either, and undo the damage we've done. Technology can certainly reduce future harm that we may do the environment, and I believe that it will do so, but it's not a magic wand capable of turning back the clock. We've already irreversibly changed the climate and now the best we can do is to stop making things worse.

That's it for this post. I implore you to read the original Solomon et al paper which details exactly how and why (in terms of processes) the changes we've inflicted are irreversible. There was just too much detail to do justice in the video and keep it accessible, so I leave it to the professionals to communicate the details.