The horrible, horrible, error in the IPCC's latest report

Oh dearie me, this is something of an error at the heart of the IPCC's latest report into the perils of climate change. And it all stems from a thoroughly incomplete look at the economic models about what might happen. Here's what they say:

Without additional efforts to reduce GHG emissions beyond those in place today, global emission growth is expected to persist driven by growth in global population and economic activities (Figure 3.1) (high confidence). Global GHG emissions under most scenarios without additional mitigation (baseline scenarios) are between about 75 GtCO2eq/yr and almost 140 GtCO2eq/yr in 210016, which is approximately between the 2100 emission levels in the RCP 6.0 and RCP 8.5 pathways (Figure 3.2)17. Baseline scenarios exceed 450 parts per million (ppm) CO2eq by 2030 and reach CO2eq concentration levels between about 750 ppm CO2eq and more than 1300 ppm CO2eq by 2100. Global mean surface temperature increases in 2100 range from about 3.7°C to 4.8 °C above the average for 1850-1900 for a median climate response. They range from 2.5 °C to 7.8 °C when including climate uncertainty (5th to 95th percentile range)18.

It's important to understand something here. "Additional efforts" does not mean that we simply install more solar panels (just as an example) for price, ethical or market reasons. It means that policy is changed so that more solar panels (again, just as an example) are installed. It means that we've got to change the incentives under which people operate, through legislation or regulation, in order to get people to change their behaviour.

This has been true right from the start of the worries about climate change: business as usual forecasts of emissions look at varying levels of wealth, population and technology and assume that all of those various scenarios could happen without government intervention. "Mitigation", like "effort" here, means intervention to reduce emissions below some or any of those business as usual scenarios.

And here's the problem with the assumption they're making about future emissions. Absolutely no one (no one sane at least) believes that we're ever going to get anywhere near the levels they've just assumed above. As Matt Ridley has put it:

The IPCC commissioned four different models of what might happen to the world economy, society and technology in the 21st century and what each would mean for the climate, given a certain assumption about the atmosphere’s “sensitivity” to carbon dioxide. Three of the models show a moderate, slow and mild warming, the hottest of which leaves the planet just 2 degrees Centigrade warmer than today in 2081-2100. The coolest comes out just 0.8 degrees warmer.

Now two degrees is the threshold at which warming starts to turn dangerous, according to the scientific consensus. That is to say, in three of the four scenarios considered by the IPCC, by the time my children’s children are elderly, the earth will still not have experienced any harmful warming, let alone catastrophe.

But what about the fourth scenario? This is known as RCP8.5, and it produces 3.5 degrees of warming in 2081-2100. Curious to know what assumptions lay behind this model, I decided to look up the original papers describing the creation of this scenario. Frankly, I was gobsmacked. It is a world that is very, very implausible.

For a start, this is a world of “continuously increasing global population” so that there are 12 billion on the planet. This is more than a billion more than the United Nations expects, and flies in the face of the fact that the world population growth rate has been falling for 50 years and is on course to reach zero – i.e., stable population – in around 2070. More people mean more emissions.

Second, the world is assumed in the RCP8.5 scenario to be burning an astonishing 10 times as much coal as today, producing 50% of its primary energy from coal, compared with about 30% today. Indeed, because oil is assumed to have become scarce, a lot of liquid fuel would then be derived from coal. Nuclear and renewable technologies contribute little, because of a “slow pace of innovation” and hence “fossil fuel technologies continue to dominate the primary energy portfolio over the entire time horizon of the RCP8.5 scenario.” Energy efficiency has improved very little.

These are highly unlikely assumptions.

They're not just highly unlikely assumptions: they're near insane ones.

What has actually been done is to take current emissions levels (actually, from a few years ago) and then draw a straight line inference about what will happen if they carry on growing as they have been. Completely ignoring the fact that we've already done a great deal to change what's likely to happen in the future. After all, as we keep being told, solar PV is now just about cost competitive with coal and will be cheaper in only a few short years (by 2020 is a serious and sober prediction). At which point why on earth would people start to use more coal than we do today? For a higher portion of our energy desires?

That simply doesn't make any sense whatsoever. And that brings us to that distinction between "effort" and market processes. If solar PV does become cheaper than coal (as is obvious it will) then it becomes a market process to install it. No "effort" in the sense of government action is required.

Another way to make this same point is that the IPCC is completely ignoring all of the work that we've already done to try to beat climate change. They're not taking account of the fall in the costs of renewables and therefore not including the obvious fact that more renewables are going to be installed in coming years. Whatever governments do or propose. The same can be said for LED light bulbs (not quite right yet but they very soon will be) and myriad other technologies that have been developed in recent years.

It's a basic and obvious piece of logic that if we see that we've got a problem ahead of us we should, when we consider what we should do about it, take into effect the results of the things that we've already done to solve said problem. And it's this that the IPCC is not doing. They are predicting future emissions without taking account of the technologies we've already developed which will reduce emissions. They are thus arguing that there's too much still to do.

It's a horrible, horrible, mistake.