Sorry, They’re Lying About California And Megafloods, No, Really, They Are

Yes, yes, we all know that views on climate change differ. Climate always has changed and always will, perhaps adaptation would be better than mitigation, and then all the way through to the Greenpeace line, we’ll be cannibals cooking each other in the water of the last ice floe using the oil of the last whale to heat it.

It’s still possible for climate change to be real, happening, something we’re causing and even something we should do something about – and also for certain of the climate scientists to be lying through their teeth. The sadness being that many of them are.

This is ever so slightly technical so bear with me.

A wintertime megaflood in California could turn out to be the worst natural disaster in U.S. history by far, and we are making it much more likely, according to an alarming study published this week in Nature Climate Change.

The odds are good that such a flood will happen in the next 40 years, the study says. By the end of the century, it’s a near certainty. (And then another one hits, and another — three such storms are possible by 2100). By juicing the atmosphere, extreme West Coast rainstorms will happen at five times their historical rate, if humanity continues on roughly a business-as-usual path, the new research predicts.

This all turns around that phrase “business as usual.”

The paper is here and this is what they’re modelling:

….under RCP 8.5 forcing.

Now this is wrong and wrong for two reasons. It’s also entirely common and occurs in near all climate change papers we see these days. Yes, sadly, we are being lied to.

The first reason this is wrong:

Guess which one gets used as business a usual?

We have four different sets of ideas about what emissions are going to be in the future. That’s what gives us the radiative forcings being used. No, sorry, we’re not going to start shouting that this is all dangly bits and hairy ones to boot. That’s not the point here.

Instead this is something much less controversial. It’s a standard insistence that all of these are possible. They’re all, in fact, business as usual. It just depends upon what happens to things like population, technological advancement, globalisation and so on. As you will note there’s quite a spread there of radiative forcings – and all should be described as business as usual. Further, when we work out what might happen as a result of climate change we should in fact be looking at what will happen under each of the four sets of assumptions. Because that’s actually how you do it – we’ve some unknowns. Therefore we prepare the results of our modelling according to those varied unknowns.

When you don’t do this you get Jim Hanson’s famous result, that the carbon tax should be $1,000 a tonne CO2-e. That’s not actually what he found. He found that the correct carbon tax could be up to $1,000 per tonne CO2-e. But that was the extreme value if everything, but just everything, went wrong. What we want to know for policy purposes is what is the accurate weighted value of the carbon tax? There’s – to invent numbers – a 1% chance that it should be minus $100, a 1% chance that it should be plus $1,000 and a 98% chance it should be $80. OK, sure, we can adjust for those two 1% possibilities. We could even accept Marty Weizman’s point about fat tails in the probability distribution and so on. But the carbon tax shouldn’t be at $1,000, it should be around and about $80.

This is exactly what our intrepid researchers are not doing here. They are not adjusting for the probability among the varied business as usual pathways. They are only giving us the outcome of the one, the most extreme, pathway.

Sorry, that’s lying.

It’s actually worse than this which gives us our second reason. We do actually know that RCP 8.5 has zero chance of coming to pass. For we’ve already done the things which mean it won’t happen. That is, we’ve changed those other motors of society, globalisation, fertility, population size, technology and so on. 8.5 just won’t happen.

One point is that in about 50 years time we will be using more coal than we do now. In fact, we’ll get a larger portion of our energy from coal than we did 15 years ago. Before all the coal mines started going bust. Before fracking meant we don’t, in North America at least, use coal much to make electricity – we’re certainly not building new plants to do so. Before we made solar cheap (er).

RCP 8.5:

Underlying assumptions about main scenario drivers of the RCP8.5, such as demographic and economic trends or assumptions about technological change are based upon the revised and extended storyline of the IPCC A2 scenario published in Riahi et al.

The A2 scenario:

The A2 marker scenario (A2-ASF) was developed using ASF (see Appendix IV), an integrated set of modeling tools that was also used to generate the first and the second sets of IPCC emission scenarios (SA90 and IS92). Overall, the A2-ASF quantification is based on the following assumptions (Sankovski et al., 2000):

Relatively slow demographic transition and relatively slow convergence in regional fertility patterns.
Relatively slow convergence in inter-regional GDP per capita differences.
Relatively slow end-use and supply-side energy efficiency improvements (compared to other storylines).
Delayed development of renewable energy.
No barriers to the use of nuclear energy.

We’re not in that world, we’re just not. In fact, on near all of them, we’re doing better than the most optimistic of the earlier set of emissions pathways, the SRES.

There are two lies common in current climate change research. The first is to assume that RCP 8.5 is the only business as usual forcing scenario. It isn’t. To present only the one result, from this emissions profile, is to be presenting only the worst outcome, not the range which it is agreed are likely.

Secondly, we’re simply not on RCP 8.5. We’ve already done things to the world economy which mean that we’re not. In fact, of the emissions pathways RCP 8.5 is pretty much the only one we know absolutely isn’t going to happen. Thus results scaring the knickers off us if it does aren’t really being truthful, are they?

Unlike many news organisations, we chose an approach that means all our reporting is free and available for everyone. We need your support to keep delivering quality journalism, to maintain our openness and to protect our precious independence. Every reader contribution, big or small, is so valuable.
For as little as £1 (£10 if you were at OxBridge) you can support us – and it only takes a minute. Thank you.

Click Here To Make A Contribution - Tim & The Team