One of the running jokes at the moment is that the “skeptic” argument will change from “no warming since 1998” to “no warming since 2016”. It’s really meant to be mocking the typical “skeptic” misunderstanding of this basic issue: if you pick a particularly warm year as your start year, the resulting trend will appear to be smaller than it probably actually is. It’s a classic cherry-pick. The Global Warming Policy Foundation appears not to have got the joke, as they seem to be suggesting exactly this, by asking
Is the global warming pause over for good — or will it continue once the current El Nino dies down?
So what is really being suggested? That temperatures could drop back down so that there will have been little warming since 1998? Well, that seems highly unlikely. That they could go back to a phase of slower warming after the somewhat large increases in 2014, 2015 and – possibly – 2016? Okay, but even if it did, what would that tell us? Simply that the surface doesn’t warm in some kind of smooth way. It wouldn’t suggest that it isn’t warming. Even the slowdown in the last decade or so has not really changed the long-term warming trend.
The point that many people seem to ignore (or misunderstand) is that – on average – how much we will warm will depend on how much we emit. Our emissions are currently increasing anthropogenic forcings at around 0.3W/m^2/decade. This produces a planetary energy imbalance (more energy in than out) that has to be closed by warming of the surface. However, surface warming is very sensitive to relatively small changes in ocean warming. Hence, we might have periods of faster than average surface warming, and periods of slower than average surface warming. Maybe it will warm in a step-like fashion, with periods of relatively slow warming, followed by relatively rapid/large jumps that then lead to another – but warmer – period of relatively slow warming. At the end of the day, however, the surface has to continue – on average – to warm as we continue to emit CO2.
The author of the GWPF piece happens to be their science editor, is a member of their Academic Advisory Council, and has a PhD in astrophysics. It’s rather hard to see how he doesn’t get this. On the other hand, credentials are not some kind of guarantee that someone will understand a relevant concept. Maybe he just doesn’t understand this topic very well. Possibly Richard Tol, one of their other Academic Advisors, can let us if the reason the GWPF promotes this type of stuff is because they just don’t understand it very well, or because they’re knowingly promoting mis-information. It’s hard to see an alternative option.