IPCC plus 20: a world warming but not frying

Colby Cosh points out the asterisk on the latest headline about climate change


The CBC provided us with an interesting case study in science reporting on Monday as its “community team” blog trumpeted “UN climate change projections made in 1990 ‘coming true.’

Climate change projections made over two decades ago have stood the test of time, according to a new report published Monday in the journal Nature.

The world is warming at a rate that is consistent with forecasts made by the UN’s Intergovernmental Panel on Climate Change 22 years ago.

Climate scientists from around the world forecasted the global mean temperature trend for a 40-year period, from 1990 to 2030—and at this halfway point the report authors have found the projections “seem accurate” after accounting for natural fluctuations.

These are absolutely all the numbers you are going to get out of this news item. And if you peruse the new assessment of the 1990 IPCC predictions, which was actually published on the Nature Climate Change website, what you find is a more nuanced picture than the CBC’s “They nailed it, no worries” interpretation implies.

David Frame and Dáithí Stone write that the 1990 IPCC report predicted a rise in global mean temperatures of between 0.7 degrees C and 1.5 degrees C by the year 2030; on a linear interpolation, we might have expected half the increase to have occurred by now. The actual observed warming during the past 20 years (almost all of it taking place in the first ten) has been in the vicinity of 0.35 degrees C to 0.39 degrees C, “on the borderline” of the range given in 1990. In other words, the IPCC’s point estimate was high, and the overall warming has been consistent with the outer confidence bounds of their stated prediction, but barely.

Frame and Stone think, with some justification, that this is a pretty good performance given the simplicity of the climate models available at the time. It’s especially good, they think, because the models could not predict what would happen in the economy, or below the planet’s crust. Their story is that the Earth caught a series of lucky breaks despite the substantive failure of greenhouse gas reduction efforts.

The highlighted [IPCC] prediction assumed a business-as-usual scenario of GHG emissions; three other scenarios were considered and in fact Scenario B (which assumed a shift to natural gas, a decrease in the deforestation rate, and implementation of the Montreal Protocol, all independent of global climate negotiations) was closer to the mark as of 2010, especially with respect to methane emissions… Of course, [even these Scenario B] predictions were based on idealized future scenarios that did not foresee the eruption of Mount Pinatubo, the collapse of the Soviet Bloc industry, or the growth of some Asian economies, so one could argue that the prediction is right for the wrong reasons.

The authors conclude by noting that predicting the future is a lot harder than predicting the past—and, unfortunately, the resolving power of crystal balls has not improved much since 1990.

…the 1990 prediction following [the IPCC’s] business-as-usual scenario covered a full 0.4ºC range due solely to uncertainty in the climate sensitivity that has not narrowed substantially so far, whereas a larger range was implied by the examination of further scenarios of emissions and a larger range still should have been considered owing to uncertainty in the evolution of natural forcings and internally generated variability.

Believers in and skeptics of the threat from anthropogenic climate change will both find promising fodder in this paper for conversion into mountains of delicious hay. (Mind the carbon emissions, though.) I’ll resist the temptation to join in that exercise, but it is very clear that the authors’ “Well done” message to the IPCC carries a sizable asterisk. If the CBC is going to report on a scientific paper, why not show some indication somebody has read it?


IPCC plus 20: a world warming but not frying

  1. Did the IPCC model predict a linear trend? Because that’s not how positive feedback loops work.

    • No, nor do negative feedback loops. If you don’t assume that every added ton of carbon has about the same forcing effect, then it becomes difficult to defend any prediction at all. Frame and Stone’s point is simply that the initial warming predictions are loosely on-trend on a linear assumption. There’s nothing more sophisticated to it than that.

      • Cool, thanks.

  2. Over the short term it is very difficult to predict the progression and timing of short term climate changes, because we don’t understand fully all the micro-level interactions. Frankly I think it’s irresponsible of them to have even published this stuff in the first place. I mean its interesting to scientists and an opportunity to learn to model this stuff, but it was inevitable that the public would get in a twist over this given their lack of understanding of the variable probabilities involved.

    Science has done a lousy job explaining things to people in this regard. The short term predictions notwithstanding, there is ZERO doubt concerning the long term implications of dumping vast amounts of CO2 into the atmosphere.

    We have reams of evidence showing the long term effects of CO2. The CO2 Rock-weathering thermostat model is the only existing model that explains the history of the earth’s climate, why we’ve maintained the liquid water neccesary for life, and the evidence all points to CO2 as both a driver and reinforcer of climate change.

    There is less doubt about this than just about anything we know in physics, and yet here we are reading another stupid article fixated on extremely short term predictions that say nothing about man made global warming whatsoever that anyone should take seriously. Not one thing.

    Ask a paleo-geologist what they think. They know better than you. Period.

    • I do hope Dr. Stone will enjoy this comment, should he happen to run across it.

      • He can’t argue the point so I doubt he’ll touch it with a ten foot pole.

        • He’s probably cringing in fear from your dope physics knowledge even as we speak.

          • Facts are facts Colby. You can either debate them or you can’t.
            And when you can’t, apparently you lean heavily on snide comments.

        • “Pseudoscience is often either impossible to test or excuses are made which keep it from being tested.”

          Good! Then it’s even on both sides.

      • Wow! Surprised to see the list of qualified CC scientist contains such luminaries as Fred Singer, Timothy Ball and the weatherman Watts….and god knows who else.

        I even see they got a dig in about solar activity, having now presumably dropped their former obsession with sun spots.

        • Well, if you prefer Al Gore, take that route.

          • Oh no. There are alternatives who do know first hand what they are talking about.Most of them are on a not so little panel of experts who work for the UN i believe.
            I doubt if half the people on that list even trump Gore. There are people on there who claim to be “expert reviewers of the UN panel” for lord’s sakes? What does that mean? Are they experts in the same way that i’m an expert reviewer of maclean’s articles?

          • What does it mean to be a reviewer? Not much, according to you, if one is going against the grain. Yet, when one is a scientific reviewer going with the grain, then all is well received. Gotta love that kind of logic.

          • Saying you are an expert reviewer and actually being a bona fide one is actually my point. That logical enough for you?

          • Sorry – lost your point completely.

        • Actually Bob McDonald who is the CBC’s national science commentator talked a length about the effects of sun spots on the climate the earth experiences during an interview with Peter Mansbridge. According to Bob McDonald you cannot dismiss those effects.

          • I”d have to Listen to what BM Bad to say to have an opinion. But if you google sunspots and CC you”l have Little trouble finding stories that ridicule the sunspots theory.
            Word of friendly advise – don”t take anything FV has to say on CC too seriously.

          • Nobody’s dismissing those effects. They’re one of those things actually included in the models unlike so many other things we can’t actually calculate. There’s a reason the estimate is so broad after all.

        • Tim Ball is one of the stars of my favourite Global warming video:

          (narrator)This man, threatened with death if he goes public and challenges the global warming crowd…has led June Sarpong to a small town (Victoria) at the outskirts of civilization. It’s here that a global warming critic says he’s hiding for his life…(female voice) once I get to the other side(Vancouver Island) I’m going to be out of cell phone range. I don’t know if anyone is following me or what to expect.

          (narrator)She finds a man that does not want to be seen or named….


          As sleazy as the open letter folks are, I’m still surprised they included they got the pedophile to sign. They must have been desperate.