The following is an edited transcript of key excerpts from Dr. Mojib Latif’s presentation at the World Climate Conference 3, held in Geneva in September 2009. Also see my subsequent post on misinterpretations and distortions of these remarks.
Mojib Latif is Professor for Climate Physics at the Leibniz Institute of Marine Sciences at Kiel University. He was one of five particpants in a session entitled Advancing climate prediction science at WWC-3. The following transcript is based on Latif’s PowerPoint presentation (PDF) and the session recording (MP3), both available at the session web page.
The excerpts have been edited to remove most qualifiers (“OK”, “all right”, “you know”). Key slides have been inserted at the appropriate points. Times are as in the recording of the overall series of panel presentation; Latif was the third speaker.
Excerpt 1: (“[I]t may well happen that you enter a decade or maybe even two, when the temperature cools relative to the present level.”)
So [the] first point: Why decadal prediction?
Now people who know me, at least my German colleagues, know that I do a lot of media work. There was almost no day in the year when [I’m] not called by some media person. And so they basically think about global warming as a kind of slowly evolving process and a monotonic process. So each year is warmer than the preceding year.
However we all know there is variability, and this variability may look like this. This has been actually derived from the 20th century by just removing some exponential fit. And the two of course [are] superimposed. And then the real evolution of, say, globally averaged temperature would look like this.
And then you see right away [that] it may well happen that you enter a decade or maybe even two, when the temperature cools relative to the present level. And then I know what’s going to happen. I will get millions of phone calls. “What’s going on? So is global warming disappearing? Have you lied [to] us?”
And, therefore, this is the reason why we need to address this decadal prediction issue.
Excerpt 2: “… the jury is still out about the relative contribution of this internal variability.”
Second point: Mechanisms of decadal variability
So first of all we need to understand what basically the relative contributions of external and internal forcing is. So here is just Northern Hemisphere temperature for the 20th century. I put in red the linear trend. We all believe that the long-term trend is anthropogenic in nature. In blue, we see the running mean and you see, I think, right away there is a lot of variability around the long-term trend.
And the $64,000 question then is basically how much did internal decadal variability contribute … during the recent decades and I think the jury is still out about the relative contribution of this internal variability. However, if you just look at this diagram I think you may get the impression that some part is maybe driven by internal variability.
Excerpt 3 “There is significant skill out to ten, maybe even twenty years.”
So the North Atlantic seems to be one region that has high decadal predictability potential. Now you all know the North Atlantic is the home, in a way, of the Thermohaline Circulation or the Meridional Overturning Circulation.
And we have conducted now for many years what you may call classical predictability studies, perfect model experiments. And here is just one example from a white paper of Jim Hurrell which will be published soon, where you see that the strength of the Meridional Overturning Circulation may be predictable, provided you have suitable initial conditions; you can initialize your climate model.
And there seems to be quite some skill. There is significant skill out to ten, maybe even twenty years. And since these variations in the MOC are connected to the variations of the sea surface temperature, there may be the hope that we can really predict the changes in highly societally relevant quantities.
Excerpt 4 (end) “If my name were not Mojib Latif, my name would be global warming.”
And finally to reinforce the point that we need really good climate models. And everyone who knows me knows that I’m definitely not one of the skeptics. If my name were not Mojib Latif, my name would be global warming. However, we have to ask the nasty questions ourselves, or some other people will do it. And therefore we need really [?] scientific program under the auspices of the world climate research program to realize the full decadal predictability.