Reposting: Scientists Predicted Jump in Temperatures
March 13, 2016
The new global temperature graphs from this week are causing gasps across the scientific community. I’m reposting here my 2014 interviews with Kevin Trenberth and Gerald Meehl, who both spoke about the possibility of a “step change” in global temperatures, somehow initiated by large El Nino events, such as what we saw in 1998, and this year.
Worth showing to anyone who thinks scientists do not have a handle on the basic physics of climate.
Above, my interview with Kevin Trenberth in 2014. We agreed that if certain predictions came true, that I’d make sure the video got recirculated – and with today’s new announcement by the UK Met Office, a burgeoning El Nino in the Pacific, and 2015 looking like the warmest year ever – blowing the doors off 2014 – now is that time.
Dr. Trenberth spoke about large cycles in the Pacific that are part of natural variability, and how the ocean has tended in recent years to take more heat into greater depths, where it can not show up on surface temperature measurements.
Dr. Trenberth further predicted, starting at about 9:00 above, that a new El Nino event, if strong enough, like the one we are seeing now, would jumpstart the kind of warming trend that we saw between the mid-70s and 1998.
Recent measurements show that the current El Nino is looking a lot like the 1998 mega-event.
In a recent piece in Science magazine, Trenberth expanded on the idea, with a helpful graph showing the “stepwise” motion of global mean surface temperatures, (GMST) with the swings of the Pacific Decadal Oscillation. (PDO)
The main pacemaker of variability in rates of GMST increase appears to be the PDO, with aerosols likely playing a role in the earlier big hiatus. There is speculation whether the latest El Niño event and a strong switch in the sign of the PDO since early 2014 (see the figure) mean that the GMST is stepping up again. The combination of decadal variability and a trend from increasing greenhouse gases makes the GMST record more like a rising staircase
than a monotonic rise. As greenhouse gas concentrations rise further, a negative decadal trend in GMST becomes less likely ( 13). But there will be fluctuations in rates of warming and big regional variations associated with natural variability. It is important to expect these and plan for them.
In a 2014 interview, Trenberth’s colleague at the National Center for Atmospheric Research, Gerald Meehl, spoke about the contributions of natural variability to the perception of “pause” in surface temperature. The interviews taken together give a strong impression of how well the senior climate scientists have understood and anticipated the dynamics of global temperature, even with the unpredictability of internal cycles like El Nino and PDO.
In this case, Meehl is talking about “decadal climate prediction” – a new way of climate modeling. In a traditional climate model, the model is “initialized”, or begun, with the conditions known starting in 1850 and allowed to run with the random variations playing out in the artificial system. In the new methodology, the models are “initialized” in the 1990s – updated with actual conditions at that time – and they do tend to show with some skill the slower rise in surface temperatures of the past decade or so.
Meehl points out that after the huge, and hot, El Nino of 1998, the pacific went into a large La Nina, or cooling, phase, that in effect, we had not come out of, until recently. Now the UK Met Office paper out this week is confirming that Trenberth and Meehl’s insights have been prescient.
Here, my most recent interview with Trenberth, from December 2015 :