“But you said the ice was going to disappear in 10 years!”

Almost two decades ago, some scientists predicted that Arctic summer sea ice would ‘soon’ disappear. These predictions were mentioned by Al Gore and got a lot of press. However, they did not gain wide acceptance in the scientific community, and were swiftly disproven. Unsurprisingly, this still comes up a lot. Time for a deeper dive into what happened and why…

It is unsurprising that climate contrarians bring up past ‘failed predictions’ to bolster their case that nothing need be done about climate change. [It is equally unsurprising that they don’t bother to mention the predictions that were skillful, but let’s not dwell on that!]. For a long time, their favorite supposed ‘failed prediction’ was that there was a consensus about the imminence of a new ice age in the 1970s (a topic we have covered many times), but more recently it has turned to the supposed prediction of Al Gore that “Arctic summer sea ice would disappear” in a short number of years. This has everything – the ‘But Al Gore!’ knee-jerk, a conflation of Al Gore with the scientific community, it’s sounds suitably apocalyptic and, of course, Arctic summer sea ice has not disappeared (it’s only down 40% or so):

What did Al Gore actually say?

If we go back to Dec 2007, in the immediate aftermath of the shocking decrease in sea ice that summer, Gore gave his acceptance speech for the Nobel Peace Prize he’d received jointly with the IPCC. In it he said:

Last September 21, as the Northern Hemisphere tilted away from the sun, scientists reported with unprecedented distress that the North Polar ice cap is “falling off a cliff.” One study estimated that it could be completely gone during summer in less than 22 years. Another new study, to be presented by U.S. Navy researchers later this week, warns it could happen in as little as 7 years.

What was he reporting on?

This was truthful reporting. The first study (I think) refers to a commentary piece in EOS (or perhaps a preprint of it), which noted the poor performance of climate models in tracking the Arctic sea ice loss, and made an expert guestimate that summer sea ice would be gone by around 2030. The second (upcoming) one, refers to a fall AGU 2007 presentation that would be given by Wieslaw Maslowski, who at the time ran one of the highest resolution ice models available. However, his prediction was not directly based on his ice model, but rather on a linear extrapolation of the ice volume from his model:

One might sensibly ask why a prediction made in 2007 only made it into a review paper in 2012, despite having been highly publicised at the time? We’ll get to that.

Gore continued to reference Maslowski’s prediction at least through to 2009.

Over the next few years, a few other folks got into the sea ice forecasting game using similarly somewhat unorthodox methodologies. Chief among them was Peter Wadhams, an emeritus professor at Cambridge University. Wadhams (and a group that styled themselves the “Arctic Methane Emergency Group” (AMEG)) started showing graphs of extrapolated ice thickness from the University of Washington’s PIOMASS model:

Even without being an expert in sea ice, one might question some of these methods: naive fits to noisy data being extrapolated out of range, the odd fact that the same methods applied to extent or area data gave vastly different times of ice-free conditions, and, most obviously, a lack of any physical modeling for the future state. Sure, the standard climate models (CMIP3 at the time) used in scenarios were behaving too conservatively, but to ignore them completely…?

I don’t recall whether I was at Maslowski’s talk in AGU 2007, but I recall seeing him present similar results at least a couple of times. And even if he wasn’t present, his results were discussed widely among relevant scientists at multiple workshops. As far as I recall, opinions were pretty sharply negative.

What is the physics behind your prediction?

In 2014, the Royal Society hosted a workshop on Arctic sea ice reduction. I was invited to give a talk on paleo-climate perspectives on sea ice change, modeling and methane. Notably, Peter Wadhams was there and presented a graph very similar to the one above. If you hunt around carefully in the wayback machine you can find some of the audio recordings from the meeting, and specifically, if you listen to the Q&A period from his talk, you can hear me ask [43:00] whether there was any physical basis for such an extrapolation. The answer was no. [As an aside, this was one of the first climate workshops that really embraced Twitter (as it was then) as a means of broader dissemination, though this wasn’t appreciated by this particular speaker!]. Bizarrely, Wadhams maintained his confidence that 2015 (less than a year away at this point) would be ice free in summer.

To be clear, I claim no specific brilliance in being sceptical of these predictions. Almost everyone in the field was unconvinced by these extrapolations from the initial 2007 AGU meeting presentation onward. The reason why these predictions never made it into a peer-reviewed publication? I imagine that it was the difficulty in finding any reviewers that found these methods credible.

Lessons learned?

Science is very competitive, and scientists guard their independence fiercely. For them to agree on even one thing is major effort. Thus there will always be a range of opinions and methods on any topic and people who will cling strongly to them. The desire and culture of assessments (such as the IPCC) arose specifically in order to distill that broad range across individual scientists into a more coherent and better balanced assessment that a larger majority of experts will agree to.

In retrospect, it is clear that some folks were fooled by randomness, giving too much weight to the wiggles and not to the longer-term trend (which, to be honest, is a ubiquitous problem):

One could look back at this episode and what has been made of it since and declare that scientists should have somehow prevented Maslowski and Wadhams from presenting their ideas or talking to journalists or recovering politicians. But that is absurd: No scientist or group of scientists has that power, nor would they even want it. Alternatively, other scientists could have loudly expressed their scepticism at these results and produced better assessments. But both of these things happened. Some even went further and started betting against the extreme predictions (quite successfully in retrospect). For serious people, interested in serious projections, that might be enough. However, all of this will be (and are) ignored when someone wants to get a laugh line on Fox News.

If people are really interested in what the scientific community thinks, the assessed projections from IPCC and similar are your best bet. It can be useful to look at the range of individual projections or opinions, particular in fast moving situations, but it is very hard to discuss them in a public manner that is immune from later distortion.

References

1. W. Maslowski, J. Clement Kinney, M. Higgins, and A. Roberts, "The Future of Arctic Sea Ice", Annual Review of Earth and Planetary Sciences, vol. 40, pp. 625-654, 2012. http://dx.doi.org/10.1146/annurev-earth-042711-105345