Given the recent record low in Arctic sea ice, the melting of the Arctic was the logical choice as the first topic on the new Climate Dialogue platform. We approached around ten climate scientists to participate in the discussion. Some of them declined the invitation, mostly due to time restrictions. We were very glad that Walt Meier, Ron Lindsay and Judith Curry took up the challenge to engage with each other.

We would also like to thank the many climate scientists and other interested readers who joined the discussion via the public comments. We had over 20,000 hits in the first three weeks, which exceeded our expectations for the first round of discussion. Most of the traffic came from the blogs Watts Up With That? and Real Climate. Both blogs (here and here) kindly published our guest blog explaining the goal of

With the publication of a short and an extended summary the first discussion (between the experts) is now officially closed, although discussion in the public comments can continue. It is a good moment to evaluate the first discussion and also the platform in general, because many readers are rightly worried about the lack of activity on the site.

Selection of discussants
Our choice of participants generated a lot of criticism from both sides of the blogosphere. Below we will describe how we selected the three (initially four) participants.

Our aim is to present the full or at least a wide range of views. This of course is a major challenge because for practical reasons the number of participants is limited. One of our criteria to select scientists is that (by preference) they published in the peer reviewed literature about the topic under discussion.

With these criteria in mind we went looking for the “right” discussants.  On the more skeptical side of the spectrum we invited Judith Curry. This was criticized from the skeptical side on Watts Up With That?. She was not a real “skeptic”, some complained. The problem is that no one presented an alternative that met our criteria. People suggested Richard Lindzen or Christopher Monckton, both well-known skeptics, but with no publication record on Arctic sea ice. On RealClimate people criticized Curry for not having the right expertise. However, Curry was very active in Arctic research in the nineties  and has recently picked up the topic again.

On the other side of the spectrum Peter Wadhams was a logical choice. He recently stated that the Arctic could be ice free within four years. Wadhams accepted the invitation right away but unfortunately he was too busy in the end to deliver his guest blog.

In between these positions there was more choice for suitable discussants. Most of the scientists in this specific field could be viewed as “mainstream”. We specifically sought for a participant from NSIDC because this institute is a very prominent and visible player in the field. Walt Meier was a logical choice, because in the past he has shown at Watts Up With That? that he is willing to discuss the science with people having alternative views.

The fourth scientist we invited was James Morison of the University of Washington in Seattle. He couldn’t make it when the deadline came nearer and his colleague Ron Lindsay was very kind to step in only days before we started.

From the perspective of having a rational, polite, constructive dialogue, this first discussion was a success. Too often discussions or debates about global warming quickly become aggressive in tone. Not this time. The three discussants treated each other respectfully. We moderated the public comments and also kept a close eye on the exchange between the discussants. We soon decided not to censor off-topic comments but to show these separately. This helped to keep the discussions focused.

In hindsight what made this discussion relatively ‘easy’ is that the facts are pretty undisputed: the Arctic has shown a steady decrease in sea ice in the last thirty years (both in extent and volume), which is well documented by satellite measurements. What also took the pressure of the discussion was that right in the beginning all three discussants stated that greenhouse gases must have contributed substantially to the recent decline in sea ice.

Did we get everything out of the discussion? Certainly not and in this sense we still have a lot to improve. We feel the discussion might have been too broad from the start . Also some of the wording in our introductory article was too vague (the use of the term “global warming” for example) which could have hindered the discussion. Also in a sense the discussants were maybe a bit too “friendly” towards each other. They focused on answering questions from the public and the moderators and avoided criticizing each other’s viewpoints. We are open to suggestions how to further improve the format.

There has been a considerable delay in publishing the summaries, for which we apologize. Obviously writing the summaries was pretty challenging and it took time to agree about the text, first within our own team and then in interaction with the discussants. The summaries contain likelihood statements that have been approved by the discussants. This makes the differences in their views more explicit.

But the main reason for the delay is that we gave priority to finding participants for the next discussions. It proved very difficult  to find a representative range of discussants. Or in some cases, like the hot spot in the tropics, we have found very good candidates, but due to their full agenda’s this discussion can’t start until June.

There are several reasons why invited scientists declined the invitation to participate. Most scientists cite lack of time as the reason not to participate. Some IPCC lead authors see a conflict of interest with the upcoming AR5 report. Some scientists don’t agree with our format of giving prominent airing to viewpoints which are not widely supported. Some don’t answer to our invitations even after several reminders. In general scientists on the skeptical side of the spectrum are more willing to participate than those on the mainstream side.

Near future
What to expect in the near future? A discussion about regional modeling is planned in May. Committed participants are Roger Pielke Sr. and Bart van den Hurk of KNMI. We are still looking for a third participant, but the discussion will take place anyhow.

Then in June we will discuss the hot spot (or lack thereof) in the tropics with Carl Mears, Steven Sherwood and John Christy. So these are exciting prospects.

Other topics in the pipeline are Long Term Persistence (with Demetris Koutsoyiannis as confirmed participant, we are still looking for other candidates) and Diurnal Temperature Range (Richard McNider confirmed; we are still looking for other candidates, preferentially someone from either HadCrut or NOAA). We also have a few participants confirmed for a discussion about sea level rise, but it is difficult to fit them in a well-focused topic.

We will notify anyone who registered when a new discussion starts. Meanwhile feel free to continue discussing the summaries of the Arctic sea ice discussion and/or make suggestions about our format or about future discussions (in the comment section of this post, comments will then show up in the public comments section of the side bar).