ARCUS Sea Ice Prediction Network writes in their executive summary:
Thank you to the groups that contributed to the August 2014 Outlook. We received 23 pan-Arctic contributions. Of the 23 contributions, some are unchanged from July. The median Outlook value for September extent is 5.0 million square kilometers with a quartile range from 4.58 to 5.22 million square kilometers. The overall range is between 4.0 and 5.6 million square kilometers.(WUWT is at 5.6 along with researcher Wang)
The median value for August is increased from the June and July values of 4.7 and 4.8 million square kilometers, respectively.
This increase reflects the relatively slower decline in ice extent through August than what had been projected earlier. The overall range has narrowed since July, suggesting that the projections are tending to converge, as one would expect with a shorter forecast period. There were four regional Outlooks submitted with a fairly large range in both spatial extent and ice-free dates. There have not been any significant extreme weather events this summer as was seen during the record low years of 2007 and 2012. The more quiet conditions have likely played a role in the evolution of the sea ice extent this summer. While the extent is far from a record low, all contributions will put 2014 as one of the ten lowest September extents in the 36-year satellite record.
The Sea Ice Outlook is a venue for discussion and networking and provides a transparent exercise in both scientific sea ice predictions as well as estimates from the public. The August report was developed by Walt Meier, NASA Goddard Space Flight Center, and the rest of the Sea Ice Prediction Network (SIPN) leadership team, with a section analyzing the model contributions by Francois Massonnet, Université Catholique de Louvain. The report includes comments on modeling outlooks and on regional predictions, a summary of current conditions, key statements from each Outlook, and links to view or download the full outlook contributions. See the original call for contributions for the August report here. Post-season activities of SIPN will provide more of a scientific analysis of the methodologies, relative performance, etc.
Click to magnify the image
Figure 1: Distribution of individual Pan-Arctic Outlook values (August Report) for September 2014 sea ice extent. Labels on the bar graph are rounded to the tenths for readability. Refer to the Individual Outlooks at the bottom of this report for the full details of individual submissions.
COMMENT ON MODELING CONTRIBUTIONS
Provided by François Massonnet, Université Catholique de Louvain
There were 10 model contributions to the August Sea Ice Outlook. The median predicted September sea ice extent is 5.1 million km² (4.8 and 4.7 million km² for July and June, respectively). From figure 3 below it appears that the uncertainties around individual predictions, when they are updated for this month’s report, are systematically smaller than the ones for July, themselves smaller than the ones for June (see the July report). This confirms our July statement that the later the prediction date, the more confident the predictions. In addition, it becomes clear from the figure that the inter-model spread is also reduced as the prediction start dates get closer to the month of September. The range (max-min) of predicted sea ice extent is 1.65 million km² for the August outlook, 2.03 million km² for July, and 2.6 million km² for June.
We can now put the suite of June-July-August predictions into perspective. Leaving aside the possibility of sampling issues (we have to acknowledge that the number of model contributions is small), it is encouraging first to note that the uncertainty relative to both initial conditions/atmospheric forcing are systematically reduced as time goes by. It is also encouraging to see that the inter-model spread shrinks over time. This spread—which although narrows over the season is still fairly large—reflects the uncertainty in model physics, the differences in spatial resolution, and the differences in coupling formulation across models. Unless these nine models share common systematic biases, it is thus expected that the average 2014 September Arctic sea ice extent will be in the range 3.95-5.6 million km², and likely above the trend line (5.1 million km²), a situation similar to 2013.
Figure 3: Modeling contributions to the July Sea Ice Outlook. June and July contributions are shown in light and medium shading, respectively, for comparison
The full ARCUS sea ice report is here:
Full current data can be found at the WUWT Sea Ice Reference Page here: http://wattsupwiththat.com/reference-pages/sea-ice-page/