Arctic Sea Ice

SEARCH 2011 Sea Ice Outlook: August report

SEARCH (Study of Environmental Arctic Change) has released its third Sea Ice Outlook report for August.

Here's their summary:

We received 21 responses for the Pan-Arctic report (Figure 1), with estimates in the range of just below 4.0 million square kilometers to as high as 5.4 million square kilometers for the September arctic mean sea ice extent. As in the July Outlook, the median value was 4.6 million square kilometers with quartile values of 4.3 and 4.6 million square kilometers, a rather narrow range. All contributions are well below the 1979-2007 climatological mean of 6.7 million square kilometers, and also below all values seen prior to 2007. Thus, the low values observed the last four summers are expected to continue again this September. On a regional level, the long-term downward trend is expected to continue in all regions except the Greenland Sea.

And here's the figure showing all the projections (click for a larger version):

So the median is 'stuck' at 4.6 million square km. Jinlun Zhang's projection - based on the PIOMAS sea ice thickness model - has gone up from 4.3 to 4.6 million square km. We see Lucia Liljegren from the Blackboard blog make a contribution, and of course our very own Chris Randles and Larry Hamilton have submitted their projections again. The WUWT poll went from a 5.1 to a 5.0 million square km prediction. NSIDC's Walt Meier's group started with a 4.7 million square km prediction, now 4.5 million square km.

Just for reference, these are the September average extents as calculated by NSIDC for the period 2005-2010 (in million square km):

2005 5.57
2006 5.92
2007 4.30
2008 4.68
2009 5.36
2010 4.90

August SEARCH Outlook Contribution

Here is my next contribution:

Pan Arctic Outlook

Christopher Randles

Public outlook, statistical method

1.      Extent Projection  4.438 + (End of July CT area - 4.383) * 0.9176 m km^2

+/- 95% confidence interval of 0.8 m   

2.      Method – single linear, single non-linear regression

A gompertz fit of the NSIDC September extent figures is used as a starting point.

Linear regression is then used to predict the residual from the Gompertz fit using the residual of the end of July 2011 Cryosphere Today area number from a gompertz fit of end of July area numbers.

3.      Rationale

Several contributors have used multiple linear regression. This felt inadequate when there appears to be a curved shape that other contributors have used quadratic, exponential, logistic or gompertz fits to approximate.

For the July outlook I used both area and volume data to predict the residual. For this outlook, PIOMAS volume data does not appear to improve prediction of the residual significantly and has been dropped.

 

SEARCH 2011 Sea Ice Outlook: July report

SEARCH (Study of Environmental Arctic Change) has released its second Sea Ice Outlook report for July.

Here's their summary:

We received 16 responses for the Pan-Arctic report (Figure 1), with estimates in the range of 4.0 to 5.5 million square kilometers for the September arctic mean sea ice extent. The median value was 4.6 million square kilometers; the quartile values were 4.3 and 4.7 million square kilometers, a rather narrow range given the intrinsic uncertainty of the estimates on the order of 0.5 million square kilometers. It is important to note for context that all 2011 estimates are well below the 1979–2007 September climatological mean of 6.7 million square kilometers.

And here's the figure showing all the projections:

The median went down from 4.7 million square km in the June report to 4.6 million square km. The WUWT poll submission went down to 5.1 million square, whereas the PSC's Zhang has adjusted his prediction upwards from 4.1 to 4.3 million square km. Some groups didn't submit for this others, but a few new ones did, such as Walt Meier from NSIDC and of course our very own Chris Randles. Our other horse in the race, Larry Hamilton, has the same forecast he had a month ago: 4.4 million square km.

SEARCH Outlook

Hi everyone,

I hope this first attempt at a post works. You probably know me as Gas Glo here though I usually post on the internet as crandles - that wasn't intentional just an effect of choosing to sign in with an existing google group.

Following Larry Hamiltons work on a Gompertz fits, I have submitted a method of updating that as more information about area and volume become available. I have already provided quite a bit of the detail in the posts so please excuse the repetition. Apologies also if you are not into geeky maths stuff.

Anyway enough preamble, here is what my outlook says:

SEARCH 2011 Sea Ice Outlook: June report

I'm a week late to this particular party (and some others), but this is something we'll want to reference later on (just like we did last year in June and July). SEARCH has released its first Sea Ice Outlook report, to which several people or groups of people - mostly science professionals - submit their projections for the September 2011 arctic sea extent, based on NSIDC monthly extent values.

Here's the summary for this year's June report:

The 2011 June Outlook suggests a modest decrease for summer 2011. With 19 responses for the pan-arctic (and 7 for the regional outlook), including several new contributors, the June Sea Ice Outlook projects a September 2011 arctic sea extent median value of 4.7 million square kilometers (Figure 1). This compares to observed September values of 4.7 in 2008, 5.4 in 2009, and 4.9 in 2010. The range of values is 4.0 to 5.6 million square kilometers, but the distribution is skewed toward lower values, suggesting either persistent conditions or a substantial drop below 2008 and 2010 values and the long-term downward trend. The 2011 June Outlook differs from the 2010 Outlook by not including projections of major increases in extent. It is important to note for context that all 2011 estimates are well below the 1979–2007 September climatological mean of 6.7 million square kilometers.

And here's the figure showing all the projections:

As was already noted in one of the comment sections we see that Zhang has revised his projection down from 4.5 million to 4.1 million (it was 5.0 million two months back). Zhang was very close to last year's final result, using the PIOMAS model.

Another noteworthy thing is the inclusion of the projection of Anthony Watts and his commenters over at Wattsupwiththat, based on a poll held a few weeks back. On the one hand I commend them for making a verifiable projection, which isn't something they do often and when they do they are often wrong (like last year).

SEARCH September sea ice outlook: July report

The second SEARCH sea ice outlook has just been released:

The July Outlook for arctic sea ice extent in September 2010 shows some notable adjustments from the June Outlook, with both downward and upward revisions from last month.

Downward revisions reflect in part rapid ice loss observed during June together with the presence of the Arctic Dipole Anomaly (DA), which promotes clear skies, warm air temperatures, and winds that push ice away from coastal areas and encourages melt. Upward revisions reflect the slowdown of ice loss during the first two weeks of July and a change in atmospheric conditions to cooler, cloudier weather.

The July 2010 Sea Ice Outlook Report is based on a synthesis of 17 individual pan-Arctic estimates using a wide range of methods: statistical, numerical models, comparison with observations and rates of ice loss, composites of several approaches. Two contributors to the outlook represent "public" contributions.

Including all contributors, the individual Outlook values for September 2010 range from 1.0 to 5.6 million square kilometers, with a mean of 4.6 +/- 1.10 million square kilometers. Excluding the outlier of 1.0 million square kilometers by one of the public contributors gives a range of 4.0 to 5.7 million square kilometers, with a mean of 4.8 +/- 0.62 million square kilometers. This is below the 2009 minimum of 5.4 million square kilometers and just slightly above the 2008 minimum of 4.7 million square kilometers. Only three of the Outlook contributions give a value equal to or above the long-term linear trend line (5.6 and 5.7 million square kilometers, respectively). All of the estimates remain significantly below the 1979-2007 average of 6.7 million square kilometers, and six estimates indicate a new record minimum.

SEARCH September sea ice outlook: June report

There it is, the first SEARCH sea ice outlook for September 2010 (click for a larger version):

Overall it looks a bit conservative, except for Wilson. Compare this to last year's June outlook:

A quick calculation (leaving out the outliers of 3.2 million in 2009 and 1.0 million in 2010) shows an average prediction of 4.72 in June 2009, and 5.05 million this year.