So, starting to be time to assess our various guesses. William Connolley and I made our 50 quatloo wager on over (his side) or under 5.38 million km^2 for the September average. The minimum, if we have indeed seen the minimum, is about 5.1 million. That looks favorable for my side of the bet. Though it would mean I definitely missed the September average, as I said that would be 4.92. More about that in a moment. The figure below suggests that since the extent dropped below 5.38 right about the start of September, I should be safe. Usually (see the climatological curve) the pack doesn't gain much area in September. But William could still win if we have an unusual last two weeks and the ice pack gains a lot of extent.
I've added a few lines to the NSIDC graphic of 12 September. One is the vertical line, to highlight when it is we dropped blow the climatological minimum. We've been below normal since early August. That in itself suggests a climate change. We're now about 3 standard deviations below the climatological minimum, which again, in such a short record, suggests a climate change. The significance of the extra large amount of ocean being exposed to the atmosphere, for an extra long time, is that it lets more ocean absorb more heat from the sun. Though this year looks to be a higher extent than 2007 and 2008, it's still below any year except 2007 and 2008. If we didn't know about those two years, we'd be surprised by this year being so low -- the 2005 September average extent (record before 2007) was 5.57 million km^2 -- far higher than this year is liable to average.
Still early to decide whether I owe William, or vice versa. Both of us will win our bets with Alastair. Looking down to the poll that I invited you to answer back in June, I'll say that the people who called for 7.5 million (the previous climatology) and 6.0 million km^2 are wrong. Also the 1 who went for 3, the 2 who went for 3.5, and the 4 who went for 4 million km^2 for the month's average. The 12 who went for 4.5 (which means anything in the range 4.25 to 4.75) should be pulling for a really massive storm to hit the western Arctic and obliterate huge amounts of ice extent. The main candidates are the 3 who went for 5, and the 1 who went for 5.5 (ranges of 4.75 to 5.25, and 5.25 to 5.75, respectively).
Something else this brings up (or at least this plus some comments I saw at a different site) is "How do you judge the quality of predictions?" I'll be coming back to this, using the Sea Ice Outlook estimates for my illustrations.
Posts
14 comments:
I'm slightly surprised that NSIDC have "called the bottom" this early, seems somewhat impatient to me, but quite likely they are right. I think that means I win my bet back on my site, but I don't think many people were prepared to put up this year :-(.
Don't forget to compare to the ARCUS forecasts. We need a pro-am contest!
Depending upon storms to either push arctic ice out of the area or compress into a smaller area seems counter to the use of ice as a metric for global climate.
Perhaps now is a good time to ceed future climate predictions to Punxsutawney Phil.
What is a climatology minimum? Looks to be a hair breath below average. I am 6 ft 4, my wife is 5 ft 2. Do my children suffer a humanity minimum if not at least average of the two?
"Looks to be a hair breath below average."
1.5 million square kilometres is some hair.
Ray:
S2 put it well. We're far below average.
The prediction of a single month's average is a weather prediction, not climate. As such, we can expect a lot more variability in the observations, and much larger error bounds on the predictions.
It is not at all surprising that we still are under average. The exceptional conditions during the 2007 melt season that caused a large portion of the polar ice to be blown away due to stormy weather of course caused a minmum ice extent. Now all this ice has to be built up again. What really IS surprising is that the buildup has happened so soon, which indicates really cold polar weather during the last two years. By the way, polar ice extent as of today exceeds the extent in 2005 for this date. Which of course is no indicator for what will happen the next few months. By the way, I prefer http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Extent.png .
By the way, I see from this link: http://www.dmi.dk/dmi/iskold_september_paa_toppen_af_groenland that the Greenland Summit experienced its coldest September temperature in recorded history, minus 46 degrees Celsius, on Thursday 24th.
Grayshark:
Both your notes confuse weather for climate.
On the sea ice, 2008 had more extent than 2007, but was thinner. So definitely premature to talk of 'recovery'. 2009 probably was not thinner (I haven't seen the data), and did have more extent than 2007 or 2008. But don't get your hopes up for recovery based on a day or two of cover being more extensive than 2005. It's still only days. And 2005, itself, was the record lowest for the period 1979-2005, broken by 2007, 2008, and 2009. (2006 was slightly higher, though still below the 1979-2000 climatology.)
The summit station ... again, weather will still happen. More particularly to Summit is, the station has a very short record. The US records don't extend before 1988. See the NSF resources for Summit. I've written to the DMI, asking how long a data set they have. From their article, it could be just 2007-present. A 3 or 20 year record is extremely unimpressive for weather. Says nothing about climate either way, but if you're interested in weather, the record should be for at least, say, 60 years (twice the WMO climate period -- long enough for rare events to start to be represented ok).
I am aware of the difference between weather and climate. And of course 2005-2009 is a very short period. Plus that the ice we have now must be rather thin, since a lot of the old multi-year ice disappeared in 2007.
Notwithstanding, a number of things indicate that the climate (not only the weather) shifted into a cold phase recently. This change from warm to cold, or cold to warm, has happened before, in 1878 - 1911 - 1944 and 1976. And the shift has always happened during a solar minimum, plus minus one year. Which is what we have now. Each cold or warm trend lasts for approximately 30 years, so it will get progressively colder until about 2038 if we have a repeat of what has happended before. See my diagram at http://energiminnesfonden.se/index.php?option=com_content&view=article&id=74:klimatet-och-solcyklerna&catid=36:ovrigt&Itemid=59 .
We do have an underlying warming trend, possibly due to increasing amounts of CO2 (at least in part), but it is really VERY gentle.
Grayshark:
You're straying from being on topic. At this point, little of your comment has to do with the post at hand.
To the extent it does, I'll observe that next spring you will be welcome to make a bet (quatloos again, I don't bet cash) with me regarding the sea ice extent for September 2010. Your prediction, being based on your belief of 'recovery' will be quite different from mine.
If there were no trend to temperatures, then the 10 warmest years would not all be in the last 20. For all the talk of 'cooling', most of the last 10 years are in the top 10 warmest recorded.
5.36 per
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Sep/N_09_area.txt
graphs show 5.4.
I suspect .2 either way is not significant
Oops that should have been 0.02 million Km^2 is unlikely to be clearly measurable.
If the 5.36 figure is the final value... The NSIDC site hasn't made any daily update since Sep 30, unlike IARC and CT. Probably recounting before making the report. However I would propose to declare a draw now and if relevant to call for a tie-break. That could be the October extent since the anomaly evolution is quite interesting: in 2007 the largest anomaly, 3.0 km² (CT figure), occurred during the refreezing in October. This year the refreezing seems quite hesitant and the 2008 maximum anomaly (2.0 km²) could still be surpassed, even if I don't think it will.
Results of the Lounge betting pool are available here:
http://lablemminglounge.blogspot.com/2009/10/arctic-sea-ice-prognosticator-of-year.html
Grayshark:
I got the answer back a bit ago from DMI. Their records on Summit are also only about 20 years. Coldest from among the 20 warmest years globally is hardly impressive, nor does it say much about climate.
Post a Comment