303 is the number of consecutive months we have now had with temperatures greater than the mean for the 20th Century.
303 months is a little over over 25 years, so it may sound impressive – but does it actually mean anything?
Well, yes. It means that the last 25 years have been warm, but then we already knew that. it tells us nothing about why it has been warm or what it is going to be like in the future. In isolation it is just a number, nothing more. And in a couple of weeks it will change to 304.
Some more records for the year so far:
- According to the NOAA, May 2010 was the hottest May on record. They also claim new records this year for:
- The warmest March and the warmest April
- The warmest January to April period
- The warmest January to May period
- The warmest March to May period
- In a paper submitted to Reviews of Geophysics Hansen et al claim that the last 12 months (to the end of April 2010) have been the hottest 12 month period on record.
- The NSIDC gives us the latest Arctic sea ice maximum on record, and
- The rate of Arctic sea ice decline through the month of May was the fastest in the satellite record.
All this has led to speculation about what the rest of the year might bring. Will we see a new record annual temperature, or a new sea ice minimum, or both?
On the temperature front, a lot depends on what ENSO gets up to in the rest of the year. We’re now in a neutral state; the models suggest that a La Niña is likely to develop in the latter half of the year which will cool things down a bit. I wouldn’t put money on a new record, but it is possible (note that both 1998 & 2007 went into a La Niña in the latter part of the year).
With sea ice, it’s anybody’s guess (and there’s no shortage of people prepared to guess).
ARCUS/SEARCH have a selection of predictions, nearly all of them serious. The one exception (although I’m sure the author is serious) is the one by Charles Wilson – Gareth has aleady covered this one on Hot Topic, well worth a read.
Of the others, about half place this year between 2008 and 2009 which would mean the third lowest extent on record. Only one (ignoring Wilson’s contribution) predicts a new record this year – and not by a very big margin.
I liked the approach taken by Polar Science Weekend, a nice way of involving the public.
Robert Grumbine discusses his submission on his blog, which is interesting reading. William Connolley also thinks that Grumbine’s approach is interesting, but wrong. He’s taking bets on the minimum (and betting that it will be more than 4.935 km2, again somewhere between 2008 & 2009).
In summary, then, it seems that the majority of the people who actually know about this stuff think that the downward trend will continue – but that we’re not very likely to see a new record this year.
There are other opinions, of course. Over at WUWT, on May 29th we had Watts & Goddard calculating that Arctic Ice Volume Has Increased 25% Since May, 2008. PIOMAS disagrees, but hey, who needs models when you’ve got a calculator?
On the 14th June Goddard followed this up with a confident prediction that this year will have the greatest extent since 2006.
My favourite bit is where someone asked him for a figure in sq. km. He replies that he doesn’t have a such a value, since his “measurements are in pixels”. :)
Goddard followed this up with another post on the 25th June, much to Tamino’s amusement, and then kind of shot himself in the foot on the 2nd of July (though to be fair, he acknowledges that he got it wrong).
The real point is that when you have a system with a reasonable amount of variability (like climate or Arctic sea ice) then it doesn’t really mean a lot when a record gets broken. Pretty much any record will get broken eventually if you’re prepared to wait long enough. If there happens to be a trend then the probability of a new record (in the direction of the trend) increases with time, just as the chance of one in the opposite direction decreases.
Trying to claim that Arctic sea ice has been recovering since 2007 is probably even more stupid than Monckton’s claim (in 2008) of Global cooling by 0.4 °C/decade.
Of course those of you with a knowledge of statistics will understand this. For those of you that don’t, a couple of pointers:
- 2005 had (by far) the lowest Arctic sea ice extent on record at the time.
It is now the 4th lowest (and likely to become 5th this year)
- 1997 was (at the time) the warmest year on record. It is now 12th. Every single year from 2001 onwards has been warmer than every year prior to 1998.
 – Wikimedia
 – NOAA
 – Polar Science Centre
 – Atmoz
(It should have been Dr. Roger Pielke Sr., but that site is down at the time of writing)
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