Arctic Ice Extent Understated Because of "Sensor Drift"

dtjohnson writes "The National Snow and Ice Data Center (NSIDC) has been at the forefront of predicting doom in the arctic as ice melts due to global warming. In May, 2008 they went so far as to predict that the North Pole would be ice-free during the 2008 'melt season,' leading to a lively Slashdot discussion. Today, however, they say that they have been the victims of 'sensor drift' that led to an underestimation of Arctic ice extent by as much as 500,000 square kilometers. The problem was discovered after they received emails from puzzled readers, asking why obviously sea-ice-covered regions were showing up as ice-free, open ocean. It turns out that the NSIDC relies on an older, less-reliable method of tracking sea ice extent called SSM/I that does not agree with a newer method called AMSR-E. So why doesn't NSIDC use the newer AMSR-E data? 'We do not use AMSR-E data in our analysis because it is not consistent with our historical data.' Turns out that the AMSR-E data only goes back to 2002, which is probably not long enough for the NSIDC to make sweeping conclusions about melting. The AMSR-E data is updated daily and is available to the public. Thus far, sea ice extent in 2009 is tracking ahead of 2005, 2006, 2007, and 2008, so the predictions of an ice-free north pole might be premature."

Comments

Re:alternative solutions

[Anonymous Coward]

Both the AMSR_E and SSM/I data are satellite derived products.
http://www.ncdc.noaa.gov/oa/satellite/ssmi/ssmiproducts.html
http://www.aqua.nasa.gov/about/instrument_amsr.php

Re:Oh gosh.

[Anonymous Coward]

No, the point is that no matter which data set you look at, the trend is downwards. "Deniers" are those who completely ignore all of that data and say it's not happening at all. And trust me, they're out there.

Re:Rocket science?

[Cally]

Denialists, stop your engines now...

there was a significant problem with the daily sea ice data images on February 16. The problem arose from a malfunction of the satellite sensor we use for our daily sea ice products. Upon further investigation, we discovered that starting around early January, an error known as sensor drift caused a slowly growing underestimation of Arctic sea ice extent.

So, to be clear, this issue has arisen over the last 4-6 weeks. The records for the last decade, clearly showing a significant trend towards less sea-ice, are unaffected.

Re:Rocket science?

[tick-tock-atona]

Such as the immunization and the possible link to autism, lets say it creates a 1% increase in autism how ever it saves 25% from death, the benefits out weigh the risks and the parents who avoid this are poor judges on risk assessment.

Arrgh!
Speaking of fear mongering, it has been repeatedly shown that there is absolutely no link between autism and vaccines.
Please, can't this FUD just die already? It's already caused deaths in the UK from a loss of herd immunity!

the "drift" was only for Jan/Feb 2009

[Chirs]

You might want to read TFA. The sensor drift only started in Jan 2009, and it was spotted within a few weeks.

Re:Rocket science?

[catchblue22]

To quote TFA:

Sensor drift is a perfect but unfortunate example of the problems encountered in near-real-time analysis. We stress, however, that this error in no way changes the scientific conclusions about the long-term decline of Arctic sea ice, which is based on the the consistent, quality-controlled data archive discussed above.