Slashdot Mirror
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."
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
You mean besides the overwhelming majority of the world's climate scientists?
Tic-Tac-Toe, Global Thermonuclear War, and relationships all have the same winning move.
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.
Look who's talking. BadAnalogyGuy, the reason why scientists sometimes prefer inaccurate but precise and historically consistent data over data sources which are more accurate but have not been around for long is that they are interested in trends, not absolute values.
In May, 2008 they went so far as to predict that the North Pole would be ice-free during the 2008 'melt season,'
Er, no, they said it was possible and later quote "a 59% chance of a new record minimum this year". How the media chose to report this is another matter... Oh yes, note the date: May 2008.
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.
And if you read TFA, the sensor drift started in January 2009, was spotted within a few weeks and only affected their daily images which are effectively "live" and hence haven't gone through QA.
So how exactly does an error which occurred in Jan/Feb 09, was almost immediately spotted and declared affect a (misreported) prediction made last May?
<irony>Meanwhile, I'm sure the little fairies are hard at work ensuring that the geological era's worth of sequestered CO2 we're in the process of releasing back into the atmosphere magically changes its physical properties. After all, it is made from special carbon that God put there in 4004BC for us to burn, unlike that nasty communist CO2 that exhibits the greenhouse effect in godless laboratories.</irony>
In a survey of 100 programmers, 111111 thought that duck-typing was a good idea.
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.
"None are more hopelessly enslaved than those who falsely believe they are free." -- Goethe
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!
You might want to read TFA. The sensor drift only started in Jan 2009, and it was spotted within a few weeks.
To quote TFA:
This and no other is the root from which a tyrant springs; when first he appears as a protector - Plato (423 to 327 BC)
Nonsense. The data from this particular survey are in dispute, and people here are conflating this to all of climate science. That the earth is warming, and that globally, ice is melting at an alarming rate, is not even disputed by the oil industry any more.
If the atmosphere heats up, physics predicts that the ground will heat up as well, and that ice will melt.
You're correct that the system is more complex than that, because, for example, melting ice can trigger other mechanisms that are too complex to model, currently. This doesn't refute the very basic fact that adding global heat to the atmosphere tends to melt ice.
I'd also point out that we know all of this because we've studied it scientifically, just the same way that we know that CO2 tends to heat the atmosphere, and ice tends to melt with warmer air.