More adjustments

[IanC]

New version, same outcome. It's worse than we thought, oh noes!

They managed to lose an extra MKm^2 of ice in 2012. I guess we didn't know how to read satellite maps way back then.

How utterly predictable.

 

[Toddsterpatriot]

The science is settled.......that's why we keep cheating.

 

[saveliberty]

Do any of the models predict when I can't have ice in my drink at the diner?

 

[IanC]

From the web site-

.We have updated the way the monthly average sea ice extent is calculated in the NSIDC Sea Ice Index, the source for our sea ice extent estimates. The monthly average total extent (and area) are now computed as an average of the daily values over the month. Historically, the monthly mean sea ice extent has been calculated based on the monthly mean averaged sea ice concentration field. While there is a rationale for both approaches, the new method is more intuitive and eliminates unusual and unexpected results in months when there is rapid ice growth and retreat. Most of the new monthly mean extents are smaller than the previous values with a mean extent difference between -0.45+0.24 and -0.23+0.16 million square kilometers for the Arctic and Antarctic, respectively. The largest differences for the Arctic occur during the month of October due to the rapid ice growth rates typical at that time of year, with the largest difference of -1.20 million square kilometers in October 2012. Changes in rankings and trends were much smaller because the new method tends to affect all years of a given month in a similar manner. October is also the month with the largest trend difference, increasing in magnitude from -7.4 percent per decade to -9.3 percent per decade. Changes in Arctic trends for other months are much smaller.

I am still trying to get my head around what they did to change things up.

They say they are now using daily averages to calculate the monthly averages. How, exactly, were they computing monthly averages before? First and last days of the month divided by two?

Something smells fishy. I bet there is another 'adjustment' imbedded in their new algorithm that they didn't feel was worthy of pointing out.

I could see how going from a straight average to a RMS average might make a difference if there was a fairly large discrepancy between growing and shrinking days in the year.

The bottom line is that the exact same data is being used and somehow a lot more ice has disappeared and the shrinking trend has accelerated.

Which version was closer to the 'truth'? Is there any doubt that the next version will also find more missing ice and an even greater shrinking trend? Or have they used up all the statistical tricks to push the results in their favoured direction?

The old 30% SIE showed less ice loss and was discontinued. Will we see a new 10% product to replace the 15% product now in use? We shall see.

 

[whitehall]

How does a person become a "scientist"? The left seems to bestow the title to anybody who ever shook a freaking test tube or staired at a (government) video screen as long as the findings are politically advantageous. The dirty little secret is that professors will fudge data and independent labs will come to any conclusion as long as the federal grant money keeps flowing. Lefties accuse anybody who disagrees with their global warming theory as "science deniers" but their global warming guru is a sexual pervert failed politician who has no background in science.

 

[Wuwei]

They managed to lose an extra MKm^2 of ice in 2012. I guess we didn't know how to read satellite maps way back then.

It seems to me they only lost an extra 1/2 MKm^2 because if you want a historic trend, the new algorithm drops 1/2 MKm^2 in 1979 and 1MKm^2 in 2015. The difference is 1/2.

However I do agree that surface area is such an easy thing for a satellite to see that I don't know why they thought they didn't get it right the first time around. Where did you get the graph?

 

[IanC]

They managed to lose an extra MKm^2 of ice in 2012. I guess we didn't know how to read satellite maps way back then.

It seems to me they only lost an extra 1/2 MKm^2 because if you want a historic trend, the new algorithm drops 1/2 MKm^2 in 1979 and 1MKm^2 in 2015. The difference is 1/2.

However I do agree that surface area is such an easy thing for a satellite to see that I don't know why they thought they didn't get it right the first time around. Where did you get the graph?

Maybe. But the last year charted, 2016, is less than 1/2 MKm^2 difference.

If you are on a computer, right click the image to get its source. On my phone I select the image and Google. The source is NSIDC, like it says on the graph.

Edit- sorry, I misunderstood your comment. Yes the start date amount has been lowered by almost a 1/2 M. I suppose if the starting values we're normalized the difference would appear less. But that isn't the visual impact they were looking for, is it? Even less ice, disappearing faster is the favoured result, for some reason.

 

[Wuwei]

I am still trying to get my head around what they did to change things up.

They say they are now using daily averages to calculate the monthly averages. How, exactly, were they computing monthly averages before? First and last days of the month divided by two?

Something smells fishy. I bet there is another 'adjustment' imbedded in their new algorithm that they didn't feel was worthy of pointing out.

I could see how going from a straight average to a RMS average might make a difference if there was a fairly large discrepancy between growing and shrinking days in the year.

The bottom line is that the exact same data is being used and somehow a lot more ice has disappeared and the shrinking trend has accelerated.

Which version was closer to the 'truth'? Is there any doubt that the next version will also find more missing ice and an even greater shrinking trend? Or have they used up all the statistical tricks to push the results in their favoured direction?

The old 30% SIE showed less ice loss and was discontinued. Will we see a new 10% product to replace the 15% product now in use? We shall see.

I remember seeing a time lapse video of the arctic ice over a number of years. Seasonally it kept considerably growing and shrinking. It didn't go back to the same shape from one year to the next. It seems that with such natural variation it would still be straightforward to define a yearly average.

Another puzzle is that in 2016 they came up with a MKm^2 change of 1 out of 7. That is 14% change just by fiddling with the arithmetic. Very odd.

 

[IanC]

I am still trying to get my head around what they did to change things up.

They say they are now using daily averages to calculate the monthly averages. How, exactly, were they computing monthly averages before? First and last days of the month divided by two?

Something smells fishy. I bet there is another 'adjustment' imbedded in their new algorithm that they didn't feel was worthy of pointing out.

I could see how going from a straight average to a RMS average might make a difference if there was a fairly large discrepancy between growing and shrinking days in the year.

The bottom line is that the exact same data is being used and somehow a lot more ice has disappeared and the shrinking trend has accelerated.

Which version was closer to the 'truth'? Is there any doubt that the next version will also find more missing ice and an even greater shrinking trend? Or have they used up all the statistical tricks to push the results in their favoured direction?

The old 30% SIE showed less ice loss and was discontinued. Will we see a new 10% product to replace the 15% product now in use? We shall see.

I remember seeing a time lapse video of the arctic ice over a number of years. Seasonally it kept considerably growing and shrinking. It didn't go back to the same shape from one year to the next. It seems that with such natural variation it would still be straightforward to define a yearly average.

Another puzzle is that in 2016 they came up with a MKm^2 change of 1 out of 7. That is 14% change just by fiddling with the arithmetic. Very odd.

Yes, it just seems so suspicious all the time.

This new algorithm may be totally defensible. But their explanation must be incomplete in some fashion. Surely they knew that yet another data set being 'reanalyzed' to show an increased trend would sit uneasy with the portion of the public that are already concerned that science is being politicized.

I can't understand how changing the way they determine months averages can affect the trend. They should have a detailed explanation with examples showing how this is possible. The time is long past where a simple 'trust us we're scientists' will suffice.

 

[Old Rocks]

New version, same outcome. It's worse than we thought, oh noes!

They managed to lose an extra MKm^2 of ice in 2012. I guess we didn't know how to read satellite maps way back then.

How utterly predictable.

You did not link the source article for the graph. How predictable.

 

[Old Rocks]

Maybe they are correct with the new numbers, maybe not. Doesn't really matter. In both cases, the melt is rapid, and the amount of ocean exposure continues to increase, with all the effect that has.

 

[IanC]

New version, same outcome. It's worse than we thought, oh noes!

They managed to lose an extra MKm^2 of ice in 2012. I guess we didn't know how to read satellite maps way back then.

How utterly predictable.

You did not link the source article for the graph. How predictable.

Hahahaha, now you won't be able to find it.

Unless you right click the image, Google search the image, or just read the name on the side of the graph.

 

[BlackSand]

We found your ice ... In a ditch in Louisiana.
It doesn't belong here ... Please make arrangements to retrieve it before we have to cancel school or something.

Thanks ...

.

 

[Billy_Bob]

More proof that statistics and numbers can be manipulated to say what you want.. Its no longer Science its numerology..

 

[Wuwei]

From the web site-

.We have updated the way the monthly average sea ice extent is calculated in the NSIDC Sea Ice Index, the source for our sea ice extent estimates. The monthly average total extent (and area) are now computed as an average of the daily values over the month. Historically, the monthly mean sea ice extent has been calculated based on the monthly mean averaged sea ice concentration field. While there is a rationale for both approaches, the new method is more intuitive and eliminates unusual and unexpected results in months when there is rapid ice growth and retreat. Most of the new monthly mean extents are smaller than the previous values with a mean extent difference between -0.45+0.24 and -0.23+0.16 million square kilometers for the Arctic and Antarctic, respectively. The largest differences for the Arctic occur during the month of October due to the rapid ice growth rates typical at that time of year, with the largest difference of -1.20 million square kilometers in October 2012. Changes in rankings and trends were much smaller because the new method tends to affect all years of a given month in a similar manner. October is also the month with the largest trend difference, increasing in magnitude from -7.4 percent per decade to -9.3 percent per decade. Changes in Arctic trends for other months are much smaller.

I am still trying to get my head around what they did to change things up.

They say they are now using daily averages to calculate the monthly averages. How, exactly, were they computing monthly averages before? First and last days of the month divided by two?

Something smells fishy. I bet there is another 'adjustment' imbedded in their new algorithm that they didn't feel was worthy of pointing out.

I could see how going from a straight average to a RMS average might make a difference if there was a fairly large discrepancy between growing and shrinking days in the year.

The bottom line is that the exact same data is being used and somehow a lot more ice has disappeared and the shrinking trend has accelerated.

Which version was closer to the 'truth'? Is there any doubt that the next version will also find more missing ice and an even greater shrinking trend? Or have they used up all the statistical tricks to push the results in their favoured direction?

The old 30% SIE showed less ice loss and was discontinued. Will we see a new 10% product to replace the 15% product now in use? We shall see.

From the site you quoted:

The monthly average total extent (and area) are now computed as an average of the daily values over the month. ​

That new approach seems straightforward and more intuitive, as they say in the article. It probably depends on visual band observation, but they don't say.

This is the old method:

Historically, the monthly mean sea ice extent has been calculated based on the monthly mean averaged sea ice concentration field.​

See, Sea ice concentration - Wikipedia

The sea ice concentration field is a bit more convoluted, but has applications in acquiring a picture of the temperature over the area.
It is defined as the area of sea ice relative to the total at a given point in the ocean. There are problems in using thermal radiometry in that the “pixels” are different sizes for different wavelengths due to the finite size of the detector dish and the wavelength dependent resolution of the dish. The data has to be reduced by a sort of nonlinear reconstruction.

More detail is in the wiki article. But given the complexity of using thermal sensing, I am more at ease with the reason why the two types of data reduction give markedly different results.

As far as what best describes the arctic - using a daily average vs. a sea ice concentration field - I will leave it to others to decide for themselves if there is a AGW conspiracy or not.