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Comment by soperj | Hacker News Reader

> The high-melt year of 2012 applied in perpetuity yields an ice loss commitment of 782 ± 135 mm SLR, serving as an ominous prognosis for Greenland’s trajectory through a twenty-first century of warming.

It's been a decade now and we haven't had any years really even close to 2012 in terms of minimum sea ice extent.

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That’s false. Compare 1980 was 7.54 million, 2000 was 5.98 million, 2012 was 3.39 million, and 2020 was 3.82 million. https://climate.nasa.gov/vital-signs/arctic-sea-ice/

It is noisy data with few data points, so yes 2013 was 5.05 million but both the peaks and troughs are dropping.

that's over a 10% difference between 2020 & 2012, and it was the only year under 4 million, so my point still stands.

What is the point that still stands, exactly? There are peaks and troughs with a clear downward trend. If your point is that in that trend, some years over 10 year periods look similar, then you would be correct. But in making that point, you risk drawing the wrong conclusion from the data.

My point was that you shouldn't base a prognosis on a melt year that has happened once in a 40 year record, when it so far has been an anomaly.

data that I don't like is an abberation. data that I do like is proof!

that's nonsense. It hasn't happened again in a decade despite the last 5 years being some of the warmest on record, and there was a cyclone that ripped through arctic dispersing sea ice in early August that year. It's clearly an anomaly.

Being 2 standard deviations from the trend line is hardly an anomaly, just expected variance over a sample that size.

0.05 * 40 = 2.

Your definition of "really even close" is either absurd or you don't much care about the data nearly as much as the point you wanted to make.

Do you understand the point I'm trying to make? Because it doesn't really seem like it.

The 20 years leading up to 2004 the average was > 6 million square km. 2012 was 3.4. 2020 was 3.8. In the context of the previous average, that does seem close. What was your point?

My point was don't base a prognosis on an anomaly, but clearly everyone has taken it as something else entirely, based on the tones of the replies.

2012 isn’t an anomaly just normal variation, by area it’s the current low point by volume it isn’t.

I gotta say that it really looks like you're using motivating reasoning here. That graph plainly shows the direction, and it's not upwards or even stable.

A different visualization of the same data here, https://nsidc.org/arcticseaicenews/charctic-interactive-sea-...

I guess it depends how you define "close".

All years from the last decade look pretty close to me:

http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger...

See the PIOMAS project data:

http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volum...

I'm not sure how they got data going to the end of 2022? This also doesn't show a low point in 2012, so can't be what they're basing it on.

The red line (2022 data) stops at July, and while it's hard to tell exactly it looks to me like the diamond line (not sure what to call that color) for 2012 is the lowest line between August and October.

Ahhh i see it now, 2 red lines with pluses. I was looking at 2015. That makes wayyy more sense.

There are multiple years show.

The PIOMAS project has been collecting data with a satellite over the Arctic since 1979 IIRC.

The PIOMAS project is just a calculation based on other satellite observations, the model has been verified using 2 different satellites, one launched in 2003, and another in 2010. [0] Their paper on the model was released in 2003. My mistake was that I was looking at the 2015 line, because the color and design looks exactly like 2022.

[0] - https://en.wikipedia.org/wiki/Measurement_of_sea_ice#Sea_ice...

If you read that part in Wikipedia again you will see those dates are about the ICESat and Cryosat projects (that are now contributing to PIOMAS).

But PIOMAS has been collecting Arctic ice data since 1979.

For example:

http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger...

If you don't believe, download the PIOMAS data and check it yourself.

https://psc.apl.uw.edu/research/projects/arctic-sea-ice-volu...

I understand that they've been using data collected by satellites since 1979, but they didn't even come up with the model until 99, and released the paper on it in 2003, so the model was used retrospectively on data previously collected, not specifically collected for that project.

You can see that in your own link.

Extent tends to be a noisier signal that total ice mass.

I agree entirely, but it seems that they're basing their calculation off of extent rather than volume, because 2012 isn't the low point volume.

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