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Comment by chrisco255 | Hacker News Reader

> June sea ice extent was 103% of the 1991-2020 median value.

Greenland has been gaining ice this summer, quite unusual: http://polarportal.dk/en/greenland/surface-conditions/

The planet's climate is a complex system, the state of which cannot be neatly summarized by any one statistic.

I mean, there's a reputable school of thought predicting that global warming will lead to another ice age, because higher temperatures disrupt ocean currents -- particularly the Gulf Stream, which redistributes warm water from the Gulf of Mexico to northern Europe. As the Gulf Stream makes its deposits of warm water along the coasts of Great Britain and northwest Europe, it keeps the temperatures in northwest Europe warmer than in eastern Canada, even though they both are roughly the same distance from the equator. The prediction is that, if Arctic ice melts as a result of global warming, huge amounts of fresh water will pour into the North Atlantic and slow down the Gulf Stream, cooling Europe, and triggering a feedback loop with colder and longer European winters, and more and more ice on the planet's surface.[a][b]

[a] The book "Ice Age" by Cambridge-trained astrophysicist John Gribbin and his wife Mary has a good high-level overview of this school of thought: https://reanimus.com/store/?item=1420

[b] Recent studies of circulation in the North Atlantic already show a significant reduction in currents flowing north from the Gulf Stream: https://www.realclimate.org/index.php/archives/2020/09/new-s...

We're already in an ice age, and we have been for the last 1 million years. We're just in an interglacial period (for the past 12K years). We were always going to revert back to a glacial period.

The belief is that CO2 concentration would prevent that, by causing global warming. Otherwise, if we revert to a glacial period, that is currently status quo for planet earth:

https://www.ncdc.noaa.gov/abrupt-climate-change/Glacial-Inte...

Yes, we're in an interglacial period. You're absolutely right about that. The counter-intuitive prediction from this school of thought is that global warming would precipitate or accelerate glacial period within this ice age.

Makes sense though, a lot of ice melting, water becoming cooler so the next winter you get more ice area with lower ice volume. Rinse and repeat until the whole ice sheet disappears.

No. You're literally interpreting it as the exact opposite of what is occurring.

Sea ice volume is at 30 year median: http://polarportal.dk/en/sea-ice-and-icebergs/sea-ice-thickn...

And Greenland's ice sheet is expanding over the course of this summer, when it normally goes through a melt season.

Arctic ice is pretty variable, because it floats over the water. Arctic ice is not what causes sea level rise, by the way, since it's already sitting in the ocean. It's Greenland and Antarctica that you have to watch for sea level rise influence.

And Antarctica is above average right now: https://sites.uci.edu/zlabe/antarctic-sea-ice-extentconcentr...

In other words, melting ice caps, as predicted, are not happening.

Suppose there is an ice cube with volume 1m^3 in a huge freezer, it melts when the freezer is off and then freezes back when the freezer turns on. Now the volume would be the same, the question is about the thickness. The thinner it gets, the faster it will melt/freeze leading to more variability in climate patterns. (speculation mode off)

I'm struggling to interpret the data on that site, is there any analysis links you can share talking about this issue?

That site just tracks Greenland and Arctic ice. They just measure the volume and extent. On the map of Greenland, any red areas you see are areas where ice melted over the past day. Any blue areas are where it snowed. On the chart, the grey area is the 2 standard deviation range that ice gains/losses typically see over the course of the year, and the blue line is the current year's gain/loss. If the blue line goes above or below the grey area, it's anomalous. Greenland typically melts off some in the summer, but the blue line shows that it's currently gaining ice, and has even had some way above average days this summer, for ice gains. This means its ice volume is increasing, which is counter to predictions.

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