Mini-Throughput: Ice Sheets and Data Points

One of the ways we measure the progress of global warming is monitoring ice in the northern and southern hemispheres. While not a perfect measure of what’s going on with the globe, they are a good secondary indicator. It takes an enormous amount of energy to melt a glacier so declining glaciers and sea ice are a good indication that the planet continues to warm.

One indicator is the summer minimum of Arctic Sea Ice. Every year, the extent of ice in the Arctic Circle goes through seasonal variation, reaching its minimum in mid-September. Over the last 40 years, that minimum from about 7 million square miles to about 4.5.¹ In 2012, however, sea ice extent fell off a cliff, reaching a still record low of 3.4 million miles. The reasons for that were … complicated. But the next year it “recovered” to about 5.05 million square miles.

And that’s when the global warming denialists struck. Headlines blared about a “stunning” recovery of 40% in one year and falsely claimed that the sea ice was at a record level. Of course, left out was three decades of decline. And left out was that the 40% increase was because of the stunning drop the year before. I can illustrate it with this graph:

We saw a faint echo of this last year when Arctic Sea Ice “recovered” to 4.7 million square miles — lower than the 2013 recovery, incidentally. Left out was the that 2020 saw the second lowest sea ice extent on record and that 4.7 million was still very low by any historical standard. As you can see in the plot above, the long-term trend is clear.

Well, denialist tactics never really change.

Earlier this week, the deniosphere erupted again with a supposed indication that Greenland’s ice sheet recovered a “record amount of ice” — 7 gigatons — in one day.

NEW – Greenland ice sheet gained 7 Gigatons of mass in just one day yesterday — the largest daily gain ever recorded during the summer.https://t.co/2EvukuPcAM pic.twitter.com/eQBd2SJonJ

— Disclose.tv (@disclosetv) August 30, 2022

To be fair, this hasn’t gotten nearly as much as play as the sea ice thing did a decade ago. But the usual suspects touted it as proof that global warming was a myth, etc.

But it’s equally garbage. Greenland has lost about 280 Gt of ice per year over the last two decades, adding up to nearly 5 trillion tons of ice lost. And that pace is only accelerating. That doesn’t show up in the plot above because that’s a plot of surface ice gain and loss. It says, right on the web page that this excludes glaciers, which are a major form of ice loss. One mouse click will get you to this page, which shows the total ice mass and show no change in the two-decade trend. In short, this is just noise in the long-term trend. And it’s not unprecedented either, if you look at the rest of the data. Such large variations are normal because Greenland is very large.

This is an echo, actually, of an early deception in which Christopher Monckton claimed that the Greenland ice sheet was gaining ice. He was relying on surveys on high-altitude ice, which was gaining a small amount, and ignoring surveys of low-altitude ice, which was hemorrhaging melt.²

I harp on this because these deceptions are very very common in climate denial circles. And they play a pivotal role in how I changed my mind on the issue.

The year 1998 was a record-shattering year for heat. Natural variation drove the temperature a little hotter than the long-term trends, so much so that it would be almost decade before its record was broken. A few years later, climate skeptics were crowing that NASA has reprocessed their data and that 1998 was actually not the hottest year on record, 1934 was.

By this time, I had been a scientist for almost a decade. And I immediately had several questions that sprang from my own experience in data analysis:

• Was this the hottest temperature for the planet or for the United States?
• Was this an issue where one year went from being 0.01 degree colder than the other to 0.01 degree warmer?
• Was there some other factor affecting temperatures in 1934?

The answer to those questions was just the United States, yes and the Dust Bowl. We don’t measure America warming. We measure global warming. And a temporary warming trend in the US (caused, I might note, by bone-headed agricultural policies) did not change the long-term trend. Nor was there some conspiracy. A Y2K glitch had caused the NASA pages to leave out the corrections that raised the temperature in the early 20th century and softened the overall warming trend. This was before climate skeptics decided that such corrections were an evil conspiracy.

Once I saw that I was right on that, I began to look into other issues the climate skeptics raised. And while there was occasionally something legitimate — such as the incorrect statistical method used on the hockey stick curve — most of it was that kind of tommmyrot. Data taken out of context, local phenomena blown out of proportion, short-term variations cast as disproving long-term trends. This made me … well, I don’t call myself a “believer”. This isn’t a matter of faith. This made me accept that the scientific consensus was legitimately supported by the data.³

I used that phrase with precision, though. Global warming supporters like to say that 97% of scientists think global warming is real. That statistic means nothing. Thirty years ago, 97% of scientists wouldn’t have thought dark energy was real, but it was as real as taxes. What convinced me was that the data overwhelmingly support the theory. Temperature trends obviously. But the more you look, the more you find secondary indicator after secondary indicator showing that the problem is real. And yes, Virginia, that includes sea ice and Greenland glaciers. One day or one month or one year does not reverse a decades-long trend. And I guess it’s somewhat gratifying that these deceptions seem to be playing to a smaller and smaller audience every day.

1. The decline in the volume of sea ice has been even more precipitous, from about ten million cubic kilometers to four million.
2. I don’t think it’s a coincidence that this denialist talking point emerged on the same day a new study predicted dire consequences for the Greenland ice sheet.
3. I actually disagree with many of the solutions propose to the problem. But that’s a matter of how we solve the problem, not whether the problem exists.