When it comes to Arctic sea ice, climate deniers have a hard time explaining why it has declined so far so fast. It’s one of the most telling signs of global warming, a stark message from Earth to deniers: it’s getting hot in here.
Climate deniers hate that. Since honesty and accuracy aren’t relevant to them, and doubt is their product, lately they’ve concentrated on a new tactic: use the wrong data.
The data du jour for climate deniers is sea ice extent from MASIE, the Multisensor Analyzed Sea Ice Extent. It combines satellite data (from passive microwave sensors) with visual imagery and other sources to produce an “operational product.” Its focus is to locate the sea ice edge in real time and alert users to how it’s changing, which is very useful for organizations like the U.S. Navy.
Sounds great. But should it be used to study long-term changes, to compare one year to another, to find out how this year’s sea ice stacks up agains the past? The answer is a resounding no. Says who? Says the people who produce the MASIE data, that’s who. From the documentation (emphasis mine):
While operational analyses are usually the most accurate and timely representation of sea ice, they have errors and biases that change over time. If one is interested in long-term trends in sea ice or how it responds to changing climate forcing, generally, it is best not to use an operational product, but rather one that is consistently produced and retroactively quality controlled. The NSIDC Sea Ice Index monthly ice extent, and the satellite passive microwave data sets upon which it is based, is one example. The Sea Ice Index gives a daily image of extent as well as monthly products. However, these daily images are not meant to be used for climate studies or for inferring anything longer than seasonal trends.
In case that doesn’t make it clear enough, soon after they say this:
… in general, it would not be appropriate to compare a recent MASIE extent value to one more than a few weeks old …
There’s no ambiguity about any of this. It’s not unclear. If you want to study how sea ice has changed over the years — hell, if you just want to compare one year to another — don’t use this data. The folks who make it said so.
That won’t stop climate deniers from doing exactly what they were told not to do. Why? Because the “biases that change over time” mean that sometimes the MASIE data give an answer that’s wrong, but climate deniers like.
Case in point: the GWPF (“Global Warming Policy Forum”) tells us that “Arctic Sea Ice Grows Back to 2006 Levels” because, says Susan Crockford, “Sea ice charts for 18 January from NSIDC Masie show exactly as much sea ice in 2017 as there was back in 2006 — 13.4 million km^2.”
Didn’t the MASIE documentation say “it would not be appropriate to compare a recent MASIE extent value to one more than a few weeks old“? Yes, it did. Isn’t January 18th 2017 more than a few weeks later than January 18th 2006? Yes, it is. Did anybody associated with GWPF read the documentation about this data? Maybe yes, maybe no, but if they did, then it would seem they don’t care.
What if we use the data which the MASIE documentation recommends for that kind of comparison, the sea ice index from NSIDC? Here’s how Arctic sea ice extent during the early months has changed over the years:
The values for 2017 are highlighted as a read line. The value for January 18th 2017 is marked by a blue dot with a circle around it, and was quite a bit lower than that for January 18th 2006. In fact it was lower than all previous January 18ths.
That’s what climate deniers do: use the wrong data so they can promote the wrong answer.
Of course that’s not all climate deniers do. Even if this January 18th’s extent of Arctic sea ice did dip as low as in 2006, so what? Nobody ever claimed that sea ice would decline smoothly every year so that every daily value had to be lower than all previous years’ daily values. We’ve said all along that in addition to the trend of sea ice loss, there are also fluctuations. The fluctuations are about the weather — the trend is about climate change.
And what does the trend tell us? That’s easiest to see if we translate sea ice extent to extent anomaly, the difference between a given day’s value and the long-term average for that same day. Then we can separate the climate changes from the ups and downs that come with the seasons (winter being still colder than summer). What, you wonder, do those anomalies look like? This:
The trend is downward. Fast (at about 65000 km^2 per year). The fluctuations are sizeable, but they don’t alter the trend. Yet from climate deniers we don’t hear about the trend, instead they crow about how the value for a single day might be the same as it was in 2006. And they can’t even get that right.
That’s what climate deniers do: focus on the short term, focus on “weather,” to draw attention away from the climate trend.
Of course that’s not all deniers do. They have an arsenal of weapons to spread doubt — that’s their product. They will question every study, dissect every method, and dispute every conclusion. It doesn’t matter how clear and beyond question it might be, they’ll throw doubt at it and hope something sticks. They don’t have to advance science, they just have to cloud public understanding.
They’ll even do it about something as undeniable as the loss of Arctic sea ice. If you wonder who is trying to pull the wool over your eyes, use this as a bellwether: Anybody who casts doubt on the loss of Arctic sea ice isn’t a skeptic, but a denier.
Because when it comes to Arctic sea ice, there’s no ambiguity about the trend. It’s not unclear. It’s going down faster than an Aerosmith groupie on an elevator.
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