Global Sea Ice Area

According to many sources (including National Snow and Ice Data Center), global sea ice has been drastically decreasing for a long time. Today I will show you a very legitimate source that will have you question this fact. The data comes from NASA, specifically here, or here. The relevant data variable is called FRSEAICE.

I analyzed monthly data over exactly 39 years, from 1982/10 to 2021/09. Here is my result:

Linear Regression Trend: From 0.03625 To 0.03631 is +0.171%

The “Sea Ice Area Fraction” is a proportion of the entire Earth’s surface that is ice over water. As you can see, about 3.6% (on average) of our planet’s area is covered in ice over water. In the last 39 years, ice over water has INCREASED, and not decreased, as popularly claimed.

The observed increase of 0.00006 is equivalent to ~30,600 km², roughly the size of Belgium.

Now let’s break it down by hemisphere:

North Hemisphere
Linear Regression Trend: From 0.04039 To 0.03405 is -15.707%
South Hemisphere
Linear Regression Trend: From 0.03214 To 0.03855 is +19.947%

The large loss in sea ice in the northern hemisphere is more than made up for in a larger gain in sea ice in the southern hemisphere.

That’s all. Enjoy 🙂 -Zoe


# Zoe Phin, 2021/11/27
# File:
# Run: .; require; download; ice; plot
# Data:

require() { sudo apt-get install -y gmt gnuplot; }
download() { user=username; pass=password
    let n=1; for y in {1982..2021}; do for m in {01..12}; do
        [ $y -eq 1992 ] && n=2; [ $y -eq 2001 ] && n=3; [ $y -eq 2011 ] && n=4;  
        wget -O M$y$ --user=$user --password=$pass -c $url
one() {
    ncks -HC --trd -v $1 M$2$ | awk -F '[= ]' -vy=$2 -vm=$3 '{ 
        n=2; if ($4 == "-90" || $4 == "90") { n=4; $4=89.875 }
        a=6378.137; e=1-6356.752^2/a^2; r=atan2(0,-1)/180;
        SA+=A; S+=$8*A 
    } END { printf "%.2f %.5f\n", y+m/12-1/24, S/SA }'
ice() { for y in {1982..2021}; do for m in {01..12}; do one FRSEAICE $y $m; done; done | tee ice.csv; }
plot() { 
    cat ice.csv | awk '$1>1982.8 {print}' | gmt gmtregress | awk 'NR>1{print $1" "$2" "$3}' > ice.dat

    sed -n '1p;$p' ice.dat | awk 'NR==1{S=$3} NR==2{E=$3} END { printf "\
    Trend: From %.5f To %.5f is %+.3f%\n", S, E, (E/S-1)*100 }'

    echo "set term png size 740,470; unset key; set title 'Global Sea Ice Area Fraction'
    set grid ytics xtics; set mxtics 5; set mytics 5; set ytics format '%.3f'
    set xrange [1982.5:2022.5]; 
    plot 'ice.dat' u 1:2 w l lw 1 lc rgb '#0000EE',\
         'ice.dat' u 1:3 w l lw 2 lc rgb '#000088" | gnuplot > ice.png

Note: This data requires user registration here. Replace username and password in the code.

Published by Zoe Phin

38 thoughts on “Global Sea Ice Area

  1. Thanks, Zoe. Most interesting, as usual. However, in this case you’re not looking at data. Instead, it’s the output of a computer “reanalysis” model. As the site says:

    “This collection consists of assimilated surface flux diagnostics, such as total precipitation, bias corrected total precipitation, surface air temperature, surface specific humidity, surface wind speed, and evaporation from turbulence. The “surface” in this data collection is the model surface layer.”

    Doesn’t mean it’s wrong … just makes me nervous, is all.

    My own analysis of the global sea ice is below.

    Ice Follies

    My very best to you,


    Liked by 2 people

    1. Fair enough, but how do the others do it? I don’t think they use a ruler. I assume the models I base it on are no worse than other models. I presume NASA is competent. Ice is not a very difficult thing to capture from space.

      The NSIDC data you used is very different from what my link shows. I think yours is correct, and theirs is propaganda.

      I agree with you that there is “no statistically significant overall trend in global ice area”.

      Thank you, Willis.


  2. Good morning zoe and a good Sunday. As I always say, women are capable of great things compared to us men. You are an example of this. As always great articles and it is always a pleasure to read them. Thanks again.

    Liked by 1 person

    1. Thanks, but I don’t know about that. All the data and tools I use were made by men. I just have a high IQ, so it’s easy for me to figure things out. I was raised by my single father after my mom died, and I pretty much take after him.

      Liked by 1 person

      1. Please don’t mention that you have a high IQ.
        That’s bragging.
        We came to that conclusion from your work long ago.
        Calling yourself Mrs. Smarty Pants is okay,
        because it’s funny.

        Just my two cents …
        from your low IQ reader,
        with a NY public school

        Liked by 1 person

  3. Zoe, what does it look like if you plot the winter maximum and summer minimum as separate trends?
    The similarity to snow is striking.


  4. Wonderful. Short. To the point. I agree with you that estimating sea ice extent (not volume) should not be terribly difficult for NASA. Primary point for me (and I believe there are multiple sources of data) is falsification of the idea that oceans are rising because of massive ice melt. More proof that the pillars of climate change are simply not happening, but none of the major media outlets anywhere in the world have the temerity to say so. Thank you. How ’bout a quick estimate on the range of estimates on ice volume? Not sure what data is available, but what I suspect is that altering the estimate of how much Antarctica is sinking probably swamps the estimated changes in volume due to models of underwater melting. Your number one fan in Westchester, NY 🙂 JP


    1. Petr Beckmann pointed out that both salt and uranium content in oceans are increasing–back when unnamed scientist impersonators predicted global freezing. So some sea level rise would follow from silting-up of all the mineral content flowing downriver. In physics I was taught that ice floats on salt water so that 1/9 sticks out. This does work as a mnemonic for recalling that 1/9 of humanity lives south of the Equator. Also, remember the Brewer-Dobson effect accounting for fallout measurements north and south of the equator? Zoe’s graphs bring to mind how gases and particles are slow to mix across the equator. Then again there is not much to stand on in the Southern hemisphere… Oz, Antarctica and the skinny parts of Africa and South America. So… albedo? water vapor?


    1. I can readily tell you that my code is very slow because it’s text-based parsing. It takes about 7 minutes on my laptop to transform 480 downloaded files (37 GB!) to area-averaged monthly tables. Those tables are plotted in 2 seconds.

      I do north and south hemisphere manually outside provided code, by changing one line, and rerun it. So 7 times 3 = 21 minutes.

      The download was several hours. I left it overnight.


  5. Help me out here: Which post(s)?
    I take it you have read my post? My results point to the warming of the far north, possibly being due to more volcanic activity and more release of geothermal energy. Until recently I did not even know that there are also nuclear reactions inside earth. What do you think is the reason for the warming of the earth?

    Liked by 1 person

    1. Right. If our surface was liquid, you’d see convection in real time. It’s solid, but it’s not a perfect solid. Convection still tries. We get extra heat seaping out all over the place. Sometimes it stops and we get cooling.

      Geothermal is not the full story, but I think it’s ~half. The other half is cloud cover changes, solar-cosmic rays, etc.

      Please read blog from beginning to end 🙂

      Liked by 1 person

  6. Interesting! Thanks. I will set up a plan to read all your posts.
    My wife loved watching the volcanoes erupt in Iceland and that made me wonder…..
    I could also see from my own results that somehow the heat from the Sh disappears as hot moist air to the north where it releases the energy when the moisture condenses.
    What puzzles me is that the temperature in Antarctica is generally much lower than that at the north pole. That means that the differential temperature between the Equator and the south pole is much bigger.
    So why did the (hot, moist) wind not go south?


      1. Zoe Phin December 4, 2021 at 2:52 PM

        “… SH gets more sunlight.”

        Actually and curiously, it doesn’t get more sunlight. Here’s the reason.

        When the earth is nearer to the sun, it gets stronger sunlight. BUT, it’s also moving faster, so it spends less time there.

        Conversely, when it’s further away from the sun it gets less sunlight … but because it’s moving slower, it spends more time there.

        And since both sunlight and gravity fall off as the square of the distance, these two effects exactly cancel each other out, and both hemispheres get exactly the same number of kilowatt-hours of energy per year.

        My best to you as always,


        Liked by 1 person

      2. The circumpolar current probably has a lot of influence in keeping the south pole cold. Such circulation is prohobited around the northern pole.Antarctica remained ice free for at least 20 million years after it found its location above the south pole. Why? Was it because Australia remained attached and prohibited the circumpiolar current? Also, the northpole has a large influx of heat from the Gulf Stream.

        Liked by 1 person

      3. ‘If you remove elevation….’

        True. Its elevation is about 3000m? So what you are saying is that 3 km up, the air must be ( a lot) colder above the north pole than the south pole; hence the reason why most of the warm moist air turned north. Am I correct in saying that this is what you think?
        Somehow I doubt that. I wonder if perhaps there is some gravitational /centrifugal pull that sucks (most) of the moist air northward. This may turn around in time to come by cyclic factors. (Gleisberg/Eddy)
        I liked what I saw so far on that geothermal issue, especially about that ‘0.1’ W/m2
        Would you willing to do a post on this on I can translate it for you.


        1. I’m not sure what you’re saying, and I’m sorry, I don’t have the time to figure out circulation mysteries. I sometimes struggle to answer free-form questions. What I put a great deal of thought into, I publish.


  7. Zoe Phin says (on the Dutch blog):
    And you can’t predict the inherent temperature at the surface by only knowing the geothermal heat flux!

    Hi Zoe, nice of you to come and visit us again! We like you! Perhaps you will one day do a post here? I will translate it for you.

    1) looking carefully at my results in my recent post for the warming of the oceans, Table 2
    I would bet that there is some extra warming due geothermal /volcanic action in around the arctic circle!
    D’Andrea et al (2011) used a special way to detect the Eddy cycle but mentioned as a possible cause a combination of solar and volcanic activity.
    For more about the Eddy cycle:
    2) Table 1 of my recent post shows something else. The maxima went up in the Sh but the minima went down. But the averages in the Sh (Means) stayed almost unchanged. So where did the extra heat go? It looks to me as if the hot moist air was sucked northward. Hence the increase in minima and the average temperature in the NH. I cannot believe that it is the temperature differential between the NP and the equator that is only responsible here. Why did the hot moist air not go south? We suffered droughts here for almost a decade. I am thinking that there is some extra gravitational or centrifugal force that pulled the hot moist air northward. This could be cyclic, as also my trend analysis suggested. The Gleissberg is often shown as a sinus wave and we are now moving into lower part. For more about Gleissberg , see here:
    3) land use, especially there where desert is turned green, definitely traps heat, as shown by a sharp increase in minima (Las Vegas)

    CO2 is not the problem.

    Liked by 1 person

    1. Sorry you were blocked while I was away on vacation.

      Thank you. Not sure if I can trust the volume measurements one way or another.

      Yes, geothermal has a life of its own.


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