8 ms·

Look at this graph of global sea ice extent for every year since 1978. It is insane how much an outlier the last 9 months are. Like sesame street level "one o

by dzdt 10y ago

Look at this graph of global sea ice extent for every year since 1978. It is insane how much an outlier the last 9 months are. Like sesame street level "one of these curves is not like the others" kind of outlier. https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/grf/nsidc_global_extent_byyear_b.png https://sites.google.com/site/arctischepinguin/home/sea-ice-...

drtz 10y ago
Is there data available for this prior to 1978?
- dzdt 10y ago
  No, there was no reliable measurement before satellites. Quoting wikipedia: Useful satellite data concerning sea ice began in December 1972 with the Electrically Scanning Microwave Radiometer (ESMR) instrument. However, this was not directly comparable with the later SMMR/SSMI, and so the practical record begins in late 1978 with the launch of NASA’s Scanning Multichannel Microwave Radiometer (SMMR) satellite. https://en.wikipedia.org/wiki/Measurement_of_sea_ice https://en.wikipedia.org/wiki/Measurement_of_sea_ice
M_Grey 10y ago
The worst models have always had really nasty asymptotes near the end, and it would certainly appear that we've reached that point in at least one critical system. Given the other issues arising at the same time (permafrost melting, methane release, coral bleaching...) it's not hard to see this as the beginning of the end.
- mirimir 10y ago
  Have models tended to predict disproportionate high-latitude warming?
  - johnny99 10y ago
    Yes. "When climate warms or cools, the changes are generally much more drastic at high latitudes than they are closer to equator. Temperatures measured in ice core bore holes in Greenland show, for instance, that central Greenland temperatures during the Last Glacial Maximum were about 20 degrees lower than today while the tropics were only a couple of degrees cooler." http://www.iceandclimate.nbi.ku.dk/research/climatechange/modelling_dynamics/modelling_greenhouse_warming/ http://www.iceandclimate.nbi.ku.dk/research/climatechange/mo...
    - mirimir 10y ago
      That implies that climate is at a relatively unique place. I mean, there's arguably no way that Greenland temperatures will be higher than tropical temperatures. But I guess that makes sense, in that we're in an interglacial.
nitrogen 10y ago
The scale does start somewhere around 16, though, so the relative change is like 10% to 15%.
pfarnsworth 10y ago
40 years is kind of nothing in terms of geological time. It's definitely an outlier but trend following has two different schools, that the trend will continue forever, or that the trend will revert to the mean. I'm in the camp that things will revert to mean for things like this, just like how California drought recovered so violently. I guess time will tell.
- archgoon 10y ago
  What mechanism do you propose would result in an increase in sea ice?
  - pfarnsworth 10y ago
    Obviously, humanity is going to curb its use of CO2 and the Earth will start to cool again.
    - flukus 10y ago
      It would still take centuries for the process to begin to reverse.
      - rangibaby 10y ago
        That's not really that long. If you're 20 today that will mean an inhabitable world for your great great great grandchildren. If they're really lucky, they will even be able to see some real animals.
        flukus 10y ago
        Assuming no mass extinctions or desperate wars in between.
      - pfarnsworth 10y ago
        So we should just give up? That's a stupid attitude to take.
TheNewLab 10y ago
Just out of curiosity, has someone verified that the graph is correct? (As it is no official plot and I am not sure what exact source was used.)
- dzdt 10y ago
  Yes. See https://www.google.com/amp/s/www.newscientist.com/article/2113493-global-sea-ice-has-reached-a-record-low-should-we-be-worried/amp/ https://www.google.com/amp/s/www.newscientist.com/article/21...
TeMPOraL 10y ago
I wonder what the error bars are. I mean, how much of the difference is actual, and how much can be explained by the measurement methods from 1980s being worse than contemporary? In general, why almost no one puts error bars on their charts? Or even any information about the precision/accuracy of measurements?
- splawn 10y ago
  Go to the source of the data. Both NASA and NOAA provide descriptions down to the last detail on how they get their data and what adjustments they make to it and why. Edit: In this case it's NSIDC. https://nsidc.org/ https://nsidc.org/

by dzdt 10y ago

drtz 10y ago

Is there data available for this prior to 1978?

dzdt 10y ago
No, there was no reliable measurement before satellites. Quoting wikipedia: Useful satellite data concerning sea ice began in December 1972 with the Electrically Scanning Microwave Radiometer (ESMR) instrument. However, this was not directly comparable with the later SMMR/SSMI, and so the practical record begins in late 1978 with the launch of NASA’s Scanning Multichannel Microwave Radiometer (SMMR) satellite. https://en.wikipedia.org/wiki/Measurement_of_sea_ice https://en.wikipedia.org/wiki/Measurement_of_sea_ice

M_Grey 10y ago

The worst models have always had really nasty asymptotes near the end, and it would certainly appear that we've reached that point in at least one critical system. Given the other issues arising at the same time (permafrost melting, methane release, coral bleaching...) it's not hard to see this as the beginning of the end.

mirimir 10y ago
Have models tended to predict disproportionate high-latitude warming?
- johnny99 10y ago
  Yes. "When climate warms or cools, the changes are generally much more drastic at high latitudes than they are closer to equator. Temperatures measured in ice core bore holes in Greenland show, for instance, that central Greenland temperatures during the Last Glacial Maximum were about 20 degrees lower than today while the tropics were only a couple of degrees cooler." http://www.iceandclimate.nbi.ku.dk/research/climatechange/modelling_dynamics/modelling_greenhouse_warming/ http://www.iceandclimate.nbi.ku.dk/research/climatechange/mo...
  - mirimir 10y ago
    That implies that climate is at a relatively unique place. I mean, there's arguably no way that Greenland temperatures will be higher than tropical temperatures. But I guess that makes sense, in that we're in an interglacial.

nitrogen 10y ago

The scale does start somewhere around 16, though, so the relative change is like 10% to 15%.

pfarnsworth 10y ago

40 years is kind of nothing in terms of geological time. It's definitely an outlier but trend following has two different schools, that the trend will continue forever, or that the trend will revert to the mean. I'm in the camp that things will revert to mean for things like this, just like how California drought recovered so violently. I guess time will tell.

archgoon 10y ago
What mechanism do you propose would result in an increase in sea ice?
- pfarnsworth 10y ago
  Obviously, humanity is going to curb its use of CO2 and the Earth will start to cool again.
  - flukus 10y ago
    It would still take centuries for the process to begin to reverse.
    - rangibaby 10y ago
      That's not really that long. If you're 20 today that will mean an inhabitable world for your great great great grandchildren. If they're really lucky, they will even be able to see some real animals.
      - flukus 10y ago
        Assuming no mass extinctions or desperate wars in between.
    - pfarnsworth 10y ago
      So we should just give up? That's a stupid attitude to take.

TheNewLab 10y ago

Just out of curiosity, has someone verified that the graph is correct? (As it is no official plot and I am not sure what exact source was used.)

dzdt 10y ago
Yes. See https://www.google.com/amp/s/www.newscientist.com/article/2113493-global-sea-ice-has-reached-a-record-low-should-we-be-worried/amp/ https://www.google.com/amp/s/www.newscientist.com/article/21...

TeMPOraL 10y ago

I wonder what the error bars are. I mean, how much of the difference is actual, and how much can be explained by the measurement methods from 1980s being worse than contemporary? In general, why almost no one puts error bars on their charts? Or even any information about the precision/accuracy of measurements?

splawn 10y ago
Go to the source of the data. Both NASA and NOAA provide descriptions down to the last detail on how they get their data and what adjustments they make to it and why. Edit: In this case it's NSIDC. https://nsidc.org/ https://nsidc.org/