Low Cloud Cover and Sea Surface Temperature

The International Satellite Cloud Climatology Project (ISCCP) has been collecting data on global cloud cover since 1983.  I downloaded the ISCCP data for low cloud cover (1983-2006) from KNMI Climate Explorer and I downloaded the HadSST sea surface temperature data from Wood for Trees.  Then I plotted the two data sets.  Who would have ever guessed there is an inverse correlation between low cloud cover and sea surface temperatures?

A cross-plot of low cloud cover vs. sea surface temperature yields a fairly decent r-squared of 0.36…

Correlation does not prove causation. So we don’t know if the 1998 climate shift caused the decrease in low cloud cover or if the decrease in low cloud cover caused the warming. Or if both were caused by the same thing. Or if they were unrelated… But we can pretty well rule out a positive climate feedback from low cloud cover.

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One Response to “Low Cloud Cover and Sea Surface Temperature”

  1. Mooloo Says:

    You can’t use that R-squared value or trend line for that plot.

    There are two entirely separate groupings, both of which will have individually no trend line at all, judging by eyeball. Whenever you have two separated groupings you will always get a halfway decent R2, even when there is no correlation. If the individual groupings don’t have the same trend then the correlation is an artifact and cannot be used. (Try it: make two entirely random but separated groupings and see that you will get a decent R2.)

    All you can say is lots of low cloud is associated with low temperature anomaly and few clouds is associated with higher temperatures. That’s pretty clear.

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