Are Record Ocean Surface Temperatures Due to Record Low Wind Speeds?

September 18th, 2014 by Roy W. Spencer, Ph. D.

The fortuitous revelation of record warm sea surface temperatures in August, only days before Climate Summit 2014, begs the question — why?

Why were SSTs so warm? (Not “Why announce it just before Leonardo DiCaprio’s coronation?”)

As readers here know, I follow the “ocean products” produced by RSS from the SSM/I and SSMIS satellite sensors, and a curious thing has been shaping up in the last few years.

Global average ocean surface wind speeds have been decreasing. In fact, August 2014 had the lowest surface wind speed in about 25 years.

Even after I correct for the typically lower wind speeds that occur with El Nino approaching (-0.5 m/s wind decrease per unit Multivariate ENSO Index value), it’s still at near a record-low since the satellite record began:

SSM/I and SSMIS monthly global ocean average surface wind speed anomalies.

SSM/I and SSMIS monthly global ocean average surface wind speed anomalies.

For those wondering what these wind fields look like, here are the average gridpoint wind speeds for August (1 m/sec is about 2 knots), both as absolute values and as anomalies (departures from the mean):

Grid point ocean surface wind speeds from SSMIS in August 2014, shown as absolute values and anomalies.

Gridpoint ocean surface wind speeds from SSMIS in August 2014, shown as absolute values and anomalies.

Why is Wind Speed Important to SST?

Wind-driven evaporation is the largest source of heat loss from water bodies, including the global oceans. Assuming a global average rate of ocean surface heat loss of 90 W/m2 (which is mostly evaporative), the August value of about 4-5% below the long-term average would mean about 4 W/m2 less cooling of the ocean surface.

Importantly, this 4 W/m2 reduction in heat loss is LARGER than the supposed anthropogenic radiative forcing of about 2.3 W/m2, the IPCC’s RCP6 current radiative forcing value. (The true radiative imbalance is actually less than that because warming has offset some of it with increase IR emission to space). The net result that the wind speed effect is probably at least 4 times the anthropogenic effect.

So, what’s my point? Natural variations in all kinds of things are going on, including a reduction in wind-driven evaporation, which likely contributed to “record warm” SSTs in August.

I have no strong opinions of why the reduction in wind speeds is occurring. Usually the best guess in climate is that it’s part of some cycle that will reverse itself at some point. Only time will tell.


45 Responses to “Are Record Ocean Surface Temperatures Due to Record Low Wind Speeds?”

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  1. Beta Blocker says:

    Is it possible a gradually warming world somehow results in less wind over the oceans?

    • AlecM says:

      A warmer world has lower temperature gradients Equator to Pole. Wind is set by the pressure hence temperature gradient. Therefore, there is some credence to your point.

      • TedM says:

        Except it didn’t suddenly get globally warmer in August.

        • bassman says:

          Your right TedM, It started getting warmer around March/April. Temps for NOAA and JMA are now in good position to break records for 2014. All it took was ENSO neutral conditions.

      • Streetcred says:

        We’ve had a cooler than recent winter in the SH and by all accounts the NH has had a cool summer … yes the gradient will be shallower, but by all accounts the polar regions are getting cooler once more which should continue to flatten the T gradient.

  2. gbaikie says:

    –I have no strong opinions of why the reduction in wind speeds is occurring. Usually the best guess in climate is that it’s part of some cycle that will reverse itself at some point. Only time will tell.–

    Perhaps it’s better or different measurement.

    And it seems it depends upon type of wind. A constant trade wind will be more relevant to moving water [laterally and vertically] and less about increased evaporation.

    Generally tropical water will have a lot evaporation whatever the wind is, and increased wind will mix the warmer top surface with lower water. So increase wind will cause increase in evaporation, but could end up storing more heat in the water.
    Increased wind over a solar pond will always decrease the temperature of water at meter depth, but the ocean is not a solar pond [one does not see 80 C water at meter depth] or the ocean is more similar to solar pond if solar ponds had 10 feet high waves. If one could becalm the ocean, the ocean would behave more like a deep water solar pond [like Black Sea [sort of] and increasing the wind from the state of becalmed ocean would warm surface and cause a lot evaporation.

    • Kelvin Vaughan says:

      It’s all the wind generators taking the energy out of the wind which is resulting in global warming. That would be a laugh.

  3. A C Osborn says:

    Why do you believe that the 2014 August SSTs are hottest ever?
    Satellite data shows that August 1998 was warmer, or do you disagree with that data?
    Has there been a “colour” change since 1998?

  4. Jim Curtis says:

    My totally uneducated guess is the tropic-to-polar temperature difference. I’ve always been told that that is the driver of major winds (trade winds). Your map shows most of the decrease in the NH where the pole has been warming, and some increase in the SH where temp diff is holding or increasing.

  5. MikeN says:

    So there is evidence after all for my hypothesis that renewable energy causes global warming.

  6. rick says:

    These attempts to understand the climate in detail are getting sillier and sillier.

    Reminiscent of the cautionary tale of the the blind men feeling an elephant.

    They came to wildly different conclusions – but equally stupid ones.

  7. rick says:

    I am referring to the “scientists”, not the “commenters”, in my comment above. We just get sucked into the madness!

  8. willywolfe says:

    Darn, just when Al Gore invested in a fleet of carbon friendly sailing ships for global shipping. Don’t worry though, Al will still make a profit from carbon credits even if they’re stuck in the doldrums for the next ten years!

  9. geran says:

    It is getting to the point that we have to question everything. Are the “record” SST’s real? If so, where are the hurricanes? What about El Nino?

    We live in interesting times….

  10. Bob Tisdale says:

    Hi Roy.

    Interesting observation and discussion of wind speeds. As you’re likely aware, the unusual warming is focused on the North Pacific:
    http://bobtisdale.wordpress.com/2014/08/16/on-the-recent-record-high-global-sea-surface-temperatures-the-wheres-and-whys/

    Does the wind speed data you’re using also show an anomalous slowdown in the North Pacific or is it a general weakening of surface winds globally in recent years?

    Another note: A weakening of surface winds would also reduce the amount of upwelling of cool subsurface waters, which also contributes to warming.

    Cheers

  11. bassman says:

    Check NOAA for what Roy is referring to. The last 12 months are now the hottest on record (NOAA)August was hottest on record by a good margin for JMA and NOAA, barely for NASA. A slackening of winds will cause quite a bit of excess heat as Roy mentions. Nothing unusual here, background CO2 forcing on top of natural variation breaking more records. If the PDO stays positive this will only push temps higher and likely end the hiatus.

    Rick, “Attempts to understand” is nothing to ridicule, it’s what any inquiring minds do.

    I have said many times on here that when natural variability swings back the other way, surface warming will increase at a greater rate. Here we are now about to have an ENSO neutral year break surface temp records in at least 2 data sets (NOAA and maybe JMA), NASA will likely tie or just fall short. The background forcing of CO2 will keep showing itself one way or another no matter how much “sloshing around” the atmosphere or Oceans do.

    Roy, do you think the slackening of the winds is a good indication that the niño is imminent?

  12. ossqss says:

    Bassman, I view it differently. Co2 has gone up nearly 10% over 20 years and the root expectation has not come to fruition in your scenario to date.

    I think you can substitute saturation for slosh in you statement.

    Now considering the supposed rise in warming we have seen over the prior 60 years, a more defined state of equilibrium may be impacting general wind speed and patterns. Less of a delta, atmospheric and oceanic, in temperature for energy to flow as it has historically, if you will.

    Now about the historic measuring processes for such global wind speed assessments:

    What’s the resolution and timeframe involved? Just curious.

  13. Dr. Strangelove says:

    Record warm SST cherry picking. That’s the North Pacific. What about the Southern Ocean and Arctic Ocean? Record high sea ice in Southern Ocean since 1979. Highest sea ice in Arctic since 2007. Also due to global warming?

    Let’s look at GISS data for global land and ocean. Looks like 2010, 2007, 2002 and 1998 are all warmer than 2014. Is it cooling? BTW if the ocean is at record warm and the world is still cooler than previous years, the land cooled. The cooling must be bigger since land is only 29% of surface area. Where do humans live? North Pacific or on land?

  14. bassman says:

    Dr. Stangelove, All of the oceans are included by NOAA. I shouldn’t have to state this but apparently I do. If the ocean surface is warming back to record levels (not just deeper ocean warming) then it will begin to influence land surfaces also. If we get an el nino, even a weak one, this will push 2015 into the record warmest year beating out 2014 (granted a violent return to la nina like what happened in 2010 could put a damper on this).

    The slowdown was only in surface warming, all other measures of energy gain on planet earth have remained mostly constant or even accelerated. Now that natural variability is swinging back to the positive we can expect more and more “hottest month on record”, as we have seen all spring and summer for the JMA, NOAA and NASA data sets.

    • Dr. Strangelove says:

      If you were paying attention you would realize that not all the oceans warmed. It’s the North Pacific warming as I said that pulled up the average.

      “If the ocean surface is warming back to record levels (not just deeper ocean warming) then it will begin to influence land surfaces also.”

      Nice idea. Where’s the empirical data to prove it? Data show record warm ocean but cooler world than previous years. If the data are against us, let’s dwell in the world of ideas.

      “If we get an el nino, even a weak one, this will push 2015 into the record warmest year beating out 2014”

      If you only beat 2014 that’s not “record warmest year.” It sounds scary but 2014 is not even a spectacularly warm year.

      “The slowdown was only in surface warming, all other measures of energy gain on planet earth have remained mostly constant or even accelerated.”

      Unfortunately for you but climate is in earth’s surface. If surface temperature increased by 1 C but the bottom of the Pacific Ocean cooled, will you declare global cooling?

      “Now that natural variability is swinging back to the positive we can expect more and more “hottest month on record”, as we have seen all spring and summer for the JMA, NOAA and NASA data sets.”

      Apparently your “hottest month on record” is freezing the sea ice in both poles and cooler than the previous years I mentioned. We have to wait for natural variability to warm the world? That’s an unintentional admission that humans play a minor or insignificant role in climate change.

  15. rick says:

    “…hottest month on record…”

    This, according to NASA, was January 2007 with an anomaly of +0.93 C compared to August 2014 at +0.70. This latter was a record for August. The previous record was August 2011 which was +0.69, and before that was August 1998 at +0.68.

    The 19th Century record (still according to the same NASA/GISS Table) was set in the August my Great-Great-Grand-Mother was born; August 1884 at +0.25 C.

    • Werner Brozek says:

      The actual temperature varies by 3.8 C during the year with January the coldest and July the warmest. So a hot January is still colder than a cold July or August.
      http://theinconvenientskeptic.com/2013/03/misunderstanding-of-the-global-temperature-anomaly/

      • dave says:

        “…the actual temperature varies…January the coldest…”

        If you mean “effective black-body temperature measured from space” then it certainly varies through the year – a lot.
        But it seems to me that January is the warmest time in this particular sense.

        The earth is nearest the sun about January 3. Six months later it is 3.3% farther away. That means (by inverse square geometrical considerations) that the input from the sun is 6.7% lower in July. Given that:

        1. The albedo of the earth is steady
        2. The heat budget of the earth is very close to balance
        all the time,

        it follows (by the S-B fourth power law) that the effective MODELLED temperature in July must be 1.3% lower i.e. the 3.8 C you mention.

        • Werner Brozek says:

          Please read the site that I referenced. I know that it sounds contradictory, but Earth is actually warmest when the northern hemisphere is warmest, even though, as you say, the sun is furthest away. A high sun warms land much faster than the ocean.

  16. ren says:

    The surface temperature in the eastern US on 23/09/2014.
    http://earth.nullschool.net/#2014/09/23/0600Z/wind/surface/level/overlay=temp/orthographic=-71.01,38.50,1925
    Click on the map and check.

  17. bernie says:

    Quel yawn-fest. Asked for his views on the Stock Market, the financier J P Morgan is supposed to have replied “It will fluctuate”.

  18. ren says:

    The cold central Atlantic is associated with a weak Gulf Stream.

  19. ren says:

    Roy Spencer is right. The most important is the circulation and wind strength.

  20. bernie says:

    Ren has given us links to pretty pictures. The winds off the Eastern coast of N America remind me of “Jeannie with the
    Light Brown Hair.”

    The quote below is from the Climate Prediction Center of the NOAA and is dated September 15th.

    “The most recent Oceanic Nino Index Value (June-August 2014) is 0.0 degrees C.”

    I can’t take much more of this excitement.

  21. dave says:

    “…0.0 degrees C…excitement.”

    Here comes the extreme weather. It was in the tea-leaves this morning.

  22. Kusigrosz says:

    Doesn’t wind speed have an effect on ocean albedo, especially at high solar zenith angles?

  23. bwdave says:

    Maybe, it’s all of the wind turbines taking the energy out out of the wind. 😉

  24. https://tallbloke.wordpress.com/2014/06/26/does-a-steep-drop-in-solar-activity-imply-an-equally-steep-drop-in-temperatures/comment-page-1/

    This is what the data from this study shows which is a strong correlation between solar activity and sea surface temperatures.

  25. One observation is over the past many years it seems like the Antarctic Polar Vortex has been strengthening(a more positive AAO) while the Arctic Polar Vortex has been weakening.(a more negative AO)

    This feature also seems to correlate with the wind anomalies with stronger winds in general in the S.H. in contrast to the N.H. when one looks at the data Dr. Spencer just provided.

    Which would correspond with a stronger AAO(more zonal stronger winds/ greater temp gradient pole to equator) and a weaker AO(less zonal weaker winds/ lesser temp. gradient pole to equator).

    I also think wind speeds and water temperatures are tied with one another.

    In addition because the warm up of the Northern Pacific water was so rapid from cold conditions just a few years back that that lends itself strongly to natural variability.

    If it were tied to GHG this warm up of sea surface temperatures would first of all be gradual and secondly would be global in nature which is not the case.

    Look at the map Ren sent showing sea surface temp. deviations in his recent post. Not global in nature.

  26. Ric Werme says:

    The wind speed decline at the Blue Hill Weather Observatory has been going on for 35 years. I have no idea why, some people say it’s from tree growth at the summit, some say its due to construction off the hill.

    It’s gone from about 7 m/sec in the first half of the 20th century to about 5.5. That’s a kinetic energy loss of some 38%! (Yeah, I shouldn’t compute the kinetic energy of an averaged wind speed, but I don’t have the average of the speed squared.)

    http://www.bluehill.org/climate/annwind.gif

  27. yonason says:

    Ask not for whom the wind blows. It just blows.

  28. Genghis says:

    Roy,

    I can verify that the wind through evaporation and mixing controls the skin layer temperature of the ocean.

    I have taken hundreds of surface temperature (IR gun readings) in the Bahamas and Caribbean.

  29. Alec aka daffy duck says:

    Just thought I would pass this along:

    STUDY LINKS CHANGING WINDS TO WARMING IN PACIFIC
    http://hosted.ap.org/dynamic/stories/U/US_PACIFIC_WARMING_STUDY?SITE=AP&SECTION=HOME&TEMPLATE=DEFAULT&CTIME=2014-09-22-15-40-23

    • David L. Hagen says:

      “Changing winds appear to explain a very large fraction of the warming from year to year, decade to decade and the long-term,” said study leader James Johnstone . . .
      When coastal wind speeds weaken, they result in less evaporation from the sea surface and unusually low pressure that alters ocean currents and causes temperatures to rise over time.

      The study found that weakening winds accounted for more than 80% of the warming trend along the Pacific Northwest coast between Washington and Northern California. In Southern California, weaker winds were responsible for about 60% of the increased warming.

      West Coast warming linked to naturally occurring changes
      When California news touts natural changes – that times they are a changing!

  30. Ulric Lyons says:

    Hi Roy,
    I have been developing solar based long range weather forecasts, with a particular interest in solar plasma variability, and I predicted a weaker solar signal through this August. Lower land temperatures in many regions, a negative NAO, and higher SST’s in the ENSO region and at high latitudes is just what I expected. Your idea that evaporation rates fell due to wind speed declines is very interesting, but surely lower wind speeds would reduce cold upwelling too?
    The SST rise seems to be very widespread though, as running through these weekly maps from mid July to the end of Sept shows (note what happens in the Benguela Niño region through Aug). The contrast between the end of Aug and the end of Sept is stark too:
    http://weather.unisys.com/archive/sst/
    http://weather.unisys.com/archive/sst/sst_anom-140831.gif
    http://weather.unisys.com/archive/sst/sst_anom-140928.gif