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Are California Heatwaves Getting Hotter?

October 14, 2016

By Paul Homewood




Are heatwaves in California getting worse?

I am sure that the vast majority of people would say yes. And that is certainly the relentless message put out by vested interests, and their buddies in the media.

If we check out the summer maximum temperature trends from NOAA, we find that even this summer and last year’s have not been as hot as 1960. Other summers, such as 1981 and 1996 also feature up there.




What we do find instead is that minimum temperatures have risen sharply. This strongly suggests that there is a significant UHI effect.




These trends are, of course, based on the heavily adjusted temperatures used by NOAA, which tend to cool the 1920s and 30s. To get a better perspective, we can look at whisker plots of daily temperatures, which are recorded before adjustments take place.

CDIAC list USHCN stations with the longest running and most complete data here. For California, they give eight stations. These provide a good geographical coverage (see blue flags)




The whisker plots for these stations are below. Unfortunately they are not updated for last year yet, but they consistently show that the highest temperatures have not been increasing in recent years, and for the most part were higher in the past.













Regardless of the data for last year, which we know was affected by unusual meteorological conditions, climatic, as opposed to weather, trends are quite clear – heatwaves are not getting hotter in California.

  1. A C Osborn permalink
    October 14, 2016 7:13 pm

    I thought that the “droughts” in that area were man made, ie population and farming explosions without the relevant increase stored water to cope with them.

    • A C Osborn permalink
      October 14, 2016 7:14 pm

      I should have said
      I thought that the current “droughts” in that area were man made, ie population and farming explosions without the relevant increase stored water to cope with them.

  2. Kelvin Vaughan permalink
    October 14, 2016 7:44 pm

    If you take air at 14°C and fill half a container with it. Then took some air at 16°C and filled the rest of the container with it the resultant temperature in the container would be 15°C would it not? Therefor to raise the atmosphere from 14°C to 15°C would surely need back radiation to be 16°C wouldn’t it?

  3. esalil permalink
    October 14, 2016 7:51 pm

    Kevin, no it would not.

    • kelvin Vaughan permalink
      October 15, 2016 9:15 am

      Esalil Why not?

  4. Broadlands permalink
    October 14, 2016 10:07 pm

    Paul… I have just looked at the NOAA summer (JJA) data for California 1895-2016. The linear trends for 1960-2016 are all positive, MAX, MIN, MEAN…about +0.4° per decade.

    You need to plot the trend lines from their data. If you plot the 1901-1931 average temperature trend it is +0.5°F per decade…. greater than the 1960-2016 trend. Thus, summers since 1960 have been trending warmer but not any warmer than back in the warmer parts of the last century…. before our added CO2 amounted to much?

    • Tim Hammond permalink
      October 15, 2016 9:30 am

      The post is about heatwaves, not temperature trends. Have maximums been getting higher is a different question than the one you are answering. It’s easy to have a positive trend without the maximums increasing.

      • JonA permalink
        October 15, 2016 12:46 pm

        Indeed. The post itself suggests that it’s more likely due to an increasing
        trend in minimum temps. Tav is a simple composite of Tmax + Tmin /2.

  5. dennisambler permalink
    October 15, 2016 11:17 am

    Nothing new under the sun……

    “Researchers Find Evidence Of 16th Century Epic Drought Over North America”

    “A group of researchers who study tree ring records have found evidence of a “mega-drought” in the 16th century that wreaked havoc for decades in the lives of the early Spanish and English settlers and American Indians throughout Mexico and North America.”

  6. Paul2 permalink
    October 16, 2016 10:50 am

    Interesting article here. I’d be interested to see how you see this scenario unfolding:

  7. George permalink
    October 17, 2016 6:03 am

    To the owner(s) of this blog. You seem to be a climate change denier(s). Ever watched the “Chasing Ice” documentary? It might help on settling your decision…forever.

    • October 17, 2016 9:11 am

      I don’t deny that climate changes.

      I simply deal in facts, which maybe you should pay more attention to.

  8. November 19, 2016 11:59 pm

    Reblogged this on Climate Collections.

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