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U.S. Climate Extremes Index

January 14, 2013

By Paul Homewood




As part of their US Climate Extremes Index, NCDC run one for “Days with/without precipitation, as shown above.


They define it as

The sum of (a) percentage of the United States with a much greater than normal number of days with precipitation and (b) percentage of the United States with a much greater than normal number of days without precipitation.”


A simple average of rainfall statistics may show a “normal year”, but could hide the fact that half the country is in drought, and the other half suffering floods! This index attempts to get around this problem, although it does not quantify rainfall amounts, simply rain days.

Nevertheless, it gives a good overall picture of what was happening last year. Far from the claims of extreme weather, that we are used to hearing from Katharine Hayhoe and co, 2012 was remarkably, well, unremarkable!

Days without rainfall were pretty much normal by historical standards, while areas with more wet days than normal were well below normal.

It is also noticeable that the extremes of both types, that were seen regularly in the past, have not been a feature in recent years.

  1. Jeffery permalink
    January 14, 2013 4:48 pm

    Unfortunately, the graph looks to be trending generally upward.

  2. John F. Hultquist permalink
    January 14, 2013 5:51 pm

    There are ups and downs and some fantastic outliers (the “extremes of both types”). For example, 1910 seems oddly down. Three years seem quite high, greater than 30%. 1977 was a drought year — strong in the west but not in the places that were dry last year. The meteorological explanations always involve a blocking High Pressure cell. The link below explains and has a map for 1976-77.

    [This was my first visit to “climateinw” (INW**) the name ‘abatz’ seems to be associated with ‘Joern Abatz’ writing about the climate of the **Inland Northwest USA. This is an area in eastern WA and OR and western Idaho. This has also been called the Inland Empire and, as such, can be confused with an area of the same name in southern CA.]

  3. Jeffery permalink
    January 14, 2013 8:42 pm

    Sorry to be a pest, but isn’t there a correlation between increased [global] temperature and increased atmospheric water vapor? I was under the impression that atmospheric H2O was responsible for 85% of the greenhouse effect. If it’s getting wetter, is that an indication of increased atmospheric water vapor? Sorry to be a snark, I love this site and your reports, often linking to them in other discussion forums where AGW drones toss around the latest weather reports as “proof” and have an absolute faith in catastrophic AGW, to which the solution is always nationalization of industry as if governments could do a better job running it.

    • January 14, 2013 10:47 pm

      It’s dangerous to generalise from a small part of the planet, Jeffery, but some would argue that increasing humidity leads to more clouds, which not only leads to more rain, but also lowers temperatures.

      In other words, the Climate Sensitivity argument.

    • John F. Hultquist permalink
      January 15, 2013 5:48 am

      Most of Earth’s surface is water and a majority of that gets lots of direct sun light (energy) and there is constant evaporation. There is a change of phase from liquid to vapor and the energy to do that is called the heat of vaporization. The warm liquid water is said to have sensible heat while the vapor has latent (or hidden) heat. Warm moist air is more buoyant than air without the moisture (H20 versus the O2 or N2 that it displaces) and so the air rises. Air in the equatorial zones do this almost every afternoon.

      Rising air expands and cools. The water vapor condenses at altitude and the latent heat returns as sensible heat. It has now been moved from the warm ocean surface to some place in the troposphere. With only thin atmosphere above it, that heat can escape to space.

      These processes are going on continuously and can speed up or slow down in response to the energy available and the surface. Direct sun into clear water enhances the processes. Sun on fresh snow reflects more and has minor impact.
      Paul’s comment about “sensitivity” applies here. The water is being used in processes that move heat around and promote its loss to space. If that keeps up with heat input or exceeds it, then Earth cools. Some clouds (others not) shade Earth (reflect brightly – Have you ever been in a plane above thick clouds?) and the evaporation/condensation cycle slows. Paul used the word “generalize” but that also means simplify. Earth is not simple.

    • Ron C. permalink
      January 15, 2013 3:35 pm

      Also important that water vapour is the dominant gas able to absorb IR, but clouds are made of water droplets (liquid), and reflect the sun’s rays, thus a cooling effect. The state change from H2O gas to liquid is a powerful means by which heat is transported from the surface upward to be released into space.

  4. igsy permalink
    January 15, 2013 10:41 am

    Take a look at Click on “Climate + Clouds” and you will see a bunch of helpful charts (for the entire globe, not just the US) although they only go back to 1948 or so.

    A couple of take-home points from the site: (1) “.. climate models assume that as an increasing amount of atmospheric CO2 induces slightly increasing atmospheric temperatures, the overall evaporation will increase from the planet surface, and thereby the specific humidity of the lower part of the atmosphere (the Troposphere) will increase as well.”, and the punchline (2) “..the .. diagrams indicate that none of this has been the case since 1948..”.

    In typical fashion, the Team (defensemen Dessler and Davis) have put out a paper denying the accuracy of the specific humidity data, basically arguing that the data must be wrong since the numbers disagree with the models .

  5. January 18, 2013 9:35 pm

    typo: “more wet days then normal” — than.

    Looks rather like the weather is becoming more normal than normal.


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