Reconciling Seemingly Contradictory Climate Claims

At Real Science, Steven Goddard claims this is the coolest summer on record in the US.

The NOAA reports that both May and June were the hottest on record.

It used to be the the media would reconcile such claims and one might learn something interesting from that reconciliation, but now all we have are mostly-crappy fact checks with Pinocchio counts.  Both these claims have truth on their side, though the NOAA report is more comprehensively correct.  Still, we can learn something by putting these analyses in context and by reconciling them.

The NOAA temperature data for the globe does indeed show May and June as the hottest on record.  However, one should note a couple of things

  • The two monthly records do not change the trend over the last 10-15 years, which has basically been flat.  We are hitting records because we are sitting on a plateau that is higher than the rest of the last century (at least in the NOAA data).  It only takes small positive excursions to reach all-time highs
  • There are a number of different temperature data bases that measure the temperature in different ways (e.g. satellite vs. ground stations) and then adjust those raw readings using different methodologies.  While the NOAA data base is showing all time highs, other data bases, such as satellite-based ones, are not.
  • The NOAA database has been criticized for manual adjustments to temperatures in the past which increase the warming trend.  Without these adjustments, temperatures during certain parts of the 1930's (think: Dust Bowl) would be higher than today.  This was discussed here in more depth.  As is usual when looking at such things, some of these adjustments are absolutely appropriate and some can be questioned.  However, blaming the whole of the warming signal on such adjustments is just wrong -- satellite data bases which have no similar adjustment issues have shown warming, at least between 1979 and 1999.

The Time article linked above illustrated the story of these record months with a video partially on wildfires.  This is a great example of how temperatures are indeed rising but media stories about knock-on effects, such as hurricanes and fires, can be full of it.  2014 has actually been a low fire year so far in the US.

So the world is undeniably on the warm side of average (I won't way warmer than normal because what is "normal"?)  So how does Goddard get this as the coolest summer on record for the US?

Well, the first answer, and it is an important one to remember, is that US temperatures do not have to follow global temperatures, at least not tightly.  While the world warmed 0.5-0.7 degrees C from 1979-1999, the US temperatures moved much less.  Other times, the US has warmed or cooled more than the world has.  The US is well under 5% of the world's surface area.  It is certainly possible to have isolated effects in such an area.  Remember the same holds true the other way -- heat waves in one part of the world don't necessarily mean the world is warming.

But we can also learn something that is seldom discussed in the media by looking at Goddard's chart:

click to enlarge

First, I will say that I am skeptical of any chart that uses "all USHCN" stations because the number of stations and their locations change so much.  At some level this is an apples to oranges comparison -- I would be much more comfortable to see a chart that looks at only USHCN stations with, say, at least 80 years of continuous data.  In other words, this chart may be an artifact of the mess that is the USHCN database.

However, it is possible that this is correct even with a better data set and against a backdrop of warming temperatures.  Why?  Because this is a metric of high temperatures.  It looks at the number of times a data station reads a high temperature over 90F.  At some level this is a clever chart, because it takes advantage of a misconception most people, including most people in the media have -- that global warming plays out in higher daytime high temperatures.

But in fact this does not appear to be the case.  Most of the warming we have seen over the last 50 years has manifested itself as higher nighttime lows and higher winter temperatures.  Both of these raise the average, but neither will change Goddard's metric of days above 90F.  So it is perfectly possible Goddard's chart is right even if the US is seeing a warming trend over the same period.  Which is why we have not seen any more local all-time daily high temperature records set recently than in past decades.  But we have seen a lot of new records for high low temperature, if that term makes sense.  Also, this explains why the ratio of daily high records to daily low records has risen -- not necessarily because there are a lot of new high records, but because we are setting fewer low records.  We can argue about daytime temperatures but nighttime temperatures are certainly warmer.

This chart shows an example with low and high temperatures over time at Amherst, MA  (chosen at random because I was speaking there).  Note that recently, most warming has been at night, rather than in daily highs.


  1. Tom Lindmark:

    A quick question. To what extent has urbanization, in your opinion, contributed to the increase in higher low temperature readings?

  2. Onlooker from Troy:

    Excellent balanced discussion as usual. If only we saw this happen in the "mainstream" (pipe dream, I know).

  3. morgan.c.frank:


    it's a good question.

    here is one way to answer it:

    the NOAA has TERRIBLE siting for its temperature stations.

    they have never even surveyed them themselves.

    but anthony watts and a number of volunteers armed with flir cameras did.

    they found that only 8% met the NOAA's own guidelines.

    over 70% have a warming bias exceeding 2 degrees c, which is to say, somehting like 3 times the per century trend that is being measured.

    no way are you going to be able to clean that signal up.

    there is just way to much noise relative to signal and part of that noise is higher evening temps from uhi. (asphalt etc really holds heat)

    this is what makes the hcn reference network so interesting.

    it is just their best sites. they are all well located and they do not need to be adjusted. it's a clean signal that is well spread in the CONUS.

    when looking at just these 114 stations, the US has cooled over the last decade.

    the system is only about a decade old, so the data is limited, but it really ought to give us a better yardstick going forward.

    i have not seen a comparison of min temp readings for the reference vs the whole hcn, but it would be an interesting thing to look at.

  4. Tom Lindmark:


  5. Roy_Lofquist:

    Statistical analysis presumes one or more underlying cause and effect relations that will lend some degree of predictablity to the system. If this does not pertain then the results obtained are artifacts of the statistical method. This is the case for the Michael Moore hockey stick graph. Feeding the batting averages of players in the NL West to the method yields a graph with the same shape.

    The climate is non-computable, a word coined by Roger Penrose. There are reasons why this is so.

    1. It is chaotic. Edward Lorenz, a leading figure in chaos theory:

    "Chaos: When the present determines the future, but the approximate present does not approximately determine the future."

    It is impossible to measure the initial conditions in sufficient detail - it will always be an approximate present.

    2. Many of the proposed mechanisms are theoretical and not confirmed by experiment.

    3. Many of the known mechanisms are both chaotic and discontinuous. An example is water - the temperatures of the phase transitions (vapor, steam, water, ice, snow) are dependent upon other things, such as atmospheric pressure, as well as is the precise energy absorbed/released in the phase change.

    The futility of attempting to model the climate is evident if you note that the predictions of the 40+ most referenced models are grossly at variance with what you see outside your window.

    Is the climate changing? Of course. Where is it going? See your local bookie. He can at least give you the over/under.

  6. marque2:

    NASA did actually adjust the satellite data in 1998 because it wasn't showing any upward trend. Not showing an upward trend is obviously a mistake. Showing a downward trend is also obviously a mistake. Up can never be a mistake.

  7. DavidCobb:

    The satellite data has a +0.13 per decade adjustment for orbital decay based on a RSS model. Published and implemented by RSS in 1998 and finally accepted by UHA in 2005 after a adjustment to the balloon data. UHA had argued that the adjustment was wrong because it did not match radiosonde balloon data.

  8. AnInquirer:

    Overall, a very fine post: However, I take issue with this statement: "However, blaming the whole of the warming signal on such adjustments is just wrong -- satellite data bases which have no similar adjustment issues have shown warming, at least between 1979 and 1999." I take issue -- not because it is incorrect, but because it is misleading. Satellite data bases do show warming in that time frame -- I do not believe there any dispute there. But we did not have satellites back in the 50s and 30s . . . and the point of Mr. Goddard and others is that the data adjustments is responsible for the warming trend since the 1930s. Take away the adjustments, and you have NO warming trend in the last 80 years -- or longer.
    I understand the inherent desire for adjustments because the measuring mediums often have not been stable, but the adjustments (over 80 years) is more than the trend. It is mistaken policy to get excited about a trend that is produced via the adjustments of self-serving analysts.

  9. Brian H:

    Raising of the lower bounds is a benign process; raising of the upper bounds, not so much.

  10. Brian H:

    What really needs explaining is why the adjustments are so rigourously unidirectional.