A recent article in the Jackson Hole News & Guide entitled, “In Teton park, nights are becoming warmer”, naturally caught my meteorological eye. The article was generated from a recent climate assessment done for Grand Teton National Park. That report analyzed the historic temperature data from the Moran weather station, shown in the graph provided here from Grand Teton National Park’s website.

Read the JH News & Guide article here. See the park report here.

As the article pointed out, “Between 1911 and 2022, daytime highs didn’t demonstrate a strong trend. But nighttime lows have increased between 3 and 4 degrees over the same 111-year period”.

I was curious about that, so I examined the data a little more closely. Some might appreciate the additional analysis; others may curse me!

Let me also preface this by saying I am not rejecting that there have been periods of warming in recent decades, but keep in mind, any study of weather or climate is only as good as the data that goes into it.

A Look at the Graphs

The first thing that is obvious from the upper graph is that the mid-1920’s to mid-1930’s had the warmest daytime high temperatures, or average daily max temps. That was during the Dust Bowl years. Then it cooled until the early-1950’s. Following that, max temps remained relatively steady until the mid-1980’s when average daytime high temperatures rose a little through the late 1990’s.

(Green lines are the 5-year running average. Click graph to enlarge.)

At the same time, the average overnight low temperatures, the average daily min temps on the lower graph, were relatively steady from 1912 through the early 1950’s. Then in the mid-1950’s there was a significant jump in the average minimum temperatures, of around 4 degrees Fahrenheit. After that jump, the average overnight low temperatures remained elevated and relatively steady through the late 1990’s.

There is plenty of missing data from 1999 to about 2012, I’ll explain why shortly. The last thing to note is that during the latest 10-year period, from about 2013 to 2023, the graphs show a slight downward trend of both the average maximum and minimum temperatures. There is a reason for that, which I will also explain.

The climate report made a big deal out of the 3 to 4 degrees rise in overnight low temperatures over the last 111 years, relating it to earlier season snow-melt in the mountains in recent years, and a host of other issues.

So, what caused that rapid rise in minimum temperatures in the mid-1950’s?
Could it be an Urban Heat Island effect, like what happens in big cities with ever more expansive areas of pavement, concrete, buildings, etc. surrounding the weather station, acting as a giant heat sink? No, probably not in the park, where the landscape hasn’t changed all that much in the last 100 years. Was it an increase in tourism and more cars spewing exhaust? I don’t think so. But I can tell you, it was human caused!

Data and Metadata

When doing a climate assessment of any weather station it is not only important to scrutinize the data, but also the metadata. Metadata is the station’s record of its location, elevation, topography, the surrounding vegetation, and any nearby buildings. It also indicates each time the station was relocated and when the instrumentation changed. Metadata helps determine the validity of the data.

The Moran weather station, which was used in this report, is known as “Moran 5WNW”. It is located near the Jackson Lake Dam, 5 miles west-northwest of Moran Junction. This station does have the longest continuous record of temperatures in Grand Teton National Park. However, there are some problems with the data from Moran.

The first problem with this weather station’s data is that the instruments were moved several times over the years. Originally, the official weather station was located at the old Moran townsite, on the north side of the river, in a marshy area of grass and willows. It sat just northeast of where the dam was being constructed. In 1954 it was moved approximately 0.3 miles south of its original location, to the south side of the river, and up on the river’s bench, in sage and trees.

The location of the weather instruments shifted around a few more times between 1954 and into the 2000’s, coming to rest more permanently next to the Bureau of Reclamation buildings, just south of the dam, on the second bench above the river. The official thermometer now sits over a mix of low grass and dirt, surrounded by mature conifer trees.

According to the NWS’s  Compatibility Determination for Site Moves, “Station moves where the new equipment location is within 5 miles of the original site and the difference in elevation is 100 feet or less are also assumed to be incompatible unless they pass a data compatibility evaluation. While most re-locations are expected to exhibit data incompatibility, there may be cases when the data record from the new location may be a faithful continuation of the climate record from the old location. However, the compatibility evaluation will be conducted for all relocations of less than 5 miles and/or 100 feet unless the move is deemed incompatible by the NWSREP.”

If a station moves more than 5 miles or more/less than 100 feet in elevation, then the station must be renamed. Moran 5WNW moved 0.3 miles and about 65 feet higher in elevation, according to the metadata. I am not sure if a compatibility test was ever done for the Moran site in the mid-1950’s. Although, in terrain like we have here in Jackson Hole, the micro-climate changes quite a bit with changes in the micro-terrain.

The Big Change

The relocation on November 1st, 1954, was significant, as that slight change in elevation to the bench on the south side of the river, coincides with the biggest rise in average daily minimum temperatures on the graph.

Keeping the thermometers up out of the marshy flat would get them up above the lowest level temperature inversions, which are common all year, especially along the river. That would lead to the thermometers registering warmer overnight lows as compared to pre-1954.

In 1999 the instrumentation changed from a Liquid-in-Glass thermometer system to an electronic one, an MMTS system. According to the person in charge of monitoring these stations at the NWS in Riverton, WY, the reason Moran has so much missing data from 1999 to about 2012 was because of data-logging issues when they first changed the thermometer over to an electronic system.

I would also note, that upon inspection of the Moran weather station the MMTS, the beehive housing is of the correct standard size specified by the NWS cooperative weather station standards. However, the thermometer housing is currently mounted over 8 feet above ground level. The NWS standard for official thermometers is that they are to be between 4 and 6 feet above the ground. The reason for mounting it higher at Moran is to accommodate for snow depth on the ground in the winter.

What difference would it make mounting a thermometer higher than standard above the ground? It affects the temperature readings, especially during the summer months when the ground is free of snow. In general, a thermometer that far above bare ground would yield slightly cooler daytime high temperature readings and slightly warmer overnight low temperature readings.

So, yes, it would be correct to say that the changes in temperature in the park were human caused. In this case, because humans moved the weather station.

Read more about thermometers and temperatures here.

Other Notes on the Study

In the newspaper article, the author, through the climate change report,  attempted to tie the temperatures at Moran, on the valley floor in Grand Teton National Park, to earlier season snow-melt in the Teton  mountains, claiming that, “Snow is disappearing earlier and earlier. Higher than usual nighttime temperatures, which allow snow to melt around the clock , quickly clear the mountains of frozen material in the spring.”

The article went on to state, “This July at the Moran weather station, the lowest minimum temperature – a proxy for nighttime temps – was 34 degrees Fahrenheit,  2 degrees above the average for July from 100 years of data… “.

There was no mention that in the last 100 years there have been 25 other years when the lowest minimum temperature in July at Moran was 34 degrees or warmer, including in 1925 & 1957, along with a string of years in the 1960’s, 1980’s, 1990’s and early 2000’s. July 2021 did have the warmest of these lowest minimum temperatures at 41 degrees.

There was also one gross error in the article , which stated, “Record-high minimums for June, July, and August were all set in the last 10 years”.  Moran’s data shows that the record high minimum temperature recorded in June was 58 degrees in 1927.
The warmest minimum temperature recorded in July was 59 degrees in 1960.
The warmest minimum temperature recorded in August was 59 degrees in 1991.

I think what the author meant to point out was the lowest minimum temperature in each of those months, which did occur within the last 10 years:
In June 2015 = 36 F
In July 2021 = 41 F
in August 2022 = 37 F

I suspect those records are directly related to hoisting the Moran thermometer 8 feet above the ground.

I’d also add that using July minimum temperatures as a gauge for melting snow in the mountains was rather interesting, since by July most of the snow has already melted in the mountains. May and June are the peak snow-melt months in the mountains, yet there was no mention by the author that both May and June of 2024 happened to have lowest minimum temperatures that were one degree cooler than average.

There are times when overnight low temperatures in the valley will be cooler than temperatures at say 10,000 feet, and times when overnight temperatures in the valley will be warmer than temperatures in the mountains.

Some conflicting evidence of recent melting is shown below in these photos taken from the summit of the Grand Teton. The photos show Alpha & Omega lakes still mostly frozen in early August. The first one was taken August 5th, 2024. The second one was taken a year ago, on August 1st, 2023. Which leads me to think that in the last two years these lakes have not completed melted out.

Are these observations evidence that we are perhaps entering the next Ice Age? Probably not.

At the same time, I do not disagree with the organic observations that the snow-cover may be receding earlier in the spring, other data shows that. That same data also shows that snow-cover extent across all of North America is coming earlier in the fall and increasing , and has also been increasing slightly in the winter. This analysis is according to the Rutgers University Global Snow Lab.
Their graphs are shown below.

The Computer Model Predictions

The other graph that caught my attention from the park’s report was the one showing annual average mean temperatures. The data plotted on this graph is not actually from the Moran weather station. The temperature data shown on this graph in the black line is computer generated, for a point in the middle of the park near Leigh Lake and only plots data from 1979 to 2020. The blue and red lines are what the computer models are projecting temperatures to be into the future, under two different scenarios.

Below is the graph from the report, and below that is a graph of the actual data of the average annual temperatures for Moran for 1912-2023.

The computer-generated version shows that average annual mean temperatures remained relatively flat for the last 30 years, from 1979 to 2020. Actual data from Moran shows a little more up and down.

Regardless,  it makes it difficult to fathom how computer models can project such a precipitous rise in annual average temperatures, 6 to 14 degree increase over the next 10 to 70 years, when the previous 30 years of the computer generated temperatures (as well as the actual temperature data from Moran) have shown no significant increases whatsoever.

Model Reality Check

When you look at how the models have performed globally over the past 30 years, nearly all of them over-forecast surface temperatures. An example is shown below comparing model predictions to actual surface temperatures and temperature data from satellite observations, which began in 1979, of the lower atmosphere (the troposphere). The black line is the mean of all the models, green is actual surface observations, blue is satellite data. Baseline is relative to the first 5-year period 1979-1983.  Chart shows the departure from that average through time, in degrees Celsius.

Final Thoughts

As a meteorologist, I have dealt with weather forecasts and computer models for over 40 years. For both short-range and long-range predictions. Forecasts and models are just guidance, they are not gospel.

Good or bad, day to day or over the long-haul, there are times when the forecast nails it, and there are times when it grossly misses what really happens, even for the next 24-hours!  Models have become better and much more sophisticated over the years, but the science of weather is just not all that exact. There are literally too many variables to consider to make 100% accurate predictions, in the short term or the long term.

My intention is not to dismiss the Park’s climate report, but rather to demonstrate an application of the “Scientific Method”. When a theory is put forth based on data, and  assumptions are made based on that data, then it becomes part of the process to question the data and examine its validity.

I’m not sure if the scientific method is even taught in schools anymore. My sense is we are just being told what to believe and never to question it.

As Albert Einstein once said, “Don’t listen to the person who has the answers; listen to the person who has the questions”.

With that, I will end with this final question…..

Post by meteorologist Jim Woodmencey