Following up on the prior post looking at record temperatures globally, let's zoom down to the state level.
The first half of 2023 was actually fairly cool statewide. In fact, the January–June mean temperature for the state was only 41.6F, making it the coldest January–June since 1984.
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| Source: NCEI |
By midsummer, I was thinking we might be able to finish the year below the 20th century average temperature, which is something that hasn't been done statewide since 1993. However, the latter half of 2023 was quite warm. In fact, for July–December the statewide average temperature was 55.3F, which ties for the 3rd highest on record just behind 2020 and 2021.
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| Source: NCEI |
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| Source: NCEI |
As can be readily seen from the graph above, we simply do not live in the climate of the 20th century anymore. That climate is long gone. The statewide average temperature in the 20th century was 47.6F. Over the last 20 years, it's been 49.4F or 1.8F. That works out to an even 1C if you like metric. That may not seem like a lot, but that equates to about a 500 foot increase in the mean snow level during winter storms if all other storm characteristics were held fixed.
Sigh...
I don’t doubt we’re warming, but I would be interested to read more about the methodology here. Specifically, the location of the temperature observations to compare urban vs rural temperature changes. I would imagine the increase is more dramatic in urban locations that have been affected by physical changes to the landscape.
ReplyDeleteI would need to dig into this more, but the processing techniques used likely partially account for this. The gory details are in https://journals.ametsoc.org/view/journals/clim/31/24/jcli-d-18-0094.1.xml and https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2012JD018509
DeleteWithout at least having a vague idea of the actual methodology behind those charts, I have no idea what they are saying. In particular, it's unclear to me what NCEI data that is, and how "Utah's statewide average temperature" was calculated.
DeleteQuickly looking at the second citation, the authors mention that "Urbanization has long been recognized as having the potential to impact near-surface temperature readings", and that using data from rural stations can help to correct for that. Quickly looking at a few urban vs. rural stations (e.g. SLC International, some Beaver station, etc.), the urban stations show a clearly increasing trend, the rural stations that I examined do not. Perhaps my sampling of rural stations was unlucky.
Inferring long-term temperature trends involves a great deal of effort, typically involving statistical techniques, to adjust for changes in instrumentation type, station location, land-surface use and characteristics, etc. This process, called homogenization, has to be done using all stations. Even rural sites have issues that must be addressed.
DeleteThe figure I used for this post is based on homogenized data. In most areas, this effectively removes the urban bias in long-term trends for the continental US. I do not know how well it works just for Utah. Most studies focus on larger areas. I can only hypothesize that given the homogenization of the data and the distribution of stations statewide that urbanization would make only a small contribution (if any) to the trends evident in the Utah time series. Further, if you go to https://www.epa.gov/climate-indicators/climate-change-indicators-us-and-global-temperature and click on Fig. 3, you can see that every climate zone in the western US has warmed over the past 120 years, including zones that are quite rural.
More on homogenization and urbanization at the link below, although this too is a techy article.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2012JD018509 although I suspect it won't help.
I appreciate the in depth thoughts on the issue. Quite interesting and not wanted I wanted to hear!
ReplyDelete