TheClimateChanger

Looking at the historic station thread. We also see good reason to conclude that the minimum temperatures in the 19th century and early 20th century were colder than observed. What we see is this: There was a rooftop exposure in general through 1933, at ever increasingly tall buildings - presumably to accommodate wind and other measurements. A trend which reached its zenith atop the Majestic Building some 218 feet above the ground. From at least 1881 through April 1887, the thermometer was housed in an enclosure on a northwest window of the Board of Trade Building. Looking at the stated height above ground, this appears to have been housed on a 4-6th story window of a building that appears to have been between about 6 and 8 stories high judging by the roof height reported after the station was moved to the roof on May 1, 1887. Rooftop stations have been observed to report higher temperatures than corresponding ground-based stations, and window stations even higher. With proper siting and a location away from the core urban heat island, it is likely that temperatures would have been substantially cooler than reported. For more information on the Majestic Building, see: Majestic Building (Detroit) - Wikipedia

In recent decades, the difference between the two sites has gotten smaller as development has increased near the international airport. City Airport still tends to observe higher minima, however. The difference has shrunk to a bit less than 1F. City Airport [2010-2024] DTW [2010-2024]

In fact, we see the 1960s and 1970s "cold" spell pretty much evaporates when we correct for site location. Meaning the extreme cold minima present in those decades in Detroit are largely an artifact of moving the official observation site from the urban City Airport location to a low-density, semi-rural or ex-urban site well to the southwest. We see a mean minima of 20.2F at City Airport for the period 1934-1950. The so-called warm winter period. Shockingly, from 1966 to 1980 [the so-called cold winter period], the mean minimum temperature at Detroit City Airport was nearly 1F higher. But at the official observation site [KDTW], it was much colder with a mean minimum temperature more than 2F cooler than the 1934-1950 mean at City Airport and more than 3F cooler than the mean at City Airport for the corresponding time frame. No comparative data for 1934-1950 are available, since record keeping did not begin at the site until 1958. It became the official site for Detroit on July 1, 1966.

The threaded record does show a positive regression, from a predicted value of 19.6F in 1875 to a predicted value of 21.3F in 2024. The LOESS curve helps to highlight the fact that the vast majority of recent winters have seen mean minima well above the values predicted by a linear regression, suggesting the linear regression is not fully capturing the trend and there has been an acceleration in the increase in winter minima since around 2000. In fact, the trend is greatly affected by changes in site location and instrument exposure, suggesting mean winter minima have warmed faster than shown here. This will be addressed in a follow-up post. Detroit [ThreadEx] Detroit City Airport [KDET] Detroit Metropolitan Wayne Airport [KDTW]

Here's Hagerstown, Maryland for somewhere outside of the core urban area. Not much difference. 9 of top 11 since 2010.

I think this "future" is reality in a lot more places than we'd like to admit. Here's Washington, D.C. - 2024 obviously not done yet, but will almost certainly be in top 5, with decent chance for #1. 9 of top 10 since 2010, only 1 prior to 2000.

The "future" is here in some locations. Future summers could regularly be hotter than the hottest on record | NCAR & UCAR News

I suspect the urban heat island was a lot worse in the 1930s. I have seen a lot of photos from that era, and there were like zero trees anywhere. Pittsburgh, no trees. Even the Blue Ridge Parkway was mostly devoid of trees. Basically clear cut everywhere. I think we have billions more trees today than 100 years ago. This probably played a factor in some of the daytime heat.

Count me as a denier. Here is the county-by-county minimum temperature ranks for July 1936. What do we see from this map? First, we see it was actually very cold. Second, there's a VERY odd pattern to the map. The rankings are almost inversely proportional to population density. The coldest locations are some of the least densely populated in the Commonwealth. The warmest are the most densely populated counties. If UHI was affecting the trends, we would expect to see the most populated counties look colder on this map, but in fact the opposite is true. USHCN applies some sort some of urban heat island correction, but it looks to me like the correction is in the wrong direction and the UHI was more significant in 1936.

Season to date [through July 16], temperature and precipitation percentiles: Mean Temperature Total Precipitation

Matches the longest streak of 100+ at both sites. Should it reach 101F, that would be the first time at both locations with 4 consecutive days of temperatures at or above 101.

Imagine spending all this taxpayer money to install an ASOS in Central Park solely for the purpose of "continuity" and placing it in the location least representative of New York City that you can find, so that there is no reliable continuity in the records. Had to be deliberate.

Wow! Look at this photo I found on Wikimedia dated May 24, 2024. This is absolutely absurd. Who was the decisionmaker that identified this as an appropriate location to install the ASOS? It doesn't comply with any siting standards. Most backyard thermometers are more reliably sited than this.

If we don't get any tomorrow, looks like awhile before any more chances.

Through the first half of the summer, it has been 2F warmer than 1995. In 1995, the second half of summer [July 16 - August 30] averaged 77.7F. To match 1995's final summer temperature (75.1F), it would need to average about 75.7F for the remainder of summer.

Morgantown topped out at 94F, ending its streak of 95+ days at 3. That was the longest streak since the 5-day streak ending on August 3, 1995. There were two other occurrences of consecutive 95+ days since then, both of which occurred in 2012 - June 28 & 29, 2012 and July 6 & 7, 2012. Clarksburg, West Virginia reached 98F yesterday and 96F today. The 98F reading was the highest since August 21, 1983, when it also reached 98F. It is the first time in the threaded record with consecutive days of 96F or better since June 26 & 27, 1969.

Elkins, West Virginia reached at least 96F today [elevation: ~2000 feet]. The last time it was hotter was July 16, 1988, when the temperature climbed to 99F. The only other hotter days in the threaded record are September 3, 1953 (97F), August 6, 1918 (99F), August 7, 1918 (98F), and August 11, 1911 (97F).

Clarksburg, West Virginia reached 96F today before thunderstorms brought daytime warming to a quick stop. Yesterday's 98F was the hottest day since August 21, 1983. This is the first time two consecutive days of 96F+ has been observed in the Clarksburg area since June 26 & 27, 1969.

Notably warm first half of summer. Easily the warmest on record at the airport, besting 1994 by nearly 1F. Officially, sixth in the threaded record... although I'm a little skeptical of these 19th century summertime readings. 3rd warmest in the Morgantown Area thread. A lot of the same years show up. Seems to agree 1876 was a hot first half of summer, but not to the tune of nearly 2.5F warmer than this year. 1892 was tossed due to missing the entire month of June.

Also the concept of a 30-year climatological normal wasn't in widespread practice until the late 1940s. If we look at earlier years, the departures were simply calculated from the long-term means. In 1940, these were the 60-year means for Detroit [mostly from the city office] used to calculate departures from normal. If we look strictly at the progression of the annual normal mean at Detroit Metro Wayne Airport, we find the following: 1931-1960: 48.9F 1941-1970: 49.1F 1951-1980: 48.6F 1961-1990: 48.6F 1971-2000: 49.7F 1981-2010: 50.3F 1991-2020: 50.6F

Normals for Boston Logan Airport 1931-1960 on the left, 1961-1990 on the right And for Buffalo Niagara Airport: As you can see, at Boston, winters were only slightly cooler in the 1961-1990 normals versus the 1931-1960 normals. At Buffalo, the winters were actually warmer in the 1961-1990 normals versus the 1931-1960 normals.

Not as much as you might like to think. The normals were corrected for location and site exposure and not just averages of records from various locations. From what I could glean from the Local Climatological Data publications, the normals for each site were as follows: Detroit Metropolitan Wayne Airport 1931-1960 [1967 revision, after it became the official climate site in 1966] 1961-1990 So yeah, it was quite a bit colder during the winter, but there were seasonal variations. Spring was warmer in the 1961-1990 normals, and summer pretty similar. Fall was fairly similar but with some interesting ups [November] and downs [October].

97F at Morgantown, hottest since July 7, 2012.

And how many of these winters would be cooler than the 1961-90 normals?