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Relevant to this discussion is the way UHI works. UHI Effect - This is the increase in temperature as a result of land use changes. It is a real phenomenon. UHI Bias - This is the error that is introduced into spatial averages as a result of oversampling either urban or rural stations in a grid cell. This is not a real phenomenon. Instead it is an artifact of the methodology chosen. It is is really important to understand that while the UHI Effect is always positive the UHI Bias can either be positive or negative depending on which stations are oversampled. The movement of the Coatesville station to a more rural site introduces a negative UHI Bias on spatial averages. It is worth repeating and boldening. The UHI Bias can and often is negative. [Wickham et al. 2013] analyzed the bias UHI caused in the Berkeley Earth dataset. They concluded "We observe the opposite of an urban heating effect over the period 1950 to 2010, with a slope of -0.10 ± 0.24°C/100yr (2σ error) in the Berkeley Earth global land temperature average." This is statistically equivalent to no effect, however, if anything, it is more likely the effect biased the global average temperature trend too low. I'll point out that Berkeley Earth uses a unique methodology in which they do NOT perform any adjustments to station data and yet get essentially the same warming trend as every other global average temperature dataset.

With the June update the warming rates of nClimDiv and USCRN are +0.58 F/decade and +0.70 F/decade respectively over their overlap period. It is important to note that nClimDiv uses pairwise homogenization to identify changepoints and correct the biases they cause. USCRN does not perform adjustments of any kind. So for those who think NOAA's adjustments are the cause of the warming trend this is strong evidence that the hypothesis is false. In fact, the opposite may be occurring. NOAA's adjustments may still be inadequate to fully remove the low bias.

Yet another attribution study except for the 2022 (not 2021) heatwave in the Pacific Northwest. Anyway, the point is that these kinds of heatwaves will become 7.4 to 11.5 times as likely by mid to late 21st century. https://iopscience.iop.org/article/10.1088/1748-9326/ad5ab0

The final update for Las Vegas is 120 F.

Las Vegas hit 119 F breaking their all time record high. This is preliminary as additional warming may occur. I'll edit this post with the final high. Edit: 120 F is the updated high.

I'm not sure how I missed this one yesterday...Palm Springs, CA set a new all-time record high. 124 F.

Death Valley set a new record for July 5th of 127 F yesterday. All time record highs may get challenged today in California and Oregon.

And the NWS point forecast on the south side of Bad Water Basin at its lowest point in Death Valley is 132 F on Tuesday.

According to the latest NBM forecast... Las Vegas, NV has a 40% chance of achieving a new all time high temperature on Tuesday. Redding, CA has a 60% chance of achieving a new all time high temperature on Saturday.

The 111 F in Phoenixville isn't the only record high that is in question. The 134 F in Death Valley has been questioned almost from the moment it was reported. William Reid who has studied the record extensively has a very lengthy writeup that leaves little doubt that the reported temperature on July 10th, 1913 is erroneous.

BTW...this seems like a reasonable thread to throw thoughts in for the heat wave that just started for California and the desert southwest. The official NWS forecast for Redding, CA is to tie the all-time high with the NBM giving them a 50% shot at exceeding it. The GFS, ECMWF, and UKMET all say that all-time record highs are going to be challenged up and down the California Central Valley.

I can no longer reply in that thread either. I thought it was just me.

TheClimateChanger beat me to the punch. It is interesting that Hausfather's analysis matches Vose et al. 2003's analysis almost exactly. That is a change from 4pm to 6am observations equates to the cancellation of 1.0 C worth of potential warming. Clearly this is anything but a non-issue.

Relevant to the discussion is [Vose et al. 2003] which found that TOB is a significant problem. For example, 4pm and 6am observation times translate into +0.6 C and -0.4 C biases in the US average temperature. So as stations move from PM to AM observations gradually the TOB can effectively cancel 1.0 C of warming making it appear as a zero trend.

The NBM forecasts for portions of California look potentially historic. It shows Redding, CA with a 30% chance of hitting an all time record high of 120 F on Saturday. The previous record is 118 F.

July appears to be off to a warm start as well.

Relevant to this discussion is [Hausfather et al. 2016] who found that the required adjustments to USHCN (now nClimDiv) are effective when compared to USCRN. If anything, however, the adjustments still leave USHCN biased too low. During their overlap period through 2024/05 the trend is +0.56 F/decade (+0.31 C/decade) for nClimDiv compared to +0.69 F/decade (+0.38 C/decade) for USCRN.

Hansen's latest monthly email is now available. https://mailchi.mp/caa/the-world-will-cool-off-a-bit-and-other-good-news

Models are showing big ridging developing west of the Rocky Mountains with robust temperatures being forecasted for California's central valley. Should it play out like what models are showing it could be a historic heat wave.

This is a perfect illustration of the problem.

Yep. [Song et al. 2022] use equivalent potential temperature to capture the contribution from latent heat similar to using dewpoint.

The global average dewpoint for May 2024 was the highest for any May on record.

@ChescoWx The graph I posted above includes ALL adjustments. It is not limited to those required for the US stations. I'll ask my question again...does this mean you're going to start posting here about how the warming is even worse than scientists are reporting since they are adjusting a lot of it away?

I'll repeat again...the net effect of all adjustments reduces the warming relative to the raw data. @ChescoWx since you refuse to accept to corrections for known biases in the temperature record does this mean you're going to start posting here about how the warming is even worse than scientists are reporting since they are adjusting a lot of it away? https://www.carbonbrief.org/explainer-how-data-adjustments-affect-global-temperature-records/

Wow... Let's assume it's 12 C with urban areas covering 3% of the service area of Earth. That's a 12 C * 0.03 = 0.35 C influence on the global average temperature. It would be significant for sure, but still not even close to the remaining 1.0+ C of additional warming. So no, it is NOT an order of magnitude larger than greenhouse gas warming that's assuming it really is 12 C everywhere (it obviously isn't). Furthermore, the urban heat island effect (not to be confused with the bias) is a real phenomenon so it should be included in the global average temperature. Finally, it's an anthropogenic influence so the distinction between it and GHG warming seems moot in the context of the point Ryan was trying to make. BTW...Dr. Spencer UHI analysis suggests an influence on the global average temperature at around 0.03 C.