Great work by Stephen...

Great work by Stephen Connolly

https://tallbloke.wordpress.com/2025/03/10/comparing-temperatures-past-and-present-some-quality-data-analysis-from-an-interesting-angle/

Summary of Stephen Connolly's Analysis on Temperature Records

Stephen Connolly's work, featured in Tallbloke’s Talkshop, critically examines the accuracy of historical temperature records. His analysis is based on data from the Valentia Observatory in Ireland, which has some of the longest continuous temperature records available.

Key Findings:

1. Temperature Measurement Methods Have Changed Over Time

   • Early temperature measurements were often taken indoors, once per day, before standard outdoor shelters (like the Stevenson screen) were developed in the late 19th century.
   • By the 1870s, minimum and maximum thermometers became widely used, allowing for estimates of daily average temperature (Taxn), calculated as:Taxn=Tmin+Tmax2Taxn = \frac{T_{min} + T_{max}}{2}Taxn=2Tmin+Tmax
   • Modern automated stations now record hourly temperatures, allowing for a true daily average temperature (Tavg).

2. The Meteorological Approximation (Taxn) is Inaccurate

   • By comparing historical methods with more precise hourly measurements (Tavg), Connolly finds that using only Tmin and Tmax introduces significant uncertainty.
   • On average, the Taxn method underestimates true temperatures by 0.17°C, but with daily fluctuations as large as ±1°C.
   • The difference between Taxn and Tavg is not random but varies over decades, meaning long-term trends in temperature records may be distorted.

3. Illustrative Example Using the Bugatti Chiron Super Sport 300+

   • Connolly draws an analogy between temperature averaging and speed enforcement in the Dublin Port Tunnel.
   • A car traveling between 30 km/h and 490 km/h in bursts could still appear to be obeying an 80 km/h speed limit under certain averaging methods.
   • Similarly, Taxn estimates may misrepresent actual temperature trends.

4. Historical Temperature Records Have Large Uncertainties

   • Because most of our historical data is based on Taxn rather than Tavg, past temperature records have inherent uncertainties of about ±1°C.
   • This means that any specific historical temperature value should be taken with caution.
   • Connolly's analysis suggests that comparisons between past and present temperatures may be flawed due to methodological inconsistencies.

Conclusion & Implications

• The transition from historical thermometers to modern automated measurements has improved accuracy, but past temperature records remain uncertain.
• The commonly used method of averaging minimum and maximum temperatures may introduce systematic biases, affecting long-term climate studies.
• This research raises questions about the reliability of past temperature reconstructions and suggests caution when interpreting historical climate trends.