2024 - Warmest Year Globally and Third Warmest for Herefordshire

 The reign of 2023 as the warmest year globally was as brief as it could be; 2024 has just superceded it. Not only that, according to the Copernicus Climate Change Service, we surpassed the preferred 1.5 ℃ limit, agreed at COP21, for the first time (Figure 1). Note that, according to the 2015/2016 Paris Agreement, we have not yet broken the 1.5 ℃ limit; to do this requires an extended period (5 - 10 years?) where annual global temperatures are consistently above the 1.5 ℃ limit. As we move into a La Nina phase of the El Nino/Southern Oscillation (ENSO), the average global temperature for 2025 is expected to fall back below 1.5 ℃. We may breakthrough the 1.5 ℃ limit anytime from 2030 onwards.

Figure 1: Annual Global Average Temperatures Compared to the Pre-Industrial (1850-1900) Average

Most disconcerting is the fact that the last two years have not only 'smashed' the mean global temperature records but, for 2024, achieved this even as we moved from an El Nino phase (warming) to a La Nina phase (cooling) (Figure 2).

Figure 2: Monthly Sea Surface Temperatures (Nino 3.4 Index Values) from NOAA

Of course, using a single number to summarise a global effect (warming, in this case) will necessarily lose information. Not everywhere will warm, some places will warm less than the average and some places will be much hotter than the average. I was interested to see how warm the last two years (2023-2024) were in Herefordshire.

I have done a couple of blogposts on Herefordshire's climate history; see here and here. As a proxy for Herefordshire, I use weather data from the Met Office's Ross-on-Wye weather station located in the south of the County. Monthly data on temperatures (maximum and minimum), rainfall, sunshine hours and the number of air frost days are available from 1931 onwards.

In Figure 3, the mean annual temperatures for the Ross-on-Wye weather station are as a time series. There is a good deal of scatter (as you would expect from a single weather station) but also a clear warming trend.

Figure 3: Average Yearly Temperatures for Ross-on-Wye (1931 - 2024)

The same data, this time as an anomaly plot using a 1931-1960 baseline, is reproduced in Figure 4. 

Figure 4: Temperature Anomalies (1931-60 baseline) for Ross-on-Wye Weather Station

In the historical record (1931-2024), the three warmest years are 2022, 2023 and 2024 with 2023 being the warmest and 2024 the third warmest. The temperature anomalies for 2022, 2023 and 2024 are, respectively, 1.8 ℃, 1.9 ℃ and 1.7 ℃. To these values we could add 0.1 ℃ to move the temperature baseline back to the pre-industrial period (1850-1900). Unless 2025 is much cooler than 2024, it seems likely that, in terms of global warming, Ross-on-Wye (and, perhaps, Herefordshire) has already broken the 1.5 ℃ limit.