Changes In Atmospheric Circulation Contribute Up To 80% To The Summer Drying Trend In Western Europe
I’m away on holiday at the moment, tapping away frustratingly slowly on a silly phone, so forgive the brevity of this post, but I just couldn’t let this slide, what with all the media hype about ‘climate change’ causing the wildfires in Spain and France.
I’ve already written about other studies which demonstrate a significant contribution from atmospheric dynamics to extreme temperatures in Europe. This very recent study analyses soil drying trends and concludes that a huge 80% of recent soil drying in Western and Eastern Europe can be attributed to changes in atmospheric circulation, which in turn is driven largely by natural internal variability.
From that study:
Similar to temperature, soil moisture shows a negative trend after 1980, with drying rates of −0.41 mm per decade in HIST and −0.23 mm per decade in NAT, implying a 55% dynamic contribution. The thermodynamic drying is strongest in the east but otherwise evenly distributed, whereas the dynamic trend is spatially heterogeneous, with strongest drying in central and eastern Europe and positive trends in the eastern Mediterranean, the British Isles and southern Scandinavia. Hence the relative dynamic contribution to soil moisture trends is even more dominant at the regional scale than in the domain average, reaching up to 80% in western and eastern Europe.
These dynamic soil moisture trends show a high spatial correspondence with dynamic precipitation trends over the same period (Pearson correlation = 0.80), suggesting that overall drying patterns are driven to a large extent by precipitation trends. Due to the buffering capacity of soils, soil moisture reflects not only concurrent circulation patterns but also those of the preceding weeks and months. These lag effects could explain the strong dynamical soil moisture trends in western Europe despite moderate trends in JJA temperature and precipitation (Supplementary Fig. 3).
The increase in VPD is consistent with rising temperature and declining soil moisture: VPD increases in both HIST and NAT since 1980 at rates of 0.64 and 0.27 hPa per decade, respectively. The thermodynamic forcing thus emerges as the primary driver of the VPD trend at the continental scale, contributing around 58% to the overall trend. Because saturation water vapour pressure increases approximately exponentially with temperature according to the Clausius–Clapeyron relation, we find an expected high correlation between the spatial patterns of VPD and temperature trends (Pearson correlation = 0.83), with the strongest increase in southeastern Europe and Spain.
We further dissect the dynamic trends by isolating the discrete weather regimes (WRs) that show changes in frequency between 1980 and 2024. We classify summertime atmospheric circulation patterns using k-means clustering (k = 5) applied to the 500-hPa stream function, identifying three weather regimes with statistically significant trends since 1980 that are consistent with previous studies (Fig. 3a,b; two WRs with non-significant trends are shown in Supplementary Fig. 4). These three WRs are related to a decreasing frequency in cyclonic conditions over Northern Europe (WR1)38, a decreasing frequency of a bipolar pattern with anticyclonic conditions over the Atlantic and cyclonic conditions over southeastern Europe (WR2)23,24 and an increasing frequency of anticyclonic conditions over the Mediterranean and Central Europe (WR3)22,23,24.
Our results show that atmospheric circulation has played a dominant role in Europe’s long-term summer drying. Circulation changes not only drive soil moisture decline but also amplify thermodynamic warming, thus intensifying hydroclimatic variability and extremes. This interplay underscores the need to consider both dynamic and thermodynamic processes when interpreting past trends and assessing future drought risk. Until now, these different mechanistic trends have not been quantified because observation-based studies relied on correlative evidence, whereas climate models fail to reproduce the observed European circulation trends18,21. By applying circulation nudging, we overcome this limitation and represent observed circulation changes within an Earth system model, enabling process-based storyline attribution of European drying. A remaining key uncertainty is whether historical circulation trends were externally forced or arose from internal variability, which is crucial for evaluating, interpreting and constraining historical and future climate model simulations: if externally forced, continued intensification of drought—beyond what is expected from thermodynamic changes alone—may be expected. Conversely, if internally generated, a reversal could temporarily offset future drying. Disentangling these drivers is essential to constrain projections and to design robust adaptation strategies for a drying Europe.
https://www.nature.com/articles/s41561-026-02050-w
Oh, and here’ a photo of the Whin Sill:
Recent warm weather and dry conditions have nothing to do with the burning of fossil fuels. It is all down to something called weather. In summer, whenever we get a region of high pressure sitting on top of us, it brings warm air from the tropics. Nothing to do with climate change. Wildfires are due to mismanagement of areas of grassland or forest. Simples!
I think it was Freeman Dyson way back who stated that none of the models were anywhere near handling soil dynamics wrt moisture properly.
https://www.carbonbrief.org/freeman-dysons-views-on-climate-in-the-independent