A past, present and future perspective on the European summer vapour pressure deficit

Abstract

Abstract. The response of evapotranspiration to anthropogenic warming is of critical importance to the water and carbon cycle. Con-flicting observations about changes of evapotranspiration stem mostly from the brevity of observations in time and space as well as a high degree of internal variability. Here we present the first gridded reconstruction of the European summer vapour pressure deficit (VPD) for the past four centuries. The gridded reconstruction is based on 26 European tree-ring oxygen iso-tope records and is performed using a Random Forest approach. Based on our reconstruction, we show that from the mid-1700s a trend towards higher VPD occurred in Central Europe and the Mediterranean region which is based on the simulta-neous increase in temperature and decrease in precipitation. This increasing VPD trend continues throughout the observation-al period and recent times. Climate model projections show this increase in VPD for the Mediterranean region continuing until the end of the 21st century, whereby the extent depends on the amount of greenhouse gas emissions. In contrast, pro-jected VPD in North and Central Europe shows a tendency towards higher VPD only in the highest emission scenario (the produced data is available here: https://doi.org/10.5281/zenodo.5958837 (Balting, D. F. et al., 2022).

Increasing aridity causes larger and more severe forest fires across Europe

“…Nonetheless, our study provides robust evidence for a strong link between summer aridity and maximum fire size as well as maximum burn severity across Europe. As continued increases in summer aridity are projected for Europe (Balting et al, 2022), we conclude that the stable development of area burned observed for Europe over the past decades will likely change to increased fire activity in the near future. Forest management and policy in Europe thus need to prepare for a future with larger and more severe fires, and develop strategies to mitigate fire-related impacts on forest carbon (Carnicer et al, 2022), resilience (Turner et al, 2022) and biodiversity (Palm et al, 2022).…”

The 1820s Marks a Shift to Hotter‐Drier Summers in Western Europe Since 1360

“…It is consistent with climate modeling study showing SM‐temperature coupling was mostly related to multi‐decadal trends in SM, instead of its sub‐seasonal or interannual variability (e.g., concurrent dry‐hot conditions due to short‐term feedbacks or atmospheric driving conditions) (Vogel et al., 2017). Moreover, the summer VPD in WE and temperature were exhibited in‐phase coherencies at multi‐decadal frequencies since the 1800s (Figure S10 in Supporting Information , Balting et al., 2022), with a slightly earlier onset than the significant SM‐temperature relationship (Figure 3b). It probably implied that the increasing temperature drove up higher VPD and evapotranspiration first (Balting et al., 2022), leading to drier soil condition soon afterward.…”

“…June–July–August vapor pressure deficit (VPD) reconstruction since 1750 CE in WE (10°W–10°E, 40°N–55°N, 1° × 1°) was derived to investigate the VPD‐temperature relationship (Balting et al., 2022, https://doi.org/10.5281/zenodo.5958836). Besides, two millennia‐long tree‐ring reconstructions were compared with our reconstruction, namely the June–July–August scPDSI reconstruction for central Europe (Büntgen et al., 2021, https://www.ncdc.noaa.gov/paleo/study/32292) and June–July–August scPDSI gridded data in WE (10°W–10°E, 40°N–55°N, 0.5° × 0.5°) derived from the OWDA (E. R. Cook et al., 2015, https://www.ncdc.noaa.gov/paleo/study/19419).…”

“…Moreover, the summer VPD in WE and temperature were exhibited in-phase coherencies at multi-decadal frequencies since the 1800s (Figure S10 in Supporting Information S1, Balting et al, 2022), with a slightly earlier onset than the significant SM-temperature relationship (Figure 3b). It probably implied that the increasing temperature drove up higher VPD and evapotranspiration first (Balting et al, 2022), leading to drier soil condition soon afterward. As Figure S11 in Supporting Information S1 suggests, the SM was decreasing while evapotranspiration was increasing since the 1980s, and there were strong negative correlations between them.…”

“…June-July-August vapor pressure deficit (VPD) reconstruction since 1750 CE in WE (10°W-10°E, 40°N-55°N, 1° × 1°) was derived to investigate the VPD-temperature relationship (Balting et al, 2022, https://doi.org/10.5281/ zenodo.5958836). Besides, two millennia-long tree-ring reconstructions were compared with our reconstruction, namely the June-July-August scPDSI reconstruction for central Europe (Büntgen et al, 2021, https://www.ncdc.…”