New Paper Published

Observed drought indices show increasing divergence across Europe

Observed drought indices show increasing divergence across Europe

Posted by Jim Stagge on October 25, 2017

Our new paper, titled “Observed drought indices show increasing divergence across Europe”, has been published in the journal Scientific Reports.

This research shows that drought frequency measured by two widely used drought indices, the SPI and SPEI, have begun to deviate from one another throughout Europe. The onset and consistently increasing trend is a clear signal, not random noise, pointing towards climate change. Further, the spatial patterns resemble climate hcange projections for Europe, providing more confirmation. The divergence has been driven by increases in evapotranspiration, caused primarily by increases in temperature.

Major Implications

  • Our study adds support to the growing evidence that climate change effects are already being felt as changes in drought.

  • Drought monitors must take care when defining drought because different drought indices may drift in different ways in a non-stationary climate.

Monthly change

Fig. 1. Reproduced from article. Difference in percent European area in drought as defined by SPEI6 and SPI6. Historical values for both the WFD and WFDEI are shown in grey, while the fitted common trend in shown in black. Statistically significant trends are shown in red. A grey bar at the bottom shows the reference period.

SCE map

Fig. 2. Reproduced from article. Spatial distribution of (A) k_SPI6, (B) k_SPEI6, and (C) k_DIFF6. Stipples represent statistically significant trends. The distribution of trends for all grid cells is shown below the corresponding map. The color scale for k_DIFF6 is modified slightly to match its smaller variance.