Turning up the heat: how land management impacts heatwaves and droughts
Understanding the roles land management and its uses play in the overall climate system is critical to mitigating the potential effects of climate change. EU-funded research is helping to enhance our knowledge of these interactions.
© Toini Lindroos, Blick 2012
Droughts and heatwaves are a regular occurrence in Europe, particularly in southern Europe. Their impact has been growing year on year, as evidenced by the increasing frequency and scale of wide-spread fires and water shortages. These events have a significant impact on the populations concerned, both with regard to safety and the pressures put on different water consumers, such as agriculture, industry, tourism and households.
Over five years, the EU project DROUGHT-HEAT, funded by the European Research Council, focused on researching and understanding the processes that lead to extreme weather events, like droughts and heatwaves. In particular, it investigated how these are related to land processes and human activity.
By integrating the latest land-observation data, such as satellite geo-observational information, and using novel methodologies to extract functional relationships within the data, the project was able to identify key gaps in the existing earth system models (ESMs) used to predict the impact of climate change.
We wanted to improve our understanding of the feedback cycles that exist for land processes. So, for instance, when the temperature rises, the land can get dryer. This in turn causes the heat to rise as a result of less vapour transpiration, explains principal investigator and head researcher Sonia Seneviratne of the Swiss Federal Institute of Technology in Zurich (ETH Zurich). The hope is that this information can be used to optimise land management and point to possible solutions for reducing or offsetting global warming.
Land and climate interactions
One of the project aims was to assess the impact of human activity on rising temperatures. By understanding how land processes affect droughts and heatwaves, we wanted to provide insight into how we could potentially optimise land management. By helping to either reduce or offset increasing global temperatures this would contribute to the goal set by the Paris Agreement to keep warming below 1.5°C above the pre-industrial temperature, Seneviratne explains.
DROUGHT-HEAT carried out a study on the 2018 heatwave in Europe, the US and Asia which identified the clear impact human CO2 emissions had on the event. The researchers also found that land management can be very important in affecting regional climatic changes, although this can work both ways. For example, extensive irrigation can help to reduce increases in temperature regionally but it also masks the impact of rising global temperatures, thereby potentially creating a false sense of security. In the event that growing pressure on water resources made irrigation impossible, then a dramatic rather than a gradual rise in temperature could result. Thus, it is essential to undertake land management in a sustainable way in order to find viable long-term solutions.
The project also identified an extremely strong correlation between droughts and the level of CO2 in the atmosphere. This suggests that when the land is too dry it loses its capacity to absorb CO2, or that the greater number and extent of fires can create higher levels of CO2. According to Seneviratne, this correlation has not been taken into account adequately in existing ESMs.
Our research raises concerns that the effect of the relationship between land processes and climate change is being underestimated, says Seneviratne. Our priority should be to stop emissions as quickly as possible and help design a sustainable strategy for intelligent land management. This project has brought us significantly further in our understanding of land-climate interactions and enables us to provide much more precise projections. A lot of what we found should also inform the development of the new Green Deal for Europe.