Past climate extremes and their impact on the terrestrial carbon cycle (SAT-EX)

Start-End 01/10/2014 -  30/09/2018
Programme STEREO 3
Contract SR/00/306
Objective Meteorological droughts, rainfall extremes and heatwaves are major natural disasters with diverse socio-economical and environmental consequences. There is a perception that these climatic events are becoming unusually abundant after recent droughts in Western United States (2011) or North-Eastern China (2009), unprecedented wet periods accompanied by floods in U.K. (2007) or Pakistan (2010), and unparalleled mega-heatwaves in Europe (2003, 2010). These events caused the failure of the agricultural and food production systems, natural biomass loss, the spread wild fires, air pollution, water scarcity, and multiple other consequences that raised the mortality tolls by tens of thousands. As we progress into the future, our climate models predict that the exacerbation and proliferation of such events will continue, following the expected rise in greenhouse gases.

The five objectives of SAT-EX are:

  1. To provide new observational evidence of how droughts, heatwaves and extreme rain events have changed in time and space over the satellite era.

  2. To identify the drivers behind these changes, e.g., intensification of the hydrological cycle, widening of the tropical belt, ocean-atmospheric oscillations, anthropogenic emission, etc.

  3. To provide satellite-based observational insights into the past changes in global vegetation and the role of extreme hydrological and climatic events on these changes.

  4. To show if IPCC ESMs reproduce the past changes in climatic extremes shown in the satellite records and understand the sources of discrepancies.

  5. To show if IPCC ESMs reproduce the observed changes in vegetation with particular emphasis on the extremes and the vegetation response to hydrological and climatic extremes.
Method The term 'extreme' is applied to those climatic events that are significantly larger than expected, considering a non-changing (stationary) climate as reference. While this concept still depends on the definition of stationary conditions and the setting of extreme thresholds, a wide range of statistical indices have been used in recent years aiming to minimize the subjectivity on the characterization of what is considered 'extreme'. Analysing these events is challenging given that, by definition, their frequency of occurrence is low. This is especially problematical when using remote sensing data due to the characteristic short lifespan of satellite platforms and sensors. However, recent scientific efforts have yielded global consistent records of climatic and environmental variables through the combination of data from multiple satellite sensors. In this blending of multi-sensor data, several cross-calibration techniques have been applied, validation exercises against in-situ measurements have been performed, and error estimates have been calculated. Now, records of 30–35 years are available for some variables (e.g., temperature, soil moisture, vegetation physical properties, evaporation). This timespan is still short, but appears long enough to start assessing some of the critical aspects of the changes in climate extremes and global vegetation dynamics in recent decades.

Assuming a sufficiently long, high-quality time series of a given climatic variable (e.g. precipitation, temperature), the number of extremes should remain constant over time for a stationary climate. Therefore, if a trend in the number or intensity of these extremes were detected, this would be indicative of climate change, i.e. a long-term change in the mean and/or the shape of the probability density function of that climatic variable. In our context, this climatic change may reflect:

  1. the direct impact of greenhouse gases, aerosols or land-use change on the radiation budget,
  2. the subsequent intensification or deceleration of the hydrological cycle,
  3. a reorganization of the large-scale preferential climatic and hydrological patterns (e.g. the widening of the tropical belt),
  4. the 'confounding effects' from multi-year and decadal climatic oscillations. All these different processes lead to impacts on the terrestrial biosphere, and especially on the variability and distribution of continental vegetation. SAT-EX aims to use traditional climate extreme indices derived from recent remote sensing long-term records, to detect and attribute changes in climatic and environmental extremes using a combination of spatiotemporal clustering methods, fingerprint analysis and random forest machine- learning
Result The main products that  can be expected are new methodologies and insights into the application of remotely-sensed observations and enhanced knowledge regarding recent changes in the Earth climate system.  The  products  will  initially  be  delivered  in  the  form  of  contributions  to  different  international conferences, publications  in peer-reviewed journals, and through datasets  advertised via the project website. In addition, end-users will be informed on the advances made through this project, and how these may benefit their services.
Website link
Team Member: REGNIER Pierre A.G. ULB - Biogeochemistry and Earth System Modelling
Project Leader: MIRALLES Diego UGent - Laboratory of Hydrology and water management (LHWM)
Project Leader: VERHOEST Niko UGent - Laboratory of Hydrology and water management (LHWM)
Team Member: WAEGEMAN Willem UGent - Research Unit Knowledge-based Systems
Team Member: de Jeu Richard Vrije Universiteit Amsterdam - Department of Earth Sciences
Sensors used
Applications Agriculture
Forest & natural vegetation
Hydrology & freshwater resources
Weather & climate
Related presentations BEODay 2016 - 08. SAT-EX: Sensing the impact of global climate and climate extremes on vegetation
Related publications SAT-EX - La fluorescence comme indicateur de stress de la végétation
SAT-EX - Fluorescentie als indicator van vegetatiestress
Datasets used