The series of heatwaves we are currently experiencing in western Europe is a clear sign of human-induced global warming. ESA's climate applications scientist, Clement Albergel, explains how we monitor these events using satellites such as the Copernicus Sentinel-3 mission and puts them in the context of the long-term climate data record generated via ESA’s Climate Change Initiative.
Heatwaves and climate change - video transcript
Heatwaves, defined as abnormally high temperatures, observed for several consecutive days, are among the most worrying climatic extremes with regard to the vulnerability of our societies.
The heatwaves experienced since June in western Europe are the clearest signs of global warming caused by human activities, as shown by the various reports from the Intergovernmental Panel on Climate Change (IPCC). They give us a glimpse of our future climate.
Increase in extreme events
The latest reports published by the IPCC indicates that heatwaves and more generally extreme hydro-climatic events are increasing, both in intensity and frequency due to climate change linked to human activities and in particular to our emissions. of greenhouse gases in the atmosphere.
To understand them better we need observations
Earth Observations satellites such as those operated by the European Space Agency (ESA) in partnership with the European Commission under the Copernicus programme allow us to monitor these extreme events and to confirm already some of the conclusions from the IPCC.
Sentinel-3 – Land Surface Temperature
Sentinel-3, for example, has a radiometer that measures land surface temperature. This is not air temperature in the meteorological sense but rather the actual amount of radiant energy from the Earth - and indicates the actual temperature of Earth's surface. Of course, the high air temperatures are reflected in the temperature values of the earth's surface.
Sentinel-3 has recorded extreme Land Surface Temperature in recent weeks, more than 45 in the UK, 50 in France and 60 in Spain
These observations can also be combined with those of other instruments on board other Earth observation satellites to develop long time series, allowing a better understanding of the climate system.
And that’s what we do in the context of ESA’s climate programme, the climate change initiative, setting up long term, global scale, robust time series of key components of the climate system
For example, we have recently set up a 25-yr global land surface temperature database. The data record shows a stable increase in land surface temperature (LST) of 0.2C per decade, with strong regional variability within this.
Wildfire – increasing risk
When high temperatures are combined with low humidity, low rainfall and/or high winds there is an increased risk of wildfire in case there is a source of ignition. This combination of conditions is now observed over longer period over much of the world, including Europe, and are linked to climate change.
Human induced climate change increases the frequency and/or severity of periods with high fire risk.
Satellites are extremely useful in the context of fire monitoring and permit to monitor different fire characteristics: areas that are dry and prone to wildfire outbreak, actively flaming and smouldering fires, burned area, as well as smoke and trace gas emissions.
Satellites can measure electromagnetic radiation, the light reflected, and the heat emitted from our planet.
We can use different types of instruments, sensors, such as visible and infrared detectors, the visible ones can detect smoke plumes from fires as well as burn scars. The thermal infrared one can detect actual hotspots and active fires. We identify from space, areas on the ground that are distinctly hotter than their surroundings and flags them as active fires. The difference in temperature between the areas that are actively burning with respect to neighbour areas allows the identification and mapping of active fires.
If we put the notion of risk monitoring and risk assessment aside, we focus on Fire in the context of climate because vegetation on land disturbed by wildfire has the potential to release significant amount of greenhouse gas and particulate matter into the atmosphere.
Long-term satellite observations have the capacity to support effective policy making, policy implementation monitoring it is estimated, that about 25%-35% of Greenhouse gases (GHG) result from biomass burning and therefore they are considered an important factor in climate change.
The spectre of drought
Another consequence of heatwaves combined with low levels of precipitation is drought. Soils are getting drier and many rivers across Europe have reach record low levels. Images acquired by Sentinel-2 show the Po valley near Piacenza in Italy, and reveal how the river has shrunk between June 2020 and June 2022. This is partially due to lower than normal levels of precipitation across in northern Italy, combined with extremely high temperatures and lower meltwater levels resulting from a lack of snow from the nearby mountains that usually feed the river.