Climate change, what are the images taken from the sky for?

Climate change, what are the images taken from the sky for?

Green spaces transformed into huge brown spots. Only the images taken from the sky allow such an observation. The latest example, the fires in Gironde: the before/after comparison using images from the Sentinel 2 satellite, from the European Space Agency (ESA), has made it possible to realize the extent of the hectares burned. “These images are particularly interesting because we see several characteristics of fires that can only be observed from space, such as burned areas or smoke emissions,” explains Clément Albergel, researcher in the climate office at ESA.

Observe constantly

Combined with a set of satellite data, these images make it possible to monitor the entire surface of the earth. “Laying sensors on the ground can sometimes be complicated, especially on maritime surfaces or in the middle of Antarctica”, explains the head of satellite data development at the Space Weather Center, Sylvain Le Moal, who emphasizes the usefulness of satellite images for observing the evolution of melting ice at the poles or the decrease in lake levels and the flow of watercourse.

“We understand the evolution of climate change in a global way, where we could not have data before”adds Freja Vamborg, scientist in the climate service of the Copernicus program.

Used since the 1960s, satellite images allow comparisons to be made over several years and give scientists the possibility of drawing a “climate signal” when certain phenomena appear or increase. “Since 1980, we have taken an image of the Arctic every July to compare and observe its reduction”, adds Freja Vamborg.

These images are complementary both with more specific measurements from meteorological stations and with images taken by drone, at lower altitude, “who can make precise observations at a lower cost”, continues Sylvain Le Moal. This weekend, firefighters used a drone to measure the extent of the fires in the Dordogne.

The clash of images

Whether taken by drone or satellite, photos also have the ability to challenge, shock, “what series of numbers don’t always havedetails the scientist. This is the power of images. » Clément Albergel notably takes the example of the 2019 fires in Australia, where the photos made it possible to realize that a territory equivalent to Belgium had gone up in smoke.

When showing familiar places, these images are all the more powerful: “A lake near your home, it’s not easy to see it shrink. But if you see a series of photos over ten years where you see it drying up, that’s very strong, very telling. In the event of a fire, you can also see where you live in relation to it », illustrates the ESA scientist. As a result, each image taken from the sky shared on social networks creates “the buzz” and is regularly taken up in the media.

On the other hand, Clément Albergel underlines the need to remain cautious in the face of certain images, in particular the recent comparison of photos of France seen from the sky in July 2021 and in July 2022 to note the drought. “Not all of them necessarily show the effects of climate change, but sometimes a temporary meteorological phenomenon. Two photos from one year to the next is not enough”warns the scientist, who still advocates the dissemination of such pictures, accompanied by explanations, “to raise awareness of the effects of climate change”.


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