Since 2020, the Horn of Africa has experienced prolonged droughts punctuated by short, heavy rains that can lead to flash floods, causing acute food insecurity for more than 4 million people. A new report from the World Weather Attribution international academic collaboration finds that not only does human-induced climate change increase the likelihood of these events, it also increases the severity of their impact.
Much of the data enabling surveys like this, and many others, have been provided for decades by Earth observation satellites, which are crucial for understanding the components of the planet’s climate, their interaction with each other, and the effect of factors such as activity Human.
About 80 satellites operated by more than 30 agencies crisscross the skies, largely undetected, collecting data on topics ranging from sea level change to atmospheric carbon dioxide levels.
Combining brute force with precision, satellites, some the size of SUVs, are launched into orbits hundreds of kilometers from where they were designed to deliver constant data, often for years.
The Grace satellites, which have been operational for 15 years since 2002 and their successors since 2018, the Grace-FO satellites, are a collaboration between NASA and the German Aerospace Center.
Their role is to track changes in masses on Earth such as water and ice, using a simple principle: mass exerts a gravitational attraction, and measuring this attraction allows the deduction of the equivalent mass.
Most of the observation satellites’ instruments are pointed at Earth, but Grace-FO’s instruments are pointed at each other as they follow the same polar orbit, 200 kilometers apart.
A mass such as a glacier or an aquifer will pull on the spacecraft as they fly past it, causing changes in distance between them, as shown in the sequential diagram below.
The changes are minimal, but the onboard microwave system can detect changes one-tenth the width of a human hair.
Grace-FO is equipped with an additional experimental laser distance system to provide even more accurate measurements. The GPS signals then link the changes in distance to the location of the traction-inducing mass on the Earth. Repeated observations build a dynamic picture of Earth’s mass changes.
The satellite pairs, dubbed Tom and Jerry, observed major developments triggered by climate change during their 21-year chase.
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