NASA’s PACE satellite addresses the biggest uncertainty in climate science

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Sslow things it can have serious consequences. Take the plankton that lives in the Earth’s oceans. When zooplankton eat them, the phytoplankton release a chemical called dimethyl sulphide (DMS) and this is what people refer to when they talk about “the smell of the sea”. Chemical reactions in the atmosphere reverse DMS into sulfur-containing particles that provide a surface for water vapor to dry on. Do that enough times and the result is a cloud. Clouds, in turn, affect both the local weather and, by reflecting sunlight into space, the world’s climate.

Other small things have similar effects. Sulfur from ship funnels also forms particles that seed clouds, producing layers of puffy white “ships” seen in satellite images. At the same time, juice has another effect from burning fossil fuels. It is made of dark particles that absorb the sun’s energy, warming the air around them and discouraging cloud formation. If sulfur particles make it high enough in the atmosphere (due to a volcanic eruption, perhaps) they can form a haze that prevents some sunlight from reaching the Earth’s surface.

But while scientists generally know how these processes work, measuring them is much more difficult. Uncertainty about the behavior of “aerosols”, as a number of small particles in the air together, is one of the main sources of scientific uncertainty in climate models. They are therefore a large factor in the error bars surrounding projections of how hot the Earth will be for a given increase in the amount of carbon dioxide in its atmosphere.

Climate scientists hope so NASAnew satellite, PACE (for “Plankton, Aerosol, Cloud, Ocean Ecosystem”), which is scheduled to launch on February 8, reduces this uncertainty regarding aerosols. When in Earth’s orbit, PACEthe cameras sweep the planet every couple of days to create a constantly updated record of the tiny things suspended in the oceans (plankton) and the air (aerosols).

PACEThe main camera is sensitive to the light spectrum between the ultraviolet and the near infrared. For the oceans, that means PACE they will be able to identify different types of phytoplankton. “That’s powerful because diatoms fuel fisheries [and] cyanobacteria can be harmful,” said Jeremy Werdell, a marine biologist at NASA Who is PACEis a leading expert. Two more machines mounted PACE we provide information on the size and shape of aerosols, making it possible for the first time to distinguish soot from sea spray and particles from burning fossil fuels.

That could be “transformative” for climate models, says Gavin Schmidt, a climate scientist who also works at NASA. Models have had to compensate for the limited availability of aerosol data with informed measurement work. As a result, different climate models vary greatly in their estimates of how aerosols will affect the climate.

Such uncertainty affects questions about how air pollution affects climate change. Laws in Europe and North America have cut the amount of air pollution from fossil fuels since the 1980s. This benefits people’s health. But it has also built a smokescreen that hid some of the warming caused by greenhouse gas emissions. Cleaning up air pollution could be one of the most important impacts on the climate in the coming decades. Better data allows better modeling.

Similarly, climate experts are divided over the impact of regulations adopted by the International Maritime Organization, part of the United Nations, which will limit the amount of sulfur in marine fuel starting in January 2020. .the extremely hot temperatures recorded around the world in 2023. Others believe that the impact was minimal.

There are plenty more questions that clinicians would like to answer. Written on the whiteboard in Kirk Knobelspiesse’s office at NASAThe Goddard Space Flight Center in Greenbelt, Maryland, is a list of 18 projects. It ranges from collecting live data on volcanoes and forest fires to answering what happens when soot from agricultural clearing fires that burn annually in West Africa rises above sea clouds, darkness against which they appear to the sun. The answers to these questions all depend on the behavior of tiny objects. After decades of uncertainty, answers may be on the way.

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