NASA’s PACE satellite will address the biggest uncertainties in climate science

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comeStool stuff Can have a big impact. Take the plankton plants that populate Earth’s oceans. When zooplankton eat them, phytoplankton release a chemical called dimethyl sulfide (DMS) and this is what people mean when they talk about “the smell of the sea”. Chemical reactions take place in the atmosphere DMS In sulfur-containing particles that provide a surface for water vapor to condense. That’s enough times and the result is a cloud. Clouds, in turn, affect both local weather and the world’s climate by reflecting sunlight into space.

Other small things have similarly massive effects. Sulfur from ship funnels also produces particles that seed clouds, creating the string of white “shiptracks” seen in satellite images. Burning fossil fuels, however, has the opposite effect. It is made up of dark particles that absorb solar energy, warming the air around them and discouraging cloud formation. If sulfur particles make it high enough in the atmosphere (thanks 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, quantifying them is much more difficult. Uncertainty about the behavior of “aerosols,” as the various small particles in the air are collectively known, is one of the main sources of scientific uncertainty in climate models. So they’re a big factor in the error bars surrounding estimates of how much warmer the Earth would get due to an increase in atmospheric carbon dioxide.

Climate scientists hope so NASAIts new satellite, speed (for “Plankton, Aerosol, Cloud, Ocean Ecosystem”), which is scheduled to launch on February 8, will reduce those uncertainties around aerosols. When it is in Earth’s orbit, speedIts cameras will sweep the planet every one to two days to create a constantly updated census of the very small objects suspended in the ocean (plankton) and air (aerosol).

speedIts main camera is sensitive to the light spectrum between ultraviolet and near-infra-red. For the ocean, that means speed Be able to distinguish different types of phytoplankton. “This is powerful because diatoms fuel fisheries [and] “Cyanobacteria can be harmful,” says Jeremy Wardell, an oceanographer NASA who speedIts chief scientist. Two more devices are installed speed will present information on the size and shape of aerosols, making it possible for the first time to distinguish soot from sea spray and particles produced by burning fossil fuels.

This could be “transformational” for climate models, said Gavin Schmidt, a climate scientist who also works here. NASA. Modelers have had to compensate for the limited nature of existing aerosol data with informed assumptions. As a result, different climate models vary significantly in their estimates of how strongly they influence climate.

Such uncertainty affects questions about how air pollution affects climate change. Legislation in Europe and North America has reduced air pollution from fossil fuels since the 1980s. It is a boon for human health. But it also lifted a smog that masked some of the warming caused by greenhouse gas emissions. Cleaning up air pollution could be one of the most important impacts on climate in the coming decades. Better data will allow better modeling.

Similarly, climate experts are divided on the impact of rules adopted by the International Maritime Organization, part of the United Nations, which limit the amount of sulfur in ship fuel from January 2020. Some believe that the reduction of sulfur in ship exhaust may contribute to this. 2023 records exceptionally hot temperatures around the world. Others think its impact was minimal.

There are many more questions climatologists want to answer. Writing on the whiteboard in Kirk Nobelspace’s office NASAGoddard Space Flight Center in Greenbelt, Maryland, a list of 18 projects. From gathering live data on volcanoes and forest fires to answering what happens when the agricultural clearing fires that burn every year in West Africa end up in marine cloud tops, they face the sun. The answer to all these questions depends on the behavior of small things. After decades of uncertainty, there may be answers.

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