Excess dust in the atmosphere could mask the real effects of climate change

Earth satellite image

A dust storm covering the Persian Gulf and the Middle East in 2014.

It’s no secret that humans have made major changes to the Earth and its atmosphere. But as greenhouse gases accumulated in the air and the average surface temperature of our planet rose, a less well-known phenomenon occurred.

Earth’s atmosphere has become much dustier since the pre-industrial era. And it’s possible that all of these extra particles are subtly working to counter some of the effects of climate change — cooling the planet a bit, according to Review study It was published Tuesday in the journal Nature Reviews Earth & Environment.

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According to the new analysis, the effects of atmospheric dust are absent from almost all climate studies and projections. Meaning, these models can underestimate the warming associated with human-caused climate change. And if the atmosphere becomes less dusty, we could see rapid temperature rises.

“We want climate projections to be as accurate as possible, and this increase in dust could mask up to 8% of global warming,” said Jasper Cook, the study’s principal investigator and an atmospheric physicist at the University of California, Los Angeles. Press release. He continued that by adding dust effects to future climate models, scientists can improve them. “This is critical because better predictions can help make better decisions about how to mitigate or adapt to climate change.”

Cook and colleagues arrived at this 8% figure via a complex set of models, building on a wealth of previously published studies.

First, they had to find out how atmospheric dust has changed over time. Using computer modeling and existing data from ice samples and sediment records, they found that the amount of large dust particles in the atmosphere has risen by about 55% today, compared to the pre-industrial era. There are many reasons behind the increase in dust in the planet, but it is due to changes in land use such as increased agriculture and development, along with climatic changes such as drought, according to the researchers.

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Next, the study authors had to determine the overall climatic effects of this dust.

Dust interacts with the climate in many different ways. By scattering and absorbing heat from the sun and the Earth’s surface, dust particles can Both Cools and warms the planet. Dust can, for example, reflect heat from the sun back into space. Or it can absorb and retain the heat given off by the Earth itself. Effects also vary by region: dust over reflective deserts, ice and snow lead to increased warming, while dust over oceans and dark forests lead to cooling.

The direction and magnitude of the dust effect on global temperature also depends on factors such as particle size, the radiation wavelength involved, and the ground cover beneath the atmospheric dust. Dust can also react chemically with water and other compounds in the atmosphere to shift heat around, and dust particles can change cloud cycles. Finally, the dust that eventually settles in the water carries nutrients with it, and so can increase phytoplankton productivity and increase the amount of carbon dioxide our oceans absorb – indirectly affecting climate change.

TL; DR: It’s hard to know exactly how and by how much atmospheric dust actually changes global temperature. To arrive at their final estimate, Kok and crew calculated the thermal effects of 12 different dust-related parameters — some of which increased the temperature of the dust and some of which contributed to cooling — and combined them together. They found that the net power flux was somewhere between “significant cooling” (-0.7 +/- 0.18 watts per square metre) and “slight warming” (+0.3 watts per square metre), with an average of -0.2 watts per square metre. Hence, the maximum cooling effect calculated is about 8%.

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Previous research has documented how to use particulate matter and aerosols Pollution can cause planetary cooling. For example, colder temperatures are a known side effect of Some volcanic eruptionsand a whole subset of Geoengineering hinges on this concept. But Tuesday’s review is fresh for its focus on naturally occurring dust.

Their model isn’t perfect, and the researchers note that there is a lot of uncertainty in their calculations — in large part because they were among the first scientists to attempt such estimates. “This is the first review of its kind that really brings all these different aspects together,” Gisela Winkler, a climate scientist at Columbia University who was not part of the new research, said. he told the Guardian. But for all this uncertainty, the study says, “Dust is more likely to cool the climate than warm it” — bad news for our understanding of climate change.

“We’ve long predicted that we’re headed for a bad place when it comes to rising global warming,” Cook told the Guardian. “What this research shows is that, until now, we’ve had emergency brakes.”

An accidental temperature buffer may not stay in place forever. Although atmospheric dust concentrations have been rising since the pre-industrial era, they peaked in the 1980s and have declined since then. If this decline continues or intensifies, warming could catch up with us even more quickly – a troubling prospect in the future Already broke the recordhot reality.

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