Extra dust in the atmosphere could mask the true effects of climate change

satellite image of earth

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

It’s no secret that humans have made great changes to the Earth and its atmosphere. But as greenhouse gases have built up in the air and our planet’s average surface temperature has risen, a lesser-known phenomenon has occurred.

Earth’s atmosphere has become dustier since pre-industrial times. And all those extra particles have likely subtly neutralized some of the effects of climate change, cooling the planet down a bit, according to a study published Tuesday in the journal Nature Reviews Earth & Environment.

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The effects of atmospheric dust are absent from almost all climate studies and projections, according to the new analysis. This means that these models could underestimate the warming associated with human-induced climate change. And, if the atmosphere becomes less dusty, we could face even faster temperature spikes.

“We want the climate projections to be as accurate as possible, and this increase in dust could have masked up to 8% of greenhouse warming,” said Jasper Kok, the study’s lead researcher and a physicist from the study. atmosphere at the University of California, Los Angeles. A press release. By adding the impacts of dust into future climate models, scientists could improve them, he continued. “This is critically important because better predictions can inform better decisions about how to mitigate or adapt to climate change.”

Kok and his co-researchers reached this 8% figure via a complex combination of models, based on a multitude of previously published studies.

First, they had to understand how atmospheric dust had changed over time. Using computer modeling and existing data from ice cores and sediment records, they found that the amount of large dust particles in the atmosphere had increased by about 55% at present, compared to the pre-industrial era. The reasons for our increasingly dusty Earth are manifold, but it boils down to land use changes like increased agriculture and development, as well as climate changes like drought, according to the researchers.

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

Dust interacts with the climate in different ways. By scattering and absorbing heat from the Sun and the Earth’s surface, dust particles can both cool and warm the planet. Dust can, for example, radiate heat from the Sun back into space. Or, it can absorb and retain heat radiating from the Earth itself. Effects also vary by region: dust on reflective deserts, ice, and snow increases warming, while dust on oceans and dark forests leads to cooling.

The direction and magnitude of dust’s impact on global temperature is further dependent on factors such as particle size, the wavelength of the radiation involved, and the land cover beneath the atmospheric dust. Dust can also react chemically with water and other compounds in the atmosphere to displace heat, and dust particles can alter cloud cycles. Finally, the dust that eventually settles in the water carries nutrients with it, which can increase the productivity of phytoplankton and increase the amount of carbon dioxide absorbed by our oceans, which indirectly affects climate change.

TL; DR: Exactly how and to what extent atmospheric dust actually changes global temperature is difficult to determine. To arrive at their final estimate, Kok and his team calculated the thermal effects of 12 different dust-related parameters — some in which dust increased warming and others in which it contributed to cooling — and added them all up. They found that the net energy flow was somewhere between a “substantial cooling” (-0.7 +/- 0.18 Watts per square meter) and a “slight warming” (+0.3 Watts per meter square), with a median of -0.2 W/square meter. Therefore, a calculated maximum cooling effect of approximately 8%.

Previous research has documented how particulate and aerosol pollution can cause planetary cooling. For example, colder temperatures are a well-known side effect of some volcanic eruptions, and a whole subset of geoengineering relies on this concept. But Tuesday’s review is new for its focus on natural dust.

Their model isn’t perfect, and the researchers note there’s a lot of uncertainty in their calculations, largely because they’re among the first scientists to attempt such estimates. “This is the first review of its kind to really bring all these different aspects together,” Gisela Winckler, a Columbia University climatologist who was not part of the new research, told The Guardian. But despite all that uncertainty, “dust is more likely to cool the climate than it warms it,” the study says, which is bad news for our understanding of climate change.

“We’ve long predicted that we’re headed for a bad place when it comes to greenhouse warming,” Kok told the Guardian. “What this research shows is that so far we have activated the emergency brake.”

That accidental temperature buffer might not stay put forever. Although atmospheric dust concentrations have increased since the pre-industrial era, they peaked in the 1980s and have since declined. If this decline were to continue or intensify, warming could catch up with us more quickly – a troubling possibility in an already record-breaking and searing reality.

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