A dust storm covers the Persian Gulf and the Middle East in 2014.
It’s no secret that humans have made huge changes to 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 been occurring.
Earth’s atmosphere has gotten dustier since the pre-industrial era. And all those extra particles have probably been subtly counteracting some of the effects of climate change, cooling the planet a bit, according to a review 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. Which means these models could be underestimating the warming associated with human-caused climate change. And, if the atmosphere becomes less dusty, we could face even faster temperature spikes.
“We want climate projections to be as accurate as possible, and this increase in dust could have masked up to 8 percent of the greenhouse warming,” said Jasper Kok, lead researcher on the study and an atmospheric physicist at the University of California, Los Angeles. , it’s a statement. a press release. By adding dust impacts into future climate models, scientists could improve them, he continued. “This is of tremendous importance because better predictions can inform better decisions about how to mitigate or adapt to climate change.”
Kok and his co-investigators reached that 8% number through a complex combination of models, based on a large number of previously published studies.
First, they had to find out how atmospheric dust has changed over time. Using computer models and existing data from ice cores and sediment records, they found that the number of large dust particles in the atmosphere has increased by about 55% today, compared to the pre-industrial era. The reasons behind our increasingly dusty Earth are manifold, but they are land-use changes like increased agriculture and development, along with climate changes like drought, according to the researchers.
The study authors then had to determine the overall climate effects of that dust.
Dust interacts with the weather in many different ways. By scattering and absorbing heat from the Sun and Earth’s surface, dust particles can both cold and warm planet. Dust can, for example, reflect the Sun’s heat back into space. Or, it can absorb and retain the heat that the Earth itself radiates. The 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 the impact of dust on global temperature also depends on factors such as the size of the particles, the wavelength of the radiation involved, and the land cover beneath the atmospheric dust. Dust can also chemically react with water and other compounds in the atmosphere to displace heat, and dust particles can change cloud cycles. Finally, the dust that eventually settles in the water carries nutrients with it, so it can increase the productivity of phytoplankton and increase the amount of carbon dioxide our oceans absorb, indirectly affecting climate change.
TL; DR: It’s hard to figure out exactly how and how much atmospheric dust is actually changing global temperature. To arrive at their final estimate, Kok and his team calculated the effects of heat for 12 different dust-related parameters, some where dust increased warming and others where it contributed to cooling, and added them all up. They found that the net power flow was somewhere between “substantial cooling” (-0.7 +/- 0.18 watts per square meter) and “mild heating” (+0.3 watts per square meter), with a median of -0.2 W/square meter. Therefore, a calculated maximum cooling effect of around 8%.
Previous research has documented how particles and aerosols Pollution can cause planetary cooling. For example, colder temperatures are a well-known side effect of some volcanic eruptionsand a whole subset of geoengineered hinges about that concept. But Tuesday’s review is novel for its focus on natural powder.
Their model is not perfect, and the researchers note that there is a lot of uncertainty in their calculations, largely because they are some of the first scientists to attempt such estimates. “This is the first review of its kind that really brings all these different things 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 warm it,” the study says, which is bad news for our understanding of climate change.
“We have been predicting for a long time that we are heading to a bad place when it comes to the greenhouse effect,” Kok told The Guardian. “What this investigation shows is that, until now, we have had the emergency brake activated.”
That accidental temperature damper might not stay in place forever. Although atmospheric dust concentrations have increased since the pre-industrial era, they peaked in the 1980s and have been declining ever since. If that decline were to continue or intensify, warming could catch up with us faster, a puzzling possibility in a already breaking recordshot reality.
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