Dust and aerosol pollution from Asia travels across the ocean and sullies the air in the United States and Canada, possibly worsening the effects of climate change, a NASA-backed study showed on August 02.
About half of the aerosol particles in North America come from foreign sources, and most are just from naturally occurring dust rather than from burning coal or other fossil fuels, said the research published in the journal Science.
About 64 million tons of dust, pollution and other particles that have potential climate and human health effects survive a trans-ocean journey to arrive over North America each year, the space agency said.
That rivals the 69 million tons of aerosols produced domestically from natural processes, transportation and industrial sources.
"This first-of-a-kind assessment is a crucial step toward better understanding how these tiny but abundant materials move around the planet and impact climate change and air quality," said lead author Hongbin Yu, a NASA atmospheric scientist.
Since dust emissions could rise as a result of increasingly dry weather, drought and desertification brought on by climate change, efforts by North America alone to curb pollution would not be enough, the study said.
Instead, all nations must work together to cut back on harmful emissions in the environment, the study urged.
The imported aerosols could be harming the environment by absorbing radiation from the sun, altering cloud formation along with rain and snow patterns, and speeding snow melt in the western US mountains, said the study.
Aerosols can have a cooling effect by reflecting sunlight back to space. The researchers found that imported particles account for one third of the reduction in solar radiation, or solar dimming, over North America.
"Globally this can mask some of the warming we expect from greenhouse gases," said co-author Lorraine Remer, an atmospheric scientist at the University of Maryland.
The research was based on data from a US-French environment satellite called CALIPSO that allowed scientists to separate which particles were natural dust and which were pollutant based.
"To mitigate aerosol impacts on regional climate change, actions by a single nation are inadequate. The world must work co-operatively and act synchronically to meet the challenges of global health on a changing planet," said the study.
It also called for more study on how dust itself may affect climate.
"Dust emissions can respond to climate changes, such as changes of wind, precipitation and vegetation. It is thus essential to acquire better understanding of the interactions between dust and climate," the study said.
Researchers noted that their current focus was on foreign dust and aerosols carried into the United States and Canada, but that aerosols emitted and produced in North America certainly affect other regions in much the same way.
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