Dust and it’s Impact on Climate

Dust and its Impact on Earth’s Climate System – State of the planet
BY GISELA WINCKLER|JUNE 17, 2010

Most often, we think of dust simply as the stuff that accumulates on our windowsills, but those fine particles floating in the air play an important role in the global climate system.

Dust influences the radiative balance of the planet in two different ways, either directly by scattering and absorbing incoming solar radiation, or indirectly by changing the optical properties of clouds, themselves an important player in the climate system. Dust also contains iron, a limiting nutrient in many areas of the ocean, so when dust falls onto the ocean, it can act as a fertilizer for the growth of algae, or phytoplankton, which uses CO2. Dust not only affects climate, but also is influenced by it: its production, atmospheric transport and deposition are sensitive to climatic conditions.

During Earth’s history, dust has been strongly linked with climatic conditions: Ice cores and marine sediments tell us that the ice age world was much dustier than today’s world. Thus dust is both a driver and a passive recorder of climate change under different climatic regimes of the Earth’s past. However, its exact role in past climate change remains poorly constrained. Understanding the links between dust and climate in the past will be crucial to evaluate the future impacts of dust on the Earth’s climate system in a warming world.

Because dust affects and interacts with the climate system in so many different ways, a wide range of disciplines—atmospheric modelers, paleoclimatologists, geologists, ice core scientists, biogeochemists, chemical oceanographers, and many others – are required to evaluate its role and impact. The Lamont conference (DUSTSPEC: Dust records for a warming world), organized by Gisela Winckler (a researcher at Lamont and an adjunct professor at Columbia), Natalie Mahowald of Cornell, and Barbara Maher of Lancaster University, aimed to bring people from all those different, specialized fields together into one room.

Dust researchers from different realms of science have come together in the past—most notably, the DIRTMAP project, initiated in 2001, aggregated dust deposition data on land and in the ocean. It is a fabulous resource, but it is limited to two snapshots in time: the modern or late Holocene, and a snapshot from the Last Glacial Maximum (~20,000 years ago, when the planet was much colder than it is today), and certain areas of the planet are undersampled, like the Southern Ocean.


Scientists Warn Climate Change Could Bring the Dust Bowl Back Out of the History Books – Tom McKay – Gizmodo

If there’s anything that just about sums up the desperation of the Great Depression in one filthy package, it’s photos of the Dust Bowl, when over-farming resulted in roving dust storms choking large swathes of the Great Plains region. Now, scientists are projecting that climate change could bring those hardscrabble days to a dystopian landscape near you.

In a study published on July 17 in the journal Scientific Reports, researchers at Princeton University and the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory used satellite data from 2003-2015 to resolve some of the lingering uncertainty on prior dust activity models. Their research projects that “climate change will increase dust activity in the southern Great Plains from spring to fall in the late half of the twenty-first century – largely due to reduced precipitation, enhanced land surface bareness, and increased surface wind speed.”

In other words, deforestation and the mega-droughts which are increasingly becoming a feature of our changing climate are likely to create conditions ideal for the return of massive dust storms. On the flip side, the researchers projected a decrease in dust activity in the northern Great Plains during the spring due to “increased precipitation and reduced bareness.”

Exposure to the dust itself is, obviously, very unpleasant but is also linked to a wide variety of respiratory and other ailments, including the possibility of potentially deadly pathogens and agricultural chemicals like fertilizer and pesticide hitchhiking on the storms.

The original Dust Bowl accelerated the flight of hundreds of thousands of people from 19 states in the region; the storms were so bad cattle and residents choked from “dust pneumonia,” residents were forced to dust-proof homes and static electricity stalled cars and charged random metal objects.

Though the researchers noted the original Dust Bowl was caused in large part by rapid agricultural development of the Great Plains region combined with “improper” farming techniques like lack of irrigation or use of “dust mulch,” they wrote the “influences of land use on future dust emission are minor compared to climate change.”

The new data is merely preliminary, according to Princeton researcher Bing Pu, but it lays the groundwork for the climate community to gauge the level of the threat.

“Few existing climate models have captured the magnitude and variability of dust across North America,” Pu said in a statement on Princeton’s website. “… This is an early attempt to project future changes in dust activity in parts of the United States caused by increasing greenhouse gases. Our specific projections may provide an early warning on erosion control, and help improve risk management and resource planning.”

Dust on snow controls springtime river rise in West – Global Climate Change – By Carol Rasmussen,
NASA’s Earth Science News Team

A new study has found that dust, not spring warmth, controls the pace of spring snowmelt that feeds the headwaters of the Colorado River. Contrary to conventional wisdom, the amount of dust on the mountain snowpack controls how fast the Colorado Basin’s rivers rise in the spring regardless of air temperature, with more dust correlated with faster spring runoff and higher peak flows.

The finding is valuable for western water managers and advances our understanding of how freshwater resources, in the form of snow and ice, will respond to warming temperatures in the future. By improving knowledge of what controls the melting of snow, it improves understanding of the controls on how much solar heat Earth reflects back into space and how much it absorbs — an important factor in studies of weather and climate.

When snow gets covered by a layer of windblown dust or soot, the dark topcoat increases the amount of heat the snow absorbs from sunlight. Tom Painter of NASA’s Jet Propulsion Laboratory in Pasadena, California, has been researching the consequences of dust on snowmelt worldwide. This is the first study to focus on which has a stronger influence on spring runoff: warmer air temperatures or a coating of dust on the snow.

Windblown dust has increased in the U.S. Southwest as a result of changing climate patterns and human land-use decisions. With rainfall decreasing and more disturbances of the land, protective crusts on soil are removed and more bare soil is exposed. Winter and spring winds pick up the dusty soil and drop it on the Colorado Rockies to the northeast. Historical lake sediment analyses show there is currently an annual average of five to seven times more dust falling on the Rocky Mountain snowpack than there was before the mid-1800s.

Painter and colleagues looked at data on air temperature and dust in a mountain basin in southwestern Colorado from 2005 to 2014, and streamflow from three major tributary rivers that carry snowmelt from these mountains to the Colorado River. The Colorado River’s basin spans about 246,000 square miles (637,000 square kilometers) in parts of seven western states.

The researchers found that the effects of dust dominated the pace of the spring runoff even in years with unusually warm spring air temperatures. Conversely, there was almost no statistical correlation between air temperature and the pace of runoff.

“We found that when it’s clean, the rise to the peak streamflow is slower, and generally you get a smaller peak.” Painter said. “When the snowpack is really dusty, water just blasts out of the mountains.” The finding runs contrary to the widely held assumption that spring air temperature determines the likelihood of flooding.

Coauthor McKenzie Skiles, an assistant professor in the University of Utah Department of Geography, said that while the impacts of dust in the air, such as reduced air quality, are well known, the impacts of the dust once it’s been deposited on the land surface are not as well understood. “Given the reliance of the western U.S. on the natural snow reservoir, and the Colorado River in particular, it is critical to evaluate the impact of increasing dust deposition on the mountain snowpack,” she said.

Painter pointed out that the new finding doesn’t mean air temperatures in the region can be ignored in considering streamflows and flooding, especially in the future. “As air temperature continues to climb, it’s going to have more influence,” he said. Temperature controls whether precipitation falls as snow or as rain, for example, so ultimately it controls how much snow there is to melt. But, he said, “temperature is unlikely to control the variability in snowmelt rates. That will still be controlled by how dirty or clean the snowpack is.”

Skiles noted, “Dust on snow does not only impact the mountains that make up the headwaters of Colorado River. Surface darkening has been observed in mountain ranges all over the world, including the Alps and the Himalaya. What we learn about the role of dust deposition for snowmelt timing and intensity here in the western U.S. has global implications for improved snowmelt forecasting and management of snow water resources.”

The study, titled “Variation in rising limb of Colorado River snowmelt runoff hydrograph controlled by dust radiative forcing in snow,” was published today in the journal Geophysical Research Letters. Coauthors are from the University of Utah, Salt Lake City; University of Colorado, Boulder; and University of California, Santa Barbara.

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