Dust and its Impact on Earth’s Climate System

Last month, Columbia’s Lamont-Doherty Earth Observatory hosted a conference on dust in the climate system as part of the NOAA funded Abrupt Climate Change in a Warming World (ACCWW) project. 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.

A major goal of this meeting was to create the next generation of a dust database that would better incorporate the wealth of paleo-data that researchers have collected. Ideally, the hypothetical new database would incorporate both paleo and modern data, an even more challenging task.

Over the course of two days around half of the attendees gave talks, covering a huge range of topics. Atmospheric scientists talked about their observational records and how they have observed change in a warming world: Joe Prospero, the pioneer of dust research, described the wealth of data that he and his colleagues have gathered over 45 years and hammered home the point the value of long-term observational records. Terrestrial geologists like Helen Roberts talked about how their loess records allow them to interpret complex temporal and climatic changes. Marine researchers described challenges that are inherent to their realm, like the difficulties in figuring out what in their sediment cores is actually dust. Jan-Berend Stuut’s mathematical-analytic method to identify dust sparked a lively discussion, and Sujoy Mukhopadhyay’s brand new data using corals as a paleo archive of dust made people perk up their ears.

After 2 days of talks and an energetic poster session and conversation, it was time to figure out how to work together most effectively. Community consensus on goals can lead to progress. For example, in the 1990’s the formerly disparate oceanographic community came together to form WOCE (World Ocean Circulation Experiment), and for 10 years ships went around the world sampling the oceans in a systematic and organized way to acquire data that is now invaluable to the earth science community.

A comparable observational/experimental program for dust research is probably unlikely, though much conversation at the conference skirted the edges of such an idea. A more realistic project is to compile all the existing data into an organized database: a sort of next generation of the DIRTMAP project, with broader contents and broader goals.

This new database, with the working title DUSTSPEC, would include dust time series data over the entirety of the last glacial cycle (~ 130,000 years). In a series of plenaries and small-group discussions, the conference attendees started to identify the next steps —the most important data types to be included in the database, the most important regions to target, the most valuable projects to propose in the future. There is deep concern that long-term observational datasets such as Prospero’s, will be lost or discontinued in the future, once the people running them retire.

Details of the configuration of such a data base still need to be worked out and will be coordinated with other databases and platforms, such as NOAA’s National Climatic Data Center (NCDC) or SedDB, a new geochemical database for marine sediments. The ultimate objective is to compile a database that is readily accessible for those who study and model global climate in all of its disciplinary complexity.

Dust is a global phenomenon. Where it comes from, where it goes, and how it impacts climate and the biogeochemistry of land and oceans are questions that span all the realms of earth science. In order to understand its function in Earth’s climate system, researchers from all fields need to collaborate together. This conference provided a forum wherein the attendees could figure out what they, as a group, want for the future and how this could eventually allow them to figure out the role that dust has played in Earth’s history, and most importantly, what role it will play in the future.

By Alejandra Borunda and Gisela Winckler

The workshop was supported by NOAA ACCWW and the International Union for Quaternary Studies (INQUA). Stay tuned for more information, including a meeting summary and pdfs of the presentations on the DUSTSPEC workshop.