NASA Earth Observatory

Aerosols—and clouds seeded by them—reflect about a quarter of the Sun’s energy back to space.

For all we know about climate change and the Earth’s atmosphere, it’s amazing how much more there is to learn. Earlier this month, a team of researchers led by University of Colorado’s Roy “Lee” Mauldin III announced the discovery of a brand new atmospheric compound tied to both climate change and human health.

Above certain parts of the earth, they found, the new compound is at least as prevalent as OH, also called the hydroxyl radical, long thought to be the primary oxidant responsible for turning sulfur dioxide, an industrial pollutant, into sulfuric acid. The new compound, it turns out, can play an equally important role. Sulfuric acid contributes to acid rain and results in the formation of aerosols, airborne particulates associated with a variety of respiratory illnesses in humans and known to seed the formation of clouds.

Mauldin made the discovery by investigating background levels of sulfuric acid in atmospheric samples that were not attributable to OH. He inferred that another compound must be responsible for the effect and was able to isolate it through a series of tests. No one else had ever made the connection before.

“As soon as I realized that we were observing a new oxidant, the light clicked on all over the place,” Mauldin said in an interview. “With anything that can produce sulfuric acid, if you can come up with something that occurs on a daily basis, or in this case 24/7, it can affect all sorts of things, including climate and human health.”

In few places is that effect more pronounced than in California. “Aerosols are a major public health problem in the Central Valley,” said Ron Cohen, Director of the Berkeley Atmospheric Sciences Center at the University of California. In fact, they’re worse in the Valley than just about anywhere else in the country — except maybe Los Angeles.

Mauldin believes that the new compound is emitted more heavily by trees than by man-made sources, meaning it may be less important to aerosol formation above the Central Valley than it is above the Finnish Boreal Forest where field research was conducted. But we don’t know that for sure. Nor do we know precisely how to calculate aerosols’ role in climate change.

In fact, aerosols are one of the least-understood variables in climate models, Cohen said. We do know that aerosols contribute to cloud formation, commonly understood to have a cooling effect on the earth. However, we don’t know whether aerosols are changing the height of clouds, which has complex implications for temperature: low clouds tend to have a cooling effect, while high clouds actually trap heat in the atmosphere. Furthermore, some aerosols reflect heat, while others absorb it.

The new compound offers science a new way of charting the formation of aerosols today as well as an important tool for determining what the atmosphere was like before we came along. Both uses are likely to fine-tune our ability to understand and forecast climate change moving forward. As far as what, precisely, it’ll tell us — well, that remains to be seen.

Molly Samuel

Researchers found that heavy snowfall in the Sierra is connected to the amount of dust floating over from Asia.

In a weird twist on the “butterfly effect,” evidence is that Asian dust storms can mean more snow in the Sierra. The strange finding surfaced in research by scientists working on NOAA’s CalWater program. Scientists compared two Sierra storms, and found the one that contained dust particles from Asia had 40% more precipitation than the one that did not. The other storm had more particulate matter from sources in California, for instance, from burning trees or grass.

The researchers, including Kim Prather and Doug Collins from the Scripps Institute of Oceanography at UC San Diego compared the two storms from the air.

In a series of test flights, scientists flew a zig-zag pattern from the former McClellan Air Base, east of Sacramento, toward the Sierra, using a specially outfitted C-130 research aircraft based at the National Center for Atmospheric Research in Boulder, Colorado.

NCAR

A C-130 research aircraft was outfitted with special probes to collect cloud droplets and ice particles during the cloud fly-throughs.

Prather, who directs the Center for Aerosol Impacts on Climate and the Environment at UC San Diego, said there’s still a lot to learn about the precise “interfacial” chemistry that goes on among cloud particles. Only one particle in a thousand is likely to become an ice crystal, the basic building block of snow. Prather says there’s “something chemically magical about ice crystals.” Apparently so, as clouds remain one of the most difficult aspects of climate modeling. “Aerosols” is the term scientists use to refer to all sorts of particulate matter drifting around in the air.

After a Friday presentation at the American Association for the Advancement of Science (AAAS) in Vancouver, Prather told me that no flights were scheduled this winter because of the unusual dearth of rain clouds, but that they planned to resume cloud-probing flights next winter.

The dust connection is another piece to the California water puzzle, and will help researchers better understand why we get precipitation when we do, and help them make better projections.

There’s more about the research in this article from the Bay Citizen.

Eruption of Eyjafjallajökull Volcano, Iceland (Photo: NASA Earth Observatory)

The ongoing eruption of Mt. Eyjafjallajokull in Iceland is disrupting flights across Europe, shutting down some of the busiest airports and aviation corridors in the world. But could it also disrupt the climate system, leading to a temporary cooling trend this summer?

Not likely, according to Rutgers University environmental sciences professor Alan Robock, an expert on how volcanoes alter the composition of the Earth’s atmosphere. According to Robock, the Icelandic eruption hasn’t contributed enough sulfur dioxide to the upper atmosphere to significantly alter the climate.

“From what I’ve seen from the observations so far, there hasn’t been enough put into the atmosphere to have a large climate effect,” he said in a telephone interview.

It is well known that volcanic eruptions can affect the climate. Just ask historians, who can tell you about the “year without a summer” that followed the enormous eruption of Mt. Tambora in Indonesia in 1816. More recently, the 1991 eruption of Mt. Pinatubo in the Philippines, which contributed about 20 megatons of volcanic material to the atmosphere, cooled global average surface temperatures by about one degree Fahrenheit in the year following the eruption.

By vaulting particles of sulfur dioxide and other reflective aerosols high into the stratosphere, volcanic eruptions can reduce the amount of solar radiation reaching the planet’s surface. However, this only results in temporary cooling, since chemical processes and air currents remove the particles over time.

NOAA plot showing a decrease in solar radiation reaching the Earth's surface after major volcanic eruptions

In addition to causing short-term cooling, volcanoes also contribute carbon dioxide (CO2) to the atmosphere, which in the very long-term balances slow CO2 losses from other causes. The volcanic contribution of CO2 to the atmosphere is estimated to be well less than the recent human contribution, on average.

Robock noted that the ash cloud that is canceling flights would not alter the climate, since it will fall out of the air in a matter of days. “What’s dangerous for airplanes is not what causes climate to change,” he said.

The volcano’s climate impacts may also be limited by its high-latitude location, since the air circulation in the upper atmosphere in the high latitudes tends to be more efficient at getting rid of volcanic material, compared to lower latitudes where sulfur dioxide particles from volcanoes can linger for years.

Robock noted that Icelandic eruptions have disrupted climate in the past, such as a long duration event in 1783-4 that cooled temperatures in Europe, catching then US ambassador to France Benjamin Franklin’s attention. According to the National Oceanic and Atmospheric Administration, Franklin was a pioneer in linking a volcanic eruption to climate change.

It’s still possible that this volcano, which is continuing to erupt, may yet send more volcanic material into the upper atmosphere, thereby causing a cooler summer in the northern hemisphere.

Aside from the political and economic risks associated with geoengineering, which we explored in Monday’s radio segment on The California Report, critics warn that climate intervention strategies involve some serious potential environmental consequences as well.

In one 2008 study, scientists at the Lawrence Livermore National Lab found that one of the leading geoengineering ideas–blocking solar radiation by pumping sulfur aerosol into the stratosphere–may lead to decreased precipitation across the globe.

Climate scientist Phil Duffy, now of the education organization Climate Central and one of the authors of the 2008 study, says that the decrease in precipitation would follow a slowdown of the overall hydrologic cycle, caused by a decrease in evaporation.  Blocking sunlight reduces evaporation, and since what comes down much first go up, less evaporation means less rain and snow.  As this geoengineering scheme is being proposed as an emergency brake to counter effects of climate change like drought, this is problematic news.

Stratospheric sulfur injection could also seriously damage the Earth’s ozone layer above the Arctic, another 2008 study found.  And opponents fear that it could lead to acid rain, which could exacerbate the growing problem of ocean acidification.

Ken Caldeira of the Carnegie Institute for Science says that computer modeling from his lab indicates that even if the strategy improved living conditions for 90% of the people on the planet, it’s likely that 10% would suffer negative environmental consequences, and, he says, it would be hard to predict where on the planet that 10% would be.

“We’ve come to the conclusion that there are no experiments that will tell you ahead of time what the regional effects will be,” said Caldeira.

Another high-profile strategy involves fertilizing the ocean with iron as a way to  encourage algae blooms for carbon sequestration.  Algae absorb carbon dioxide as they grow, and the theory is that when they die, they’ll sink to the bottom of the ocean and take the CO2 with it.  There is conflicting research about whether this could work as a long-term sequestration strategy, but a recent study suggests that regardless of whether it’s effective at sequestering CO2 or not, fertilizing the oceans with iron could harm marine ecosystems.   The research shows that increases in algae from the genus Pseudonitzschia can promote concentrations of domoic acid, a poison that can kill birds and marine mammals.  Richard Black has more on the new findings at the BBC website.

For more on the potential risks of geoengineering, Alan Robock‘s article “20 Reasons Why Geoengineering May Be a Bad Idea” appears in the May/June issue of the Bulletin of Atomic Scientists.

Smoke fans out from L.A. fires this week. Clickable image: NASA

My colleague Dan Brekke, an ardent watcher of elemental stuff like water and fire, featured a map of the spreading haze in his personal blog.

By Wednesday evening Brekke relayed that flames had consumed an area about the size of Chicago (and no, he couldn’t resist the low-hanging Mrs. O’Leary reference). With less than 30% containment, smoke had spread over about three-quarters of the state. Beyond California, NOAA had tracked the plumes “northward and eastward…across southern Nevada, Utah, Colorado, and Kansas.”

Front page of Wednesday's Denver Post

From The Denver Post:

“Joe Ramey, a meteorologist with the National Weather Service in Grand Junction, said that a high-pressure system is continuing to pump smoke from several California fires and 17 fires currently burning in Utah into the state. He said a fire near Nucla in south-central Colorado also may be contributing to the haze…Most of the smoke, however, is being generated by the 190-square-mile fire burning near Los Angeles, he said.”

While the current pall is not entirely California-born, it does make the point that large wildfires cast a surprisingly long shadow.

Atmospheric scientists classify smoke as an “aerosol” (any airborne particulate matter), which has a complicated set of feedbacks on the climate. For instance, aerosols encourage cloud formation and clouds have both positive and negative feedback effects on global warming. But it’s clear that smoke plumes generate greenhouse gases and also carry toxic air pollutants such as carbon monoxide.

Briefing journalists last month at the National Center for Atmospheric Research (NCAR)–in Boulder, no less–atmospheric chemist Gabriele Pfister said that wildfires have multiple effects on the atmosphere. They “disturb the carbon cycle,” interfering with energy exchanges and generating greenhouse gases. Itinerant smoke can generate ozone pollution far from the initial fires. This presents a challenge for local regulation of “ground-level” ozone, since it’s often likely an import from distant fires.