Monthly Archives: August 2011

Black Carbon's Day on the Hill

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Drew Shindell (left), Veerabhadran Ramanathan, and Tami Bond speak with Representative Edward Markey after the three scientists testified. Credit: NASA/Voiland

Leading aerosol scientists, including NASA’s Drew Shindell, explained the intricacies of a sooty component of smoke called black carbon to members of the Select Committee on Energy Independence and Global Warming during a hearing on Capitol Hill last month.

Their message: controlling black carbon emissions could be a win-win for both human health and the environment.

Not only can partially combusted particles of carbon lodge in the human respiratory system and cause disease, the panelists explained, they also contribute to climate change by warming the atmosphere and changing the way Earth reflects sunlight back into space.

Three lawmakers—Representative Edward Markey (D-Mass.), Representative Jay Inslee (D-Wash.), and Representative Emanuel Cleaver (D-Mo.)—questioned the scientists.

Tami Bond, a black carbon specialist from the University of Illinois, began the hearing by offering a summary of black carbon’s potent short-term climate impacts. She noted, for example, that:

•     One ounce of black carbon absorbs as much sunlight as would fall on an entire tennis court.

•     A pound of black carbon absorbs 650 times as much energy during its one-to-two week lifetime as one pound of carbon dioxide gas would absorb during 100 years.

•     An old diesel truck driving 20 miles would emit about one-third of an ounce of black carbon and 70 pounds of carbon dioxide. The carbon dioxide from that truck would have five times the warming power of the black carbon, but it would spread out over 100 years. The truck’s more potent black carbon impact would have an effect in the span of a few weeks.

Drew Shindell, a climate modeler from NASA’s Goddard Institute for Space Studies (GISS) in New York City, provided more details about where black carbon comes from and how much impact it has on Earth’s climate.

As seen in this scanning electron microscope still image, small chain-like aggregates of soot cling to larger sulfate aerosol particles.  Credit: Arizona State University/Peter Buseck

Diesel vehicles, agricultural burning and wildfires, and residential cooking stoves are key sources of black carbon. However, combustion that occurs at higher temperatures — such as the type that takes place in power plants — does not produce much of the substance.

Shindell said climate models from NASA GISS and elsewhere show that 15 to 55 percent of global warming is due to black carbon. The wide range is primarily because of incomplete knowledge about how black carbon and clouds interact.

One of the more interesting questions came from Rep. Inslee, who asked the scientists whether black carbon’s impact is due to the fact that it absorbs sunlight and warms the atmosphere, or because it covers snow and ice with dark soot, which reduces Earth’s albedo and makes the planet less reflective.

Veerabhadran Ramanathan , a professor at the Scripps Institution of Oceanography, responded: “The albedo effect contributes about 10 percent of the total black carbon effect. But if you look in the Arctic or in the alpine glaciers, then the darkening effect may be the dominant effect.”

Shindell added that the scientific understanding of black carbon’s impact varies by region. “In places like the Himalayas, the results are somewhat ambiguous,” said Shindell. Over Himalayan glaciers, large amounts of dust — which also absorb radiation — and other pollutants in the air may dampen the effect. “In the Arctic, which tends to be very far from dust sources, the snow is very clean, so the effect is extremely large.” Increasing levels of black carbon combined with decreasing levels of sulfates may account for more than half of the accelerated warming in the last few decades, Shindell’s research suggests. 

Inslee also expressed frustration about the lack of understanding of science and climate change among his fellow lawmakers.”If I was scientist and I knew what was going on out there, I’d be in somebody’s grill, telling them we need action,” he said. “And yet you just don’t see that from the scientific community….Why doesn’t that happen? Should it happen?”

 Drew Shindell testifies as Veerabhadran Ramanathan looks on.
Credit: Committee on Energy Independence and Global Warming

The scientific method and the culture of scientists, Bond replied, makes it very difficult for scientists to lobby lawmakers or advocate a policy position and remain credible. “This is a difficult question and has to do with the nature of scientists and how they approach science,” she said. “If you have an action outcome, one is almost afraid that you’ll affect the science because you’re supposed to look at it dispassionately. How we conduct our business, 99.9 percent of the time, we must step back from what we want the outcome to be. We’re not allowed to want an outcome.”

Adam Voiland, NASA’s Earth Science News Team

Tracking Hurricane Irene?

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As Hurricane Irene strengthens and threatens the East Coast, it seems a particularly apt time to dust off this 2007 video that explains how hot towers – immensely tall cumulonimbus clouds at the center of tropical cyclones – play a key role in strengthening storms. In 2004, researchers at Goddard Space Flight Center found that a tropical cyclone with a hot tower in its eyewall (the part of a storm the most damaging winds and rain occur) was twice as likely to intensify within the next six hours than a cyclone that lacked a tower. NASA satellites did, as detailed here, observe hot towers in Irene before forecasters elevated the storm to hurricane status.

Tracking Irene? Here are some useful links:

The National Hurricane Center
NASA’s Hurricane Resource Page
The Earth Observatory’s Irene Page
The Tropical Rainfall Measuring Mission (TRMM) Page

Text by Adam Voiland. Image from the Earth Observatory.

Research Roundup: Wandering Storms, Arctic Ozone Loss, and More

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Wandering Storms in a Warming World
Most people know climate change is causing glaciers to retreat in Earth’s polar regions, but that’s hardly the only change warming temperatures can produce. A new study, led by Frida Bender of the Scripps Institute of Oceanography and published in Climate Dynamics, shows that the tracks of mid-latitude storms – the type that drives the weather systems that affect Americans the most – have shifted poleward and narrowed over the last 25 years as a result of climate change. What’s more, as the Jet Propulsion Laboratory’s Graeme Stephens notes in a Nature Climate Change article about the study, Bender’s satellite-based research shows that the cloudiness of the storm tracks has decreased over the same period. That’s important as it suggests the decline may have increased the net flux of radiation at the top of Earth’s atmosphere over storms – a process that could amplify warming over time.

Ocean Temperatures a Factor in Arctic Ozone Loss
In March of 2011, the World Meteorological Organization put out a statement announcing an unprecedented loss of stratospheric ozone over the Arctic. Between the beginning of winter and late March ozone levels declined by 40 percent due to unusually cold temperatures in the Arctic stratosphere. (Cold temperatures hasten ozone destruction by making it possible for a certain type of cloud to form that hosts ozone-depleting chemical reactions). But what caused the cold spell? A new study authored by Margaret Hurwitz of Goddard Space Flight Center and published in Atmospheric Chemistry and Physics Discussions points out that unusually warm sea surface temperatures in the North Pacific likely played a key role. The phase of the solar cycle, greenhouse gas emissions, nor El Niño/La Niña oscillations can fully the explain the unusual conditions, she notes.

Can Satellites Help Save the Burrowing Owl?
Burrowing owls, one of the world’s smallest owl species, live in the abandoned tunnels of small mammals such as ground squirrels and prairie dogs. The long-legged birds, which typically weigh just 6 ounces, are losing ground to development and some conservation groups put the number of breeding burrowing owls at a mere 10,000. A new study, published in the Canadian Journal of Remote Sensing, suggests that crop classification imagery from Landsat satellites could be used to evaluate owl demographics and help with conservation plans as agricultural areas experience short-term changes.

Hang Tight, LandSat 5
Speaking of LandSat, Landsat 5, launched in 1984, is still operating more than a quarter of a century later despite having an original design life of three years. However, the reality that LandSat 5’s critical Thematic Mapper instrument, which many agencies around the world rely upon, won’t last indefinitely is becoming increasingly difficult for scientists to ignore as the satellite ages. Since Landscape 6 failed to reach orbit and LandSat 7’s Enhanced Thematic Mapper, which reached orbit in 1999, has a glitch that omits key strips of images, there’s a real possibility that top-tier LandSat images won’t be available until the Landsat Data Continuity Mission launches in December of 2012, a new study in the Canadian Journal or Remote Sensing cautions. The Australian authors of the study tested some of the alternative satellite data products, but none of them quite measured up to LandSat 5 in their view.

Locavores Take Note
Climate models generally assume that the carbon agricultural crops take up later reenters the atmosphere in approximately the same geographic area, but in reality food gets shipped long distances before we consume it. A new paper, authored by Tristram West of the Pacific Northwest National Laboratory (PNNL) and published in Biogeosciences, accounts for the mobile nature of food and shows how regions that rely on food from distant areas end up releasing the carbon that comes with it into the atmosphere. Overall, as noted in the PNNL press release, the researchers found that crops take in — and later return — about 37 percent of the U.S.’s total annual carbon dioxide emissions, but that the amount varies significantly by region. Agriculturally active regions of the Midwest, Great Plains, and along the southern half of the Mississippi (shown in blue below) release more carbon than they take in, while more urban parts of the Northeast, Southeast, Western U.S. and Gulf Coast (shown in red below) take in more than they release.

Text by Adam Voiland. Extratropical storm imagery from the Earth Observatory. Burrowing owl imagery from the city of BoulderAgricultural carbon sink and source map from Science Daily.

What on Earth is That #9

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What on Earth is That?

  Here at What on Earth we’re offering an extra special “no prize” if you can correctly identify the large blob-like objects and the smaller objects pointed at by the arrows. Post your guesses in the comments section, and check back next week for the answer.

Here’s the question from last time
And a time before that
And that

Ice Conditions — Not Just Japanese Tsunami — Key to Antarctic Iceberg Break Off

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Today’s big Earth science news was that the earthquake and tsunami that struck Japan in March was strong enough to send waves that snapped a Manhattan-sized chunk of ice off the Sulzberger Ice Shelf some 8,100 miles away.

That’s true, but as pointed out at the end of this piece there’s more to this story than just the strength of the earthquake. Though it’s not making it into the headlines, the condition of the ice in the region was also key. Specifically, the lack of nearby sea ice, coastal ice (also called fast or landfast ice) and pack ice made the portion of the Sulzberger Ice Shelf that broke off particularly susceptible to the incoming waves from the tsunami. Here’s how Kelly Brunt, the Goddard scientist who made the discovery, explained it in her Journal of Glaciology paper [pdf]. The bolding is mine.

The recent calving from the Sulzberger Ice Shelf suggests that, while the rifts provide the ice-shelf front with a zone that is weakened with respect to stress, and while tsunamis arrive episodically to cause vibrational disturbances to these rifts, some additional enabling condition must be satisfied before a given tsunami can lead to the detachment of an iceberg.

The timing of the earthquake and tsunami in Japan coincided with the typical summer sea-ice minimum (Zwally and others, 2002). As observed in the MODIS imagery and confirmed in the ASAR imagery, the region north of the Sulzberger Ice Shelf was devoid of either fast or pack ice at the time of predicted arrival of the tsunami. Fast ice is an important factor in ice shelf stability (Massom and others, 2010). Additionally, the absence of sea ice meant that the energy associated with the tsunami incident on the ice-shelf front was not damped by sea-ice flexure. With a distant tsunami source, over an irregular ocean bathymetry, and taking into account the dispersion of high-frequency components of the tsunami outside the shallow-water approximation, a complex pattern of dispersed waves is predicted in the wake of the leading front of the tsunami (NOAA/PMEL/Center for Tsunami Research; As these waves interacted with the ice shelf over a period of hours to days, flexural modes may have been resonantly excited, each with the potential to trigger iceberg calving (Holdsworth and Glynn, 1978), in a pattern reminiscent of the delayed response of harbors documented in the far field during the 2004 Sumatra tsunami (Okal and others, 2006).

This study presents the first observational evidence linking a tsunami to ice-shelf calving. Specifically, the impact of the tsunami and its train of following dispersed waves on the Sulzberger Ice Shelf, in combination with the ice-shelf and sea ice conditions, provided the fracture mechanism needed to trigger the first calving event from the ice shelf in 46 years

Text by Adam Voiland. Imagery from the European Space Agency/Envisat.