THE SKY IS NOT FALLING: POLLUTION IN EASTERN CHINA CUTS LIGHT, USEFUL RAINFALL

0 comentarios 9/02/2009 04:59:00 PM Publicado por Jorge Franchín
Etiquetas: Ecology
New research shows that air pollution in eastern China has reduced the amount of light rainfall over the past 50 years and decreased by 23 percent the number of days of light rain in the eastern half of the country. The results suggest that bad air quality might be affecting the country's ability to raise crops as well as contributing to health and environmental problems.

The study links for the first time high levels of pollutants in the air with conditions that prevent the light kind of rainfall critical for agriculture. Led by atmospheric scientist Yun Qian at the Department of Energy's Pacific Northwest National Laboratory, the study appears August 15 in the Journal of Geophysical Research-Atmospheres.

"People have long wondered if there was a connection, but this is the first time we've observed it from long-term data," said Qian. "Besides the health effects, acid rain and other problems that pollution creates, this work suggests that reducing air pollution might help ease the drought in north China."

China's dramatic economic growth and pollution problems provide researchers an opportunity to study the connection between air quality and climate. Rain in eastern China — where most of the country's people and pollution exist — is not like it used to be.
Over the last 50 years, the southern part of eastern China has seen increased amounts of total rainfall per year. The northern half has seen less rain and more droughts. But light rainfall that sustains crops has decreased everywhere. A group of climate researchers from the U.S., China and Sweden wanted to know why light rain patterns haven't followed the same precipitation patterns as total rainfall.

Previous work has shown that pollution can interfere with light rain above oceans, so the team suspected pollution might have something to do with the changes over land. Light rain ranges from drizzles to 10 millimeters of accumulation per day and sustains agriculture. (Compared to heavy rain that causes floods, loss of light rain has serious consequences for crops.)

While the light rains have diminished, pollution has increased dramatically in China in the last half of the 20th century. For example, while China's population rose two and a half times in size, the emissions of sulfur from fossil fuel burning outpaced that considerably — rising nine times.

Air pollution contains tiny, unseen particles of gas, water and bits of matter called aerosols. Aerosols — both natural and human-caused (anthropogenic) — do contribute to rainfall patterns, but the researchers needed to determine if pollution was to blame for China's loss of rain and how.

To find out, the team charted trends in rainfall from 1956 to 2005 in eastern China, which has 162 weather stations with complete data collected over the entire 50 years.

From this data, the team determined that both the north and south regions of eastern China had fewer days of light rain — those getting 10 millimeters per day or less — at the end of the 50 year timespan. The south lost more days — 8.1 days per decade — than the north did, at 6.9 days per decade. However, the drought-rattled north lost a greater percentage of its rainy days, about 25 percent compared to the south's 21 percent.

"No matter how we define light rain, we can see a very significant decrease of light rain over almost every station," said Qian.

To probe what caused the loss of rainfall, the team looked at how much water the atmosphere contained and where the water vapor traveled. Most parts of eastern China saw no significant change in the amount of water held by the atmosphere, even though light rains decreased. In addition, where the atmosphere transported water vapor didn't coincide with light rain frequency.

These results suggested that changes in large-scale movement of water could not account for the loss of the precipitation. Some of pollution's aerosols can seed clouds or form raindrops, depending on their size, composition and the conditions in which they find themselves. Because these skills likely contribute to rainfall patterns, the researchers explored the aerosols in more depth.

Cloud droplets form around aerosols, so the team determined the concentration of cloud droplets over China. They found higher concentrations of droplets when more aerosols were present. But more droplets mean that each cloud droplet is smaller, in the same way that filling 10 ice cream cones from a quart of ice cream results in smaller scoops than if the same amount were put in only five cones.

This result suggested that aerosols create smaller water droplets, which in turn have a harder time forming rainclouds. The team verified this with computer models of pristine, moderately polluted or heavily polluted skies. In the most heavily polluted simulation, rain fell at significantly lower frequencies than in the pristine conditions.

An examination of the cloud and rain drops showed that these water drops in polluted cases are up to 50 percent smaller than in clean skies. The smaller size impedes the formation of rain clouds and the falling of rain.

Qian said the next step in their research is to examine new data from the DOE's Atmospheric Radiation Measurement Climate Research Facility in the central eastern Chinese city of Shouxian. The data was collected from April to December of 2008.

"This work is important because modeling studies of individual cases of pollution's effect on convective clouds have shown varying results, depending on the environmental conditions," said coauthor Ruby Leung. "The ARM data collected at Shouxian should provide more detailed measurements of both aerosols and clouds to enable us to quantify the impacts of aerosols on precipitation under different atmospheric and pollution conditions."

Pacific Northwest National Laboratory

TRACKING TRASH

8/05/2009 04:28:00 PM Publicado por Jorge Franchín
Etiquetas: Engineering


What if we knew exactly where our trash was going and how much energy it took to make it disappear? Would it make us think twice about buying bottled water or "disposable" razors?

A team of MIT researchers today announced a major project called Trash Track, which aims to get people thinking about what they throw away. Trash Track relies on the development of special electronic tags that will track different types of waste on their journey through the disposal systems of New York and Seattle. The project will monitor the patterns and costs of urban disposal and create awareness of the impact of trash on our environment - revealing the last journey of our everyday objects.

"Trash is one of today's most pressing issues - both directly and as a reflection of our attitudes and behaviors," says Professor Carlo Ratti, head of the MIT SENSEable City lab. "Our project aims to reveal the disposal process of our everyday objects, as well as to highlight potential inefficiencies in today's recycling and sanitation systems. The project could be considered the urban equivalent of nuclear medicine - when a tracer is injected and followed through the human body.

"The study of what we could call the 'removal chain' is becoming as important as that of the supply chain," the lab's associate director, Assaf Biderman, explains. "Trash Track aims to make the removal chain more transparent. We hope that the project will promote behavioral change and encourage people to make more sustainable decisions about what they consume and how it affects the world around them."

Trash Track will enlist volunteers in two target cities - New York and Seattle - who will allow pieces of their trash to be electronically tagged with special wireless location markers, or "trash tags." Thousands of these markers, attached to a waste sample representative of the city's overall consumption, will calculate their location through triangulation and report it to a central server, where the data will be analyzed and processed in real time. The public will be able to view the migration patterns of the trash online, as well as in an exhibit at the Architectural League in New York City and in the Seattle Public Library, starting in September 2009.

Trash Track was initially inspired by the Green NYC Initiative, the goal of which is to increase the rate of waste recycling in New York to almost 100 percent by 2030. Currently, only about 30 percent of the city's waste is diverted from landfills for recycling. "We hope that Trash Track will also point the way to a possible urban future: that of a system where, thanks to the pervasive usage of smart tags, 100 percent recycling could become a reality," says project leader, Musstanser Tinauli.

"Carlo Ratti and his team have come up with a visionary project to help people take ownership of their pollution," says Roger Highfield, editor of New Scientist magazine, which will be helping to deploy a third batch of tags in London, U.K. "It's all too easy to throw something in the garbage and wash your hands of it if you don't know what effect you are directly having on the environment."

(Photo: E Roon Kang at SENSEable City Lab)

Massachusetts Institute of Technology

The first global map of ammonia emissions measured from space

Paris, June 21, 2009

The first complete map of global ammonia emissions has recently been achieved using to satellite data. It reveals an underestimation of some of the ammonia concentrations detected by current inventories, and identifies new hotspots. This work, carried out by a team from LATMOS-IPSL (CNRS/UPMC/UVSQ) in collaboration with Belgian researchers from the Université Libre de Bruxelles, was facilitated by the infrared measurements of the French IASI instrument, part of the MetOp meteorological satellite developed by CNES. These results were published online in Nature Geoscience on 21 June 2009.
Ammonia (NH3) contributes significantly to the formation of the particles that give rise to pollution episodes. It mainly emanates from the use of agricultural fertilizers and increasingly intensified livestock breeding practices. Ammonia is the least well-understood pollutant regulated by European Directives on air quality. Mapping of its emissions are imprecise and systematic global monitoring of this compound is difficult. Once emitted, ammonia only remains in the atmosphere for a short period but triggers a cascade of environmental effects. At a local level, high ammonia concentrations affect fauna, flora and air quality.

Although the IASI instrument (part of the MetOp meteorological satellite) was not initially intended to detect ammonia in the Earth's atmosphere, researchers developed a methodology that could isolate the signature of ammonia from its background signal. By filtering the data and accumulating them continuously over a one-year observation period (more than a million measurements per day, with two passes over each part of the globe), the scientists were able to generate maps of its concentrations and to compare them with recent atmospheric models.

This work has demonstrated an underestimation of the ammonia emissions supplied by current inventories in agricultural valleys of the northern hemisphere, and particularly in the USA (the regions of San Joaquin in California and Snake River Valley in Idaho) and Europe (the Po and Ebre valleys). The most marked differences were found in Central Asia, with the identification of some sources not mentioned in current inventories.


--------------------------------------------------------------------------------

© Image MODIS © L. Gonzalez/C. Deroo LOA; Image IASI © ULB & INSU-CNRS

Distribution of ammonia in 2008, measured using the IASI instrument on board the /MetOp satellite, superimposed on an image of Europe obtained on August 30, 2008 by MODIS. Yellow to red colors indicate regions with high ammonia concentrations. The white structures are clouds.

--------------------------------------------------------------------------------



--------------------------------------------------------------------------------

© CNES/Eumetsat

The MetOp satellite launched at the end of 2006. The IASI instrument is shown by an arrow.

--------------------------------------------------------------------------------


Notes:
1) Laboratoire atmosphères, milieux, observations spatiales (CNRS/UPMC/UVSQ), which forms part of Institut Pierre-Simon Laplace

2) The measurements available are local, occasional or even inexistent in some regions.

3) Interféromètre Atmosphérique de Sondage Infrarouge (Infrared Atmospheric Sounding Interferometer), an instrument constructed by CNES and launched on board the MetOp satellite at the end of 2006

4) The MetOp program is a CNES/Eumetsat partnership that for 15 years will generate continuous observations of the atmosphere's composition through the launch of three successive satellites.


References:
Global ammonia distribution derived from infrared satellite observations, Lieven Clarisse, Cathy Clerbaux, Frank Dentener, Daniel Hurtmans, Pierre-François Coheur, Nature Geoscience, online 21 June 2009.

Plants may affect the effect of wildfires

LIVERMORE, Calif. – Rising temperatures may lead to more tinder-dry vegetation, but that doesn’t mean there will be a higher risk for wildfires in a particular area.

It all depends on the type of vegetation in the area.

A new study on the cover of the May issue of Ecological Monographs shows that, in some cases, the types of plants growing in an area could override the effects of climate change on wildfire occurrence.

Lawrence Livermore National Laboratory scientist Tom Brown along with Philip Higuera of Montana State University and colleagues looked at the direct and indirect impacts of millennial scale climate change on fire occurrence in the south-central Brooks Range in Alaska.

The team looked at historical fire occurrence by analyzing sediments found in the bottom of lakes.

Using the Lab’s Center for Accelerator Mass Spectrometry, they carbon dated the deposits in the sediment and reconstructed fire occurrences from 15,000 B.C. to the present. They then measured the amount of plant parts, such as fossil pollen, to figure out what type of vegetation dominated the area during the different time periods. Like rings in a tree, different layers of sediment represent different times in the past.

The conclusion: historical changes fire frequencies coincided with changes in the type of vegetation in the area, more so than to rising temperatures alone.

Although changing temperatures and moisture content set the stage for changes in wildfire frequency, they can often be trumped by changes in the distribution and abundance of plants.

Earlier studies have shown that the area burned across arctic and boreal regions will increase over the next century as climate change lengthens the fire season, decreases moisture and increases ignition rates. However, vegetation can alter the direct link between climate and fire by influencing the abundance, structure and moisture content of fuels across space and time, Brown said.

“There’s a complex relationship between fuels and climate,” he said. “Vegetation can have a profound impact on fire occurrences that are opposite or independent of climate’s direct influence on fire.”

In the recent study, the researchers found that changes in climate were less important than changes in vegetation. Despite a transition from a cool, dry climate to a warm, dry climate about 10,500 years ago, the researchers found a sharp decline in the frequency of fires. Their sediment cores from that time period revealed a vegetation change from flammable shrubs to fire-resistant deciduous trees.


The research implies that the impacts of climate change on modern-day fire frequencies could be strongly mediated by changes in vegetation. Thus, in some cases, the impacts of climate change on fire may be less intuitive than initially perceived.

“This could give fire managers a good indication that vegetation can substantially alter the direct effects of climate change on fire occurrence,” Brown said.

Other contributors include the University of Washington and the University of Illinois-Urbana.

NASA Satellite Detects Red Glow to Map Global Ocean Plant Health

05.28.09
This data-based map shows the "fluorescence yield" of phytoplankton in the oceans during 2004. "Fluorescence yield" is the fraction of absorbed sunlight that is given off by the plants as fluorescence and it changes with the health or stress of the phytoplankton. More fluorescence is emitted when waters are low in key nutrients such as iron. Credit: NASA's Scientific Visualization Studio

The MODIS instrument on NASA’s Aqua satellite compiled this global view of the amount of fluorescent light emitted by phytoplankton in the ocean. The amount of fluorescent light is not constant; it changes with the health of the plant life. Credit: Mike Behrenfeld, Oregon State University

Phytoplankton -- such as this colony of chaetoceros socialis -- naturally give off fluorescent light as they dissipate excess solar energy that they cannot consume through photosynthesis. Credit: Maria Vernet, Scripps Institution of Oceanography
› Larger image


This data-based map shows iron dust deposition on the oceans in spring 2004. Areas with low dust deposition have high fluorescence yields. Credit: NASA's Scientific Visualization Studio
› Larger image
Researchers have conducted the first global analysis of the health and productivity of ocean plants, as revealed by a unique signal detected by a NASA satellite. Ocean scientists can now remotely measure the amount of fluorescent red light emitted by ocean phytoplankton and assess how efficiently the microscopic plants are turning sunlight and nutrients into food through photosynthesis. They can also study how changes in the global environment alter these processes, which are at the center of the ocean food web.

Single-celled phytoplankton fuel nearly all ocean ecosystems, serving as the most basic food source for marine animals from zooplankton to fish to shellfish. In fact, phytoplankton account for half of all photosynthetic activity on Earth. The health of these marine plants affects commercial fisheries, the amount of carbon dioxide the ocean can absorb, and how the ocean responds to climate change.

“This is the first direct measurement of the health of the phytoplankton in the ocean,” said Michael Behrenfeld, a biologist who specializes in marine plants at the Oregon State University in Corvallis, Ore. “We have an important new tool for observing changes in phytoplankton every week, all over the planet.”

The findings were published this month in the journal Biogeosciences and presented at a news briefing on May 28.

Over the past two decades, scientists have employed various satellite sensors to measure the amount and distribution of the green pigment chlorophyll, an indicator of the amount of plant life in the ocean. But with the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite, scientists have now observed “red-light fluorescence” over the open ocean.

“Chlorophyll gives us a picture of how much phytoplankton is present,” said Scott Doney, a marine chemist from the Woods Hole Oceanographic Institution and a co-author of the paper. “Fluorescence provides insight into how well they are functioning in the ecosystem.”

All plants absorb energy from the sun, typically more than they can consume through photosynthesis. The extra energy is mostly released as heat, but a small fraction is re-emitted as fluorescent light in red wavelengths. MODIS is the first instrument to observe this signal on a global scale.

“The amount of fluorescent light emitted is not constant; it changes with the health of the plant life in the ocean,” said Behrenfeld. “The challenge with global MODIS fluorescence data is to uncover the important biological information that is hidden in it.”

Red-light fluorescence reveals insights about the physiology of marine plants and the efficiency of photosynthesis, as different parts of the plant’s energy-harnessing machinery are activated based on the amount of light and nutrients available. For instance, the amount of fluorescence increases when phytoplankton are under stress from a lack of iron, a critical nutrient in seawater. When the water is iron-poor, phytoplankton emit more solar energy as fluorescence than when iron is sufficient.

The fluorescence data from MODIS gives scientists a tool that enables research to reveal where waters are iron-enriched or iron-limited, and to observe how changes in iron influence plankton. The iron needed for plant growth reaches the sea surface on winds blowing dust from deserts and other arid areas, and from upwelling currents near river plumes and islands.

The new analysis of MODIS data has allowed the research team to detect new regions of the ocean affected by iron deposition and depletion. The Indian Ocean was a particular surprise, as large portions of the ocean were seen to “light up” seasonally with changes in monsoon winds. In the summer, fall, and winter – particularly summer – significant southwesterly winds stir up ocean currents and bring more nutrients up from the depths for the phytoplankton. At the same time, the amount of iron-rich dust delivered by winds is reduced.

“On time-scales of weeks to months, we can use this data to track plankton responses to iron inputs from dust storms and the transport of iron-rich water from islands and continents,” said Doney. “Over years to decades, we can also detect long-term trends in climate change and other human perturbations to the ocean.”

Climate change could mean stronger winds pick up more dust and blow it to sea, or less intense winds leaving waters dust-free. Some regions will become drier and others wetter, changing the regions where dusty soils accumulate and get swept up into the air. Phytoplankton will reflect and react to these global changes.

“NASA satellites are powerful tools,” said Behrenfeld. “Huge portions of the ocean remain largely unsampled, so the satellite view is critical to seeing the big picture that complements the process-oriented understanding we get from work on ships and in laboratories.”

The research was funded by NASA and involved collaborators from the University of Maine, the University of California-Santa Barbara, the University of Southern Mississippi, NASA’s Goddard Space Flight Center, the Woods Hole Oceanographic Institution, Cornell University, and the University of California-Irvine.

‘Invasive aliens’ threaten global biodiversity

While the implications of climate change for biodiversity have been widely recognised, the insidious effect of invasive alien species (IAS) on global biodiversity stays under the radar.
22 May 2009
That is why this year’s theme for the United Nations’ International Day for Biological Diversity (IDB) on 22 May is IAS.

The International Convention on Biological Diversity sees IAS as “one of the greatest threats to biodiversity, and to the ecological and economic well-being of society and the planet”.

“All our efforts in managing the impact of climate change on biodiversity could be brought undone by invasive species,” CSIRO Biodiversity Research Director, Dr Mark Lonsdale said.

“All our efforts in managing the impact of climate change on biodiversity could be brought undone by invasive species,” CSIRO Biodiversity Research Director, Dr Mark Lonsdale said.“Increasing globalisation has led to greater movement of new species around the world, and native species killed or stressed by global change will all too often be replaced by these weeds and feral animals.

“Invasive species are already a major cause of biodiversity loss and we need new tools to tackle them.

“Because of this CSIRO is putting considerable resources into research on IAS and their effect on Australia’s biodiversity, as well as actively participating in international groups such as DIVERSITAS and the Global Invasive Species Programme.”

Current CSIRO research targets invasive species already in Australia as well as trying to anticipate and avert the next generation of IAS. The threats are diverse and hard to predict so excellence in risk-based research to make sense of the complexity is essential.

“Our research ranges from weeds, rabbits, carp and risk analysis of potential invasive species to biological collections that underpin much of the research,” Dr Lonsdale said.

“Our weeds research, for example, ranges from individual weeds such as lantana to the resistance of our ecosystems to weed invasion.”

The Australian National Herbarium, with its collection of native and exotic plants, underpins much of Australia’s weeds research and provides a vital resource when a new invasive plant species is found.

Dr Lonsdale stressed that invasive species are one of many direct threats to global biodiversity and, in Australia, CSIRO is responding to the magnitude of the challenge.

Download images at: 'Invasive aliens' threaten global biodiversity

The Fragility of the World's Coral is Revealed Through a

April 6, 2009


Click for downloadable image
This map of the
Northwestern Hawaiian Islands,
which stretch over 2,000
kilometers beyond the principal
Hawaiian islands, shows how much
humans have impacted the
region's coral reefs



Click for downloadable image
Pocillopora coral at
Maro Reef in the
Northwestern Hawaiian Islands.

Photo courtesy
of PNMN/NOAA



Click for downloadable image
Benjamin S. Halpern and
Kimberly A. Selkoe



(Santa Barbara, Calif.) –– A new study by researchers from UC Santa Barbara's National Center for Ecological Analysis and Synthesis (NCEAS) sheds light on how threats to the world's endangered coral reef ecosystems can be more effectively managed.

In a recent issue of the journal Coral Reefs, lead authors Kimberly A. Selkoe and Benjamin S. Halpern, both of NCEAS, explain how their maps of the Northwestern Hawaiian Islands (NWHI) –– a vast area stretching over 1,200 miles –– can be used to make informed decisions about protecting the world's fragile reefs.

Coral reef ecosystems are at risk due to the direct and indirect effects of human activities. This study was designed to help natural resource managers make decisions on issues such as surveillance priorities, granting of permits for use, and discernment of which areas to monitor for climate change effects.

"Our maps of cumulative human impact are a powerful tool for synthesizing and visualizing the state of the oceans," said first author Selkoe, who is also affiliated with Hawaii Institute of Marine Biology at the University of Hawaii. "The maps can aid in strategically zoning uses of oceans in an informed way that maximizes commercial and societal benefits while minimizing further cumulative impact."

"President (George W.) Bush declared the Northwestern Hawaiian Islands a National Monument in 2006, in part because it is one of the last places in the oceans that have not been heavily altered by human activities," said Halpern. "Our maps of cumulative human impact on these islands show that, despite their extreme isolation, humans are already significantly impacting this special place, and that many of the key threats, such as those associated with climate change, are not mitigated with Monument designation. We must continue to act to protect these islands and coral atolls if we hope to preserve them for future generations."

The authors studied 14 threats specific to NWHI. The threats, all generated by humans, included alien species, bottom fishing, lobster trap fishing, ship-based pollution, ship strike risks, marine debris, research diving, research equipment installation, and wildlife sacrifice for research. Human-induced climate change threats were also studied, including increased ultraviolet radiation, seawater acidification, the number of warm ocean temperature anomalies relevant to disease outbreaks and coral bleaching, and sea level rise.

Risk of increased rates of coral disease due to warming ocean temperature was found to have the highest impact, along with other climate-related threats. However, the authors noted that climate issues cannot be resolved by managers at the regional level. It was noted that threats related to ship traffic are most easily managed by regional management.

"With the scientific justification provided by our study, the managers of the Monument have an opportunity to make addressing the worst threats a top priority as they decide on management strategies," said Selkoe. "By updating the map of cumulative impacts through time, success of management plans in reducing cumulative impacts can be measured, and permits for new uses can be evaluated in the context of how they add to the landscape of cumulative impacts.

"The coral reefs of the Northwestern Hawaiian Islands make up the majority of U.S. coral reef area, and we should all be proud that they are some of the most pristine in the world, and fully protected under U.S. law," said Selkoe. "However, threats like marine debris, pollution from shipping, climate change effects and alien species still threaten to degrade these reefs. Our effort to systematically inventory and map the ongoing threats to these reefs, as we have done in this project, is an important part of protecting them."

The authors note that this analysis can serve as a case study for other areas and managers who are interested in mapping region-specific cumulative human impacts and in making assessments.

NCEAS, located in downtown Santa Barbara, is a research center of UCSB, largely funded by the National Science Foundation. NCEAS supports cross-disciplinary research that uses existing data to address fundamental issues in ecology and allied fields, and their application to management and policy. NCEAS is a unique institution with an explicit mission to foster synthesis and analysis, turn information into understanding and, through effective collaboration, alter how science is conducted.