Science & Technology
26 Dec 2013:
Solar Activity Not a Major
Factor in Climate Change, Study Finds
Solar activity has had minimal impact on climate over the past millennium, new research
from the United Kingdom indicates. The findings counter the long-held view that periodic fluctuations in the sun's energy output have led to lengthy periods of warm or cold weather in the past. Looking at climate records from the Northern Hemisphere over the past 1,000 years, the scientists found that greenhouse gases have been the primary drivers of climate change since about 1900. Volcanic activity, which adds particles to the atmosphere that block sunlight, dominated climate patterns until roughly 1800, the study found. "Until now, the influence of the sun on past climate has been poorly understood," said Andrew Schurer of the University of Edinburgh and lead author of the study, which was published in Nature Geoscience
. "We hope that our new discoveries will help improve our understanding of how temperatures have changed over the past few centuries, and improve predictions for how they might develop in future."
18 Dec 2013:
Mapping Course and Software
Make Forest Monitoring Widely Accessible
Citizen scientists interested in tracking the health of the planet's forests have a new tool at their disposal. New software that uses satellite technology to map and
monitor changes in forested areas is being made available to the public
through a free online course. Users who complete the course, hosted by Stanford University
, can receive a license to operate the software, called CLASlite. CLASlite, or the Carnegie Landsat Analysis System lite, is a highly automated system for converting satellite imagery from its original, raw format into maps that can be used to detect deforestation, logging, and other disruptions. It was developed by Carnegie researcher Greg Asner to help governments, nongovernmental organizations, and academic institutions conduct high-resolution mapping and monitoring of forests
. "We are making the science of forest monitoring broadly available to people who want and need to participate in tracking and managing the health of their forests," said Asner.
Photo Essay: Documenting the Swift
Change Wrought by Global Warming
For 25 years, photographer Peter Essick has traveled the world for National Geographic
magazine, with many of his recent assignments focusing on the causes and consequences of climate change. In a Yale Environment 360
photo essay, we present a gallery of images he took while on assignment in Antarctica, Greenland, and other far-flung locales affected by climate change. View the photo gallery.
16 Dec 2013:
Volume of E-Waste
Projected to Soar by 2017, Study Says
The volume of electronic waste generated worldwide is expected to climb by 33 percent by 2017
to 65 million tons, according to a study conducted by a partnership of United Nations organizations, industry, governments, and scientists. So many computers, televisions, mobile
phones, and other devices are being tossed away annually that within four years the volume of e-waste would fill a 15,000-mile line of 40-ton trucks, the report
said. The report, released by a group called StEP
( Solving the E-Waste Problem Initiative) said that in 2012, 50 million tons of e-waste was generated worldwide, about 15 pounds for every person on the planet. China generated the most electronic waste last year, with 11.1 million tons, followed by the U.S. with 10 million tons. But in per capita generation, the U.S. dwarfed China and most other countries, with each American producing 65 pounds of e-waste, the study said. “The explosion is happening because there is so much technical innovation,” said Ruediger Kuehr, executive secretary of StEP.
13 Dec 2013:
U.S. Energy Department
Invests in Small-Scale Nuclear Reactors
Small, nearly meltdown-proof nuclear reactors are receiving a big boost from the U.S. Department of Energy
. The department will give a company in Corvallis, Oregon, as much as $226 million to develop so-called "small modular reactors," which can be used with many local power grids that can't accommodate conventional nuclear reactors. Because of the extremely low likelihood of meltdown, the next-generation, small-scale reactors are safer than many currently operating reactors, engineers say. The company, NuScale Power, plans to encase their reactors in something akin to a large thermos, which would sit at the bottom of a pool. If a reactor fails and threatens to overheat, the container would fill with water and remove excess heat without pumps or valves, which can sometimes fail. The Energy Department's investment is the second one in a $452 million, multi-year program to accelerate the development of such reactors. The reactor designs use water as a coolant, which is technologically conservative and increases the likelihood that the small modular reactors would be approved by the Nuclear Regulatory commission, The New York Times
03 Dec 2013:
Microplastic Pollution Harms
Worms at Bottom of Food Chain, Study Finds
As plastic trash accumulates in ocean ecosystems, it may be damaging worms and other sensitive marine life at the bottom of the food chain, scientists report. Two British studies found
that microplastics — tiny remnants, less than 5 mm in diameter, from the breakdown of plastic trash — made seafloor worms eat
Beach sediments churned by a lugworm
less and transferred pollutants from the plastics to the worms. Because they ate less, the worms had less energy to invest in important functions
such as growth, reproduction, and churning sediments, one of their most important roles in the ocean ecosystem. The worms also absorbed harmful chemicals from the debris
, including hydrocarbons, antimicrobials, and flame retardants, researchers said. Lugworms, often called the "earthworms of the sea," are considered an indicator species because they feed on ocean floor sediments. Microplastics have been accumulating in those sediments since the 1960s, and, although each particle is nearly invisible, taken together microplastics are the most abundant form of solid-waste pollution on the planet.
Fish 2.0: A Contest Seeks to Foster
A More Sustainable Seafood Industry
Twenty pioneers in the sustainable seafood business climbed a stage at Stanford University in November in an effort to woo the judges at the Fish 2.0 contest
Click to Enlarge
HM Terry Co.
The winning project connects fishermen directly to customers.
with proposals on how to change the way the U.S. catches, distributes, and markets fish. A business competition at heart, Fish 2.0 brought together entrepreneurs and investors to spur innovation in the tradition-bound seafood industry. Competitors's proposals ranged from converting waste at fish processing plants to expanding a Hawaiian network of aquaponic growers, who raise fish and vegetables together in tanks, into the developing world. One proposal aimed to create a data system to track catches in real time, enabling fisheries managers to hold the line on harvests. Contestants headed home with more than $75,000 in prize money. Read more.
22 Nov 2013:
Majority of Americans
Uninformed About Fracking, Survey Finds
Most Americans are uninformed and lack opinions on hydraulic fracturing, or fracking, a process used to extract oil and gas from rock formations, a new survey says
. Fifty-eight percent of people surveyed specifically reported that they knew nothing at all about fracking, and the same percentage said they didn't know whether they supported fracking or opposed it. Seven percent said they were aware of some of the process's environmental impacts, and 3 percent said they knew of positive economic and energy supply impacts of fracking. Of those who held an opinion on it, 20 percent were opposed to fracking and 22 percent supported it. "Broadly speaking, our results paint a picture of an American populace that is largely unaware and undecided about this issue," the study says. The study
— conducted by researchers at Oregon State, George Mason, and Yale universities — was recently published in the journal Energy Policy
15 Nov 2013:
Groundbreaking Mapping Project
Depicts Forest Change Around the Globe
Scientists from Google, U.S. universities, and federal agencies have for the first time produced a high-resolution global map showing in striking detail the extent of deforestation across the globe.
The project — which relied heavily on expertise from the computing
center Google Earth Engine — documents a loss of 888,000 square miles of forest between 2000 and 2012, along with a gain of 309,000 square miles of new forest. The rate of deforestation is equal to losing 68,000 soccer fields of forest every day for the past 13 years, or 50 soccer fields every minute, says the World Resources Institute
. Brazil, once responsible for a majority of the world's tropical forest loss, is now the global leader in scaling back forest destruction, cutting its deforestation rate in half over the past decade, researchers report in Science
. Over the same period, Indonesia has more than doubled its annual rate of forest loss, despite a supposed 2011 Indonesian government moratorium on new logging licenses.
11 Nov 2013:
Ozone Treaty From 1987
Has Also Slowed Global Warming
The 1987 Montreal Protocol, an international treaty designed to protect the ozone layer by banning chlorofluorocarbons (CFCs), has also slowed global warming since the mid-1990s, a new analysis has found
. The ban has lowered global temperatures by about 0.2 degrees F since it was enacted, scientists report in the journal Nature Geoscience
. Researchers say that's a significant decline considering the planet has warmed by an average of 1.6 degrees F since 1900. CFCs, a class of refrigerants banned because of their ozone-depleting qualities, are also powerful greenhouse gases, with warming potentials many thousands of times higher than CO2. A widely used replacement for CFCs — hydrofluorocarbons, or HFCs — are less powerful greenhouse gases, but negotiations are underway to amend the Montreal Protocol to apply to HFCs as well. The study's lead author, Francisco Estrada of the National Autonomous University of Mexico, told Climate Central that by "pure luck" the Montreal Protocol has effectively slowed global warming, even more so than the Kyoto Protocol, which was was directly aimed at reducing greenhouse gas emissions.
Interview: Using Robots to Unlock
Mysteries of CO2 and the Oceans
As climate change accelerates, scientists are focusing on the key role the world’s oceans play in absorbing half the planet’s carbon dioxide. But the precise mechanisms
Robotic Wave Glider
by which the oceans remove carbon from the atmosphere and the consequences for marine life remain poorly understood. That has led Tracy Villareal, a professor of marine science at the University of Texas at Austin, to devote his research to diatom phytoplankton. To better understand how these tiny organisms mitigate climate change, Villareal has become a pioneer in the use of a wave- and solar-powered ocean-going robot, known as the Wave Glider. In an interview with Yale Environment 360
, Villareal discusses why unlocking the secrets of diatoms is critical to understanding climate change and how deploying robots will revolutionize marine science. “There are all sorts of wild robotic systems under development,” he says. Read the interview.
08 Nov 2013:
Antarctic Researchers Discover
Strips of Rock That Slow Flow of Glaciers
Narrow ribs of dirt and rock beneath Antarctic glaciers help slow the glaciers' flow into the sea, according to new research
from scientists at Princeton University and the British Antarctic Survey. Using satellite measurements of the Pine Island Glacier and Thwaites
Glacier, both in West Antarctica, researchers discovered bands they call "tiger stripes" underlying the glaciers. The stripes serve as zones of friction and prevent sliding, much like non-slip flooring, the researchers report in Science
. Understanding the factors that control the glaciers' flow to the sea is important because their melting contributes significantly to sea level rise. The Pine Island and Thwaites glaciers are particularly important, as together they've contributed about 10 percent of the observed global sea level rise over the past 20 years.
24 Oct 2013:
Electric Vehicle Sales
On the Rise in 2013, New Analysis Shows
By the end of August, 59,000 electric vehicles had been sold in the U.S. this year — more than during all of 2012, a new report from the Union of Concerned Scientists (UCS)
shows. Over the past three years,
Americans purchased more than 140,000 electric vehicles (EVs), which have saved more than 40 million gallons of gas each year, the report notes. California is the leader, with 29 percent of all U.S. plug-in vehicle purchases made this year. EV sales rates have more than doubled in that state over the past year, according to the report. Although East and West coast cities continue to be hotspots for EV sales, purchases are picking up in cities like Denver, St. Louis, and Dallas, the report says
22 Oct 2013:
Southern Amazon Rainforest
In Danger as Dry Season Expands, Study Says
The dry season in the southern part of the Amazon rainforest is lasting three weeks longer than it did 30 years ago, putting the forest at higher risk for fires and tree mortality, according to new research from the University of Texas
. The most likely culprit is global
warming, says lead researcher Rong Fu. Even if future wet seasons become wetter, rainforest soil can only hold so much water, Fu explained. That water must sustain the forest throughout the entire dry season, and as the dry season lengthens the rainforest becomes increasingly stressed, vegetation growth slows, and the risk of fire rises. During a severe drought in 2005, the Amazon actually released a large amount of carbon dioxide into the atmosphere, rather than acting as a net carbon sink. Should dry seasons continue to expand, conditions like those in 2005 could become the norm, accelerating the buildup of CO2 in the atmosphere, the researchers wrote in the Proceedings of the National Academy of Sciences
17 Oct 2013:
Animals May Play Significant
Role in Carbon Cycling, Researchers Say
Wildlife may play a more important role in the global carbon cycle than researchers have previously given it credit for, according to a study
from an international group of scientists. Although models generally include
Muskoxen in Alaska
carbon cycling by plants and microbes, they often ignore the ways animals contribute to the process. That's a mistake, says Oswald Schmitz, an ecologist at Yale who led the study, because the actions of wildlife can affect carbon cycling through "indirect multiplier effects." For example, the massive loss of trees in North America triggered by the pine beetle outbreak has caused a net carbon change on scale with British Columbia's current fossil fuel emissions, the researchers reported in Ecosystems
. And in the Arctic, where about 500 gigatons of carbon is stored in permafrost, large grazing mammals like caribou and muskoxen can help maintain the grasslands that have a high albedo and thus reflect more solar energy. "We're not saying that managing animals will offset these carbon emissions," Schmitz said. "What we're trying to say is the numbers are of a scale where it is worthwhile to start thinking about how animals could be managed to accomplish that."
10 Oct 2013:
Carbon Capture and Storage
Projects Lagging Worldwide, Study Finds
Major projects aiming at capturing and burying carbon dioxide underground have slowed worldwide, according to a study by the Global CCS Institute in Australia
. Despite the common view among experts that carbon
Otway CCS project, Victoria, Australia
capture and storage (CCS) technologies could play a crucial role in slowing the atmospheric buildup of greenhouse gases, the number of major CCS projects fell from 75 to 65 over the past year. Although the U.S. currently leads the world in CCS projects, most of them involve pumping carbon into old oil wells to stimulate additional oil production. China, the world's largest producer of carbon dioxide, seems poised to become the new leader in CCS, with 12 projects in the works, the study noted. A major hurdle for the growth of CCS has been the lack of investments in projects based on new technologies, the analysts said. CCS technology has so far not proven to be commercially viable, The New York Times
09 Oct 2013:
Antarctic Research Operations
To Be Halted Amid U.S. Government Shutdown
The National Science Foundation (NSF) says it is curtailing the 2013-2014 Antarctic research season because the U.S. government shutdown has delayed funding for operations there. The U.S. Antarctic
Program, which is managed by the NSF, announced yesterday
that the three U.S. research stations, ships, and other facilities there will switch to "caretaker status" when funds are exhausted around October 14. All research activities not essential to human safety and preservation of property will be suspended, according to the statement. Because of the remote location and long lead time necessary for planning and travel, the NSF has already started the process of shuttering research facilities. Once funding is restored, some research operations could be restored, the U.S. Antarctic Program said. Around 700 scientists typically travel to the continent between October and February each year, according to Nature
04 Oct 2013:
New Hurricane Sandy Models
Are Most Detailed Visualizations To Date
The most striking visualizations to date of Hurricane Sandy, which devastated parts of the U.S. East Coast last year, show in great detail
the storm's evolution and path. Developed using state-of-the-art computer models
at the National Center for Atmospheric Research (NCAR)
, the images are based on data with spatial resolution 5,500 times greater than NOAA's highest-resolution hurricane forecast model. The visualizations show how several well-studied weather phenomena coincided to create the superstorm. They also show how, about a day before it made landfall, cool air began to envelop the storm's warm core. This ultimately tempered Sandy's power, but it also could have intensified winds at the storm's lower levels. The computer model includes 150 layers of vertical data, which means the model calculated weather conditions at more than 4 billion points within the storm each second, said meteorologist Robert Henson of the University Corporation for Atmospheric Research, which manages NCAR.
19 Sep 2013:
Fracked Shale Formations
Could Store Carbon Dioxide, Study Says
Storing carbon dioxide in the same shale formations that produce natural gas may be an effective way to sequester carbon dioxide produced by fossil fuel-burning power plants, according to a U.S. study
. Computer models by researchers at the University of
Virginia suggest the Marcellus Shale, a 600-square-mile formation in the northeastern U.S. that is a center of hydrofracturing natural gas, is capable of storing half the CO2 emitted by U.S. coal plants from now to 2030. Fracked shale wells are good candidates for carbon storage because CO2 can be injected in much the same way that natural gas was extracted, the researchers say. Fracking involves injecting pressurized fluids in wells to fracture the shale rock, which creates cracks that let gas seep out. The authors of this study suggest those networks of cracks could be filled with CO2 before sealing the natural gas wells.
10 Sep 2013:
New Prize is Created to
Improve Measurements of Ocean Acidity
Philanthropist Wendy Schmidt is offering $2 million in prize money
to inventors who can develop inexpensive and easily deployable sensors to measure ocean acidification. The Wendy Schmidt Ocean Health X Prize
is offering $1 million to the team that invents the most accurate sensors to measure the ocean’s acidity and $1 million to the team that devises the most affordable and easy-to-use sensors. Biologist Paul Bunje, a senior executive for oceans at the X-Prize Foundation, said that because current ocean acidity sensors can cost more than $5,000, very little is known about the pace of ocean acidification in various regions and depths. The goal, said Bunje, is to deploy many thousands of sensors worldwide. Rising concentrations of atmospheric carbon dioxide mean that more CO2 is being dissolved in the oceans, steadily making them more acidic.
09 Sep 2013:
Grid-Scale Batteries Make Sense
For Solar Energy, But Not Wind, Study Says
When renewable energy sources such as solar and wind farms generate more electricity than consumers need, storing the excess doesn't always make sense, say researchers from Stanford University
. Large, grid-scale batteries capable of storing the extra electricity are resource-intensive and costly to manufacture and maintain — sometimes more so than the energy they're used to store. "You wouldn't spend a $100 on a safe to store a $10 watch," said Michael Dale, who co-authored the study in the journal Energy & Environmental Science
. "Likewise, it's not sensible to build energetically expensive batteries for an energetically cheap resource like wind." Economically, it makes more sense to shut down wind energy production when consumer demand is low than it does to maintain battery systems to store excess wind energy, the study said. But battery storage does make sense for photovoltaic systems, the researchers say
, because solar panels and solar farms require more energy to build and maintain.
06 Sep 2013:
Immense Pacific Volcano Is
Among The Largest in the Solar System
A massive underwater volcano the size of New Mexico has been discovered 1,000 miles east of Japan, Nature Geoscience reports
. Covering an area of 120,000 square
miles, the volcano is 50 times larger than Hawaii's Mauna Loa, making it the largest volcano on Earth, according to a team of researchers
from the U.S., Japan, and the U.K. The newly discovered volcano, named Tamu Massif, is only 25 percent smaller than the immense volcano on Mars, Olympus Mons, which is large enough to spot with a backyard telescope. Tamu Massif is a shield volcano, with a low, broad shape and gradually sloped flanks. Its name derives from Texas A&M University, where the lead researcher taught for three decades.
How High Tech Is Helping
Bring Clean Water to Rural India
Social entrepreneur Anand Shah runs Sarvajal, a company that seeks to bring clean water to remote villages in India by deploying solar-powered “water
ATMs,” which dispense water to residents with the swipe of a prepaid smart card. Sarvajal, launched in 2008, currently serves more than 110,000 rural customers and is now is moving into India’s urban slums, where people often spend hours a day waiting for trucks to deliver clean water. In an interview with Yale Environment 360
, Shah talks about the challenges of expanding access to clean water in India and the lessons his company has learned from its first five years of operation. “The solutions came from what we actually saw in the field, rather than being invented elsewhere,” he says, “and that’s what makes it work.”
Read the interview.
26 Aug 2013:
Ocean Acidification Could
Amplify Global Warming, Study Says
The increasing acidification of the world’s oceans caused by rising concentrations of atmospheric carbon dioxide not only poses a threat to marine creatures, but also could lead to an intensification of planetary warming,
according to a new study. A team of U.S., British, and German researchers conducted experiments in seawater enclosures, known as mesocosms
, showing that the increasing acidification of the ocean leads to a drop in production of an important sulfur compound, dimethylsulphide, or DMS. Marine emissions of DMS are the largest natural source of atmospheric sulfur,
and those sulfur aerosols play an important role in reflecting the sun’s energy back into space and cooling the planet. Reporting in the journal Nature Climate Change
, the scientists found that when they created acidic conditions in the seawater enclosures that match pH levels expected in 2100, emissions of DMS fell by roughly 18 percent. The scientists said their study was the first to prove the link between rising ocean acidification and the potential decrease in planet-cooling sulfur dioxide aerosols.
22 Aug 2013:
Satellite Images of Fire
Help Guide Restoration Projects
The U.S. Forest Service is using NASA satellite images of fires in the American West to help rapidly restore burned areas
before the upcoming rainy season causes floods and washouts that could threaten lives and property.
This image of the Silver Hill fire in New Mexico, which burned 138,000 acres in June, was taken using infrared technology — mounted on NASA’s Landsat satellite — that distinguishes between vegetated and burned areas. The most severely burned areas are depicted in red, followed by areas of moderate-severity burn in yellow and low-severity burn in green. NASA began supplying the Forest Service with images as the fire raged, and in the wake of the fire the Forest Service has undertaken restoration efforts to stabilize the ground and prevent flooding during the rainy season in late summer.
14 Aug 2013:
Bears Using Wildlife Corridors
In Canadian Park, Genetic Tests Show
Genetic testing has revealed that bears in Canada’s Banff National Park routinely cross the bridges and underpasses along the Trans-Canada Highway
, evidence that the ecological corridors provide safe
A grizzly passes through a Banff underpass
passage along a busy roadway that otherwise threatens to fragment wildlife habitat
. Using 420 wire snag “hair traps” and 497 rub trees at 20 crossings to collect hair from passing bears, researchers from Montana State University determined that 15 individual grizzly bears and 17 individual black bears used the passages over a three-year period. According to researchers, those accounted for about 20 percent of the park’s bear populations, suggesting the passageways are providing enough connectivity to maintain a healthy ecosystem for bears and other large mammals. Twenty-five passages were installed in the 1990s
when the government widened a highway that includes a 100-mile stretch bisecting Banff.
12 Aug 2013:
Live Video Stream Provides
Rare Glimpse of Deepsea Marine World
The U.S. National Oceanic and Atmospheric Administration (NOAA) this month is streaming online a live video feed from the deep-sea canyons off the northeastern U.S. coast
, offering a real-time glimpse of
the marine diversity on the ocean floor. In a 36-day expedition launched last month
, NOAA researchers are using a remote-controlled vehicle tethered to the research ship Okeanos Explorer
to capture video footage of rare marine creatures, deep coral communities, and cold vents, or seeps, from largely unexplored U.S. waters. NOAA is employing a remotely operated vehicle, known as Deep Discoverer
, and a sophisticated camera sled to explore and broadcast video — accompanied by real-time narration from scientists — from depths of up to 6,000 meters, or nearly 20,000 feet. The project will continue until August 17.
07 Aug 2013:
Mimicking Cactus Design,
Scientists Devise Oil Spill Cleanup Method
Chinese researchers have developed a method of removing oil from polluted water using tiny barbed spikes that mimic the natural design of a cactus
The cactus opuntia microdasys
Writing in the journal Nature Communications
, the Beijing-based researchers describe how arrays of tiny copper spikes, similar to the cone-shaped spikes of a type of cactus known as Opuntia microdasys
, are able to collect micron-sized oil droplets that might otherwise be difficult to remove from water. The copper spikes are extremely thin at their point but get wider as they get closer to the base, creating a pressure difference that pulls droplets of oil toward the artificial skin-like surface. The oil then coalesces at the base of the cone, which can then be removed from the water. “Each conical needle in the array is a little oil collection device,” said Lei Jiang, lead author of the report. In tests, the researchers found that the needle arrays were able to remove about 99 percent of oil content from water, suggesting that the design could lead to new methods of cleaning up oil spills.
05 Aug 2013:
New Deep-Rooted Rice
Shows Greater Resistance to Drought
Japanese scientists say they have developed a rice plant with deeper roots
that could yield a more drought-resistant variety of rice. Writing in the journal Nature Genetics
, a team of scientists describes the discovery of gene that causes a rice strain known as Kinandang Patong, grown in the dry upland of the Philippines, to send longer roots into the soil, allowing the plant to extract water from deeper soil layers. After splicing the gene with a commonly grown rice strain, called IR64, the scientists found that the maximum root depths were more than twice those of the typical plants. After exposing both strains to moderate and severe drought conditions, the researchers found that yields of the standard variety fell significantly in moderate drought conditions and collapsed altogether in severe drought, while the modified strains were not affected by moderate drought and yields declined only 30 percent in severe drought.
01 Aug 2013:
Whales Shown to Flee
From Mid-Frequency Military Sonar
Two new studies show that the use of military sonar can provoke whales to flee
, providing evidence that the naval operations may be a factor in mass strandings of whales and dolphins worldwide. According to one study
A blue whale
most marine mammal strandings related to naval sonar exercises involve beaked whales, a notoriously shy species that responds to noise levels well below those used by the U.S. Navy. Scientists believe the beaked whales may interpret the sonar noises as the sounds of killer whales. A separate study
found that even mid-frequency sonar affected the behavior of blue whales, the largest animals on earth, especially during feeding. After exposing tagged blue whales to simulated military sonar and other mid-frequency sounds, the animals often ceased feeding, increased swimming speeds, and traveled away from the sound. “Noise pollution threatens vulnerable populations, driving them away from areas important to their survival, and at worst injuring or even causing the deaths of some whales and dolphins,” Sarah Dolman of the non-profit group Whale and Dolphin Conservation told the Guardian