Science & Technology
Five Questions for IPCC Chairman
On Future of Climate Change Action
The UN Intergovernmental Panel on Climate Change issued a report last month on steps the world can take
to avoid the worst impacts of future climate change. It was the final interim report before the IPCC’s major Fifth Assessment Report due to be released in October. Yale Environment 360
asked Rajendra K. Pachauri, who has served as IPCC chairman since 2002, five questions about the latest report and about the prospects that the international community will finally take decisive action to address climate change at talks scheduled in Paris in 2015.Read more.
21 Apr 2014:
Massive Data Crunch
Shows Steady Rise in Warmer Days
The proportion of days in the United States that are warmer than the long-term average increased from 42 percent in 1964 to 67 percent today,
according to an analysis of 3.2 million temperature anomalies over the last
50 years. Enigma.io
, a New York City-based company that specializes in searches of information from public databases, examined data from 2,716 U.S. weather stations to track the temperature anomalies. The company found that since 1964, temperature anomalies characterized as warm or “strong warm” have increased by an average of .5 percent a year. Enigma’s data show, for example, that in 2012, 84 percent of temperature anomalies in the U.S. skewed on the warm side. The company forecast that by the 2030s more than 70 percent of anomalous temperatures in the U.S. are likely to be higher than the historical average, rather than colder.
17 Apr 2014:
Five Kamchatka Volcanoes
Erupt Simultaneously, NASA Images Show
A NASA satellite passing over Russia's Kamchatka Peninsula this week photographed five simultaneous volcanic eruptions
. The erupting volcanoes, from north
to south, are Shiveluch, Klyuchevskaya, Bezymianny, Kizimen, and Karymsky. Karymsky, a 1,536-meter (5,039-foot) peak that has erupted regularly since 1996, is the most active of the five. The tallest, Klyuchevskaya, is 4,750 meters (15,580 feet) high. Of the planet's roughly 1,550 volcanoes that have erupted in the recent geologic past, 113 are found on the Kamchatka Peninsula, in Russia's far northeast, according to NASA. Forty volcanoes on Kamchatka are active, meaning they are either erupting now or capable of erupting at any time. Kamchatka's fiery landscape is driven by plate tectonics: The Pacific Plate is slowly colliding with and sliding beneath the Okhotsk Plate. As the Pacific Plate melts, magma migrates up toward the surface, causing volcanic eruptions.
Studying a Polar Menagerie
On an Island in Arctic Russia
Ninety miles from the Russian mainland and 300 miles above the Arctic Circle, Wrangel Island is home to an eclectic assortment of fauna and flora — muskoxen,
Second in a series of blog posts from the Russian Arctic
polar bears, wolves, reindeer, wolverines, walruses, Asia’s only population of snow geese, and 417 plant species. Joel Berger, a field biologist with the Wildlife Conservation Society and the University of Montana, spent several weeks on Wrangel Island this spring. In the second of three blog posts for e360
, he describes the arduous conditions under which Russian and U.S. scientists collect data on the island’s odd assortment of creatures.
15 Apr 2014:
Possible with Advances in Semiconductors
New semiconductor technology is advancing the development of house windows that could double as solar panels, according to scientists
from Los Alamos National Lab and Italy. Their research into so-called
Solar-harvesting materials under UV light
"quantum dots" — ultra-small bits of semiconductors that transmit energy extremely efficiently and can be tuned toward specific colors — shows that quantum dots can be used in transparent materials to harvest sunlight with efficiencies comparable to standard solar panels. When highly transparent materials are embedded with quantum dots, they are known as luminescent solar concentrators (LSCs); the structures can absorb sunlight and re-radiate it at longer wavelengths directed toward the edge of the slab, where the energy is collected by a solar cell. In tests using large LSC slabs (sized in tens of centimeters), researchers reported harvesting photons at roughly 10 percent efficiency. Typical photovoltaic solar panels have an average efficiency of about 15 percent.
11 Apr 2014:
Parasitic Flatworm Could Be
Major Threat to Coral Reefs, Scientists Say
A coral-eating flatworm with a unique camouflaging strategy could be a major threat to the world's coral reefs, according to
researchers in the U.K. The parasite, called Amakusaplana acroporae
, infects a type of staghorn coral known as acropora, a major component
Amakusaplana acroporae, a parasitic coral flatworm
of reefs, and can destroy its coral host very quickly. The parasite has been detected at the Great Barrier Reef, and because it has no known natural predators, researchers are concerned it could spread quickly and decimate reefs worldwide. A novel camouflaging strategy makes the flatworm difficult to detect and monitor, the researchers say. When eating the coral tissue, the worm also ingests the coral's symbiotic algae. Instead of digesting the algae completely, the worm keeps a fraction of them alive and distributes them, along with the fluorescent pigments that give coral its characteristic hue, throughout its gut so that it perfectly mimics the appearance of the coral. The parasite has been identified in numerous aquarium-based corals, and biologists worry that it could spread rapidly if aquarium-raised coral, fish, or seaweed are introduced to natural reef environments.
07 Apr 2014:
Newfound Atmospheric 'Hole'
Threatens Polar Ozone Layer, Scientists Say
Researchers have discovered
a large opening in the Earth's atmosphere that is enabling pollutants to rise
Pacific atmosphere hole an elevator to the stratosphere
into the stratosphere and destroy ozone. The hole, which is in a part of the lower atmosphere called the "OH shield," is several thousand kilometers long and is centered over the tropical west Pacific Ocean. It's relatively close to Southeast Asia, a region with a booming population and rapidly increasing air pollution. The hole is a major concern because the OH shield usually scrubs air of chemical compounds emitted near the ground before they can reach the stratosphere, where those compounds can persist for long periods of time, reacting with and destroying ozone, say researchers at Germany's Alfred Wegener Institute who identified the hole. The newly discovered phenomenon acts as a sort of elevator, researchers say, drawing chlorofluorocarbons, sulfur dioxide, and other contaminants straight up to the stratosphere and bypassing the OH shield scrub.
E360 Announces Contest
Yale Environment 360
For Best Environmental Videos
is holding a contest to honor the best environmental videos. Entries must be videos that focus on an environmental issue or theme, have not been widely viewed online, and are a maximum of 15 minutes in length. The first-place winner will receive $2,000, and two runners-up will each receive $500. The winning entries will be posted on Yale Environment 360
. The deadline for entries is June 6, 2014. Read further contest information.
04 Apr 2014:
Solar Panels Could Beam Power
From Space Down to Earth, U.S. Navy Says
Researchers from the U.S. military are developing technology that would harvest solar energy in space and beam it down to Earth, according to
the Naval Research Laboratory. Although the concept seems futuristic, the
Navy is currently testing two prototype designs, both of which combine solar panels with electronic components that convert the energy to radio waves and transmit it to Earth. Eventually, engineers plan to use robotic vehicles to transport the panels to space and assemble them into a 1-kilometer wide satellite orbiting the planet. Theoretically, harvesting solar energy in space is more efficient than on Earth, because panels can collect sunlight around the clock and regardless of weather conditions. The U.S. military, currently the world's largest oil consumer, is eager to develop the technology to save money on fuel and simplify military deployments. But the private sector also has plans for the technology: California utility company Pacific Gas & Electric plans to buy space solar power by 2016.
03 Apr 2014:
Deforestation of Sandy Soils
Increases the Release of CO2, Study Finds
The texture of the soil that microbes live in determines how much carbon they release after deforestation, with sandy soils sending the most carbon into the atmosphere, according to research
led by Yale scientists.
Soils most affected by forest loss in red; least in yellow.
Subterranean microbes regulate carbon emissions from soil, and drastic changes to the microbial community, such as those that follow deforestation, can allow more CO2 to escape into the atmosphere and exacerbate global warming. The texture of soil, rather than such factors as temperature or nutrient concentrations, was the most important factor governing the release of CO2, the researchers found. Muddy, clay-like soils provide the most stable environment for microbial communities, likely because they're better at retaining nutrients than loose, sandy soils. The team used the findings to map areas in the U.S. where soil microbial communities would be most and least affected by deforestation, which could help inform land management practices.
31 Mar 2014:
IPCC Issues Stark Report
On Present and Future Climate Impacts
Rapidly rising levels of greenhouse gases are already having a major impact on the earth’s natural systems and the problem is likely to grow significantly worse
unless these emissions are brought under control, according to a new report by the Intergovernmental Panel on Climate Change (IPCC). The report
, released in Yokohama, Japan, said that steadily rising temperatures are melting polar ice caps, sharply diminishing Arctic sea ice, intensifying heat waves and heavy rains, causing the death of coral reefs, and placing water and food supplies under stress. The report on climate impacts, drafted by several hundred of the world’s leading climate scientists, emphasized that the world’s food supply is at considerable risk. Already, the report said, heat waves and water stress are affecting the output of wheat and corn on a global scale, impacts that are only expected to intensify in the future, further exacerbating food shortages. “Nobody on this planet is going to be untouched by the impacts of climate change,” said IPCC chairman Rajendra K. Pachauri.
28 Mar 2014:
West Antarctic Glacial Loss
Is Rapidly Intensifying, New Study Shows
Six massive glaciers in West Antarctica are dumping far more ice into the Southern Ocean than they were 40
An 18-mile crack in the Pine Island Glacier
years ago and now account for 10 percent of the world’s sea level rise
, according to a new study. Reporting in Geophysical Research Letters
, an international team of scientists said that the amount of ice draining from the six glaciers has increased by 77 percent since 1973. The scientists said that the ice loss from the six glaciers is so substantial that it equals the amount of ice draining annually from the entire Greenland Ice Sheet. The scientists used satellite data from 1973 and 2013 to gauge the ice loss from the six glaciers. The Pine Island Glacier
is moving more rapidly to the sea than any of the other six, with its speed increasing from 1.5 miles per year in 1973 to 2.5 miles per year in 2013. The glaciers are dumping more ice into the sea primarily because warmer ocean waters are loosening the ice sheets’ hold on the sea floor, which speeds up glacial flow.
27 Mar 2014:
Wind Turbine in a Blimp
Can Bring Power to Remote Locations
A Massachusetts company will soon deploy a portable wind energy system using a conventional turbine blade inside a cylindrical blimp that floats about 1,000 feet above the ground
, drawing on the stronger winds at
. The Buoyant Airborne Turbine (BAT), developed by Altaeros
, is designed to be used in off-the-grid locations where importing diesel fuel or other energy is expensive. The company recently announced a $1.3 million demonstration project in Alaska that will supply power to about a dozen homes. Altaeros says it is also working on deals to install projects in remote locations in Canada and Australia. The BAT, made of industrial fabric, sends power back via high-strength tethers that hold it to the ground. Altaeros is one of several companies developing wind turbines that hover above the earth or fly, including Makani
, which has invented a turbine that looks like a flying wing. Makani was acquired last year by Google X.
26 Mar 2014:
New Satellite Tracks Global
Precipitation in Unprecedented Detail
Launched into space late last month, a new Earth-observing satellite from NASA and the Japan space agency has captured its first images
, which show an
extra-tropical cyclone off the coast of Japan at unprecedented resolution. The satellite, called the Global Precipitation Measurement (GPM) Core Observatory, combines two powerful instruments that allow scientists to monitor precipitation around the globe in great detail, as the cyclone image demonstrates. One instrument, the Dual-frequency Precipitation Radar, captured a three-dimensional cross-section of the storm, with the heaviest precipitation shown in red and yellow. The second tool, a GPM Microwave Imager, observed different types of precipitation across a broad swath of the storm. Together, the instruments will help scientists more accurately predict rainfall and calculate how much precipitation falls to the Earth's surface.
Five Questions for Mario Molina
On Climate Science’s PR Campaign
The American Association for the Advancement of Science (AAAS), the world’s largest scientific society,
recently launched the “What We Know”
campaign, designed to cut through the fog of misinformation about climate change and convey to the public the current state of climate science. Chairing that effort is Mario J. Molina, a chemist who won a 1995 Nobel Prize for his work on the threat to the world’s ozone layer. Yale Environment 360
asked Molina five questions about the AAAS campaign and why it might succeed where previous efforts have failed.
24 Mar 2014:
Ride-Sharing Could Cut Taxi
Trips by 40 Percent in NYC, Analysis Shows
New interactive maps from MIT analyze the potential environmental and economic savings of ride-sharing in dense urban areas — in particular, the benefits of sharing taxicabs in New York City. The project, called
, uses data from 170 million trips made by New York City's 13,500 taxis in 2011. High-resolution GPS coordinates and timestamps for each trip allowed researchers to pinpoint locations in the city that are high-traffic hubs for taxi pick-ups and drop-offs, as well as calculate fare savings, decreases in total miles traveled, and cuts in CO2 emissions if ride-sharing existed. The researchers found that taxi-sharing could reduce the number of trips by 40 percent with only minimal inconvenience to the passengers. The findings highlight the potential benefits of ride-sharing in New York and other cities, including lower vehicle emissions, reduced congestion, and savings in time and money.
20 Mar 2014:
The 2013-2014 Winter Was
The 34th Coldest on Record in U.S., NASA Says
Although many residents of eastern North America may feel like they’ve just suffered through a winter of record cold, the fact is that the winter of 2013-2014 was only
the 34th coldest in 119 years of record keeping in the U.S. As this map
from the U.S. National Climatic Data Center shows, temperatures in the eastern and southern U.S. from Dec. 1, 2013, to Feb. 28th, 2014, were as much as 8 degrees C (14 F) colder than the 2000 to 2013 average for those months. But the western U.S. and Alaska saw unusually warm weather, with California experiencing its hottest winter on record. Overall, temperatures this past winter in the U.S. were about 1 degree F above average. Meanwhile, temperatures in Russia, Asia, and much of Europe were well above average this winter, and land temperatures globally for December, January, and February were the 10th warmest on record.
19 Mar 2014:
CO2 Levels Have Crossed
400 ppm Threshold Far Earlier This Year
Concentrations of carbon dioxide in the atmosphere have reached the 400 parts per million threshold two months earlier this year than last, an indication that the planet will soon experience the 400 ppm level year-round, according to
scientists from the Scripps Institute of Oceanography. Last year was the first time in hundreds of thousands of years that the 400 ppm threshold was crossed. Scripps scientists expect
CO2 levels to hover around 400 ppm for the next two months, when the Northern Hemisphere spring will go into full bloom and plants will suck CO2 from the atmosphere until going dormant in the fall. "It’s just a matter of time before it stays over 400 forever," said Ralph Keeling, who took over the CO2 monitoring program from his father, Charles David Keeling, who started it in 1958. Since then, atmospheric CO2 levels have risen steadily from 313 ppm as the world continues to burn fossil fuels. Scientists estimate it's been 800,000 to 15 million years since the planet has seen concentrations this high.
17 Mar 2014:
Northeast Greenland Glaciers
Are Now Melting Rapidly, Study Finds
The glaciers of northeast Greenland, long thought to be the most stable part of the massive Greenland ice sheet, are melting at an accelerating pace, losing roughly 10
billion tons of ice annually for the past decade, say researchers
from the U.S. and Denmark. The finding will likely boost estimates of global sea level rise, which had previously not accounted for massive ice loss from that region, scientists say. The Zachariae ice stream in northeast Greenland, which drains 16 percent of the ice sheet, has retreated roughly 12.4 miles in the past decade, outpacing the fast-moving Jakobshavn glacier, which has retreated 21.7 miles over the last 150 years. Ice loss from the region is likely accelerating, the researchers say, because ice dams in nearby bays that had been blocking the glaciers' paths are now also melting, freeing the way for the glaciers to flow into the ocean.
14 Mar 2014:
Major Winds Have Lashed
North Atlantic This Winter, NOAA Map Shows
Forty-three hurricane-force winter storms have lashed the North Atlantic since late October, boosting the region's average wind speed in January and February by more than 12 miles per hour, as shown in this map
the U.S. National Oceanic and Atmospheric Administration (NOAA). The blue colors indicate areas where wind speeds exceeded the 1981-2010 average; browns indicate winds that were lower than average. In the North Atlantic, an unusually high number of hurricane-force storms, with winds exceeding 74 mph, battered southeastern Greenland, Norway, and the coast of western Europe. The U.K. Met Office recently issued a report on the December and January storms that ravaged the British coast, saying
, "For England and Wales this was one of, if not the most, exceptional (two month) periods of winter rainfall in at least 248 years." No studies have confirmed a link between these intense winter storms and climate change, but some scientists think climate-driven changes in the jet stream
may be behind the wild weather.
11 Mar 2014:
'Space Frame' Wind Tower
Allows Turbines to Be Built in Remote Places
New wind power technology could bring turbines to hard-to-reach locations, according to engineers from General Electric
. The company has developed a new
type of wind tower, dubbed the "Space Frame Tower," consisting of metal latticework wrapped in weather-resistant fiberglass. Unlike conventional steel tube wind towers, the latticework can be bolted together on-site, which means the tower's framework can be transported using standard shipping containers and trucks, allowing taller wind towers to be installed in locations previously inaccessible to the longer trucks needed to transport conventional towers. The Space Frame Tower also has a five-leg base that's wider than conventional towers, increasing stability and ultimately allowing it to reach heights up to 450 feet — an advantage at sites where higher turbines can reach stronger winds. A 318-foot tall prototype is up and running in Tehachapi, California, with a 2.75 megawatt turbine nearly 400 feet wide.
06 Mar 2014:
Warm River Water Plays Major
Role in Arctic Sea Ice Melt, Study Finds
Relatively warm water flowing into the Arctic Ocean from rivers contributes significantly to Arctic sea ice melt each summer, a phenomenon that will intensify as the region warms, according to NASA researchers
. The river discharge not only melts coastal sea ice, it also has
a wider climate impact as it creates more open water, which is darker than ice and absorbs more heat from sunlight. As these NASA images show, when water from Canada's Mackenzie River flowed into the Beaufort Sea in the summer of 2012, average surface temperature of the open water rose by 6.5 degrees C (11.7 degrees F) after the pulse of river water. Flow from the Mackenzie raised sea surface temperatures as far as 350 kilometers (217 miles) from the coast. The researchers note that river discharge is becoming an increasingly important contributor to melting Arctic sea ice because the volume and temperature of fresh water discharge is increasing as inland Arctic areas warm more each summer.
05 Mar 2014:
Routes of Young Sea Turtles
Shed Light on Mystery of Turtles' Lost Years
By placing satellite tags on newborn sea turtles along the coast of Florida and tracking them in the western Atlantic Ocean, researchers have gained new insights
into the early migrations of threatened and endangered
turtles during their so-called "lost years" between hatching and returning to coastal waters as large juveniles. Rather than swimming in the currents of the North Atlantic gyre, as scientists had assumed, the young turtles actually leave the gyre and travel to the Sargasso Sea, which lies in the middle of the North Atlantic Ocean. While there, sensors on the turtles' shells registered more heat than the scientists expected, leading them to believe
that the young turtles swim near the surface of the Sargasso, basking in sunlight and feeding on a type of seaweed that grows in deep ocean waters. "From the time they leave our shores, we don't hear anything about them until they surface near the Canary Islands, which is like their primary school years," said an author of the study.
04 Mar 2014:
Atlanta Leads U.S. in
Electric Vehicle Sales Growth
Atlanta is the fastest growing market for electric cars in the U.S., according to an analysis
by the electric vehicle charging network ChargePoint. Electric vehicle (EV) sales in Atlanta jumped by 52 percent from the third quarter to the fourth quarter of 2013, with more than
3,000 EVs sold in the final three months of the year, according to state motor vehicle records. Washington, D.C., was the second-fastest growing market, with a 21 percent increase in sales, and Portland, Oregon, had the third-fastest growth, at 19.4 percent. While Los Angeles added the most EVs — more than 5,000 — to its streets, for a 19 percent growth rate, Atlanta outpaced it on a per capita and percent growth basis. Nationally, EV sales grew by nearly 450 percent
in the first three quarters of 2013 compared to the same period in 2012. ChargePoint's CEO speculated that popularity is increasing because charging station networks have expanded and EV designs have improved. "We’re well on our way to having twice the number of EVs on the road by the end of 2014," he said.
03 Mar 2014:
Harsh Winter Causing Large
Die-off of Invasive Insects, Researchers Say
As a frigid winter takes a toll on the United States and Canada, invasive insect populations are also taking a hit. The U.S. Forest Service estimates that up to 80 percent
of emerald ash borers, which have been decimating ash tree populations, were killed by long
Emerald ash borer
stretches of bitter cold in the the upper Midwest this year. Several other insect pests, many of which have migrated northward because of milder winters in recent years, also are faring poorly this winter, including corn earworms and gypsy moths. Researchers remain skeptical, however, that the die-offs will have lasting effects on pest populations. Emerald ash borers in Chicago, for example, survived the sub-zero weather because Chicago temperatures fell only to -17 degrees F, rather than Minnesota's -20 degrees F, which seems to be a critical temperature threshold for the pests.
28 Feb 2014:
Seafaring Drones Could Reveal
Mysterious Lives of Sharks, Researchers Say
New automated watercraft
are helping scientists understand the secret lives of great white sharks, which gather in large numbers each winter in an area nicknamed the "White Shark Cafe." Although this stretch of ocean between Baja California and Hawaii
contains relatively few food sources, the sharks congregate and display strange behaviors, perhaps related to mating or feeding, one researcher explained to the San Francisco Chronicle
. Scientists haven't had a way to efficiently track and observe sharks in this environment, but new seafaring drone technologies might change that. For example, drones could follow migrations by homing in on acoustic tags on the sharks themselves. Marine biologists at Stanford
were recently able to track two great whites on their journeys from California to Hawaii and the White Shark Cafe, as the map shows, but current technology only allows scientists to recreate the sharks' journeys after monitoring tags pop off and are recovered. The new drones may prove useful not only for tracking sharks and other pelagic fish in real time, but also for collecting important ocean data such as temperature, acidity, and salinity, researchers said.
27 Feb 2014:
Pine Forest Aerosols Play
Significant Role in Climate, Study Says
Pine forest vapors form small aerosol particles that may significantly cool the climate by reflecting the sun's energy back into space, according to new findings
. Scientists have known for decades that gases from pine
Hyytiälä pine forest in Finland
trees can form particles that grow from just 1 nanometer in diameter to 100 nanometers in about a day. The new research, published in Nature
, shows the rapid growth of these particles relies on a chemical chain reaction among pine-scented molecules and atmospheric ozone and oxygen. The growing particle then grabs others like it, eventually snowballing into a 100-nanometer particle — one that's large enough to condense water vapor, prompt cloud formation, and, ultimately, influence climate. Boreal or pine forests give off the largest amount of these compounds, so the finding is especially relevant for the northern parts of North America, Europe, and Russia. But other types of forests emit similar vapors, and the scientists think these may undergo similar rapid chemical reactions.
26 Feb 2014:
Large Offshore Wind Farms
Could Soften Blow of Hurricanes, Study Says
Offshore wind farms with thousands of wind turbines could have sapped much of the power of hurricanes Sandy, Katrina, and Isaac, significantly slowing their wind speeds, decreasing their accompanying storm surges, and possibly preventing billions of dollars in damages, according to a new study
. Computer models
used in the study said that deploying tens of thousands of offshore wind turbines could absorb enough energy from a hurricane to reduce peak wind speeds by 56 to 92 mph and storm surges by 6 to 79 percent. "We found that when wind turbines are present, they slow down the outer rotation winds of a hurricane," said Stanford engineer Mark Jacobson, who led the research. "This feeds back to decrease wave height ... which in turn slows the winds of the entire hurricane and dissipates it faster." For Hurricane Katrina, a massive turbine array could have slowed wind speeds by 58 percent and storm surge by 79 percent, and for Sandy wind speeds could have been cut by 14 percent and storm surge by 34 percent, according to findings published in Nature Climate Change
25 Feb 2014:
Massive Alaska Avalanche
Depicted in NASA Satellite Photograph
Southeastern Alaska recently experienced the largest landslide the planet has seen since 2010, and the aftermath is captured in this NASA satellite image
Triggered by the collapse of a near-vertical mountain face on the flanks of Mount La Perouse, 75 million tons of snow and sediment formed a debris flow nearly five miles long. The avalanche material appears light brown in contrast to the snow in the photo. Researchers at Columbia University first detected the event when seismic records from the region showed a large number of low-frequency waves; this satellite image and other aerial photos confirmed their hunch. The American Geophysical Union also posted this blog
featuring photographs from an Alaskan pilot who flew over the landslide.
21 Feb 2014:
Rewritable Paper and Water Ink
Could Cut Paper Waste, Scientists Report
A new type of rewritable paper that uses water as ink could slash the amount of paper that's wasted daily, researchers say
. The paper contains hydrochromic dyes — chemicals that change color when wet — and a single
page can be reused dozens of times, the scientists report in Nature Communications
. Other types of rewritable papers have been developed, but they are all more expensive and energy-intensive to produce, and some versions use inks that pose environmental and safety hazards. The new system costs less than 1 percent of standard inkjet printing, the researchers estimate, primarily because ink cartridges are expensive. The researchers found they could refill cartridges with water and use them, along with the rewritable paper, in typical desktop printers. Print on the rewritable paper is only visible for about 22 hours, or as long as it takes the paper to dry completely. The scientists note that, while 90 percent of business information is retained on paper, most printed documents are read only once before being discarded.