Monday, August 31, 2009

Short List of LCROSS Candidate Impact Craters

Monday, August 31, 2009
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Impact: 4:30 a.m. PDT, October 9, 2009

LCROSS Candidate Impact Craters
Designation
Crater Name
Sun Mask
Eath Mask
Latitude
Longitude
SP A Faustini
2.3
0.9
-87.2°
89°E
SP B Shoemaker
3.5
-0.6
-88.5°
50°E
SP C Cabeus
3.0
8.5
-85°
35.5°W
SP CB Cabeus B
0.9
-0.5
-81.7°
54.5°W
SP CC none
2.5
0.1
-83.5°
16°W
SP D Hawworth
2.7
0.8
-87.4°
5°W
SP F none
1.8
0.5
-82.3°
12°E
SP G none
2.4
0.4
-84.3°
1°E








Sun Mask is the depth, in kilometers, of the crater below where the sun's light does not penetrate. Earth mask is the depth of the crater below that is not visible from Earth. At various time of the year, the libration or wobble of the moon on its axis gives Earth obsevers the ability to look deeper into the permanenty shadowed craters on the south pole.

This list of candidate craters is based on current information about the age, depth and structure of the selected craters. Approximately 30 days before impact, the LCROSS science team will announce the selection of the final impact crater. The selection will take into account any additional information, especially from the Lunar Reconnaissance Orbiter, collected about the candidate craters.

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Lighting Up the Night

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Viewed from the Banana River Viewing Site at NASA's Kennedy Space Center in Florida, space shuttle Discovery arcs through a cloud-brushed sky, lighted by the trail of fire after launch on the STS-128 mission. Liftoff from Launch Pad 39A was on time at 11:59 p.m. EDT. The first launch attempt on Aug. 24 was postponed due to unfavorable weather conditions. The second attempt on Aug. 25 also was postponed due to an issue with a valve in space shuttle Discovery's main propulsion system.

The STS-128 mission is the 30th International Space Station assembly flight and the 128th space shuttle flight. The 13-day mission will deliver more than 7 tons of supplies, science racks and equipment, as well as additional environmental hardware to sustain six crew members on the International Space Station. The equipment includes a freezer to store research samples, a new sleeping compartment and the COLBERT treadmill.

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Lighting Up the Night Sky

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Lightning over the Kennedy Space Center's Launch Pad 39A competes with the xenon lights on the pad illuminating space shuttle Discovery waiting for a scheduled liftoff on the STS-128 mission. Launch was scrubbed due to the weather and another launch attempt is scheduled for Aug. 28. Discovery's 13-day mission will deliver more than 7 tons of supplies, science racks and equipment, as well as additional environmental hardware to sustain six crew members on the International Space Station. The equipment includes a freezer to store research samples, a new sleeping compartment and the COLBERT treadmill. The mission is the 128th in the Space Shuttle Program, the 37th flight of Discovery and the 30th station assembly flight.

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NASA Sets Briefing, TV Coverage of Japan's First Cargo Spacecraft

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NASA will hold a news briefing at 12:30 p.m. CDT on Wednesday, Sept. 2, to preview the maiden launch and flight of Japan's unpiloted H-II Transfer Vehicle (HTV) cargo spacecraft to the International Space Station.

NASA Television will broadcast the briefing live from NASA's Johnson Space Center in Houston. Participants in the briefing will include officials from NASA and the Japan Aerospace Exploration Agency (JAXA). NASA TV also will broadcast live HTV's launch and flight.

The HTV is scheduled to lift off on an H-IIB rocket from JAXA's Tanegashima Space Center in southern Japan at approximately noon Sept. 10 (about 2 a.m. Sept. 11 Japan time). NASA TV coverage of the launch will begin at 11:45 a.m. The HTV will augment the European Space Agency's Automated Transportation Vehicles and the Russian Progress ships that deliver supplies to the space station.

NASA conducted an HTV readiness review on Aug. 27. The HTV was formally approved for flight and rendezvous. The launch window will be open from Sept. 10-30. In the event of a launch postponement after the H-IIB rocket is fueled, a 72-hour turnaround will be required before the next launch attempt.

As the 16.5-ton cargo craft makes its week-long journey to the space station, flight controllers in Tsukuba, Japan, and at Mission Control in Houston will conduct a number of tests of HTV's rendezvous and navigation systems.

NASA TV coverage of the cargo craft's arrival at the station will begin at 2 p.m. Sept. 17. As the HTV moves within about 40 feet of the orbiting laboratory, space station crew members will capture the craft using the station's Canadarm2 robotic arm. The crew then will attach the HTV to an Earth-facing docking port on the station's Harmony connecting module. The robotic maneuvers are set to begin at about 2:50 p.m. Sept. 17.

The HTV will remain attached to the station for about six weeks while supplies are transferred. In addition to interior supplies and equipment, two new experiments carried on the exterior of the HTV will be moved to the Japanese Kibo module's external experiment porch using a combination of maneuvers with the station's Canadarm2 and Kibo's robotic arm.

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NASA Selects 16 Small Business Research and Technology Projects

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NASA has selected 16 small business projects to address important research and technology needs. The awards are part of NASA's Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs.

The SBIR program selected 12 proposals for negotiation of phase II contracts, with a total value of approximately $7.2 million. The awards went to 12 small, high technology firms in nine states.

The STTR program selected four proposals for negotiation of phase II contract awards, with a total value of approximately $2.4 million. The awards went to four small high technology firms in four states partnered with three research institutions in three states.

These selections are supplementary to the 142 phase II SBIR awards announced Oct. 28, 2008, and the 16 STTR phase II awards announced on April 15, 2009.

SBIR and STTR are part of the Innovative Partnerships Program Office at NASA Headquarters in Washington. The office partners with U.S. industry to infuse innovative technologies into NASA missions and transition them into commercially available products and services for the agency and other markets.

A few of the research areas being pursued among this group of selected proposals include:

- Innovative technologies for improvement in design and analysis of flight deck automation
- Technologies for long-term cryogenic propellant storage applications in-space, on the lunar surface and on Earth. The technologies also include fluid system components, cryogenic insulation and conditioning systems.
- Development of advanced power conversion, energy storage and power electronics to enable or enhance the capabilities of future science missions
- Technologies providing novel approaches in reconfigurable, reprogrammable communication systems for human and robotic missions

NASA's Ames Research Center at Moffett Field, Calif., manages the SBIR and STTR programs for the Innovative Partnerships Program. Individual projects are managed by NASA's field installations.

For a list of selected proposals, visit:

http://www.nasa.gov/offices/ipp/technology_infusion/sbir/index.html

For more information about the Innovative Partnerships Program, visit:

http://www.ipp.nasa.gov


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NASA's Shuttle Discovery Launches to Enhance Space Station Science

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Space shuttle Discovery, with its seven-member crew, launched at 11:59 p.m. EDT Friday from NASA's Kennedy Space Center in Florida. The shuttle will deliver supplies, equipment and a new crew member to the International Space Station.

Inside the shuttle's cargo bay is the Leonardo Multi-Purpose Logistics Module, a pressurized "moving van" that will be temporarily installed to the station. The module will deliver storage racks; materials and fluids science racks; a freezer to store research samples; a new sleeping compartment; an air purification system; and a treadmill named after comedian Stephen Colbert. The name "Colbert" received the most entries in NASA's online poll to name the station's Node 3. NASA named the node Tranquility.

Shortly before liftoff, Commander Rick Sturckow said, "Thanks to everyone who helped prepare for this mission. Let’s go step up the science on the International Space Station!"

The 13-day flight will include three spacewalks to replace experiments outside the European Space Agency's Columbus laboratory, install a new ammonia storage tank and return the used one. Ammonia is needed to move excess heat from inside the station to the radiators located outside.

Sturckow is joined on the STS-128 mission by Pilot Kevin Ford, Mission Specialists Pat Forrester, Jose Hernandez, Danny Olivas and European Space Agency astronaut Christer Fuglesang. NASA astronaut Nicole Stott will fly to the complex aboard Discovery to begin a three-month mission as a station resident. She replaces NASA's Tim Kopra, who will return home on Discovery. Ford, Hernandez and Stott are first-time space fliers.

The mission marks the start of the transition from assembling the space station to using it for continuous scientific research. Assembly and maintenance activities have dominated the available time for crew work. As completion nears, additional facilities and the crew members to operate them will enable a measured increase in time devoted to research as a national and multinational orbiting laboratory.

Discovery's first landing opportunity at Kennedy is scheduled for Thursday, Sept. 10, at 7:09 p.m. EDT. This mission is the 128th space shuttle flight, the 30th to the station, the 37th for Discovery and the fourth in 2009.

NASA is providing continuous television and Internet coverage of Discovery's mission. NASA Television features live mission events, daily mission status news conferences and 24-hour commentary. For NASA TV streaming video, downlink and schedule information

Hernandez and Stott are providing mission updates on Twitter. For their Twitter feeds and other NASA social media Web sites, visit:

http://www.nasa.gov/collaborate

Live updates to the NASA News Twitter feed will be added throughout the shuttle mission and landing. To access the NASA News Twitter feed, visit:

http://www.twitter.com/nasa

Daily news conferences with STS-128 mission managers will take place at NASA's Johnson Space Center in Houston. During normal business hours of 8 a.m. to 5 p.m. EDT Monday through Friday, reporters may ask questions from participating NASA locations. Please contact your preferred NASA facility before its daily close of business to confirm its availability before each event.

Johnson will operate a telephone bridge for media briefings that occur outside of normal business hours. To be eligible to use this service, reporters must possess valid media credentials either issued by a NASA center or issued specifically for the STS-128 mission.

Media representatives planning to use the service must contact the Johnson newsroom at 281-483-5111 no later than 15 minutes prior to the start of a briefing in which they wish to participate. Newsroom personnel will verify their credentials and transfer them to the phone bridge. The capacity of the phone bridge is limited and will be available on a first-come, first-serve basis.

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Warped Debris Disks Around Stars Are Blowin’ in the Wind

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The dust-filled disks where new planets may be forming around other stars occasionally take on some difficult-to-understand shapes. Now, a team led by John Debes at NASA's Goddard Space Flight Center in Greenbelt, Md., finds that a star's motion through interstellar gas can account for many of them.

"The disks contain small comet- or asteroid-like bodies that may grow to form planets," Debes said. "These small bodies often collide, which produces a lot of fine dust." As the star moves through the galaxy, it encounters thin gas clouds that create a kind of interstellar wind. "The small particles slam into the flow, slow down, and gradually bend from their original trajectories to follow it."

Far from being empty, the space between stars is filled with patchy clouds of low-density gas. When a star encounters a relatively dense clump of this gas, the resulting flow produces a drag force on any orbiting dust particles. The force only affects the smallest particles -- those about one micrometer across, or about the size of particles in smoke.

"This fine dust is usually removed through collisions among the particles, radiation pressure from the star's light and other forces," explained Debes. "The drag from interstellar gas just takes them on a different journey than they otherwise would have had."

Working with Alycia Weinberger at the Carnegie Institution of Washington and Goddard astrophysicist Marc Kuchner, Debes was using the Hubble Space Telescope to investigate the composition of dust around the star HD 32297, which lies 340 light-years away in the constellation Orion. He noticed that the interior of the dusty disk -- a region comparable in size to our own solar system -- was warped in a way that matched a previously known warp at larger distances.

"Other research indicated there were interstellar gas clouds in the vicinity," Debes said. "The pieces came together to make me think that gas drag was a good explanation for what was going on."

"It looks like interstellar gas helps young planetary systems shed dust much as a summer breeze helps dandelions scatter seeds," Kuchner said.

As dust particles respond to the interstellar wind, a debris disk can morph into peculiar shapes determined by the details of its collision with the gas cloud. In a face-on encounter, such as that of the star HD 61005 in the constellation Puppis, the disk's edge bends gently away from the direction of motion. Fine dust trails behind, forming a cylindrical wake. If the disk instead slices edgewise through interstellar gas, the resulting headwind blows away fine dust from the portion inside the cloud, resulting in a lop-sided disk.

"The drag from interstellar gas only affects the outskirts of the disk, where the star's gravity can't really hold onto the material," Weinberger said.

The systems studied are about 100 million years old and resemble our own solar system shortly after the major planets formed. Although astronomers don't know whether planets lurk within the disks of these systems, a better understanding of processes affecting a disk's outer regions will shed light on how "ice giant" planets like Uranus and Neptune -- and the more distant swarm of small, icy bodies known as the Kuiper Belt -- formed within the solar system.

Astronomers have sometimes attributed warps and bends in debris disks to the presence of undiscovered planets or to past encounters with another star. "But we expect interstellar gas to be around -- it's everywhere," Debes said. "It's important to consider the ecology of these debris disks before running to such conclusions, and this model explains a lot of the weirdly shaped disks we see."

A paper describing the model appears in the September 1 issue of The Astrophysical Journal.

Related link:

NASA Supercomputer Shows How Dust Rings Point to Exo-Earths
http://www.nasa.gov/centers/goddard/news/topstory/2008/dust_rings.html

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Saturday, August 29, 2009

Watch 24x7 Space Live Channel

Saturday, August 29, 2009
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Friday, August 28, 2009

Global Climate Change Uncertainties

Friday, August 28, 2009
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Unresolved questions about Earth's climate

Extreme Ultraviolet Imaging Telescope (EIT) image of the sun with a huge, handle-shaped prominence, taken in 1999. While there is no evidence of a change trend in solar output over the past half century, long-term changes in solar output are not well-understood.

This website presents a data-rich view of climate and a discussion of how that data fits together into the scientists' current picture of our changing climate. But there's a great deal that we don't know about the future of Earth's climate and how climate change will affect humans.

For convenience and clarity, climate scientists separate things that affect climate change into two categories: forcings and feedbacks (see sidebar at right).

Also, climate scientists often discuss "abrupt climate change," which includes the possibility of "tipping points" in the Earth's climate. Climate appears to have several states in which it is relatively stable over long periods of time. But when climate moves between those states, it can do so quickly (geologically speaking), in hundreds of years and even, in a handful of cases, in only a few decades. These rapid 'state changes' are what scientists mean by abrupt climate change. They are much more common at regional scales than at the global scale, but can be global. State changes have triggers, or "tipping points," that are related to feedback processes. In what's probably the single largest uncertainty in climate science, scientists don't have much confidence that they know what those triggers are.

Below is an explanation of just a few other important uncertainties about climate change, organized according to the categories forcing and feedback. This list isn't exhaustive. It is intended to illustrate the kinds of questions that scientists still ask about climate.

Forcings

  1. Solar Irradiance. The sun has a well-known eleven-year irradiance cycle that produces a .08% variation in output.1 Solar irradiance has been measured by satellite daily since the late 1970s, and this known solar cycle is incorporated into climate models. There is some evidence from proxy measurements-sunspot counts going back centuries, measurements from ancient trees, and others-that solar output varies over longer periods of time, too. While there is currently no evidence of a trend in solar output over the past half century, because there are no direct observations of solar output prior to the 1970s, climate scientists do not have much confidence that they understand longer-term solar changes. A number of U.S. and international spacecraft study the sun.

  2. Aerosols, dust, smoke, and soot. These come from both human and natural sources. They also have very different effects on climate. Sulfate aerosols, which result from burning coal, biomass, and volcanic eruptions, tend to cool the Earth. Increasing industrial emissions of sulfates is believed to have caused a cooling trend in the Northern Hemisphere from the 1940s to the 1970s. But other kinds of particles have the opposite effect. The global distribution of aerosols has only been tracked for about a decade from the ground and from satellites, but those measurements cannot yet reliably distinguish between types of particulates. So aerosol forcing is another substantial uncertainty in predictions of future climate.

Feedbacks

  1. Clouds. Clouds have an enormous impact on Earth's climate, reflecting back into space about one third of the total amount of sunlight that hits the Earth's atmosphere. As the atmosphere warms, cloud patterns may change, altering the amount of sunlight absorbed by the Earth. Because clouds are such powerful climate actors, even small changes in average cloud amounts, locations, and type could speed warming, slow it, or even reverse it. Current climate models do not represent cloud physics well, so the Intergovernmental Panel on Climate Change has consistently rated clouds among its highest research priorities. NASA and its research partners in industry, academia, and other nations have a small flotilla of spacecraft and aircraft studying clouds and the closely related phenomenon of aerosols.

  2. Carbon cycle. Currently, natural processes remove about half of each year's human carbon dioxide emissions from the atmosphere, although this varies a bit year to year. It isn't well understood where this carbon dioxide goes, with some evidence that the oceans are the major repository and other evidence that land biota absorbs the majority. There is also some evidence that the ability of the Earth system to continue absorbing it may decline as the world warms, leading to faster accumulation in the atmosphere. But this possibility isn't well understood either. The upcoming Orbiting Carbon Observatory mission will mark NASA's first attempt to answer some of these questions via space observations.

  3. Ocean circulation. One very popular hypothesis about climate change is that as the Earth as a whole warms, ocean circulation in the Atlantic will change to produce cooling in Western Europe. In its most extreme form, this hypothesis has advancing European ice sheets triggering a new ice age. A global-warming induced ice age is not considered very likely among climate scientists. But the idea highlights the importance of ocean circulation in maintaining regional climates. Global ocean data sets only extend back to the early 1990s, so there are large uncertainties in predictions of future ocean changes.

  4. Precipitation. Human civilization is dependent upon where and when rain and snow fall. We need it for drinking water and for growing our food. Global climate models show that precipitation will generally increase, but not in all regions. Some regions will dry instead. Scientists and policymakers would like to use climate models to assess regional changes, but the models currently show wide variation in their results. For just one example, some models forecast less precipitation in the American southwest, where JPL is, while others foresee more precipitation. This lack of agreement on even the direction of change makes planning very difficult. There's much research to be done on this question.

  5. Sea level rise. In its 2007 Fourth Assessment Report, the Intergovernmental Panel on Climate Change used new satellite data to conclude that shrinkage of ice sheets may contribute more to sea level rise than it had thought as recently as 2001. The panel concluded that it could not "provide a best estimate or an upper bound for sea level rise" over the next century due to their lack of knowledge about Earth's ice. There are 5-6 meters worth of sea level in the Greenland ice sheet, and 6-7 meters in the West Antarctic Ice Sheet, while the much larger East Antarctic Ice Sheet is probably not vulnerable to widespread melting in the next century. Many hundreds of millions of people live within that range of sea level increase, so our inability to predict what sea level rise is likely over the next century has substantial human and economic ramifications.

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Global Climate Change Evidence

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Climate change: How do we know?

The Earth's climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about seven thousand years ago, marking the beginning of the modern climate era —and of human civilization. Most of these changes are attributed to the very small changes in the Earth’s orbit changing the amount of solar energy the Earth receives.

The current warming trend is of particular significance because most of it is very likely human-induced and proceeding at a rate that is unprecedented in the past 1,300 years.

Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. Studying these climate data collected over many years reveal the signals of a changing climate.

Certain facts about Earths climate are not in dispute:

  • The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century. Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many JPL-designed instruments, such as AIRS. Increased levels of greenhouse gases must cause the Earth to warm in response.
  • Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in solar output, in the Earth’s orbit, and in greenhouse gas levels. They also show that in the past, large changes in climate have happened very quickly, geologically-speaking: in tens of years, not in millions or even thousands.

The evidence for abrupt climate change is compelling:


Global sea level rose about 17 centimeters (6.7 inches) in the last century. In the last decade, however, the rate of rise nearly doubled.







Levels of Carbon Dioxide are higher today than at anytime in past 650,000 years.

Scientists reconstruct past climate conditions through evidence preserved in tree rings, coral reefs and ice cores. For example, ice cores removed from 2 miles deep in the Antarctic contain atmospheric samples trapped in tiny air bubbles that date as far back as 650,000 years. These samples have allowed scientists to construct a historical record of greenhouse gas concentration stretching back hundreds of thousands of years.





Global surface air temperatures rose three-quarters of a degree Celsius (almost one and a half degrees Fahrenheit) in the last century, but at twice that amount in the past 50 years. Eleven of the last 12 years (1995-2006) are the warmest since accurate recordkeeping began in 1850.






The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.18 degrees Fahrenheit since 1955.











The Greenland and Antarctic ice sheets have shrunk in both area and mass. Data from JPLs Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005.








Mountain glaciers and snow cover have declined on average in both hemispheres, and may disappear altogether in certain regions of our planet, such as the Himalayas, by 2030.











Many species of plants and animals are already responding to global warming, moving to higher elevations or closer to the poles.










Precipitation and evaporation patterns over the oceans have changed, as evidenced by increased ocean salinity near the equator and decreased salinity at higher latitudes.









Resources:

The following are the key sources of data and information contained on this page:
Further Reading

Essay: "The Discovery of Global Warming" (external site)


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Global Climate Change Causes

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The greenhouse effect


A layer of greenhouse gases – primarily carbon dioxide, methane and nitrous oxide – act as a thermal blanket for the Earth, absorbing heat and warming the surface to a life-supporting average of 59 degrees Fahrenheit (15 degrees Celsius).







Most scientists agree the main cause of the current global warming trend is human expansion of the "greenhouse effect" -- warming that results when the atmosphere traps heat radiating from Earth toward space.

Certain gases in the atmosphere behave like the glass on a greenhouse, allowing sunlight to enter, but blocking heat from escaping. Long-lived gases, remaining semi-permanently in the atmosphere, which do not respond physically or chemically to changes in temperature are described as "forcing" climate change whereas gases, such as water, which respond physically or chemically to changes in temperature are seen as "feedbacks."

Gases that contribute to the greenhouse effect include:

  • Water vapor. The most abundant greenhouse gas, but importantly, it acts as a feedback to the climate. Water vapor increases as the Earth's atmosphere warms, but so does the possibility of clouds and precipitation, making these some of the most important feedback mechanisms to the greenhouse effect.
  • Carbon dioxide (CO2). A minor but very important component of the atmosphere, carbon dioxide is released through natural processes such as respiration and volcano eruptions and through human activities such as deforestation, land use changes, and burning fossil fuels. Humans have increased atmospheric CO2 concentration by a third since the Industrial Revolution began. This is the most important long-lived "forcing" of climate change.
  • Methane. A hydrocarbon gas produced both through natural sources and human activities, including the decomposition of wastes in landfills, agriculture, and especially rice cultivation, as well as ruminant digestion and manure management associated with domestic livestock. On a molecule-for-molecule basis, methane is a far more active greenhouse gas than carbon dioxide, but also one which is much less abundant in the atmosphere.
  • Nitrous oxide. A powerful greenhouse gas produced by soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.
  • Chlorofluorocarbons (CFCs). Synthetic compounds of entirely of industrial origin used in a number of applications, but now largely regulated in production and release to the atmosphere by international agreement for their ability to contribute to destruction of the ozone layer. They are also greenhouse gases .
On Earth, human activities are changing the natural greenhouse. Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2). This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO2. To a lesser extent, the clearing of land for agriculture, industry, and other human activities have increased concentrations of greenhouse gases.

The consequences of changing the natural atmospheric greenhouse are difficult to predict, but certain effects seem likely:



  • On average, Earth will become warmer. Some regions may welcome warmer temperatures, but others may not.
  • Warmer conditions will probably lead to more evaporation and precipitation overall, but individual regions will vary, some becoming wetter and others dryer.
  • A stronger greenhouse effect will warm the oceans and partially melt glaciers and other ice, increasing sea level. Ocean water also will expand if it warms, contributing further to sea level rise.
  • Meanwhile, some crops and other plants may respond favorably to increased atmospheric CO2, growing more vigorously and using water more efficiently. At the same time, higher temperatures and shifting climate patterns may change the areas where crops grow best and affect the makeup of natural plant communities.

The role of human activity

In its recently released Fourth Assessment Report, the Intergovernmental Panel on Climate Change, a group of 1,300 independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there's a more than 90 percent probability that human activities over the past 250 years have warmed our planet.

The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels from 280 parts per million to 379 parts per million in the last 150 years. The panel also concluded there's a better than 90 percent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide have caused much of the observed increase in Earth's temperatures over the past 50 years.

They said the rate of increase in global warming due to these gases is very likely to be unprecedented within the past 10,000 years or more. The panel's full Summary for Policymakers report is online at http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf.

Solar irradiance

It's reasonable to assume that changes in the sun's energy output would cause the climate to change, since the sun is the fundamental source of energy that drives our climate system.

Indeed, studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity is thought to have triggered the Little Ice Age between approximately 1650 and 1850, when Greenland was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.

But several lines of evidence show that current global warming cannot be explained by changes in energy from the sun:

  • Since 1750, the average amount of energy coming from the Sun either remained constant or increased slightly.
  • If the warming were caused by a more active sun, then scientists would expect to see warmer temperatures in all layers of the atmosphere. Instead, they have observed a cooling in the upper atmosphere, and a warming at the surface and in the lower parts of the atmosphere. That's because greenhouse gasses are trapping heat in the lower atmosphere.
  • Climate models that include solar irradiance changes can’t reproduce the observed temperature trend over the past century or more without including a rise in greenhouse gases.

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Global Climate Change CURRENT-MISSIONS

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PROPOSED

The following is an alphabetical list of Earth science satellites and instruments developed and managed by the Jet Propulsion Laboratory. For a complete list of all NASA Earth-science missions, visit NASA Science: Earth.

The ACRIMSAT misson. ACRIMSAT
Launched in 1999, AcrimSat studies the sun's energy output with uniform sensitivity from the far-ultraviolet to the far-infrared wavelength range. Its data are used to improve knowledge of the sun's role in global change.

More information
The AIRS mission. AIRS
This instrument flies aboard NASA's Aqua satellite to make highly accurate measurements of air temperature, humidity, clouds and surface temperatures

Mission home page
The AQUARIUS mission. AQUARIUS
Planned for launch in 2010, the Aquarius instrument will provide the first-ever global maps of salt concentration in the ocean surface needed to understand heat transport and storage in the ocean. The project is being developed by NASA and the Space Agency of Argentina.
Mission home page
The ASTER mission ASTER
The Advanced Spaceborne Thermal Emission and Reflection Radiometer is an imaging instrument flying on NASA's Terra satellite. It is designed to obtain high-resolution global, regional and local images of Earth in 14 color bands.

Mission home page
The CLOUDSAT mission. CLOUDSAT
Launched in April 2006, CloudSat monitors the state of the Earth’s atmosphere and weather with a sophisticated radar system. The instrument, jointly developed with the Canadian Space Agency, can predict which clouds produce rain, observe snowfall, and monitor the moisture content of clouds.
Mission home page
The Grace mission GRACE
The twin Gravity Recovery and Climate Experiment (GRACE) spacecraft observe and measure the gravitational field of the Earth. The findings from this mission shed light on the shape and composition of the planet and the distributions of water and ice. The mission was launched in March 2002.
Mission home page
The JASON 1 mission JASON 1
Launched in December 2001, the Jason-1 spacecraft uses microwaves to monitor the height of the water of the Earth’s oceans. This information helps scientists understand weather patterns like El Niño, predict the formation of hurricanes, and observe the mean height of the oceans as they rise due to climate change.
Mission home page
The MISR mission. MISR
Launched aboard NASA's Terra satellite, the Multi-angle Imaging Spectro-Radiometer (MISR) instrument is a sophisticated imaging system that collects images from nine widely spaced angles as its satellite glides above Earth.

Mission home page
The MLS mission. MLS
This instrument, which flies aboard NASA's Aura spacecraft, is designed to improve our understanding of ozone, especially how it is depleted by processes of chlorine chemistry.

Mission home page
The OSTM  (JASON-2) mission. OSTM (JASON-2)
Scheduled for launch in 2008, the Ocean Surface Topography Mission (OSTM) is a follow-on to the Jason-1 mission. It will monitor the height of the water of the Earth’s oceans to help scientists understand weather patterns like El Niño, predict the formation of hurricanes, and observe the mean height of the oceans as they rise due to climate change.

Mission home page
The QUIKSCAT mission. QUIKSCAT
QuikSCAT is primarily known as a powerful weather-monitoring tool that bounces bursts of microwaves off of the Earth’s surface to measure wind speeds. This information is important to scientists who study the impact climate change has on weather patterns and severity. QuikSCAT was launched in June 1997.
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The TROPOSPHERIC EMISSION SPECTROMETER mission. TROPOSPHERIC EMISSION SPECTROMETER
This instrument, which flies aboard NASA's Aura spacecraft, is an infrared sensor designed to study Earth's troposphere – the lowest region of our atmosphere – and look at ozone.

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Global Climate Change PROPOSED-MISSIONS

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CURRENT
PROPOSED

The Decadal Survey will generate consensus recommendations from the Earth and environmental science and the applications communities regarding a systems approach to space-based Earth Science observations. The following is an chronological list of Earth science satellites and instruments proposed by JPL for consideration by the Decadal Survey.
CLARREO
Will measure solar radiation, spectrally resolved forcing and response of the climate system.

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SMAP
Will measure soil moisture and freeze/thaw for weather and water cycle processes.

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ICESat-II
Will measure ice sheet height changes for climate change diagnoses.

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DESDynI
Will measure surface and ice sheet deformation for understanding natural hazards and climate; vegetation structure for ecosystem health.

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HyspIRI
Will monitor land surface composition for agriculture and mineral characterization and vegetation types for ecosystem health.

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ASCENDS
Will measure the number density of Carbon Dioxide (CO2) in the column of air beneath the aircraft. Will also measure ambient air pressure and temperature.

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SWOT
Will track ocean, lake, and river water levels for ocean and inland water dynamics.

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GEO-CAPE
Will monitor atmospheric gas columns for air-quality forecasts and ocean color for coastal ecosystem health and climate emissions.

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ACE
Using lidar, ACE will create aerosol and cloud profiles for climate and water cycles.

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LIST
Will measure land surface topography to look for landslide hazards and water runoff.

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PATH
Will perform high frequency, all-weather temperature and humidity soundings for weather forecasting and sea surface temperature.

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GRACE-II
Will measure Earth's gravity field in order to track large-scale water movement.

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SCLP
Will measure snow accumulation for fresh water availability.

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GACM
Will monitor ozone and related gases for intercontinental air quality and stratospheric ozone layer prediction.

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3D-Winds
Will monitor tropospheric winds for weather forecasting and pollution transport.

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