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Tackling Clouds for Improved Predictions of Future Climate
October 15th, 2009
Today, JPL Earth scientist Hui Su joins thousands of other bloggers in more than 130 countries around the world for the Blog Action Day ‘09 Climate Change.
Blog Action Day is an annual event that unites the world’s bloggers in posting about the same issue on the same day, with the aim of sparking discussion around an issue of global importance. The theme of this year’s event, climate change, affects us all and will be the topic of international climate negotiations taking place in Copenhagen, Denmark, this December.
As a world leader in studying Earth’s climate, NASA researchers play a vital role in shaping our understanding of global change. In today’s post, Su discusses the critical role clouds play in climate, and why learning more about them is a key to predicting how our climate will change in the future.
For more information on Blog Action Day, visit: http://www.blogactionday.org .
Hui Su
Clouds are among the most fascinating natural phenomena and have inspired countless works of literature and art. Their ever-changing forms make them a great challenge to atmospheric scientists working to predict how our climate will change in the future in response to increasing greenhouse gases such as carbon dioxide.
Clouds occur at many different heights in our atmosphere and take many different forms. There are three main types of clouds: stratus, cumulus and cirrus. Stratus clouds are low clouds, usually within 2 kilometers (7,000 feet) above the surface. They look like a gray blanket, extending thousands of kilometers across the sky. Cumulus clouds look like puffy cotton balls and extend vertically for large distances. The third type is wispy and feathery-looking cirrus. Cirrus clouds are usually high in the sky, about 7 kilometers (23,000 feet) above the surface. These three types of clouds have different impacts on Earth’s climate due to their unique abilities to reflect sunlight and trap heat radiated from Earth’s surface.
Artist’s concept of NASA’s CloudSat spacecraft, which is providing the first global survey of cloud properties to better understand their effects on both weather and climate. Image credit: NASA/JPL
Su et al. (2008, Journal of Geophysical Research) suggested that cirrus clouds increase as sea surface temperature becomes warmer, further enhancing surface warming. Image credit: NASA/JPL/Caltech
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Stratus clouds can effectively block sunlight from reaching the surface; therefore, they act as an umbrella that cools Earth. Cirrus clouds are relatively transparent to sunlight but can trap terrestrial radiation, JUST AS carbon dioxide does, so they have a net warming effect on Earth. Cumulus clouds can block sunlight and also trap terrestrial radiation. Their net effect varies greatly depending on their actual heights and thicknesses.
Climate scientists have long struggled to quantify how different types of clouds change when global warming occurs. For example, an increase in stratus clouds may cool Earth’s surface, compensating for global warming; while an increase in cirrus clouds may further warm Earth’s surface, exacerbating global warming. Up to now, scientists have not been able to come to a consensus as to whether stratus, cumulus or cirrus clouds will increase or decrease as global temperatures increase.
A key advancement in cloud studies in recent years has been the availability of global satellite observations of clouds, especially the measurements of clouds at different heights provided by NASA satellites like CloudSat, managed by NASA’s Jet Propulsion Laboratory (JPL). These observations are allowing scientists to better simulate clouds in climate models, which are the primary tools climate scientists use to predict future climate change. Up till now, the dynamic nature of clouds has made them very difficult to simulate in current climate models. But by applying space data, we at JPL are working closely with modelers to improve cloud simulations and thereby improve predictions of future climate change.
To learn more about JPL’s research in this field and the CloudSat mission, visit:
http://cloudsat.atmos.colostate.edu/home .
Comets and Life On Earth
August 17th, 2009
Donald Yeomans
With the recent discovery of the amino acid glycine in the comet dust samples returned to Earth by the Stardust spacecraft, it is becoming a bit more clear how life may have originated on Earth. Water is a well-known ingredient in both comets and living organisms, and now it appears that amino acids are also common to comets and living organisms. Amino acids are used to make proteins, which are chains of amino acids, and proteins are vital in maintaining the cell structures of plants and animals.
Amino acids had previously been identified in meteorite samples, and these samples are thought to be the surviving fragments from asteroid collisions with the Earth. So now it appears that both comets and asteroids in the Earth’s neighborhood, the so-called near-Earth objects, delivered some of the building blocks of life to the early Earth.
Asteroid Eros - Mosaic of Northern Hemisphere. Image Credit: NASA/JPL/JHUAPL
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Impacts of comets and asteroids with the early Earth likely laid down the veneer of carbon-based molecules and water that allowed life to form. Once life did form, subsequent collisions of these near-Earth objects frustrated the evolution of all but the most adaptable species. The dinosaurs checked out some 65 million years ago because of an impact by a six mile-wide comet or asteroid off the coast of the Yucatan peninsula. Fortunately, the small, furry mammalian creatures at the time were far more adaptable and survived this impact event. Thus, present day mammals like us may owe our origin and current position atop Earth’s food chain to these near-Earth objects, one of which took out our dinosaur competitors some 65 million years ago.
Today, most of the attention directed toward near-Earth objects has to do with the potential future threat they can pose to life on Earth. However, the recent Stardust discovery of a cometary amino acid reminds us that, were it not for past impacts by these objects, the Earth may not have received the necessary building blocks of life, and humans may not have evolved to our current preeminent position on Earth. While giving thanks to these near-Earth objects, we still need to make sure we find the potentially hazardous comets and asteroids early enough so we don’t go the way of the dinosaurs.
For more information on near-Earth objects, see: http://www.jpl.nasa.gov/asteroidwatch/index.cfm
Five Things About Viewing Mars in August
August 6th, 2009
Jane Houston Jones
If you’re like me, you may have received an e-mail this summer telling you go outside on August 27 and look up in the sky. The e-mail, most likely forwarded to you by a friend or relative, promises that Mars will look as big as the moon on that date, and that no one will ever see this view again. Hmmm, it looks like the same e-mail I received last summer and the summer before that, too. In fact this same e-mail has been circulating since 2003, but with a few important omissions from the original announcement.
I’m Jane Jones, an amateur astronomer and outreach specialist for the Cassini mission at Saturn, and I’m here to set the record straight on when and how you can actually see Mars this month.
1. How did the “Mars in August” e-mail get started in the first place?
In 2003, when Mars neared opposition — its closest approach to Earth in its 22-month orbit around the sun — it was less than 56 million kilometers (less than 35 million miles) away. This was the closest it had been in over 50,000 years. The e-mail that circulated back then said that Mars, when viewed through a telescope magnified 75 times, would look as large as the moon does with the unaided eye. Even back in 2003, to the unaided eye, Mars looked like a reddish star in the sky to our eyes, and through a backyard telescope it looked like a small disc with some dark markings and maybe a hint of its polar ice cap. Without magnification, it never looked as large as the moon, even back in 2003!
2. Can the moon and Mars ever look the same size?
No. The moon is one-quarter the size of Earth and is relatively close — only about 384,000 kilometers (about 239, 000 miles) away. On the other hand, Mars is one-half the size of Earth and it orbits the sun 1-1/2 times farther out than Earth’s orbit. The closest it ever gets to Earth is at opposition every 26 months. The next opposition is in January 2010.
At that time, Mars will be 98 million kilometers (61 million miles) from Earth, almost twice as far as in 2003. So from that distance, Mars could never look the same as our moon.
3. Is Mars visible in August 2009?
Mars rises in the east at about 1:30 a.m. this month and is best seen closer to dawn. It is a ruddy star-like object about the same brightness as the brightest stars you’ll see. Look for Mars above the constellation Orion in the pre-dawn sky. The moon is close by on the mornings of August 15 and 16. The brighter object in the sky below and left of Mars is Venus!
4. Can I see Mars and the moon at the same time this month?
If you get up before sunrise on August 15 and 16, you can see the waning crescent moon pass by Mars. The next two mornings, August 17 and 18, you’ll see the moon pass by Venus, which is the bright object below Mars in the morning sky. This will be a great time to compare the sizes of the moon and Mars for yourself!
5. Will the “Mars in August” e-mail return next year?
Most certainly! But next year, you’ll be armed with facts, and perhaps you will have looked at the red planet for yourself and will know what to expect. And you will know exactly where to put that email. In the trash!
About This Blog
The JPL Blog seeks to inform and involve the public in the breadth of JPL's missions and projects exploring Earth, Mars, the solar system and the universe beyond. A variety of engineers and scientists contribute posts about the endeavors they are pursuing for NASA and JPL. Selected comments are published and are moderated.You are currently browsing the NASA’s Jet Propulsion Laboratory Blog blog archives.
