Andrew Yee
January 24th 06, 08:08 PM
New Jersey Institute of Technology
Contact:
Sheryl Weinstein, Public Relations
973-596-3436
Jan. 23, 2006
NJIT Solar Physicists Report Paradox in Eos: Less Sunlight, But Temps Rise
NEWARK -- Less sunlight reaching the Earth's surface has not translated
into cooler temperatures, according to a team of solar physicists at New
Jersey Institute of Technology (NJIT). The scientists, who monitor the
Earth's reflectance by measuring what is known as the moon's earthshine,
have observed that the amount of light reflected by Earth -- its albedo --
has increased since 2000. The result has been less sunlight reaching the
Earth's surface.
"Our findings have significant implications for the study of climate
change," said Philip R. Goode, PhD, principal investigator and
distinguished professor of physics at NJIT. "The results raise questions
about how global temperatures can still rise when the amount of sunlight
reaching the surface has decreased." The scientists find that the
seemingly paradoxical result is due to an increase in the cloud cover
coupled with a peculiar re-arrangement of the clouds, but are unsure why
this is happening. This large variability of the clouds and albedo
presents a fundamental, unmet challenge to our ability to understand and
predict the Earth's climate.
Goode is the director of Big Bear Solar Observatory, California, where the
observations were carried out. NJIT has owned and operated the observatory
since 1997. Goode's findings are reported tomorrow in "Can the Earth's
Albedo and Surface Temperatures Increase Together," published tomorrow by
Eos (Jan. 24, 2006), the weekly newspaper of geophysics published by the
American Geophysical Union. The National Aeronautics and Space
Administration funded the research.
"Recently analyzed cloud data from the International Satellite Cloud
Climatology Project (ISCCP) confirm the trend in reflectance," said Goode.
"The data also reveal that from 2000 to now the clouds have changed so
that the Earth may continue warming, even with declining sunlight. These
large and peculiar variabilities of the clouds, coupled with a resulting
increasing albedo, presents a fundamental, unmet challenge for all
scientists who wish to understand and predict the Earth's climate."
Co-authors with Goode are post-doctoral associates Enric Palle and Pilar
Montanes-Rodriguez, who work at the observatory, and Steven E. Koonin, a
professor of theoretical physics at California Institute of Technology
(Cal Tech).
Climate depends on sunlight, less the part of sunlight that is promptly
reflected plus how well the Earth holds heat. At any moment, more than
half the Earth is swathed in clouds, and they dominate the Earth's
reflectance. Both the sunlight reaching Earth and the amount of
atmospheric heat trapped are sensitive to clouds, which both cool the
Earth (especially low thick clouds) by reflecting the sunlight and warm
the Earth by acting as blankets (especially high thin clouds).
It has been argued that an increasing albedo during the past five years
would be inconsistent with the observed behavior in the global land and
sea-surface temperatures because, in principle, an increase in the albedo
would seem to imply that the decrease in the sunlight absorbed by the
planet would lead to cooler temperatures.
The just-released update of the 20-year sequence of ISCCP satellite cloud
data shows that during the first 15 years of observations, the percent
difference between high-lying and low-lying clouds remained steady at 7-8
percent. But in the last five years, for some unknown reason, the
difference has almost doubled to 13 percent. The ISCCP data is a careful
compilation of cloud observations covering the entire Earth from a range
of meteorological satellites.
"That increase in the difference signals a relative decrease in the
cooling effect of clouds," said Goode. "Thus, the rising reflectance of
the Earth has not led to a reversal of global warming from the increase in
sunlight being reflected back into space." What has happened is that the
low, cooling clouds have decreased during the most recent years, while
high, warming clouds have increased even more. Thus, the cloud data also
reveal an increase in total cloud amount during 2000-2004. That increase
is consistent with the earlier earthshine result of growing reflectance
throughout that period.
Goode noted that the Earth's reflectance depends primarily on cloud
properties. Recent ground-based and satellite studies of the albedo have
shown a surprisingly significant inter-annual and decadal variability.
From about 1985-2000, the Earth steadily received more sunlight, before
the recent reversal of the trend from 2000-2004. "This is not the first
time such a situation occurred," Goode said.
Ground-based radiometers hint at a similar reversal from the 1960's
through the mid-1980's, which some scientists have dubbed global dimming.
Thus, it seems there may be a large, unexplained decadal variation in
sunlight reaching the Earth, as well as a large effect of clouds
re-arranging by altitude.
"From these data and results, we caution scientists against concluding
that global dimming would mean a cooler Earth, and that clouds need a
better treatment in climate models" said Goode.
The earthshine studied by Goode and his colleagues can be seen as a
ghostly glow associated with the moon's "dark side" -- or the portion of
the lunar disk not lit by the Sun. The cloudier the Earth, the brighter
the earthshine. "The phenomenon of earthshine was first observed by
Leonardo DaVinci," said Goode.
New Jersey Institute of Technology, the state's public technological
research university, enrolls more than 8,200 students in bachelor's,
master's and doctoral degrees in 100 degree programs offered by six
colleges: Newark College of Engineering, New Jersey School of
Architecture, College of Science and Liberal Arts, School of Management,
Albert Dorman Honors College and College of Computing Sciences. NJIT is
renowned for expertise in architecture, applied mathematics, wireless
communications and networking, solar physics, advanced engineered
particulate materials, nanotechnology, neural engineering and eLearning.
Contact:
Sheryl Weinstein, Public Relations
973-596-3436
Jan. 23, 2006
NJIT Solar Physicists Report Paradox in Eos: Less Sunlight, But Temps Rise
NEWARK -- Less sunlight reaching the Earth's surface has not translated
into cooler temperatures, according to a team of solar physicists at New
Jersey Institute of Technology (NJIT). The scientists, who monitor the
Earth's reflectance by measuring what is known as the moon's earthshine,
have observed that the amount of light reflected by Earth -- its albedo --
has increased since 2000. The result has been less sunlight reaching the
Earth's surface.
"Our findings have significant implications for the study of climate
change," said Philip R. Goode, PhD, principal investigator and
distinguished professor of physics at NJIT. "The results raise questions
about how global temperatures can still rise when the amount of sunlight
reaching the surface has decreased." The scientists find that the
seemingly paradoxical result is due to an increase in the cloud cover
coupled with a peculiar re-arrangement of the clouds, but are unsure why
this is happening. This large variability of the clouds and albedo
presents a fundamental, unmet challenge to our ability to understand and
predict the Earth's climate.
Goode is the director of Big Bear Solar Observatory, California, where the
observations were carried out. NJIT has owned and operated the observatory
since 1997. Goode's findings are reported tomorrow in "Can the Earth's
Albedo and Surface Temperatures Increase Together," published tomorrow by
Eos (Jan. 24, 2006), the weekly newspaper of geophysics published by the
American Geophysical Union. The National Aeronautics and Space
Administration funded the research.
"Recently analyzed cloud data from the International Satellite Cloud
Climatology Project (ISCCP) confirm the trend in reflectance," said Goode.
"The data also reveal that from 2000 to now the clouds have changed so
that the Earth may continue warming, even with declining sunlight. These
large and peculiar variabilities of the clouds, coupled with a resulting
increasing albedo, presents a fundamental, unmet challenge for all
scientists who wish to understand and predict the Earth's climate."
Co-authors with Goode are post-doctoral associates Enric Palle and Pilar
Montanes-Rodriguez, who work at the observatory, and Steven E. Koonin, a
professor of theoretical physics at California Institute of Technology
(Cal Tech).
Climate depends on sunlight, less the part of sunlight that is promptly
reflected plus how well the Earth holds heat. At any moment, more than
half the Earth is swathed in clouds, and they dominate the Earth's
reflectance. Both the sunlight reaching Earth and the amount of
atmospheric heat trapped are sensitive to clouds, which both cool the
Earth (especially low thick clouds) by reflecting the sunlight and warm
the Earth by acting as blankets (especially high thin clouds).
It has been argued that an increasing albedo during the past five years
would be inconsistent with the observed behavior in the global land and
sea-surface temperatures because, in principle, an increase in the albedo
would seem to imply that the decrease in the sunlight absorbed by the
planet would lead to cooler temperatures.
The just-released update of the 20-year sequence of ISCCP satellite cloud
data shows that during the first 15 years of observations, the percent
difference between high-lying and low-lying clouds remained steady at 7-8
percent. But in the last five years, for some unknown reason, the
difference has almost doubled to 13 percent. The ISCCP data is a careful
compilation of cloud observations covering the entire Earth from a range
of meteorological satellites.
"That increase in the difference signals a relative decrease in the
cooling effect of clouds," said Goode. "Thus, the rising reflectance of
the Earth has not led to a reversal of global warming from the increase in
sunlight being reflected back into space." What has happened is that the
low, cooling clouds have decreased during the most recent years, while
high, warming clouds have increased even more. Thus, the cloud data also
reveal an increase in total cloud amount during 2000-2004. That increase
is consistent with the earlier earthshine result of growing reflectance
throughout that period.
Goode noted that the Earth's reflectance depends primarily on cloud
properties. Recent ground-based and satellite studies of the albedo have
shown a surprisingly significant inter-annual and decadal variability.
From about 1985-2000, the Earth steadily received more sunlight, before
the recent reversal of the trend from 2000-2004. "This is not the first
time such a situation occurred," Goode said.
Ground-based radiometers hint at a similar reversal from the 1960's
through the mid-1980's, which some scientists have dubbed global dimming.
Thus, it seems there may be a large, unexplained decadal variation in
sunlight reaching the Earth, as well as a large effect of clouds
re-arranging by altitude.
"From these data and results, we caution scientists against concluding
that global dimming would mean a cooler Earth, and that clouds need a
better treatment in climate models" said Goode.
The earthshine studied by Goode and his colleagues can be seen as a
ghostly glow associated with the moon's "dark side" -- or the portion of
the lunar disk not lit by the Sun. The cloudier the Earth, the brighter
the earthshine. "The phenomenon of earthshine was first observed by
Leonardo DaVinci," said Goode.
New Jersey Institute of Technology, the state's public technological
research university, enrolls more than 8,200 students in bachelor's,
master's and doctoral degrees in 100 degree programs offered by six
colleges: Newark College of Engineering, New Jersey School of
Architecture, College of Science and Liberal Arts, School of Management,
Albert Dorman Honors College and College of Computing Sciences. NJIT is
renowned for expertise in architecture, applied mathematics, wireless
communications and networking, solar physics, advanced engineered
particulate materials, nanotechnology, neural engineering and eLearning.