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The atmosphere is a life-giving blanket of air that surrounds
our Earth; it is composed of gases that protect us from the
Sun’s intense heat and ultraviolet radiation, allowing life to
flourish. Greenhouse gases like carbon dioxide, ozone, and
methane are steadily increasing from year to year. These
gases trap heat radiating from Earth’s surface, causing the
atmosphere to warm. Conversely, aerosols in the air such
as dust, smoke, and ash reflect the Sun’s radiative energy,
which leads to cooling. This delicate balance of incoming
solar radiation and reflected energy is critical to sustaining
life on Earth.
Research using computer models and satellite data from
NASA’s Earth Observing System enhances our understanding
of the physical processes affecting trends in temperature,
humidity, and clouds, and helps us assess the impact of a
changing atmosphere on the global climate.
The Earth From Space
This true-color image of the Earth is,
in fact, not a photograph as we know
it. It was created using several
different data products derived from
the Moderate Resolution Imaging
Spectroradiometer (MODIS) aboard
NASA’s Terra satellite. These data
are gathered over the entire globe
every day and then composited over
8-, 16-, and 30-day periods to
provide information on such areas of
study as land, ocean, and
atmospheric processes.
Image created by Reto Stockli, Nazmi El Saleous,
and Marit Jentoft-Nilsen, NASA/GSFC, using data
from the MODIS Science Team and NOAA
Anatomy of a Heat Wave
Watts per Square Meter
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The image above shows emitted longwave radiation escaping the top of Earth’s atmosphere as measured by the
Clouds and the Earth’s Radiant Energy System (CERES ) instrument on May 25, 2001. Record-breaking heat waves
in southern Asia, northern Africa, and southwestern U.S. killed dozens of people during the month of May as seen in
the yellow areas denoting large amounts of thermal energy escaping into space. CERES data are being used to
accurately predict this emission of thermal energy as our world experiences changes in surface reflectivity, clouds,
atmospheric temperatures, and key greenhouse gases.
Image credit: CERES Science Team, NASA Langley Research Center
Carbon Monoxide
Carbon monoxide (CO) is a colorless, odorless, toxic gas. CO reduces the oxygen-carrying capacity of blood in the
body and in day-to-day life can impair mental abilities, especially for those with heart and respiratory conditions.
Its production is a direct result of combustion caused predominantly by industrial processes and biomass burning.
Carbon monoxide levels have been increasing in the atmosphere. In this global image of carbon monoxide from
March 13-15, 2000, lavender indicates high CO values and blues indicate low values. The high concentrations of CO
in west central Africa are largely due to widespread biomass burning.
Image credit: Scientific Visualization Studio, NASA/GSFC, using data from the MOPITT Science Team
Smoke and Haze Over Southern Africa
These images are a collection of Multi-
Nadir
70˚ Backward
Aerosol Optical
Thickness
angle Imaging SpectroRadiometer (MISR)
data acquired over eastern Angola and
northeastern Namibia on August 30, 2000.
MISR has nine cameras that focus at
different angles. The panel on the left is a
true color composite from the vertical-
viewing (nadir) camera. The second panel
is a true color composite from the
backward-viewing 70° camera. This angle
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enhances the appearance of smoke in the
atmosphere and highlights the presence of
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many individual smoke plumes. Retrieved
aerosol amounts are given in the panel on
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the right. The images are roughly 380
kilometers (236 miles) in width.
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Image credit: MISR Science Team, Jet Propulsion
Laboratory
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0.0
Ozone Depletion
Stratospheric ozone protects all life forms
from the sun’s harmful ultraviolet
radiation. These images from the Total
Ozone Mapping Spectrometer (TOMS)
show the progressive depletion of
stratospheric ozone over Antarctica from
Dobson Units
1983 to 1997. High concentrations of
500
ozone are shown in red, low
concentrations in blue.
400
September 1983
September 1987
The Antarctic ozone hole develops each
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year between late August and early
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October. By September, 1998 it had
grown to cover 10.5 million square miles.
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Scientists hope to see a reduction in
ozone loss as emissions of ozonedestroying CFCs (chlorofluorocarbons)
are reduced.
Image credit: Greg Shirah, NASA/GSFC Scientific
Visualization Studio
September 1993
September 1997
Ozone Depletion
This is an animation of the
stratospheric ozone hole over
Antarctica, as measured by Earth
Dobson Units
Probe TOMS from July 15, 2001
through October 9, 2001. Red and
yellow denote regions of high
ozone and dark blue denotes
500
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regions of low ozone.
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Animation credit: Greg Shirah, NASA/GSFC
Scientific Visualization Studio
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Click on image to start movie
Layers of the Atmosphere
The troposphere is the lowest layer of the
Earth’s atmosphere, extending to a height of
8-15 kilometers (about 5-9 miles),
depending on latitude. The stratosphere,
warmer than the upper troposphere, is the
next layer and rises to a height of about 50
kilometers (about 31 miles). Temperatures
in the mesosphere, 50 to 80 kilometers (31
to 50 miles) above the Earth, decline with
altitude to -70° to -140°C (-94° to -220°F),
depending upon latitude and season.
Temperatures increase again with altitude in
the thermosphere, which begins about 80
kilometers (50 miles) above the Earth. They
can rise to 2,000°C (about 3600°F). The
exosphere begins at 500 to 1,000 kilometers
(about 310-621 miles) and the few particles
of gas there can reach 2,500°C (about
4500°F) during the day.
Earth’s Radiation Components
The Earth’s surface is kept warm
through one source: the Sun. It is the
primary source for Earth’s energy.
Some of the incoming sunlight and
heat energy is reflected back into
space by the Earth’s surface, gases in
the atmosphere, and clouds; some of it
is absorbed and stored as heat. When
the surface and atmosphere warm,
they emit heat, or thermal energy, into
space. The “radiation budget” is an
accounting of these energy flows. If
the radiation budget is in balance,
then Earth should be neither warming
nor cooling, on average.
Clouds, atmospheric water vapor and
aerosol particles play important roles
in determining global climate through
their absorption, reflection, and
emission of solar and thermal energy.
Cloud Types - Examples
What types of clouds have you seen in
the sky? They come in four types:
High clouds consisting of cirrus,
cirrostratus and cirrocumulus; middle
clouds consisting of altostratus and
altocumulus; and low clouds
consisting of cumulus, stratocumulus,
nimbostratus and cumulonimbus.
The study of clouds, how they form,
and their characteristics, may well be
a central key to understanding climate
change. Low thick clouds primarily
reflect solar radiation and cool the
surface of the Earth. High, thin clouds
primarily transmit incoming solar
radiation; at the same time, they trap
some of the outgoing infrared
radiation emitted by the Earth and
radiate it back downward, thereby
warming the surface of the Earth.
Carbon Dioxide Levels
This chart represents atmospheric
carbon dioxide (CO2) monthly mean
mixing ratios determined from the
continuous monitoring programs at
three NOAA Climate Monitoring and
Diagnostics Laboratory baseline
observatories: the South Pole, Mauna
Loa, Hawaii, and Barrow, Alaska.
Atmospheric CO2, a major
greenhouse gas, has increased
approximately 40 ppmv since 1958,
largely because of human activities.
The “zig-zag,” up-and-down motion
of the graph represents seasonal
cycles due to photosynthetic activity
(the processing of CO2 by
vegetation). The potential effect of
the increase in atmospheric CO2
levels, as well as other greenhouse
gases such as methane, is a major
focus of NASA’s Earth Science
Enterprise.
Global Temperatures
According to researchers at the NASA Goddard Institute for Space Studies, who analyze data collected from
several thousand meteorological stations around the world, there has been a long-term global warming trend
underway since the early 1960s, with 1998 being the warmest year in the period of satellite instrumental data.
The 1999 data show a continuation of that warming trend. The Temperature Index chart combines sea surface
temperature measurements from satellites with land surface air temperature measurements from
meteorological stations to produce a more truly global land-ocean temperature index than land stations alone
could provide.
Data source: Hansen, J. et al., J. Geophys. Res., 104, 30,997-31,022 (1999); NASA Goddard Institute for Space Studies
Global Temperatures
As demonstrated in these two charts, data from tiny air bubbles trapped in an Antarctic ice core show that
atmospheric CO2 concentrations and temperatures from 160,000 years ago to pre-industrial times are closely
correlated. Recent measurements of CO2 concentration and temperature extend this record to the present day,
and confirm that CO2 concentrations have risen to 360 parts per million by volume (ppmv) and temperatures
have increased 0.6°C (1.1°F) over the last 100 years.
Data sources: Ice core data from Barnola, J. M. et al., Nature, 329, 408-414 (1987); current data from the Carbon Dioxide Information
Analysis Center, 1997, Oak Ridge, TN
For the Classroom…
Introduce major concepts of “Air – Our Atmosphere” by dividing the
class into small teams to research several of the questions on the next
page. Students can research their answers using these slides and
other sources. Students can prepare presentations to cooperatively
instruct other teams using pre-established teacher criteria.
For the Classroom…
• Why is the study of our atmosphere important?
• Why is NASA involved in the study of atmospheric processes?
• What is haze and how does it affect incoming solar radiation in the
atmosphere?
• What can cause haze?
• Make a list of the greenhouse gases. Why are they called greenhouse
gases?
• How does each cloud type affect the radiation balance of the Earth?
• Explain the formation and destruction of stratospheric ozone and
its effects on people?
• What effect can you have on our atmosphere?