Andrew Yee[_1_]
May 16th 07, 05:11 PM
ESA News
http://www.esa.int
25 April 2007
Satellites play vital role in understanding the carbon cycle
The global carbon cycle plays a vital role in climate change and is of
intense importance to policy makers, but significant knowledge gaps remain
in our understanding of it. Several scientists at the Envisat Symposium this
week have highlighted research projects using ESA satellites to understand
better this complex process.
The total number of carbon atoms on Earth is fixed -- they are exchanged
between the ocean, atmosphere, land and biosphere. The fact that human
activities are pumping extra carbon dioxide into the atmosphere, by fossil
fuel burning and deforestation, is well known. Because of this, atmospheric
carbon dioxide concentrations are higher today than they have been over the
last half-million years or so. Scientists are now using satellite
instruments to locate sinks and sources of CO2 in the ocean and land.
Across land and sea, our world's plant life uses the process called
photosynthesis to convert incoming sunlight into chemical energy. Plants
accumulate carbon dioxide during photosynthesis and store it in their
tissues, making them carbon sinks.
Dr Nadine Gobron of the European Commission's Joint Research Centre (EC-JRC)
in Ispra, Italy, is combining daily multispectral observations from
Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument with a
sophisticated processing algorithm to reveal global photosynthesis activity
on land.
The fraction of incoming solar radiation useful for photosynthesis that is
actually absorbed by vegetation -- a value known as the Fraction of Absorbed
Photosynthetically Active Radiation (FAPAR) -- is recognised as an essential
climate variable by international organisations including the Global Climate
Observing System (GCOS). FAPAR is regularly used in diagnostic and
predictive models to compute the primary productivity of the vegetation
canopies.
The operational FAPAR MERIS product is derived with the JRC-FAPAR algorithm,
which has been designed to exploit the daily MERIS spectral measurements in
the blue, red and near-infrared bands with no prior knowledge on the land
cover.
This methodology involves a physically-based approach which can be adopted
for generating this biophysical product from various optical medium
resolution sensors. The algorithm used allows scientists to derive the
equivalent biophysical product from other optical satellite sensors, even
retired ones, to ensure the availability of a long-time series of global
FAPAR, which is essential to assess environmental trends, guide policy
making and support sustainable development activities.
"Demonstration products at the global scale are now available and are ready
to be used in state-of-the-art carbon data assimilation systems (CCDAS) for
better understanding the role of the biosphere in the global carbon cycle,"
Gobron said.
Phytoplankton, microscopic marine plants that drift on or near the surface
of the sea, absorb atmospheric carbon dioxide through photosynthesis just as
their terrestrial 'cousins' do. While individually microscopic,
phytoplankton chlorophyll collectively tints the surrounding ocean waters,
providing a means of detecting these tiny organisms from space with
dedicated ocean colour sensors, such as MERIS.
Dr Michael Buchwitz from the Institute of Environmental Physics (IUP) at the
University of Bremen in Germany presented global carbon dioxide measurements
based on observations from Envisat's SCIAMACHY instrument from 2003 to 2005.
The SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric
Chartography) instrument is the first space sensor capable of measuring the
most important greenhouse gases with high sensitivity down to the Earth's
surface because it observes the spectrum of sunlight shining through the
atmosphere in 'nadir' looking operations on a global scale.
Buchwitz explained that he and his colleagues first measure the absolute
carbon dioxide (CO2) column in number of CO2 molecules per area above the
Earth's surface. Then, they measure the oxygen (O2) column that can be
easily converted into an 'air column'.
As seen in the image above, both figures are essentially identical, as he
had expected.
"There are, however, tiny differences and this is the CO2 source/sink
information we are interested in," Buchwitz said. "To see this we compute
the CO2/O2 ratio which can be converted into a column averaged CO2 mixing
ratio."
Dr Paul Monks from the University of Leicester is using SCIAMACHY data to
measure how much CO2 is being taken up by plants. Using 20,000 individual
measurements a month, he is monitoring CO2 drawn down over Siberia, North
America and Northern Europe.
According to Monks, this view from space is providing the first evidence of
the Earth 'breathing' by allowing scientists to witness the biology drawing
down CO2 during the growing season and then releasing some of it back.
"The exciting new area breaking from this sort of data is that we begin to
be able to look at the tropics, which are the 'lungs' of the atmospheric
system," Monks said. "Using this data, we are going to be able to assess how
efficient the tropics are at modulating carbon as well as how that is
changing with time as climate change effects the tropical biosystem."
By comparing the satellite data to aircraft data and to remote-sensing sites
on the surface, Monks learned the method he and his colleagues are using is
approaching a precision of around 1%, giving them confidence in what they
see from space.
By better understanding all of the parameters involved in the carbon cycle,
scientists can better predict climate change as well as better monitor
international treaties aimed at reducing greenhouse gas emissions, such as
the Kyoto Protocol which addresses the reduction of six greenhouse gases
including carbon dioxide.
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaCP/SEMLEHMJC0F_index_1.html ]
http://www.esa.int
25 April 2007
Satellites play vital role in understanding the carbon cycle
The global carbon cycle plays a vital role in climate change and is of
intense importance to policy makers, but significant knowledge gaps remain
in our understanding of it. Several scientists at the Envisat Symposium this
week have highlighted research projects using ESA satellites to understand
better this complex process.
The total number of carbon atoms on Earth is fixed -- they are exchanged
between the ocean, atmosphere, land and biosphere. The fact that human
activities are pumping extra carbon dioxide into the atmosphere, by fossil
fuel burning and deforestation, is well known. Because of this, atmospheric
carbon dioxide concentrations are higher today than they have been over the
last half-million years or so. Scientists are now using satellite
instruments to locate sinks and sources of CO2 in the ocean and land.
Across land and sea, our world's plant life uses the process called
photosynthesis to convert incoming sunlight into chemical energy. Plants
accumulate carbon dioxide during photosynthesis and store it in their
tissues, making them carbon sinks.
Dr Nadine Gobron of the European Commission's Joint Research Centre (EC-JRC)
in Ispra, Italy, is combining daily multispectral observations from
Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument with a
sophisticated processing algorithm to reveal global photosynthesis activity
on land.
The fraction of incoming solar radiation useful for photosynthesis that is
actually absorbed by vegetation -- a value known as the Fraction of Absorbed
Photosynthetically Active Radiation (FAPAR) -- is recognised as an essential
climate variable by international organisations including the Global Climate
Observing System (GCOS). FAPAR is regularly used in diagnostic and
predictive models to compute the primary productivity of the vegetation
canopies.
The operational FAPAR MERIS product is derived with the JRC-FAPAR algorithm,
which has been designed to exploit the daily MERIS spectral measurements in
the blue, red and near-infrared bands with no prior knowledge on the land
cover.
This methodology involves a physically-based approach which can be adopted
for generating this biophysical product from various optical medium
resolution sensors. The algorithm used allows scientists to derive the
equivalent biophysical product from other optical satellite sensors, even
retired ones, to ensure the availability of a long-time series of global
FAPAR, which is essential to assess environmental trends, guide policy
making and support sustainable development activities.
"Demonstration products at the global scale are now available and are ready
to be used in state-of-the-art carbon data assimilation systems (CCDAS) for
better understanding the role of the biosphere in the global carbon cycle,"
Gobron said.
Phytoplankton, microscopic marine plants that drift on or near the surface
of the sea, absorb atmospheric carbon dioxide through photosynthesis just as
their terrestrial 'cousins' do. While individually microscopic,
phytoplankton chlorophyll collectively tints the surrounding ocean waters,
providing a means of detecting these tiny organisms from space with
dedicated ocean colour sensors, such as MERIS.
Dr Michael Buchwitz from the Institute of Environmental Physics (IUP) at the
University of Bremen in Germany presented global carbon dioxide measurements
based on observations from Envisat's SCIAMACHY instrument from 2003 to 2005.
The SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric
Chartography) instrument is the first space sensor capable of measuring the
most important greenhouse gases with high sensitivity down to the Earth's
surface because it observes the spectrum of sunlight shining through the
atmosphere in 'nadir' looking operations on a global scale.
Buchwitz explained that he and his colleagues first measure the absolute
carbon dioxide (CO2) column in number of CO2 molecules per area above the
Earth's surface. Then, they measure the oxygen (O2) column that can be
easily converted into an 'air column'.
As seen in the image above, both figures are essentially identical, as he
had expected.
"There are, however, tiny differences and this is the CO2 source/sink
information we are interested in," Buchwitz said. "To see this we compute
the CO2/O2 ratio which can be converted into a column averaged CO2 mixing
ratio."
Dr Paul Monks from the University of Leicester is using SCIAMACHY data to
measure how much CO2 is being taken up by plants. Using 20,000 individual
measurements a month, he is monitoring CO2 drawn down over Siberia, North
America and Northern Europe.
According to Monks, this view from space is providing the first evidence of
the Earth 'breathing' by allowing scientists to witness the biology drawing
down CO2 during the growing season and then releasing some of it back.
"The exciting new area breaking from this sort of data is that we begin to
be able to look at the tropics, which are the 'lungs' of the atmospheric
system," Monks said. "Using this data, we are going to be able to assess how
efficient the tropics are at modulating carbon as well as how that is
changing with time as climate change effects the tropical biosystem."
By comparing the satellite data to aircraft data and to remote-sensing sites
on the surface, Monks learned the method he and his colleagues are using is
approaching a precision of around 1%, giving them confidence in what they
see from space.
By better understanding all of the parameters involved in the carbon cycle,
scientists can better predict climate change as well as better monitor
international treaties aimed at reducing greenhouse gas emissions, such as
the Kyoto Protocol which addresses the reduction of six greenhouse gases
including carbon dioxide.
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaCP/SEMLEHMJC0F_index_1.html ]