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 Monitoring a single country's net emissions from above could not
only become an important tool to establish whether it had met its
promises to slow global warming, a point of contention at climate
talks in Paris, but also help emitters to pinpoint the sources of
greenhouse gases more quickly and cheaply.
"The real success of a deal here fundamentally revolves around
whether we can see emissions and their removals," said John-O Niles,
director of the U.S.-based Carbon Institute, which studies methods
of carbon dioxide (CO2) measurement.
"We know satellite technology is evolving so that there is an
increasing ability to actually tell whether countries are telling
the truth."
Most estimates of greenhouse gas emissions are now based on
calculations of energy use and other proxy data, rather than
on-the-ground measurements, leaving a huge margin of error when
nations submit their figures to the United Nations.
While space-based measurement is unlikely to be mentioned in any
deal agreed by the nearly 200 countries negotiating in Paris, the
European Union is leading a push for a universal system of
measuring, reporting and verifying emissions data.
CHINA PUZZLE
European and Japanese satellites have been monitoring overall carbon
concentrations in the atmosphere since 2002, but calculating
emissions at a national or local level is far harder.
For example, the margin of error for China, presumed to be the
world's top carbon polluter, is greater than the entire carbon
footprint of Europe, according to experts.
Earlier this year, new data showed that China had consumed
substantially more coal in 2014 than earlier reported, causing big
revisions to carbon calculations. An earlier report showed its
carbon output between 2000 and 2013 was about 3 billion tonnes less
than previously estimated.
China announced plans ahead of the Paris talks to launch its first
emissions-monitoring satellites next year. But it says trade
restrictions are hampering cooperation.
"NASA and Japan are sharing the best sensors, but not China," said
Yi Liu, a lead scientist in China's effort. "This is a problem. We
need to work together to make this work."
RED AND ORANGE BLOBS
The U.S. National Aeronautics and Space Administration (NASA),
launched its first satellite to measure atmospheric CO2 in July last
year.
 The challenge now is to convert the images - which pick up carbon
concentrations in the form of yellow, orange, and red blobs - into
emissions data, said Steven Pawson, chief of the Global Modelling
and Assimilation Office at NASA's Goddard Space Flight Center.
"What we can measure right now is the total column of CO2 in the
atmosphere," he said. "The current technology is not strong enough
to give absolute values, but if there were a gross misrepresentation
(of one country's emissions), it would be quite possible to see."
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NASA scientist Lesley Ott said that the satellite, named OCO-2, also
showed there was potential to zoom into urban areas to record carbon
pollution. A new device with that capability, OCO-3, has been
developed for use on the International Space Station, but has been
delayed by budget constraints, she said.
Scientists are also struggling to measure changes in forests that
absorb CO2, a key part of the calculation for net emissions, from
space. Trees bind carbon while they are growing, but stop once they
are mature.
Masanobu Shimada, a researcher at the Japanese Aerospace Exploration
Agency JAXA, is working on distinguishing between the two on a
global scale.
"We can get an idea about biomass from the shading of its images,"
he said. But for now, the imagery is too fuzzy for certainty.
DOWN TO EARTH
Back on earth, climate activists hope a Paris deal will include
helping poor countries to measure their own net carbon emissions on
the ground, a process that can be difficult and costly.
Michael Gillenwater, of the not-for-profit Greenhouse Gas Management
Institute, said that kind of monitoring was better suited than
satellites to pinpointing the source of emissions.
"We need to know where emissions are coming from - which factory,
what process," he said.
But calculating net emissions at a single poultry farm in China, for
example, requires a 54-page, U.N.-certified rulebook that factors in
everything from the amount of methane removed from the chicken
manure to local temperatures and animal weight to come up with a
figure.
At some point, that kind of detailed analysis may also be possible
from space.
A Canadian satellite company called GHGSat has launched a
small-scale effort to do exactly that. Its nanosatellite, nicknamed
CLAIRE, will launch in April aiming to provide a way for energy
producers to measure their carbon footprint.
(Editing by Kevin Liffey)
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