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Posted 1 June 2011


Scientists review challenges to observe greenhouse gases

Accurate tracking for carbon dioxide and other greenhouse gases needs to be a priority for scientists and decision-makers, said participants in a meeting on Monday 30 May to discuss greenhouse gas observations during the WMO 16th Congress.

Two studies released the same day highlighted the importance of greenhouse gas monitoring. Carbon dioxide emissions hit a record high in 2010, said the International Atomic Agency, while the US National Snow and Ice Data Centre said that melting permafrost is likely to turn the Arctic from being a carbon “sink” to a carbon source by around 2025.

Scientists reviewed the challenges at a side event entitled “An urgent, emerging challenge for WMO: Supporting greenhouse gas management strategies with observations, modelling, and analysis.”

Understanding carbon weather is complex. Half of carbon dioxide emitted since the Industrial Age is absorbed by the ocean and biosphere. “Whether carbon sinks will continue to function in the same way in the future needs close observation,” said Dr James Butler, Director of the Global Monitoring System of the Earth System Research Laboratory of the US National Oceanographic and Atmospheric Administration (NOAA). "There also could be dramatic increase in CO2 emissions from natural systems as the Earth warms in coming years," he said.

“We need ten times as many observations to understand the fluxes of carbon dioxide and other greenhouse gases on regional scales,” Dr Butler added. While the number of ground observing stations for greenhouse gases has risen steadily over the last 30 years, there are still many areas that are not covered by observations, especially in the tropics and the southern hemisphere. He noted that regional collaboration (on enhancing the required observations) is part of the solution to deal with large-scale efforts that require independent assessment.

Partnerships with private sector providers are another key to tackling the observation challenge. “We see our role as complementary to WMO and the NMHSs, and hope to accelerate the pace of climate science by contributing our efforts towards more observations,” said Robert Marshall, Chief Executive Officer of Earth Networks, a US-based private service provider investing in advanced greenhouse gas observations.

“Public-private partnerships provide sustainability, and help ensure independent measurement, reporting and verification,” said Mr Marshall. “We also believe that educating the public about “carbon weather” is important.” The company has launched a US$ 25 million project over five years to track carbon dioxide and methane in the USA, Europe and other countries. The company has partnered with Scripps Oceanography for system design, quality control, calibration and research, using reference gases from NOAA, which maintains the WMO calibration scale.

Yet another building block to gain a better understanding of the global CO2 distribution in the atmosphere is space observations. “While ground-based observations are closer to carbon sources and sinks, making them more precise, satellite observations help bridge the gap in sparsely settled areas,” said Dr. David Crisp, Principal Investigator of the NASA Orbiting Carbon Observatory (OCO) at the Jet Propulsion Laboratory of the California Institute of Technology. “The distribution of carbon around the world is complicated. A satellite like OCO can collect 100 000 cloud-free observations daily, which complement ground-based observations.” Development is underway to improve spatial resolution and sampling, resolve synoptic weather patterns, improve measurements over dark ocean surfaces using bright sun glint and enhance validation with ground-based observations.

“Improving the match between top of the atmosphere and ground observations is a new advance in carbon cycle science,” said Dr Frédéric Chevallier, Research Scientist at the Laboratoire des Sciences du Climat et de l’Environnement in France. Integrating ground and space measurements to understand carbon weather is challenging, as it incorporates chemistry into advanced weather forecasting techniques. Dr Chevallier analyzed carbon dioxide trends using data assimilation within a Numerical Weather Prediction technique for 128 stations from the WMO Global Atmosphere Watch between 1988 and 2008, and explained that eight computers worked full time for 40 days to process the data. “The technology to observe carbon dioxide is similar to weather forecasting, and we have the mathematical tools today,” he told the group. “The ability to link sources and sinks is limited by the number of observing stations.”

The meeting concluded that an integrated approach, using enhanced ground and spaceborne measurements, supported by complex numerical models, will address many of the growing needs related to CO2.

For more information:
The WMO Greenhouse Gas Bulletin
Time history of atmospheric CO2




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