Carbon Monoxide from South American Fires Blows to Australia

May 10, 2007

UTRECHT, The Netherlands (ENS) - Much of the carbon monoxide hovering over Australia during wildfire season originated from South American wildfires some 13,000 kilometers (8,000 miles) away, scientists have determined, using satellite data. Knowledge about the global distribution of carbon monoxide is important because it affects air quality and climate.

Using data from an instrument aboard the European Space Agency’s environmental satellite Envisat, Dutch scientists witnessed large quantities of released carbon monoxide above the southern continents. They saw increased concentrations of carbon monoxide above Central Australia, a desert region that is not prone to forest fires.
Plumes of carbon monoxide signal biomass, such as trees or grass, on fire. In the southern hemisphere, incineration of biomass is the biggest source of carbon monoxide in the lower layers of the atmosphere.

And apart from carbon monoxide, numerous other compounds are emitted that have consequences for air quality and climate.

'Initially we assumed that the wildfires in North Australia were responsible for this,' said Annemieke Gloudemans from SRON Netherlands Institute for Space Research. 'Yet when we took a closer look at the transport of carbon monoxide, we had to conclude that the majority originated from fires in South America,' Gloudemans said.

From 30 to 50 percent of the carbon monoxide above the fires in North Australia originated from South America, according to Gloudemans and her colleagues at Utrecht University, the Vrije Universiteit Amsterdam, and the Netherlands Meteorological Institute.

Depending on the aridity, much of Australia is prone to wildfires between October and March, and the direct consequences for humans and the environment are disastrous.

The fire season in South America, often concentrated in Brazil, Argentina, Bolivia and Venezuela, lasts from July to December and contributes up to 50 percent of the enhanced carbon monoxide levels in the atmosphere over Australia.

The scientists were able to observe the distribution of carbon monoxide using SCIAMACHY, the first satellite instrument that can measure the global distribution of carbon monoxide with nearly equal sensitivity from the uppermost layer of the atmosphere down to the Earth's surface where the carbon monoxide sources are located.

The Dutch-German satellite instrument SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY, SCIAMACHY, is an instrument whose primary mission objective is to perform global measurements of trace gases in the troposphere and in the stratosphere.

The troposphere is the first layer of atmosphere above the Earth's surface and contains half of the planet's atmosphere. Weather occurs in this layer. The stratosphere is the next higher level, where many jet aircraft fly.

'SCIAMACHY allows us to map the sources of carbon monoxide and see where they are blown to,' Gloudemans said. 'We did this for all of the continents in the southern hemisphere – South America, Australia and Southern Africa – for the years 2003 and 2004 and found surprising results.

'It has been known for many years now that carbon monoxide from forest fires can be transported over long distances, but one would expect that the plume would rapidly become more diffuse the longer it travels. So, it was very surprising to find that even over Australian biomass-burning areas still up to 30 percent of the enhanced carbon monoxide levels from forest fires originate in South America.'

Forest fires in South America produced much more carbon monoxide in 2004 than in 2003, Gloudemans said. 'These levels correlated to the amounts found over Australia for the same periods, confirming that the carbon monoxide levels over Australia are severely influenced by South American forest fires.'

'The only way to accurately follow the emission and transport of carbon monoxide is to use satellites with sensors that are sensitive enough for short-wave infrared radiation,' explains Ilse Aben, head of atmospheric research at SRON. 'That also applies for methane, after carbon dioxide the most important anthropogenic greenhouse gas.'

The SCIAMACHY instrument can do the job, but can only provide a picture of the situation once a month. In addition, Aben said, Envisat will be decommissioned in about 2010.

'Unless we work quickly on a successor, we will no longer be able to track the emission and spread of these substances,' said Aben. 'Moreover in the future, we want to measure carbon monoxide and methane on a daily basis and with a greater degree of sensitivity. Consequently at SRON, we are busy developing sensors for a new Dutch space instrument that will be able to provide a very detailed picture of the composition of the atmosphere.'

Part of the Netherlands Organisation for Scientific Research, SRON is the national center of expertise for the development and exploitation of satellite instruments for astrophysical and Earth-oriented research. The institute acts as the Dutch national agency for space research.