Tuesday, 21 September 1999
CSIRO is taking part in an international study that is monitoring the contribution that fires make to global warming.
Using satellite images, researchers are mapping fires around the world so that they can work out their impact on global warming both in terms of greenhouse gas emissions and the destruction of trees that soak up carbon dioxide.
Fires make a significant contribution to the greenhouse effect perhaps accounting for 40 percent of annual global greenhouse gas emissions, says Dr Dean Graetz of CSIRO's Earth Observation Centre.
Dr Graetz says that unlike fossil fuel emissions, at this stage we know comparatively little about where fires are occurring and how much carbon they are releasing.
"We need to know where fires are and how severe they are, because if we want to manage the problem of global warming their contribution has to be taken into account," Dr Graetz says.
The project, named World Fire Web, involves scientists from 16 countries. It is being coordinated by the European Commission's Global Vegetation Monitoring Unit (GVM) in Ispra, Italy.
World Fire Web uses satellite images to map and monitor the extent of fires across much of the globe. Each participating country is responsible for monitoring a particular area and the results are then shared over the Internet to produce daily global fire maps.
CSIRO's Earth Observation Centre has been charged with tracking fires throughout Australia, New Guinea and parts of Indonesia.
The World Fire Web's global fire maps clearly show where most of the world's fires are occurring.
"Africa is the burning continent," says Dr Graetz, "followed by South America, Southeast Asia and Australia."
CSIRO has had an additional important task in the project to help correlate what is seen in satellite images with what is actually happening on the ground. This information is crucial for all of the project's participants.
"The satellite images used in the project are continuously processed, most semi-automatically by computers, to detect 'hot spots', or probable locations of current fires," says Dr Graetz.
"But the most difficult task, not just for us, but for all of the project, is to train the computer to automatically recognize and measure burnt areas, while ignoring cloud shadows and other distractions," says Dr Graetz.
To help 'train' computers to measure the burnt areas, Dr Graetz and colleagues from CSIRO and the GVM have spent the last few months studying fires in the Northern Territory's Kakadu National Park.
"Over this year's dry season in Kakadu, we've been making measurements from the ground and from aircraft of fires lit by the park rangers. Back in the laboratory, these measurements, along with satellite images, are helping us develop more accurate methods of detecting burnt areas."
Currently, the World Fire Web network covers two thirds of the globe, but the scientists plan to expand it by the end of this year to provide an almost global coverage of fires.
More information contact:
Dr Dean Graetz (02) 6216 7199
Janelle Kennard (02) 6216 7157
A typical ground view of unburnt savanna country of The Top End in June 1999. The grassy fuel is dry and will readily burn. With skillful fire management, this fuel can be safely and patchily burned leaving enough forage for grazing animals while reducing the occurrence of hot uncontrollable fires later in the Dry Season. This annual grass cover contains about 2-3 tons of carbon per hectare. Cool early dry season fires do not burn the trees.
The intensity of a fire is all important in predicting the outcome for Greenhouse. A low intensity fire such as this one, will burn only the grassy fuels and the fine woody litter, and produce a little inert charcoal. A hot fire is more likely to kill trees and generate a large amount of charcoal. CSIRO research is refining the methods of inferring the intensity of fires that are visible to satellites during the day and night.
A satellite image of the Top End, in the early afternoon (1430 hours) of June 1, 1999. This image was acquired by the AVHRR sensor (Advanced Very High Resolution Radiometer) on board the NOAA series of polar orbiting satellites which circle the Earth continuously every 100 minutes or so. From satellite images such as this which are acquired daily, the total area and the weight of grassy fuel can be calculated and converted into the emissions of carbon dioxide (CO2), the principal Greenhouse gas responsible for global warming. Because of atmospheric interference, the image colours are false colours but interpretation is still easy. The clouds and the sea retain colours close to natural as does the long plumes of smoke streaming towards the NW. There are at 8 separate active fires visible in the area.
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