Erle Frayne Argonza
So many of our scientific models of ecological reality need gross revisions. I am aware for instance that the model for the ‘water cycle’ is badly flawed, yet the scientific community has not done much to revise it.
Here is another facet of reality—climate change—where the existing models are found to be flawed. From East Asian scientists, notably Beijing, come the observation that the existing models ‘ignore brown carbon’. It need not belabored that the models must be revised.
The news about the observations regarding the model is contained below. What is gladdening is that scientists were able to uncover the flaw, which will ensure revision of the model and the practical technologies coming out from the labs later.
[28 August 2008, Quezon City, MetroManila. Thanks to SciDev database news.]
Current climate models ‘ignoring brown carbon’
Sun Xiaohua and Jia Hepeng
15 August 2008 | EN | 中文
Smog over Bangkok, Thailand
[BEIJING] Scientists have found that air pollution from East Asia contains an abundance of ‘brown carbon’ particles and say that atmospheric models need updating to incorporate their effect.
Current climate models take into account two types of aerosol carbon — organic carbon and black carbon — that arise from the burning of fossil fuels or biomass.
Black carbon strongly warms the atmosphere by absorbing light, while organic carbon absorbs light at a negligible level and has no warming effect.
It has already been claimed black carbon plays a much larger role in global warming than estimates made by the UN Intergovernmental Panel on Climate Change’s (see Black carbon climate danger ‘underestimated’).
But this approximation is too simple, according to Peter Crozier, an associate professor at Arizona State University (ASU) in the United States, whose team published their research in Science last week (8 August).
According to the authors, the method that is currently used to measure the warming effect of different types of particle doesn’t take into account the wide variations that can occur between types of carbon from different sources.
They instead used a technique based on a specialised type of electron microscope to directly determine the optical properties of individual carbon particles, and found that samples taken from above the Yellow Sea, east of China, have an abundance of brown carbon particles.
“Brown carbon has light absorbing properties that lie between strongly absorbing black carbon and materials that only scatter light and do not absorb,” co-author James Anderson, a research scientist at ASU’s Department of Mechanical and Aerospace Engineering, told SciDev.Net.
He adds that brown carbon both cools the Earth’s surface and warms the atmosphere, resulting in a complex role in global warming, hence the necessity to incorporate it into climate models.
Hu Guoquan, a senior scientist at the Beijing-based National Climate Centre, welcomes the study, saying it highlights the uncertainties of IPCC models.
“But more studies on the chemical structure and size of brown carbon particles must be done,” he told SciDev.Net.
In addition, Hu says, as many carbon aerosols pollutants are emitted by China or India — which have massive combustion of fossil fuels and biomass — judging their accurate warming or cooling effect must be done cautiously and avoid claims without sufficient scientific evidence, as this will contribute to determining the nations’ responsibilities in global warming.