Jamstec apart, participant institutions include Wageningen University, The Netherlands; National Oceanic and Atmospheric Administration, Scripps Institution of Oceanography, University of California, MIT, Harvard University and University of Miami of USA; Commonwealth Scientific and Industrial Research Organisation of Australia, and University of Bristol, UK.

The observational data and modeling shows somewhat surprisingly that the self-cleansing power of the atmosphere does not differ substantially between the northern and the southern hemispheres. Previously, model simulations showed generally higher levels of hydroxyl, which is the determining “bleaching agent” of the atmosphere, oxidises many pollutants in the Northern Hemisphere (NH). This paper negates the hitherto hypothesis of equatorial hiatus. The study models the global distribution of the hydroxyl radical (OH), a highly reactive species responsible for keeping the Earth atmosphere clean, using measurements from aircraft and remote observing stations. The OH controls the removal and formation of air pollution species and greenhouse gases in the troposphere at altitudes up to ~10-15 km.

The Japanese media prominently carried the news. Phys,Org observed, “In view of the massive amounts of nitrogen oxides emitted by traffic, domestic heating and industry in the NH, these nitrogen oxides act as catalysts that promote the formation of ozone (ozone smog) and subsequently hydroxyl.”

Dr Patra in an email reply to this writer, said, “Actually, we are saying that both the hemispheres have equal amount of OH, while the chemistry-transport models suggest more OH concentration in the Northern Hemisphere than in the Southern Hemisphere. In the present models, we need more emissions to match the observed concentrations of Methane CH4 or Carbon Monoxide (CO), oxides of Nitrogen etc. because the models lose too much due to more OH in the northern hemisphere. Once the models are revised, we will need less emissions from the Northern Hemisphere. As you know many scientists' model often need more emissions in the Northern Hemisphere, for balancing the higher loss in the present model, and that extra emissions are often dumped over the countries that offer poor/no estimation of emissions or observations.”

The study used Atmospheric Chemistry Transport Model (ACTM), an innovation by Jamstec in the 1990s for estimating the OH concentration ration both from surface and air. “This model performs well to simulate the basic features of the nature, e.g., the inter-tropical convergence zone, as region/line that separate the northern hemispheric airmass from that of the southern hemisphere. Such clarifications were needed for estimating the hemispheric ratio of OH”, asserts Dr Patra who did his masters in physics from the University of Jadavpur.

The authors do not claim that their findings are final. “Chemical reactions simulated by the models may be incomplete and further research is needed to investigate how global/hemispheric OH responds to the wide range of human influences and to improve our ability to predict Earth’s environmental change”, they observed quite categorically.

On the propensity of many environmental scientists to underestimate the threat of methane as a GHG, the lead author made a candid submission. “At the moment it is unclear about the threat of Methane (CH4) as a GHG because the greenhouse effect of CH4 has at least three components, direct radiative forcing and through production of O3 in the troposphere and water vapour in the stratosphere. And the feedback through the O3 chemistry is basically unknown - meaning depends on the choice of chemistry-climate model. Once we can resolve the cause of the biases in NH/SH OH ratio in the models, we hope the feedbacks of OH-CH4-O3 chemistry will be better predicted.

The IPCC may use the findings to its advantage “Using our estimated OH concentration distribution, CH4 emissions are needed to be reduced by 32 giga-ton a year from the Northern Hemisphere, which is about the half of what is emitted from India or China. That will give the scientists a new puzzle to solve, meaning the inventories of CH4 emissions from swamps, bogs and rice paddies, enteric fermentation, gas and oil industry, waste management, biomass burning, or coal mining have to be revised”, Dr Patra added. (IPA Service)