(a) Asian Brown Cloud : Media reports by the United Nations Environment Programme (UT painted an alarming picture of “a vast blanket of s South Asia”. It was reported that the “Asian E i damaged agriculture, modified rainfall patterns — including the monsoon- and put thousands of people at risk through mass-scale respiratory diseases. It says slowly spreading across the whole Asian continent and could have an impact on the climate of the world. However, the UNEPC commissioned report carried out by the Centre for Clouds, chemistry and climate has several caveats about the extent of current knowledge. Many of the findings in the report itself do not support many of the claims being made harmful effects.
It is the aerosols which create the pollution, and these aerosols may be either natural, such as desert sand and sea salt, or created by human activities such as burning wood and fossil fuels. The level and composition of aerosols vary greatly across seasons and from year-to-year. The UNEP report itself points out that the aerosol content in the atmosphere over the South Asian region builds up during October, peaks during February and March, decreases in May and June, and decreases even further during July to September because of the monsoon. So effects attributed to aerosols such as those heating up the lower atmosphere and reducing the amount of sunlight reaching the ground, would also vary enormously.
The UNEP report is largely based on the Indian Ocean Experiment
(Index), which conducted its field campaign in January to April 1999. That
fact restricts the UNEP report to findings in the dry season (December to
April). The vertical and horizontal distribution of aerosols in the period
May-November is not known. There are several inconsistencies.
According to the report, the largest fraction (32 per cent) of man made aerosols found during Indoex was composed of sulphates. A graph given in the report, however, clearly shows that sulphur dioxide emissions by North America, Europe, China, and East Asia were many times larger than those of South Asia.
The report’s executive summary says that “while green-house gases warm the surface and increase rainfall, aerosols exerted a cooling and drying effect”. But the results of computer simulations given in the report, however, show that rainfall over much of India during January to March would either remain unaffected or actually increase. The report speaks of “compensated drying” during the wintertime over areas north-west of India and over the western Pacific.
Moreover, the January to March period covered by these computer simulations is after both the south-west monsoon (June to September) and the North-east monsoon (October to December). For India, the average nationwide rainfall for the entire January-March period is only about 12 cm, just 5 per cent of the total annual rainfall. So even if in percentage terms a major shift were to occur, in absolute terms the change would be quite small and its consequences, therefore, less worrisome. There is no evidence the south-west or north-east monsoons would be affected.
As for the effects on agriculture, the Wheat Growth (WTGROWS) model, when run for the index event for different wheat regions of India showed only a slight, but “statistically non-significant decrease in yield. For rice, the report suggests that there might be a reduction in yield of the rabi crop.
(b) Ozone Depletion and India Law on Ozone Protection: The Sun emits radiation over a broad range of wavelengths, to which human eye responds in the legion from approximately 400 nm to 700 nm. The range can be divided into three categories:
UVA (Ultra violet) – (320-400 nm) not absorbed by ozone.
UVB — (280-320 nm) partially absorbed by ozone.
UVC – (200-280 nm) completely absorbed by ozone
The maximum concentration (about 0.5 ppm) occurs between the altitude of 20 to 35 km and the layer at this level is, called ozone layer. The presence of ozone is an essential necessity for life on earth.
Stratospheric ozone layer absorbs dangerous UVB rays of the Sun and thus protects the Earth’s surface from these high-energy radiation. Over the past few decades Ozone, layer is thinning out because of man-made pollutants which catalyse the dissociation of Ozone, at a very fast rate. Major pollutants responsible for depletion of ozone are chlorofluoro carbons (CFCs), nitrogen oxides, hydrocarbons and oxides of chlorine and bromine.
Increased uv radiation would retard photosynthesis in plants. Moreover, it would increase earth’s mean temperature which would have disastrous consequence of flooding or submerging many low-laying islands. Recently has been found that the uv radiation degrades polymers used in paints and
Most ozones are created and destroyed in the stratosphere. The high uv rays break some of the oxygen molecules into the oxygen atoms.
en atom recombine with the oxygen molecules to form a three atoms molecule of oxygen called ozone. But ozone being highly reactive combines with other compounds present in the stratosphere. This is how ozones are created and destroyed in a balanced way be the Sun’s radiation. However, this balance is disturbed when chlorine atoms, released from the earth, react with the ozone molecules and thus reduces ozone population in the atmosphere. In the event more ozone molecules are destroyed than are created.
The chlorine, atoms, released from man-made materials such as CFCs or Cloro-fluoro Carbons, enter the atmosphere (which takes 50 to 100 years) and break down the bounds holding three atoms of ozone. The chlorine is converted into chlorine monoxide and oxygen is released; This loss of ozone molecules is known as the depletion of the ozone layers. Needless to say, the loss of ozone molecules reduces the ability of the strato sphere to filter out harmful uv rays.
Ozone depletion happens rapidly near the poles in spring because the prevailing low temperature of the stratosphere makes the ozone more vulnerable to reaction with chlorine, Normally, the nitrous oxide destroys the chlorine monoxide and hence prevent the ozone depletion. But the story is quite different in the polar regions. There the nitrous oxide freezes to form ice clouds and chorine monoxide is left free to destroy the ozone molecules.
Montreal Protocol : Considering the monumental damages ozone depletion does, the world community is taking steps to control the ozone depletion. The Montreal Protocol, adopted in 1987 and strengthened in 1990, called for phasing out CFCs and other ozone depleting substances (ODS) by 2000, established rules governing international trade in ODS and their products. Since the developing countries lack the financial and technological means to replace CFC or other ODS such as halous and carbon tetrachloride they have been given a grace period of 10 years, That is they are required to phase out CFCs by 2010.
The protocol called for a multilateral fund to assist the developing countries in the transfer of technology, that eliminates CFC or ODS India is expected to get about $19 billion under the protocol for substituting ODSs India, on its part, has stopped the trade of eight ODSs to those countires which are not signatories to the Protocol But a suitable mechanism to facititate the transfer of technology to the developing countries is still eluding.
Indian Law on Ozone Protection — India has, in response to the Motreal Protocol, notified Ozone Depleting Substance (Regulation and Control) Rules in 2000 These Rules set the deadlines for phasing out various ODS or Ozone Depleting Substances bedsides regulating their production and trade. Under the Rules, the use of CFC, except for medical purposes, will be prohibited after January 1, 2003 The Rules also call for compulsory registration of ODS producers, traders, stockiest etc. India’s per capita consumption of ODS now at less than 3 gm is, well below the permissive level of 300 gm under the Montreal Protocol.