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Vol. 16 No. 2 - April 2010

Climate Change, Towards a Booming Bane

By: Richa Dave, Rudra Deo Tripathi, Sanjay Dwivedi & S. N. Singh*

Climate change is considered as the greatest threat today to human beings and life on earth. Carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values. Methane (CH4), from rice paddy production and enteric fermentation, is increasing, as are chlorofluorocarbons (CFCs) that have been used for many years as a refrigerant and to produce foam. Methane is a much more potent greenhouse gas (GHG) than CO2. Carbon dioxide, methane, nitrous oxide and three groups of fluorinated gases (sulfur hexafluoride, HFCs, and PFCs) are the major greenhouse gases.

The amount of carbon dioxide in the atmosphere today (387 ppm) exceeds by far the natural range of the last 650,000 years (180 to 300 ppm). The current amount of methane in the atmosphere (1745 ppb) exceeds by far the natural range of the last 650,000 years (320 to 790 ppb). The primary source of the increase in carbon dioxide is fossil fuel use, but land-use changes also make a contribution. The primary source of the increase in methane is very likely to be a combination of human agricultural activities and fossil fuel use. Nitrous oxide concentrations have risen from a pre-industrial value of 270 ppb to 314 ppb. More than a third of this rise is due to human activity, primarily agriculture. Perfluorocarbons (PFCs) and sulphur hexafluoride (SF6) are greenhouse gases with atmospheric lifetimes of more than 1000 years. They are powerful greenhouse gases and today's emissions will still be affecting earth's climate in the next millennium. Man's use of fluorides has given rise to significant emissions of both PFCs and SF6 in recent years.

These gases contribute to the greenhouse effect that is warming our atmosphere day by day. The greenhouse effect results from the trapping of solar radiation that radiates back from the Earths surface by these gases. The atmosphere is essentially transparent to incoming short wave solar radiation. After striking the Earth's surface, the wavelength of this radiation increases as it loses energy. The GHGs are opaque to this lower energy radiation, and therefore trap it as heat, thereby increasing the atmospheric temperature. As these gases increase, due to natural causes and human activities, they enhance the greenhouse effect, and may raise temperatures even more. If the climate warms, the vegetation belts will tend to move northward, changing global ecological and biome patterns. Other effects may be discerned in precipitation patterns, sea level changes, and more. This leads to a complex chain of events affecting the global climate or which can be summarized as CLIMATE CHANGE, which is a long-term shift or alteration in the climate due to anthropogenic activities.

Gas

 Preindustrial level

 Current level

 Increase since 1750

 Radiative forcing (W/m2)

Carbon dioxide

 280 ppm

 387ppm

 107 ppm

 1.46

Methane

 700 ppb

 1745 ppb

 1045 ppb

 0.48

Nitrous oxide

 270 ppb

 314 ppb

 44 ppb

 0.15

CFC-12

 0

 533 ppt

 533 ppt

 0.17

One obvious consequence of the significant rise in CO2 in the northern polar latitudes would be melting of Arctic Ocean and Greenland Ice Cap ices, releasing huge quantities of stored water that would have an extremely serious impact on global sea levels.

Calculations show that the burning of fossil fuels (mainly coal, petroleum derivatives, and natural gas) adds about 6 billion metric tons of carbon (as the element) to the air annually; each year also, deforestation permits an extra 1-2 billion metric tons of carbon to reach the atmosphere. The projected climate is both wetter and warmer. There is considerable geographical variation in the magnitude of changes for both temperature as well as rainfall. North-Western India is likely to become drier, while north-eastern India is likely to become much wetter. The temperature increases in north-western India is also much more than that in the northeast. Southern and south-eastern parts of India are likely to experience only a moderate increase in temperature.

Warmer global temperatures are already causing profound changes in many of the earths natural systems. Approximately 20-30 per cent of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5-2.5C.

In all regions of the world, with faster temperature rise, the greater is the risk of damage. The climate does not respond immediately to emissions, which can last for years or decades in the atmosphere. And because of the delaying effect of the oceans which absorb and eventually release heat more slowly than the atmosphere surface temperatures do not immediately respond to greenhouse gas emissions. As a result, climate change will continue for hundreds of years even after atmospheric concentrations are stabilized.

Rising temperatures are already accelerating the hydrological cycle. A warmer atmosphere holds more moisture, becomes less stable and produces more precipitation, particularly in the form of heavy rain bursts. Greater heat also speeds up evaporation. The net effect of these changes in the cycling of water will be a decline in the quantity and quality of freshwater supplies in all the major regions. Meanwhile, wind patterns and storm tracks are also likely to change. The intensity (but not the frequency) of tropical cyclones is expected to increase, with larger peak wind speeds and heavier rains.

Climate change will increasingly alter the distribution of malarial vectors and other carriers of infectious diseases, affect the seasonal distribution of some allergy-causing pollen and increase the risks of heat waves. On the other hand, there may be casualties due to the extreme cold in some parts of the world.

The best estimate for how much further the sea level will rise due to ocean expansion and glacier melt by the end of the 21st century (compared to 1989-1999 levels) is 28-58 cm. This will worsen coastal flooding and erosion. Larger sea-level increases of up to 1 metre by 2100 cannot be ruled out, if ice sheets continue to melt as temperature rises. There is now an evidence that the Antarctic and Greenland ice sheets are indeed slowly losing mass and contributing to sea level rise. About 125,000 years ago, when the polar regions were significantly warmer for an extended period than at present, melting polar ice caused the sea level to rise by 4 to 6 metres. Sea-level rise has substantial inertia and will continue for many centuries. The oceans will also experience higher temperatures, which have implications on sea life. Over the past four decades, for example, North Atlantic planktons have migrated pole-ward by 10 degrees of latitude. Similarly, the acidification of the oceans, as they absorb more carbon dioxide, will impair the ability of corals, marine snails and other species to form their shells or skeletons.

The poorest communities will be the most vulnerable to the impacts of climate change as they have fewer resources to invest in preventing and mitigating the effects of climate change. Some of the most at-risks of people include subsistence farmers, indigenous people and coastal populations. 

Climate change and Agriculture

It seems obvious that any significant change in climate on a global scale should impact local agriculture, and therefore affect the world's food supply. Climate change presents crop production with prospects for both benefits and drawbacks. Crop species vary in their response to CO2. Thus, under CO2 enrichment, crops may use less water even while they produce more carbohydrates. At the same time, associated climatic effects, such as higher temperatures, changes in rainfall and soil moisture, and increased frequencies of extreme meteorological events, could either enhance or negate potentially beneficial effects of enhanced atmospheric CO2 on crop physiology.

In middle and higher latitudes, global warming will extend the length of the potential growing season, allowing earlier planting of crops in the spring, earlier maturation and harvesting, and the possibility of completing two or more cropping cycles during the same season. Crop-producing areas may expand poleward in countries such as Canada and Russia, although yields in higher latitudes will likely be lower due to the less fertile soils that lie there. Many crops have become adapted to the growing-season daylengths of the middle and lower latitudes and may not respond well to the much longer days of the high latitude summers. In warmer lower latitude regions, increased temperatures may accelerate the rate at which plants release CO2 in the process of respiration, resulting in less than optimal conditions for the net growth. When temperatures exceed the optimal for biological processes, crops often respond negatively with a steep drop in net growth and yield. If night time temperature minima rise more than the daytime maxima--as is expected from greenhouse warming projections--heat stress during the day may be less severe than otherwise, but increased night time respiration may also reduce potential yields. Such reduced yield has already been experienced in paddy crop. Another important effect of high temperature is accelerated physiological development, resulting in hastened maturation and reduced yield.

Moderate climate change effect on world food production may be small, as reduced production in some areas is balanced by gains in others. The same studies however, find that vulnerability to climate change is systematically greater in developing countries--which in most cases are located in lower warmer latitudes. In those regions, cereal grain yields are projected to decline under climate change scenarios, across the full range of expected warming. Agricultural exporters in middle and high latitudes (such as the U.S., Canada, and Australia) stand to gain, as their national production is predicted to expand, and particularly, if grain supplies are restricted and prices rise. Thus, countries with the lowest income may be the hardest hit.

Climate change can impact agricultural sustainability in two interrelated ways: first, by diminishing the long-term ability of agroecosystems to provide food and fiber for the world's population; and second, by inducing shifts in agricultural regions that may encroach upon natural habitats, at the expense of floral and faunal diversity. Global warming may encourage the expansion of agricultural activities into regions now occupied by natural ecosystems such as forests, particularly at mid- and high-latitudes. Forced encroachments of this sort may thwart the processes of natural selection of climatically-adapted native crops and other species.

How does global warming affect India?

The major challenges for India in terms of global warming lie in rising sea levels, melting glaciers and agricultural impacts. Global warming is causing the Gangotri glacier to recede at an annual rate of 30 metres, and the Pindari glacier is retreating at a rate of 13 metres per year. In recent years, extreme weather events like floods, droughts and catastrophes like the Mumbai floods have increased and are probable to rise drastically in the coming decades. Central and Northern India is projected to get less rainfall because of global warming and climate change. In West Bengal, Sunderban mangrove swamps may be affected because of sea level rise. With rising sea levels, salt marshes and mudflats in the Rann of Kutch, the habitat of the greater Flamingoes in Asia may be submerged. About 2000 Indian wild asses could lose their only habitat in India.

High yield states like Punjab, Haryana and Uttar Pradesh will suffer a decrease of 10%in wheat yield, if winter temperature increases by 0.5C. The data of onset of summer monsoon over Central India may become more variable. Due to increase in temperature the South Western parts of India may receive more rainfall.

About one metre rise in sea level may displace approximately 7.1 million people in India. Because of sea level rise, the entire population of Lakshadweep is at risk. Wet areas could become wetter and dry areas could become drier.

Degradation of soil and water resources is one of the main challenges for global agriculture. Climate change will further alter agriculture systems with dangerous consequences for food production and the risk of reduced food yields is greatest in developing countries, where at present 790 million people are estimated to be undernourished. India is expected to lose 125 million tones (about 18%) of its rain fed cereal production potential. If agriculture production goes down, the price of staple food commodities will increase. According to a World Bank study, a 2C rise in temperature along with a 7% increase in rainfall will reduce net agriculture revenues by 12.3% for the whole country. Agriculture in the coastal regions of Gujarat, Maharashtra and Karnataka will be severely affected. An increase in minimum temperature from 18C to 19C will result in a decrease in rice yield of 0.71 tonne per hectare, while an increase from 22C to 23C will result in a decrease of 0.41 tonne per hectare.

According to scientists, some positive effects of climate change may also be expected because of increase in CO2 in the atmosphere, which may have fertilizing effect on crop growth and yields.

Ecosystems that cannot move northwards at a rate dictated by global warming will be most at risk. These include, glacial ecosystems, coral reefs, atolls, forests and Himalayan systems. Indian winters may experience a decline of 5-25% in rainfall. More intense rainfall spells are expected in a warmer atmosphere. If rainfall decreases, water flow of rain fed rivers will decrease affecting ground water recharge. Increase in rainfall might aggravate flood situations, bringing destruction and disease.

A rise in sea surface temperature may be accompanied by an increase in tropical cyclone intensities. The intensity may increase by 10-20% with a rise of 2C - 4C in sea surface temperature. This will lead to storm surges along the eastern coast of India.

The Himalayan glaciers have been shrinking at an accelerated rate. An intensified monsoon and high temperatures may lead to retreating and thinning of glaciers, increasing the risks of flash floods.

With the right policies, the rise in the level of greenhouse gases in the atmosphere can be slowed and ultimately stabilized. If global CO2 emissions fall to 50-85 per cent of 2000 levels by 2050, global mean temperature increases could be limited to 2-2.4C above pre-industrial levels. Cleaner technologies and energy efficiency can provide solutions, allowing economic growth and the fight against climate change to proceed hand in hand. Arresting todays high levels of deforestation and creating new forests could considerably reduce greenhouse gas emissions at low costs. About 65 per cent of the total mitigation potential for forests lies in the tropics and 50 per cent can be achieved by simply avoiding deforestation. In the longer term, the best way to maintain or increase the ability of forests to sequester carbon dioxide is through sustainable forest management, which also has many social and environmental benefits.

Resources and initiatives that promote low carbon economies and life styles, such as improved energy efficiency, alternative energy sources, forest conservation and eco-friendly consumption, form the crux of sustainable development for a clean and healthy future. But the most important tool for such initiatives is sensitization of the global population towards environmental problems and mitigation. This is where the need for the youth to step in arrives. The past generation has been oblivious to the climate change problem, the present generation is in denial, and therefore, the coming generation holds the baton in the race against climate change. The responsibility of a developing country like ours doubles up, as we are one of the worst sufferers of climate change and our contribution to greenhouse build up can still be controlled effectively. The solution is more pertinent at grassroots level, which is where sensitization, awareness and instilling leadership qualities in our coming generations takes forefront. The coming generation needs to be aware of the looming danger of climate change as well as participate in green solutions more of as a habit rather than a compulsion.

The 2009 United Nations Climate Change Conference, commonly known as the Copenhagen Summit, was held at the Bella Center in Copenhagen, Denmark, between 7 December and 18 December. The Copenhagen declared that climate change is one of the greatest challenges of the present day and that actions should be taken to keep any temperature increases to below 2C.

Humans have been adapting to changing climatic conditions for centuries. However, the climate change that the world is presently experiencing is occurring far more rapidly than anything the Earth has experienced in the last 10,000 years.

Climate change is expected to exacerbate current stresses on water resources from population growth and economic and land-use change, including urbanisation. On a regional scale, mountain snow pack, glaciers and small ice caps play a crucial role in freshwater availability. Widespread mass losses from glaciers and reductions in snow cover over recent decades are projected to accelerate throughout the 21st century, reducing water availability, hydropower  potential, and changing seasonality of flows in regions supplied by meltwater from major mountain ranges (e.g. Hindu-Kush, Himalaya, Andes), where more than one-sixth of the world population currently lives. With the rising temperatures, increasing populations and booming economies at the cost of environment is leading us to the bane of irreversible climate change. The future does not hold a good promise for the coming generations unless the present generation can take up adequate steps to mitigate the menace by global efforts. The nations, developed or developing have to forego their conflicting interests for the noble cause for saving the humanity from extinction.

*Ecotoxcology and Bioremediation Group, National Botanical Research Institute, Lucknow

E-mail: richadave_2006@rediffmail.com


This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.


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