The Earth’s temperature is maintained at a level where it can sustain life by a balance between heat from the sun, and cooling from reflecting some of the heat by the Earth’s warm surface and atmosphere back to space. But atmospheric gases such as carbon dioxide, methane, nitrous oxide and halocarbons absorb some of the rays reflected back from the Earth’s surface. These are ‘greenhouse gases’ (GHGs). They act like a blanket, preventing much of the heat reflected by the earth’s surface escaping directly to space. By slowing the release of cooling radiation, these gases warm the Earth’s surface. While this is a natural process that is essential to life on Earth, the trouble starts when the concentration of these GHGs in the Earth’s atmosphere increases. The result is an increase in the Earth’s temperature, or global warming. Global warming in turn interferes with the Earth’s climatic systems, resulting in climate change. Of all GHGs, carbon dioxide is singly responsible for over half the effect of global warming. Though the gas is naturally present in the Earth’s atmosphere and in oceanic and terrestrial ‘sinks’ (such as forests), the trouble starts when carbon concentrations increase beyond limits that can be absorbed by the Earth’s natural cycle. Carbon dioxide concentrations have been increasing rapidly in the atmosphere since the start of the industrial revolution, when the world became heavily dependent on carbon-based fossil fuels. The emission of chlorofluorocarbons (CFCs) and other chlorine and bromine compounds has not only an impact on the radioactive forcing, but has also led to the depletion of the stratospheric ozone layer. Land-use change, due to urbanization and human forestry and agricultural practices, affect the physical and biological properties of the Earth’s surface. Such effects change the radioactive forcing and have a potential impact on regional and global climate. About a thousand years before the Industrial Revolution, the amount of greenhouse gases in the atmosphere remained relatively constant. Since then, the concentration of various greenhouse gases has increased. The amount of carbon dioxide, for example, has increased by more than 30 percent since pre-industrial times and is still increasing at an unprecedented rate of on average 0.4 percent per year, mainly due to the combustion of fossil fuels and deforestation. The anthropogenic emissions have resulted in a marked increase in atmospheric concentrations of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) since 1750 and now far exceed “pre-industrialization” values. The concentration of the nitrogen oxides (NO and NO₂) and of carbon monoxide (CO) are also increasing. Although these gases are not greenhouse gases, they play a role in the atmospheric chemistry and have led to an increase in tropospheric ozone, a greenhouse gas, by 40 percent since pre-industrial times. The current level or stock of greenhouse gases in the atmosphere is equivalent to around 430 ppm (parts per million) compared with only 280 ppm before the industrial revolution.  Adaptation to climate change is therefore no longer a secondary and long-term response option only to be used as a last resort. It is now prevalent and imperative, and for those communities already vulnerable to the impacts of present day climate hazards, an urgent imperative. Successful adaptation must be accomplished through actions that target and reduce the vulnerabilities poor people now face, as they are likely to become more prevalent as the climate changes. This approach calls for a convergence of four distinct communities who have long been tackling the issue of vulnerability reduction through their respective activities: disaster risk reduction, climate and climate change, environmental management, and poverty reduction. Bringing these communities together and offering a common platform, and a shared vocabulary-from which to develop an integrated approach to climate change adaptation can provide an opportunity to revisit some of the intractable problems of environment and development. The starting point for this convergence is a common understanding of the concepts of adaptation, vulnerability, resilience, security, poverty and livelihoods, as well as an understanding of the gaps in current adaptation approaches. Taken together, they indicate a need, and an opening, for adaptation measures based on the livelihood activities of poor and vulnerable communities. This places the goal of poverty reduction at the center of adaptation, as the capabilities and assets that comprise people’s livelihoods often shape poverty as well as the ability to move out of poverty.

The impact will not be felt evenly across the globe. Although some parts of the world would benefit from modest rises in temperature, at higher temperature increases, most countries will suffer heavily and global growth will be affected adversely. For some of the poorest countries there is a real risk of being pushed into a downwards spiral of increasing vulnerability and poverty. Average global temperature increases of only 1-2°C (above pre-industrial levels) could commit 15-40 percent of species to extinction. As temperatures rise above 2-3°C, as will very probably happen in the latter part of this century, so the risk of abrupt and large scale damage increases. Global warming could have many effects on the society directly (water, food, habitat, health, economic infrastructure such as energy, transport and industry) and also through the environment (rainfall, sea level rise, extreme events such as hurricanes and typhoons, floods and droughts). Polar ice melts as a result of the rising temperature and, combined with the thermal expansion of sea water, causes oceans to slowly creep up and swallow low-lying islands. According to a panel of international experts studying climate change, entire forests may disappear and biological diversity may reduce because of the disappearance of habitat or reduced migration potential. Climate systems, such as the Indian subcontinent’s monsoon system, could be dramatically affected. The possible effects of climate change on environment, temperature, water resources, agriculture, forest and land are as follows:

Effect on Environment

Climate change is likely to occur too rapidly for many species to adapt. One study estimates that around 15-40 percent of species face extinction with 2°C of warming. The warming of the 20th century has already directly affected ecosystems. Over the past 40 years, species have been moving pole wards by 6 km. on average per decade, and seasonal events, such as flowering or egg-laying, have been occurring several days earlier each decade. Coral bleaching has become increasingly prevalent since the 1980s. Arctic and mountain ecosystems are acutely vulnerable. Climate change has already contributed to the extinction of over 1 percent of the world’s amphibian species from tropical mountains Ecosystems will be highly sensitive to climate change. For many species, the rate of warming will be too rapid to withstand. Other pressures from human activities, including land-use change, harvesting/hunting, pollution and transport of alien species around the world, have already had a dramatic effect on species and will make it even harder for species to cope with further warming.

Effect on Temperature

Several Indian scientists reported that surface air temperatures over India are going up at the rate of 0.4°C per hundred years, particularly during the post-monsoon and winter season. Using models, they predict that mean winter temperatures will increase by as much as 3.2°C in the 2050s, and 4.5°C by the 2080s, due to GHGs. Summer temperatures will increase by 2.2°C in the 2050s and 3.2°C in the 2080s. Extreme temperatures and heat spells have already become common over Northern India, often causing loss of human life. In 1998 alone, 650 deaths occurred in Orissa due to heat waves.

Effects on Water Resources

Relatively small climatic changes can cause large water resource problems, particularly in arid and semi-arid regions such as northwest India. This will have an impact on agriculture, drinking water, and on generation of hydroelectric power, resulting in limited water supply and land degradation. People will feel the impact of climate change most strongly through changes in the distribution of water around the world and its seasonal and annual variability. Water is an essential and basic need resource for living organism. Globally, around 70 percent of all freshwater supply is used for irrigating crops and providing food. 22 percent is used for manufacturing and energy (cooling power stations and producing hydro-electric power), while only 8 percent is used directly by households and other purposes. Climate change will alter patterns of water availability by intensifying the water cycle. Droughts and floods will become more severe in many areas. There will be more rain at high latitudes, less rain in the dry subtropics, and uncertain but probably substantial changes in tropical areas. Hotter land surface temperatures induce more powerful evaporation and hence more intense rainfall, with increased risk of flash flooding. Differences in water availability between regions will become increasingly pronounced.

Effect on Agriculture

Increasing of temperature will impact agricultural production. Higher temperatures reduce the total duration of a crop cycle by inducing early flowering, thus shortening the ‘grain fill’ period. Increased temperature also mean increased evaporation and transpiration rates. Even a small increase of 1°C could increase the rate of evaporation by 5 to 15 percent. With no rainfall to compensate, yields will be reduced. In north India, for instance, a temperature rise of 0.5°C could reduce wheat yields due to heat stress by about 10 percent if rainfall does not increase. It is predict by several scientists that a temperature increase of 3°C will result in a 15 to 20 percent decrease in wheat yields, and also a decrease in rice yields. Rise in surface temperature will create more conducive conditions for pest infection, which is already a major constraint in achieving higher crop production in India, and hence loss of crop.

Effect on Forests

Increase in temperatures will result in shifts of lower altitude tropical and subtropical forests to higher altitude temperate forest regions, resulting in the extinction of some temperate vegetation types. Decrease in rainfall and the resultant soil moisture stress could result in drier teak dominated forests replacing Sal trees in central India. This could potentially result in species extinction and decline in biodiversity. Increased dry spells could also place dry and moist deciduous forests at increased risk from forest fires.

Effect on Land

Sea level rise will increase coastal flooding, raise costs of coastal protection, lead to loss of wetlands and coastal erosion, and increase salt water intrusion into surface and groundwater. Warming from the last century has already committed the world to rising seas for many centuries to come. Further warming this century will increase this commitment. Rising sea levels will increase the amount of land lost and people displaced due to permanent inundation, while the costs of sea walls will rise approximately as a square of the required height. Coastal areas are amongst the most densely populated areas in the world and support several important ecosystems on which local communities depend. At present, more than 200 million people live in coastal flood plains around the world, with 2 million sq. km. of land.  Many of the world’s major cities are at risk of flooding from coastal surges, including Mumbai, Calcutta, Karachi, London, Tokyo, Shanghai, Hong Kong, New York, Miami, etc. Some estimates suggest that 150-200 million people may become permanently displaced by the middle of the century due to rising sea levels, more frequent floods, and more intense droughts [1-6].

The impacts of climate change have the potential to seriously damage the world economy. Stern report forecasts that world needs to spend one percent of GDP – equivalent to about ? 184 billion, dealing with climate change now, or face a bill between 05 and 20 times higher for damage caused by retting it continue. What the world urgently needs is “global compact” to fight climate change. There two mechanisms for addressing climate change are - Mitigation and Adaption. Mitigation refers to efforts to prevent further climate change. It involves technical and policy measures to reduce the emission of greenhouse gases and stabilize their concentration in the atmosphere. Adaption is adjustment in natural or human systems in response to actual or expected climate change. Policy to reduce emissions should be based on three essential elements: carbon pricing, technology policy, and removal of barriers to behavioral change. Establishing a carbon price, through tax, trading or regulation, is an essential foundation for climate-change policy. Policies are required to support the development of a range of low-carbon and high-efficiency technologies on an urgent timescale The removal of barriers to behavioral change is a third essential element, one that is particularly important in encouraging the take-up of opportunities for energy efficiency.

1. Gedney N, Cox PM, Hunting FC. Climate feedback from wetland methane emissions. Geophysical Research Letters. 2004.
2. Hitz S, Smith JB. Estimating Global Impacts from Climate Change. The Benefits of Climate Change Policies. 2004.
3. Hope C. Integrated Assessment Model’s in Helm D. Climate-change policy, Oxford: Oxford University Press. 2005.
4. Intergovernmental Panel on Climate Change Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. 2001.
5. Smith, JB. Vulnerability to climate change and reasons for concern: a synthesis Climate Change 2001: Impacts, Adaptation and Vulnerability, Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press. 2001.
6. Stern Review Report: The Economics of Climate Change. 2018