Global warming is caused by both natural phenomena and human activities that increase greenhouse gas emissions. As greenhouse gas levels rise, more heat is trapped in the lower atmosphere, causing Earth's average surface temperature to increase. Major greenhouse gases include carbon dioxide (CO2), methane, nitrous oxide, and fluorinated gases. Human sources of these gases include burning fossil fuels, deforestation, farming, industrial processes, and landfills. Impacts of global warming include rising sea levels, changes in weather patterns and precipitation, ocean acidification, and more frequent extreme weather events. Glaciers and ice sheets are also melting, which threatens many animal populations and ecosystems.

1. INTRODUCTION

2. • Global warming is an average increase in the temperature of the
atmosphere near the Earth’s surface and in the troposphere, which can
contribute to changes in global climate patterns.
• Global warming can occur from a variety of causes, both natural and
human induced. In common usage, “global warming” often refers to the
warming that can occur as a result of increased emissions of greenhouse
gases from human activities.
• The greenhouse effect is a naturally occurring phenomenon that blankets
the earth lower atmosphere and warms the Earth. Greenhouse gases play
an important role in the balance of Earth’s cooling and warming.
• In the absence of greenhouse gases the avg. temp. of Earth would be -19
degree C instead of present 15 degree C(normal).

3. ROLE OF GREENHOUSE GASES
• Greenhouse gases in the atmosphere absorb much of the long-wave
energy (infrared radiation) emitted from the Earth’s surface,
preventing it from escaping from the Earth’s system. The greenhouse
gases then re-emit this energy in all directions, warming the Earth’s
surface and lower atmosphere.
• Anthropogenic greenhouse gas emissions have increased since the
pre-industrial era, driven largely by economic and population growth,
and are now higher than ever.

4. CAUSES OF GREENHOUSE EFFECT
• 1. Burning of Fossil Fuels: Fossil fuels like coal, oil and natural gas have become an integral part of our life. They are used on large
basis to produce electricity and for transportation. When they are burnt, the carbon stored inside them is released
which combines with oxygen in the air to create carbon dioxide. With the increase in the population, the number of vehicles have
also increased and this has resulted in increase in the pollution in the atmosphere. When these vehicles run, they release carbon
dioxide, which is one the main gas responsible for increase in greenhouse effect.
• Apart from that, electricity-related emissions are high because we are still dependent on coal for electricity generation which
releases large amount of CO2 into the atmosphere and is still the primary source of fuel for generating electricity. Although,
renewable sources are catching up, but it may take a while before we can reduce our dependence on coal for electricity
generation.
• 2. Deforestation: Forests hold a major green area on the planet Earth. Plants and trees intake carbon dioxide and release oxygen,
through the process of photosynthesis, which is required by humans and animals to survive. Large scale development has resulted
in cutting down of trees and forests which has forced people to look for alternate places for living. When the wood is burnt, the
stored carbon in converted back into carbon dioxide.
• 3. Increase in Population: Over the last few decades, there have been huge increase in the population. Now, this has resulted in
increased demand for food, cloth and shelter. New manufacturing hubs have come up cities and towns that release some harmful
gases into the atmosphere which increases the greenhouse effect. Also, more people means more usage of fossil fuels which in
turn has aggravated the problem.
• 4. Farming: Nitrous oxide is one the greenhouse gas that is used in fertilizer and contributes to greenhouse effect which in turn
leads to global warming.
• 5. Industrial Waste and Landfills: Industries which are involved in cement production, fertilizers, coal mining activities, oil
extraction produce harmful greenhouse gases. Also, landfills filled with garbage produce carbon dioxide and methane gas
contributing significantly to greenhouse effect.

5. MAJOR GREENHOUSE GASES
• CO2- Changes in CO2 emissions from fossil fuel combustion are influenced by many factors, including population growth, economic growth, changing
energy prices, new technologies, changing behavior, and seasonal temperature.
• methane(CH4)- emitted by natural sources such as wetlands. As well as human activities such as leakage from natural gas systems and raising of
livestock.
• Natural processes in soil and chemical reactions in the atm. helps remove CH4 from the atmosphere.
• Nitrous oxide (N2O)-human activities such as agricultural fossil fuel combustion, wastewater management and industrial processes are increasing
amount of N2O in the atmosphere.
• N2O is removed from the atm. when it is absorbed by certain type of bacteria or destroyed by ultraviolet radiation or chemical reactions.
• Fluorinated gases-emitted through variety of industrial processes such as aluminum and semiconductor manufacturing and substitution for Ozone-
Depleting substances.
• Fluorinated gases are removed from the atmosphere only when they are destroyed by sunlight in the far upper atmosphere.
• black carbon(soot)-is a solid particle or aerosol, (though not a gas) contributes to warming of the atmosphere.it consists of pure carbon in several
linked forms.
• Sources- biomass burning, cooking with solid fuels, and diesel exhaust etc.
• Brown carbon(aerosol)-is a ubiquitous and unidentified component of organic aerosol which has recently come into the forefront of atm. research.
• Light absorbing organic matter (other than soot) inS atm. aerosols of various origins, e.g., soil humic-like substances(HULIS), tarry materials from
combustion, bioaerosols, etc.
• Sulphur hexafluoride(SF6).

6. GLOBAL WARMING- IMPACTS
• Rise in sea level -Increase in sea level in some parts of world due to excess heating of air which has caused large scale melting of ice covers. IPCC
suggested that sea level would rise upto 90cm by 2100. If the sea level rises by 80-90 cm, perhaps many of coastal cities of world will be washed away
besides great changes in harbours and their facilities, in sea routes and in fishery industry. If the increase is to the tune of 90 cm, the world is going to
face a catastrophe.
• Changes in rainfall patterns -Change in the rainfall patterns due to variations in the convectional current (both in time and direction) caused by
difference in heating pattern of earth's air. Major changes in water resources of world due to disturbances in hydrological cycles. Heavy rainfall tracts
are gradually converted into low rainfall tracts, many humid areas being transformed into arid areas, ground water depletion is high and recharging is
very low etc. Due to change in air temperature and rainfall patterns, seasons have preponed on post-poned. Winters have extended in many places,
while summer is more severe in other places. The degree of dependability has reduced and an element of uncertainty has increased. For e.g., in India
pre-monsoon showers (summer rainfall) have reduced substantially, while cyclonic rainfall during November-December have become a regular
feature. Similarly, the length of winter with low temperature and summer with high temperature have increased in many places.
• It is very likely that regions of high surface salinity, where evaporation dominates, have become more saline, while regions of low salinity, where
precipitation dominates, have become fresher since the 1950s. These regional trends in ocean salinity provide indirect evidence for change in
evaporation and precipitation over the oceans and thus for change in the global water cycle
• The high latitudes and the equatorial Pacific are likely to experience an increase in annual mean precipitation . In many mid-latitude and subtropical
dry regions, mean precipitation will likely decrease, while in many mid-latitude wet regions, mean precipitation will likely increase. Extreme
precipitation events over most of the mid-latitude land masses and over wet tropical regions will very likely become more intense and more frequent.
• Ocean acidification- Since the beginning of the industrial era, oceanic uptake of CO2 has resulted in acidification of the ocean; the pH of ocean surface
water has decreased by 0.1 . A global increase in ocean acidification by the end of the 21st century. The decrease in surface ocean pH is in the range
of 0.06 to 0.07 (15 to 17% increase in acidity). Glaciers have continued to shrink almost worldwide . Northern Hemisphere spring snow cover has
continued to decrease in extent . There is high confidence that permafrost temperatures have increased in most regions since the early 1980s in
response to increased surface temperature and changing the snow cover.
• Increased likelihood of extreme events such as heat wave, flooding, hurricane Due to change in air temperature and rainfall patterns, seasons have
preponed on post-poned.

7. • Melting of ice caps and glaciers- due to this many animals would come under the threat of extinction and competition will increase
between them for food, shelter etc.
• Climate change is projected to increase displacement of people. Populations that lack the resources for planned migration
experience higher exposure to extreme weather events, particularly in developing countries with low income. Climate change can
indirectly increase risks of violent conflicts by amplifying well-documented drivers of these conflicts such as poverty and economic
shocks.
• Widespread vanishing of animal population due to habitat loss.
• Shifts in disease/pest cycles of plants and animals-Many insignificant pests / diseases are attaining major proportions because
composition of microbial population is affected by shift in temperature and hydrological cycles. Many diseases and pests of plants
/ animals follow a particular rhythm because of specific response of causal organism to a set of environmental conditions. Hence,
disease / pest is more likely to attack a plant/animal if the environmental situations are favourable. These are called 'pre-disposing'
factors. For e.g., sap sucking insects called 'aphids' are favourably multiplied in large number if day temperature is between 15 -
20oC and humidity is 60 - 80%. Due to change in environment, the disease/ pests may occur with greater virulence or may subside.
Hence, the attack of pests and diseases in recent years has been undergoing unpredictable changes. Many new diseases such as
neckblast in paddy, wiltin cotton, as well as new pests like Armigera in cotton, nematode attack in paddy have been reported
recently. Similarly, some diseases like black arm in cotton, blight in paddy, canker in guava have gradually reduced. Even in human
beings, the attack of some diseases is pre-disposed by many environmental factors.For e.g., low temperature and high humidity
favour asthma, coastal climate favouring elephantiasis, heavy rainfall favouring malaria. Recent spread of mosquito borne diseases
like malaria in US and dengue in India are examples of spread of tropical habitat northward favouring growth and development of
mosquito population in unconventional areas.
• Bleaching of coral reefs.
• Loss of plankton due to warming of sea.
• Reduced agricultural productivity and food shortage.
• Increased water shortage throughout the globe.

8. ADAPTATION AND MITIGATION
• Climate change has the characteristics of a collective action problem at the global scale, because most GHGs accumulate over time
and mix globally, and emissions by any agent (e.g., individual, community, company, country) affect other agents. Effective
mitigation will not be achieved if individual agents advance their own interests independently. Cooperative responses, including
international cooperation, are therefore required to effectively mitigate GHG emissions and address other climate change issues.
The effectiveness of adaptation can be enhanced through complementary actions across levels, including international
cooperation. The evidence suggests that outcomes seen as equitable can lead to more effective cooperation.
• Near-term reductions in energy demand are an important element of cost-effective mitigation strategies, provide more flexibility
for reducing carbon intensity in the energy supply sector, hedge against related supply-side risks, avoid lock-in to carbon-intensive
infrastructures, and are associated with important co-benefits. The most cost-effective mitigation options in forestry are
afforestation, sustainable forest management and reducing deforestation, with large differences in their relative importance across
regions; and in agriculture, cropland management, grazing land management and restoration of organic soils.
• Behaviour, lifestyle and culture have a considerable influence on energy use and associated emissions, with high mitigation
potential in some sectors, in particular when complementing technological and structural change (medium evidence, medium
agreement). Emissions can be substantially lowered through changes in consumption patterns, adoption of energy savings
measures, dietary change and reduction in food wastes.
• Mitigation policy could devalue fossil fuel assets and reduce revenues for fossil fuel exporters, but differences between regions
and fuels exist (high confidence). Most mitigation scenarios are associated with reduced revenues from coal and oil trade for major
exporters (high confidence). The availability of CCS would reduce the adverse effects of mitigation on the value of fossil fuel assets

9. • Five Reasons For Concern (RFCs) aggregate climate change risks and illustrate the implications of warming
and of adaptation limits for people, economies and ecosystems across sectors and regions. The five RFCs are
associated with: (1) Unique and threatened systems, (2) Extreme weather events, (3) Distribution of impacts,
(4) Global aggregate impacts, and (5) Largescale singular events.
• Policy linkages among regional, national and sub-national climate policies offer potential climate change
mitigation benefits. Potential advantages include lower mitigation costs, decreased emission leakage and
increased market liquidity.
• National governments play key roles in adaptation planning and implementation (robust evidence, high
agreement) through coordinating actions and providing frameworks and support. While local government
and the private sector have different functions, which vary regionally, they are increasingly recognized as
critical to progress in adaptation, given their roles in scaling up adaptation of communities, households and
civil society and in managing risk information and financing
• Regulatory approaches and information measures are widely used and are often environmentally effective.
Examples of regulatory approaches include energy efficiency standards; examples of information
programmes include labelling programmes that can help consumers make better-informed decisions
• Solar Radiation Management (SRM) involves large-scale methods that seek to reduce the amount of
absorbed solar energy in the climate system. SRM is untested and is not included in any of the mitigation
scenarios. If it were deployed, SRM would entail numerous uncertainties, side effects, risks and
shortcomings and has particular governance and ethical implications. SRM would not reduce ocean
acidification. If it were terminated, there is high confidence that surface temperatures would rise very
rapidly impacting ecosystems susceptible to rapid rates of change.

10. Thank you