NAME: AHMEDALI KHANROLL NO: 81TOPIC: ASSIGNMENT ON GLOBAL WARMINGSUBJECT:

1. INTRODUCTION

Our earth daily absorbs large quantity of solar energy from the sun. Most of the energy is radiated back to atmosphere by the earth, and this process maintains the balance of heat energy on the earth. There are many gases present in the atmosphere, but only carbon dioxide and water vapour absorb this infrared radiation of the earth strongly and effectively block the radiation of energy back to the atmosphere. However a considerable part of it is re-emitted to the earths surface and consequently the earths surface gets headed up. This increase in temperature of the earth is called the green-house effect. Global warming is defined as the release of green house gases into the air that trap heat on the earth, causing for warmer temperatures. Global warming is affecting the earth a lot, and it is affecting it fast too. The greenhouse effect is only troublesome when it gets too strong and warms things too much. The people of industrialized nations have extracted Earths vast buried stores of fossil fuels and burned them. All those extra greenhouse gases mean more and more solar energy is being trapped in the atmosphere, exacerbating the greenhouse effect and making things warmer. This decade has been the hottest decade in centuries (Stuart, 2005). Because of this the polar ice caps are melting, and it could change the flow of the North Atlantic Current. The change in flow could cause immeasurable effects to the Earth, and could change the weather that occurs on the earth dramatically. According to the IPP 2001 report, the Earths surface has warmed by about 1 degree Fahrenheit, and that is the biggest it has raised in centuries (Stuart, 2005). The hotter atmosphere on the earth causes the ocean temperature to rise, and coincidently hurricanes get more power from warmer waters. Not only does global warming affects the earths weather patterns, it also affect its wildlife.

2. GLOBAL WARMING2.1 CONTRIBUTORS TO GLOBAL WARMINGA majority of scientists have concluded that human activities are responsible for most global warming. Human activities contribute to global warming by enhancing Earths natural greenhouse effect. The greenhouse effect warms Earths surface through a complex process involving sunlight, gases, and particles in the atmosphere. Gases that trap heat in the atmosphere are known as greenhouse gases. Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change.

2.1.1 NATURAL CAUSESThe Sun is the only source of energy for the functioning of the Earths climate system, any changes in solar output may lead to climate change and specifically global warming. It is predicted that a change in solar output by only 1% per century may change the average temperature of the planet by 0.5 to 1.0 Celsius. Changes in the shape of the Earths orbit around the sun alter the total amount of solar energy received by the planet. This would also affect the planets temperature. Volcanic activity is yet another significant contributor to variations of Earths mean temperature. The sun, water vapour and volcanism are far more powerful agents of change in climate than carbon dioxide emissions. The worlds natural wetlands produce more greenhouse gases annually than all human sources combined. Greenhouse gases and solar forcing affect temperatures in different ways. While both increased solar activity and increased greenhouse gases are expected to warm the lowest portion of Earths atmosphere, an increase in solar activity should warm the second major layer of the atmosphere (stratosphere) while an increase in greenhouse gases should cool the stratosphere. The oceans play an important role in determining the atmospheric concentration of carbon dioxide. Carbon dioxide gas in the atmosphere and dissolved in the ocean surface reach a balance. Changes in ocean circulation, chemistry, and biology have shifted this balance in the past. Such changes may affect climate by slowly moving carbon dioxide into or out of the atmosphere.

The above graph shows the departure from the long-term average, of average global temperatures, in degrees Fahrenheit, since 1880. (Source: EPA)

2.1.2 HUMAN ACTIVITIESThe main human activities that contribute to global warming are the burning of fossil fuels (coal, oil, and natural gas) and the clearing of land. The focal point of this cause is the generation of energy for use both in industry and commercial/ private sector. Fossil fuel combustion is especially heavily used as a source of energy for industry. However, we have burned these fuels faster than the rate at which it was removed by the early tropical forests, in other words very large amounts of carbon dioxide is released at a very high rate and the nature is unable to remove it in good time. This leads to the accumulation of extra carbon in the atmosphere and consequently to global warming. For example, burning occurs in automobiles, in factories, and in electronic power plants that provide energy for houses and office buildings as well as deforestation and various agricultural and industrial practices are altering the composition of the atmosphere and contributing to climate change. These human activities have led to increased atmospheric concentrations of a number of greenhouse gases, including carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone in the lower part of the atmosphere. Carbon dioxide is produced when coal, oil, and natural gases (fossil fuels) are burned to produce energy used for transportation, manufacturing, heating, cooling, electricity generation, and other application. There are some other industry-related activities usually called industrial processes which are also significant sources of greenhouse gases. The products whose manufacturing causes emission of these gases include cement, minerals, chemicals, metals. Many activities related to industrial processes use large amounts of energy and thus produce significant amounts of greenhouse gas emissions through fossil fuel combustion.

2.1.3 LAND USELand use changes for example clearing land for logging, ranching, and agriculture lead to carbon dioxide emissions. Vegetable contains carbon that is released as carbon dioxide when the vegetation decays or burns. Normally, lost vegetation would be replaced by re-growth with little or no net emission of carbon dioxide. However, over the past several hundred years, deforestation and other land use changes in many countries have contributed substantially to atmospheric carbon dioxide increases. Methane (natural gas) is the second most important of the greenhouse gases resulting from human activities. It is produced by rice cultivation, cattle and sheep ranching, and by decaying material in landfills. Methane is also emitted during coal mining and oil drilling, and by leaky gas pipelines. Nitrous oxide is produced by various agricultural and industrial practices. When land is cleared for expansion of human settlements or for timber sales, a cocktail of pollution is released as part of this process and the main greenhouse gas emitted is carbon dioxide. Most importantly is tropical deforestation especially by forest fires and alongside other pollutants causes the release of carbon dioxide. The main greenhouse emitted as a result of waste management is methane, with some small amounts of nitrous oxide. Tropical rainforests play a very important role in regulating global and regional climate patterns. An extremely important service provided by the rainforests is the removal of carbon dioxide from the atmosphere by photosynthesis. It acts as a pollution or carbon dioxide sink and storage. Deforestation leads to release of carbon dioxide from the trees back to the atmosphere, release of carbon stores held in soil into the atmosphere and destruction of forests as carbon sinks for future carbon dioxide removal and all of these will further contribute to the global warming effect.

2.2 IMPACT OF GLOBAL WARMING2.2.1 WORLDThe impact of global warming is far greater than just increasing temperatures. Warming modifies rainfall patterns, amplifies coastal erosion, lengthens the growing season on some regions, melts ice caps and glaciers, and alters the ranges of some infectious diseases. The IPCC has concluded that global temperatures will likely rise from 1.2 to 6.5 degrees Celsius by the end of the century depending on different scenarios regarding greenhouse gas emission. Rainfall patterns will continue to change around the world. In general, global warming should accelerate the hydrological cycle. Warmer air cause more water to evaporate. A warmer atmosphere can hold more water vapour, so more water is available to fall back to Earth when it rains or snows. As a result, extreme precipitation events should become more frequent and intense leading to worse flooding. In addition, increased evaporation in some regions will lead to drier conditions, with a higher probability of drought. Ice is melting worldwide especially at the Earths poles. This includes mountain glaciers, ice sheets covering West Antarctica and Greenland, and Arctic sea ice. For more places, global warming will result in more frequent hot days and fewer cool days with the greatest warming occurring over land. Most importantly, global warming will affect on ecosystems, the plants and animals that co-exists in particular climate zone, both on land and in the ocean. Warmer temperatures have already shifted the growing season in many parts of the world. This change in the growing season affects the broader ecosystem. Migrating animals have to start seeking food sources earlier. The shift in seasons may cause the lifecycles of pollinators to be out of synch with flowering plants and trees. This mismatch can limit the ability of both pollinators and plants to survive and reproduce which would reduce food availability throughout the food chain. Global warmingandclimate changecan both refer to the observed century-scale rise in the average temperature of the Earth'sclimate systemand its related effects, althoughclimate changecan also refer to any historic change inclimate. Multiple lines of scientific evidence show that the climate system is warming.Morethan 90% of the additional energy stored in the climate system since 1970 has gone into ocean warming; the remainder has melted ice, and warmed the continents and atmosphere. Many of the observed changes since the 1950s are unprecedented over decades to millennia. Scientific understanding of global warming has been increasing. In itsfifth assessment (AR5)in 2014 theIntergovernmental Panel on Climate Change(IPCC) reported that scientists were more than 95% certain that most of global warming is caused by increasing concentrations ofgreenhouse gasesand otherhuman (anthropogenic) activities.Climate modelprojections summarized in AR5 indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to 1.7C (0.5 to 3.1F) for their lowestemissions scenariousing stringentmitigationand 2.6 to 4.8C (4.7 to 8.6F) for their highest.These findings have been recognized by the nationalscienceacademies of the major industrialized nations. Future climate change and associated impacts will be different fromregion to regionaround the globe. Theeffectsof an increase in global temperature include arise in sea levelsand a change in the amount and pattern ofprecipitation, as well as a probable expansion ofsubtropicaldeserts. Warming is expected to bestrongest in the Arctic, with the continuingretreat of glaciers,permafrostandsea ice. Other likely effects of the warming include more frequentextreme weatherevents includingheat waves,droughts, heavyrainfall, and heavysnowfall;ocean acidification; andspecies extinctionsdue to shifting temperature regimes. Effects significant to humans include the threat tofood securityfrom decreasing crop yields and theloss of habitatfrominundation. Possible responses to global warming includemitigationby emissions reduction,adaptationto its effects, building systemsresilientto its effects, and possible futureclimate engineering. Most countries are parties to theUnited Nations Framework Convention on Climate Change(UNFCCC),whose ultimate objective is toprevent dangerous anthropogenic climate change. The UNFCCC have adopted a range of policies designed to reduce greenhouse gas emissionsand to assist inadaptation to global warming. Parties to the UNFCCC have agreed that deep cuts in emissions are required,and that future global warming should be limited to below 2.0C (3.6F) relative to the pre-industrial level.

This page is about the current warming of the Earth's climate system. "Climate change" can also refer to climate trends at any point in earth'shistory. For other uses see Global warming (disambiguation)

Global mean surface temperature change from 1880 to 2014, relative to the 19511980 mean. The black line is the annual mean and the red line is the 5-yearrunning mean. The green bars show uncertainty estimates. Source:NASA GISS.

Worldmapshowing surface temperature trends (C per decade) between 1950 and 2014. Source:NASA GISS.

Fossil fuel relatedcarbon dioxide(CO2) emissions compared to five of theIPCC's "SRES" emissions scenarios. The dips are related to global recessions.