The critical nature of climate change has made people uncomfortable and feel despair. The people are overwhelmed by the enormity of the problem, coupled with the lack of political will, worldwide, so they distract themselves from their fear and grief and get on with their everyday lives. Some of the implication is the sea level has been rising more quickly over the last century, and precipitation (rain and snowfall ) has increased across the globe on average. There are several problems that cause global warming some are Deforestation, burning of fossil fuels, pollution of the automobile, and Industrialization. . The state of the environment has changed over the past 50 years; the average global temperature has increased at the fastest rate in recorded history. Therefore these are what makes this idea dangerous. Global warming, also referred to as climate change, is the observed century-scale rise in the average temperature of the Earth’s climate system and its related effects. Multiple lines of scientific evidence show that the climate system is warming.Many of the observed changes since the 1950s are unprecedented in the instrumental temperature record which extends back to the mid-19th century, and in paleoclimate proxy records covering thousands of years. Data indicate that Earth’s climate has changed over almost every conceivable timescale since the beginning of geologic time and that the influence of human activities since at least the beginning of the Industrial Revolution has been deeply woven into the very fabric of climate change.The scenarios referred to above depend mainly on future concentrations of certain trace gases, called greenhouse gases, that have been injected into the lower atmosphere in increasing amounts through the burning of fossil fuels for industry, transportation, and residential uses. By the middle of 2014, carbon dioxide concentrations had briefly reached 400 ppm, and, if fossil fuels continue to be burned at current rates, they are projected to reach 560 ppm by the mid-21st century—essentially, a doubling of carbon dioxide concentrations in 300 years. Deforestation has many definitions. The United Nation Food and Agriculture Organization define it as” a nontemporary change in land mass from forest to depletion of forest crown. After deforestation and the removal of the stump shortly followed by reforestation this is not considered deforestation”. In 2005 over 9,765 million acres of forest was recorded in the world. According to the Food and Agriculture Organization. The Russian Federation has over 808.79 million hectares of forestland in the world followed by Brazil, with 477.70 million hectares; and Canada with 310.13 million hectares. Stated by the Food and Agriculture Organization. According to the Food and Agriculture Organization, from the year1990 to 2000, deforestation occurred at a rate of 8.87 million hectares per year and from to 2000 to 2005, over 7.32 million hectares per year. From 1990 to 2000, Brazil has had the highest rate in deforestation, which stood at 2.68 million hectares per year, and has increased to a whapping 3.1 million hectares per year from 2001 to 2005. The second country that have a high level of deforestation is is Indonesia with a whapping 7.66 million acres per year from 1990 to 2005. However, China has the largest gain in forest area, with 4.91 million acres per year from 1990 to 2000, and 10.03 million acres per year from 2001 to 2005. Until relatively recently, industrial efficiency tended to revolve around ways to transform various materials into finished goods in the quickest, cheapest way, with limited regard for byproducts that may have had value if processed or reprocessed. Waste minimization was not a high priority because the costs of limiting pollution appeared to exceed the cost of releasing toxins into the air, soil, and water. In fact, for generations, economists tended to write off pollution costs as an externality, a price paid by someone else, not the industrial operation creating the pollution. The sheer abundance of natural resources in North America masked wider environmental effects of industrialization. Those who questioned industrial pollution, even if they had support from scientific data, faced criticism because they were said to oppose growth and development. Improved scientific techniques have increased knowledge about pollution and implications of industrialization on the global climate. Critical analyses tend to focus on negative impacts of wealth concentration into fewer hands, worker exploitation, and, to some extent, local impacts of pollution. By the 1860s, nascent conservationists were beginning to develop scientific techniques to measure hydrological impacts of widespread deforestation driven by insatiable timber demands, of coalmines, railroads, and construction that underpinned the growing industrial economy. Meanwhile, other researchers, especially in Europe, were beginning to research the impacts of what are now called greenhouse gases on climate.Coal, petroleum, and natural gas are known as fossil fuels, which are formed over millions of years by anaerobic decomposition of dead and decaying organic matter. On burning, the compounds of carbon, nitrogen, and sulfur present in fossil fuels, react with air to form gaseous oxides. Fast expanding industries, transportation, and power generation sectors are the biggest consumers of fossil fuels and hence are the major sources of pollution.The gases released by burning fossil fuels, if inhaled, can cause dysfunction of various organs of living beings or may cause death. Present solid-state gas sensors like metal oxide sensors are used since last few decades for the detection of toxic gases, however, their use have been limited due to higher opSmoke released by burning fossil fuels contain carbon, nitrogen and sulfur which react with atmospheric oxygen to form their monoxides and dioxides (CO, CO2, NO, NO2 and SO2) and when these gases come in contact with water vapors produce acids. Chemical interactions of gases, released by burning fossil fuels, with carbon nanotubes and their effects on the resistance of nanotubes are discussed in the following sub-sections.erating temperature, power requirements, and selectivity issues.Carbon monoxide and carbon dioxide are the major environmental pollutants. Presence of relatively large concentration of carbon monoxide in atmosphere results in the formation of photochemical smog and ground level ozone on interaction with moisture, nitrogen oxide and aldehydes like acetaldehyde. Indoor air pollution and poor urban air quality are listed as two of the world’s worst toxic pollution problems in the 2008 Blacksmith Institute World’s Worst Polluted Places report.1 According to the 2014 World Health Organization report, air pollution in 2012 caused the deaths of around 7 million people worldwide,2 an estimate roughly echoed by one from the International Energy Agency. The particulates of most concern with regard to their effects on human health are solids less than 10 ?m in diameter, because they can be inhaled deep into the lungs and become trapped in the lower respiratory system. Major sources of particulate emissions include fossil-fuel power plants, manufacturing processes, fossil-fuel residential heating systems, and gasoline-powered vehicles. Carbon monoxide is an odourless, invisible gas formed as a result of incomplete combustion. Power plants emit relatively little carbon monoxide because they are carefully designed and operated to maximize combustion efficiency. Exposure to carbon monoxide can be acutely harmful since it readily displaces oxygen in the bloodstream, leading to asphyxiation at high enough concentrations and exposure times. A colourless gas with a sharp, choking odour, sulfur dioxide is formed during the combustion of coal or oil that contains sulfur as an impurity. It also reacts with oxygen and water vapour in the air, forming a mist of sulfuric acid that reaches the ground as a component of acid rain. Acid rain is believed to have harmed or destroyed fish and plant life in many thousands of lakes and streams in parts of Europe, the northeastern United States, southeastern Canada, and parts of China. The state of the environment has worsen over the last 50 years, due to the causes of cause global warming some are Deforestation, burning of fossil fuels, pollution of automobile, and Industrialization.