Chemistry of the atmosphere

• For 200 million years, the proportions of different gases in the atmosphere have been much the same as they are today: • about four-fifths (approximately 80%) nitrogen • about one-fifth (approximately 20%) oxygen • small proportions of various other gases, including carbon dioxide, water vapour and noble gases.
• Theories about the Earth's early atmosphere and how it was formed have changed and developed over time
• Evidence for the early atmosphere is limited due to the 4.6 billion year time scale
• One theory suggests that intense volcanic activity during the first billion years of Earth's existence released gases that formed the early atmosphere and water vapor that condensed to form the oceans
• At the start of this period, the Earth's atmosphere may have been similar to Mars and Venus today, consisting mainly of carbon dioxide with little to no oxygen gas
• Volcanoes also produced nitrogen which gradually built up in the atmosphere, along with small proportions of methane and ammonia
• When the oceans formed, carbon dioxide dissolved in the water and carbonates were precipitated, producing sediments and reducing the amount of carbon dioxide in the atmosphere
• Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis, which can be represented by the equation:carbon dioxide + water--> oxygen+ glucose Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
• Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis. Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.
• Since the industrial revolution, humans have caused a big change in the composition of the atmosphere and significantly increased the amount of greenhouse gases in the atmosphere. These gases cause the atmosphere to trap more heat – like a greenhouse – leading to long-term changes in our climate.
• Crude oil and natural gas were formed from simple plants and tiny animals which were living in oceans and lakes. These small organisms died and their remains sank to the bottom where they were buried under sediments.
• Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life. Water vapour,carbon dioxide and methane are greenhouse gases.
• Greenhouse effect is the heating of the planet's surface due to the absorption of outgoing infrared or thermal radiation by atmospheric greenhouse gases such as methane, carbon dioxide, and water vapor
• The greenhouse effect occurs naturally without any human emissions
• It is a vital component of an inhabitable Earth, keeping the surface at a livable temperature
• Without the greenhouse effect, Earth would be much colder, with an average temperature of about -18°C
• The existence of the greenhouse effect is essential for maintaining a comfortable temperature on Earth
• Figure 1 illustrates how the natural greenhouse effect works on Earth
• Some human activities increase the amounts of greenhouse gases in the atmosphere. These include: • carbon dioxide • methane.
• Burning fossil fuels, cutting down forests and farming livestock are increasingly influencing the climate and the earth’s temperature.This adds enormous amounts of greenhouse gases to those naturally occurring in the atmosphere, increasing the greenhouse effect and global warming.
• Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change. However, it is difficult to model such complex systems as global climate change. This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased.
• An increase in average global temperature is a major cause of climate change. There are several potential effects of global climate change.
• The earth’s ocean temperatures are getting warmer, too—which means that tropical storms can pick up more energy. In other words, global warming has the ability to turn a category 3 storm into a more dangerous category 4 storm.Scientists agree that the earth’s rising temperatures are fueling longer and hotter heat waves, more frequent droughts, heavier rainfall, and more powerful hurricanes.
• The earth’s ocean temperatures are getting warmer, too—which means that tropical storms can pick up more energy. In other words, global warming has the ability to turn a category 3 storm into a more dangerous category 4 storm.Scientists agree that the earth’s rising temperatures are fueling longer and hotter heat waves, more frequent droughts, heavier rainfall, and more powerful hurricanes.
• Rising sea levels will lead to even more coastal flooding on the Eastern Seaboard, especially in Florida, and in other areas such as the Gulf of Mexico.Forests, farms, and cities will face troublesome new pests, heat waves, heavy downpours, and increased flooding. All of these can damage or destroy agriculture and fisheries.Disruption of habitats such as coral reefs and alpine meadows could drive many plant and animal species to extinction which decrease biodiversity
• The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event. The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane.
• How long does it take to form fossil fuels?

  Fossil fuels take millions of years to form
• How long does it take to form fossil fuels?

  Fossil fuels take millions of years to form
• Why did nitrogen build up in the atmosphere?

  Nitrogen is unreactive, so it built up in the atmosphere
• Which gas is produced during incomplete combustion of a hydrocarbon fuel?

  Carbon monoxide