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Humans and Climate Change

This article explores the relationship between humans and climate change, focusing on human impacts, greenhouse gas production, energy transfer, and temperature changes in the atmosphere. It discusses the greenhouse effect, selective absorption and emission of gases, the carbon cycle, trace gases, ozone layer depletion, and the evidence of global warming.

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Humans and Climate Change

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  1. Humans and Climate Change Human impacts • Green house gas production • Land use • Deforestation • Pollutants • “bad” compounds for the atmosphere…

  2. Atmosphere’s Greenhouse Effect Forms of Energy Kinetic energy: Energy associated with motion. Potential energy: Energy stored within a physical system. Heat: energy transferred from one body or system to another . Radiation is an important mechanism of energy transfer

  3. Radiation

  4. (W/m2µm) 6000K 300K

  5. What Happens to Incoming Solar Radiation Selective absorption and emission of atmospheric gases 1. Energy level of atoms or molecules Quantum jump: transition between different energy levels 2. Different energy form of a molecule or atom

  6. Greenhouse gases, like CO2, H2O, have vibration And rotation energy modes. The transition between these modes can only be excited by longwave radiation, i.e., They can only interact with longwave but not shortwave radiation.

  7. CO CO2

  8. Greenhouse effect: shortwave solar radiation is nearly transparent to the atmosphere, but longwave terrestrial radiation is trapped by greenhouse gases, causing the increase of surface temperature.

  9. Water vapor Water Phase Changes

  10. Relationship among water vapor, saturation, and temperature The higher temperature, the more water vapor can be held in the atmosphere. The more water vapor in the atmosphere, the stronger greenhouse effects, leading to the further increase of temperature.

  11. Carbon Cycle The lifetime of CO2 in the atmosphere is about a decade. But this uptake and release Is balanced. It just recycle it. Ocean can dissolve some CO2 as a removal mechanism. But it is a very slow process (hundreds or thousands of years). But excessive use of fossil fuels break the balance.

  12. Use of fossil fuels adds carbon dioxide to the atmosphere 1quadrillion=1012 or a million million 1 btu = 1055.056 Joules

  13. Increases in Atmospheric Carbon Dioxide

  14. Trace gases, other important greenhouse gases CFC-11 CFC-12 HCFC-22

  15. These trace gases are generated for different reasons Methane: produced by microbes in oxygen-poor environment by consuming organic matter. Most of methane is released into the atmosphere. Agriculture, mainly, rice cultivation and livestock, has increased methane production. Nitrous Oxide: a natural byproduct of microbes in soils and ocean. But anthropogenic sources, such as, nitrogen fertilizer, deforestation, and burning of fossil fuels, have increased the flow of N2O into tthe atmosphere.

  16. Chlorofluorocarbons (CFCs): no major natural source, mainly produced by refrigerators. It is now known that they are not only the culprit for destructing ozone layer, but also the strong greenhouse gases. Relative amounts of Greenhouse Gases Why trace gases are so important to climate with such a small amount?

  17. Atmospheric window and trace gases Highly un-reactive (long lifetime cycle) trace gases, such as CFCs, have strong absorption lines right in the atmospheric window.

  18. Ozone layer and climate Photodissociation by ultraviolet Solar ultraviolet photon Ozone is a loosely bonded molecule and can be easily dissociated .

  19. Ozone 10-50 km (stratosphere) Formation of Ozone Sustaining Ozone Depletion of Ozone

  20. Ozone Ozone Depletion

  21. The Ozone Hole Ozone concentration drops sharply over Antarctica

  22. 1. Polar winter leading to the stronger circumpolar wind belt (polar vortex) to isolate the cold air within it. The Ozone Hole Cold air -80C Polar vortex 2. As the cold temperatures persist over the polar, polar stratospheric clouds form. 3. Chlorine reservoir species HCl and ClONO2 become very active on the surface of polar stratospheric clouds.

  23. Greenhouse gases on the rise

  24. The recent dramatic increase of greenhouse gases is unlikely caused by natural processes Scientific evidence 1. Ratio of radioactive C-14 that forms in the upper atmosphere is dropping, while carbon in fossil fuels, deep ocean, and volcano ash is non-radiative. 2. Ratio of C-13/C-12 is dropping as well. C-12 was congealed into Earth system 5 billion years ago. Ratio of C-13/C-12 is constant. However, photosynthesis prefers C-12. So, fossil fuels contain more C-12. The dropping of C-13/C-12 can only be caused by burning fossil fuels.

  25. It’s getting hotter down here! Temperature change is not horizontally homogeneous

  26. Global Temperature Anomalies

  27. Is our atmosphere really warming? Based on what you know, can you explain why the stratosphere is cooling?

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