Global Warming !

What is Global Warming ? Global warming is the increase in the average temperature of earth’s near-surface air and oceans. Evidence for warming of the climate system includes observed increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.

Temperature Changes Temperature changes vary over the globe. Since 1979, land temperatures have increased about twice as fast as ocean temperatures. Ocean temperatures increase more slowly than land temperatures because of the larger effective heat capacity of the oceans and because the ocean loses more heat by evaporation. The Northern Hemisphere warms faster than the Southern Hemisphere because it has more land. The thermal inertia of the oceans and slow responses of other indirect effects mean that climate can take centuries or longer to adjust to changes in forcing.

Greenhouse Gases A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would be on average about (59 °F) colder than at present. Since the beginning of the Industrial revolution, the burning of fossil fuels has substantially increased the levels of carbon dioxide in the atmosphere.

Aerosols and Soot Global dimming is caused by aerosol made by volcanoes and pollutants. These aerosols exert a cooling effect by increasing the reflection of incoming sunlight. The effects of the products of fossil fuel combustion—CO2 and aerosols—have largely offset one another in recent decades, so that net warming has been due to the increase in non-CO2 greenhouse gases such as methane. Carbon dioxide has a lifetime of a century or more, and as such, changes in aerosol will only delay climate changes due to carbon dioxide. ON the other hand Soot may cool or warm the surface, depending on whether it is airborne or deposited. Atmospheric soot aerosols directly absorb solar radiation, which heats the atmosphere and cools the surface. Atmospheric soot always contributes additional warming to the climate system.

The Sun Until about 1960,  measurements by scientists showed that the brightness and warmth of the sun, was increasing. Over the same period temperature measurements of the air and sea showed that the Earth was gradually warming. It was not surprising and for most scientists to put together and assume that it was the warming sun that was increasing the temperature of our planet. Between the 1960s and today the same solar measurements have shown that the energy from the sun is now decreasing. At the same time temperature measurements of the air and sea have shown that the Earth has continued to become warmer and warmer.  This proves that it cannot be the sun; something else must be causing the Earth's temperature to rise.

Chlorofluorocarbon Chlorofluorocarbon (CFC) is a family of chemical compounds developed back in the 1930's as safe, non-toxic, non-flammable alternative to dangerous substances like ammonia for purposes of refrigeration and spray can propellants. Their usage grew enormously over the years. One of the elements that make up CFCs is chlorine. Very little chlorine exists naturally in the atmosphere. But it turns out that CFCs are an excellent way of introducing chlorine into the ozone layer. Under the proper conditions, this chlorine has the potential to destroy large amounts of ozone. This has indeed been observed, especially over Antarctica. CFCs have been found to pose a serious environmental threat. Studies say scientists during the 1970s revealed that CFCs released into the atmosphere accumulate in the stratosphere, where they had an effect on the ozone layer; even a small decrease in the stratospheric ozone concentration can result in an increase of skin cancer in humans and in genetic damage in many organisms. In the stratosphere the CFC molecules break down by the action of solar ultraviolet radiation and release their constituent chlorine atoms. These then react with the ozone molecules, resulting in their removal. CFCs have a lifetime in the atmosphere of about 20 to 100 years, and consequently one free chlorine atom from a CFC molecule can do a lot of damage, destroying ozone molecules for a long time.

The Cfc Problem …

Effects of Global Warming : O Effects of global warming are felt in many ways now and this will worsen. Effects are, and will, be increasingly noticeable in these areas Extreme weather Rising oceans Food and water resources Human health Economic War and conflicts Further global warming

Quick ? ‘s What is this PowerPoint about ? What is Global Warming ? T or F :Ocean temperatures increase more slowly than land temperatures? What’s a Greenhouse gas ? T or F: is the sun the reason the temperature in earth is rising ? What is one element that makes up a CFC ? A) Water B) Ammonia C) Chlorine Name 3 effects that we will be able to tell that's worsening ?

Thee Enddd !!! Created By: Roxana A. Jorge B. nd& Lucia V. :P