Monica+T.

=How Climate Can Be Influenced By Human Activities = //TOPIC 5: Describe how climate can be influenced by human activities (eg. Greenhouse gases, depletion of ozone layer) //

Human activities play a part to climate change by causing modifications to Earth’s atmosphere in the number of greenhouse gases, cloudiness, and aerosols (small particles). The largest contribution comes from the burning of fossil fuels, which releases carbon dioxide gas to the atmosphere. Greenhouse gases and aerosols affect climate by changing incoming solar radiation and out going infrared radiation that are a part of Earth’s energy balance. Changing the atmospheric quantity or properties of these particles and gases can lead to a warming or cooling of the climate system. Ever since the start of the Industrial era, the effect of human activities on climate has been a warming influence. The human impact on climate has been known to do changes in natural processes, such as volcanic eruptions and solar changes. The burning of coal, oil, and natural gas, as well as deforestation and other agricultural and industrial practices, are changing the composition of the atmosphere and contributing to climate change. These human activities have led to increased atmospheric concentrations of a various number of greenhouse gases, including carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone in the lower part of the atmosphere.

 Most scientists believe that human activity is changing the composition of the atmosphere by the increase in concentration of greenhouse gases (GHGs). Greenhouse gases happen naturally in the atmosphere and their presence results in what atmospheric scientists call the greenhouse effect. It's important to know that the greenhouse effect is what helps keep the earth warm enough to be habitable. The current worry is directed at an enhanced greenhouse effect, one that would put heat-absorbing gases into the atmosphere, thereby increasing global temperatures. The enhanced greenhouse effect has been connected to increased GHG emissions from human activities.

 The recent attention given to global warming and the greenhouse effect is mainly based on the increases in concentrations of some of the greenhouse gases due to human activity. Of particular interest are water vapor, carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone. With the exception of chlorofluorocarbons, all of these gases occur naturally and are also produced by human activity.



Water vapor is the most important GHG on the planet. Unlike a lot of the other atmospheric gases, water vapor is considered to be a 'variable' gas; that is, the percentage of water vapor in the atmosphere can vary depending on the location and source of the air. For example, over the tropical oceans, water vapor may account for 4% of the total volume of gases, while at high altitudes or over deserts, it may be almost absent. A lot of the times, when discussing global warming, people often don't consider water vapor. The main reason is that human activity does not directly change water vapor content. Though, we do, in fact, directly influence other GHGs. Although other GHGs are separately less important than water vapor, increasing their concentrations may affect global climate in significant ways.

 Carbon dioxide is considered the most important human-influenced GHG. Scientific measurements reveal an unmistakable global increase that is swift and growing. This increase arises mainly from the burning of fossil fuels (motorized vehicles, electric power plants, and homes heated with gas or oil) and the burning and clearing of forested land for agricultural reasons.

 Methane is largely a product of natural biologic processes, but its output can be accelerated by human activities. Methane is emitted from the decay of organic matter in waterlogged soils (for example, rice paddies and wetlands) and from the digestive tracts of grazing animals (for example, ruminants). The additions from human activities include the addition of rice agriculture, the growing number of livestock, the increased number of landfills, and leakage from natural as pipelines.

 Chlorofluorocarbons (CFCs) have no natural source; they're produced by human activity. CFCs have historically been used widely as refrigerants in air conditioners, refrigerators, freezers and heat pumps. They are found in some foam plastics and used in some electronics manufacturing. Even though CFC production has been greatly reduced, these compounds stay in the atmosphere for a large amount of time; we will see their effects as GHGs for many years.

 Nitrous oxide is a naturally occurring GHG, which has increased brilliantly in recent years because of human activity. Nitrous oxide is emitted from coal-burning power plants and can be relieved from the breakdown of chemical fertilizers in the soil.

 Ozone is also a greenhouse gas. It's important to not mix up the presence of the ozone in the stratosphere, with the presence of the ozone in the troposphere. In the troposphere, ozone can be a big part of urban smog - damaging crops and aggravating respiratory problems as well as enhancing the greenhouse effect. More about the ozone layer is written below.

 The concentrations of these GHG are increasing (but, thanks to recent global agreements, CFCs are being largely eliminated and their concentrations have begun to drop in the lower atmosphere). Most of emissions come from the most developed countries, where power generation, power consumption, and living standards are highest.



 The ozone layer shields the Earth from the ultraviolet rays sent down by the sun. If the ozone layer is depleted by human activity, the effects on the planet could be dangerously catastrophic. Ozone is present in the stratosphere. The stratosphere reaches 30 miles on top of the Earth, and at the very top it contains ozone. The sun's rays are absorbed by the ozone in the stratosphere and therefore do not reach the Earth. Ozone is a bluish gas that is created by three atoms of oxygen. The form of oxygen that humans breathe in is made up of 2 oxygen atoms. When discovered on the surface of the planet, ozone is considered a hazardous pollutant and is one substance responsible for generating the greenhouse effect.The highest regions of the stratosphere take in about 90% of all ozone.

 In recent years, the ozone layer has been the topic of much discussion. And it's a good thing, because the ozone layer protects both plant and animal life on the planet. The fact that the ozone layer was being depleted was realized in the mid-1980s. The main reason of this, is the release of CFCs, chlorofluorocarbons. Antarctica was an early victim of ozone devastation. A large hole in the ozone layer right above Antarctica now endangers not only that continent, but many others that could be the victims of Antarctica's melting icecaps. In the future, the ozone problem will have to be solved so that the protective layer can be saved.



=<span style="color: #000000; font-family: Georgia,serif;">Bibliography = <span style="color: #000000; font-family: Georgia,serif;">http://library.thinkquest.org/26026/Environmental_Problems/ozone_depletion.html <span style="color: #000000; font-family: Georgia,serif;">http://oceanservice.noaa.gov/education/pd/climate/factsheets/howhuman.pdf <span style="color: #000000; font-family: Georgia,serif;">http://www.ucar.edu/learn/1_4_2_20t.htm <span style="color: #000000; font-family: Georgia,serif;">http://www.gcrio.org/ipcc/qa/04.html