Scientific Explanation Behind Various

Causes Of Climate Change.

The causes of climate change can be divided into two categories, human and natural causes.

It is now a global concern that the climatic changes occurring today have been speeded up because of man's activities.

The natural variability and the climate fluctuations of the climate system have always been part of the Earth’s history however there have been changes in concentrations of greenhouse gases in the atmosphere growing at an unprecedented rate and magnitude. The United Nations, governments and many top scientists around the world believe that we must act now to stabilise and arrest further changes.

To understand climate change fully, the causes of climate change must be first identified. Scientists divide the causes into two categories, natural and human causes.

Natural Causes of Climate Change

The earth’s climate is influenced and changed through natural causes like volcanic eruptions, ocean current, the earth’s orbital changes and solar variations.

Volcanic eruptions - When a volcano erupts it throws out large volumes of sulphur dioxide (SO2), water vapour, dust, and ash into the atmosphere. Large volumes of gases and ash can influence climatic patterns for years by increasing planetary reflectivity causing atmospheric cooling. Tiny particles called aerosols are produced by volcanoes. Because they reflect solar energy back into space they have a cooling effect on the world. The greenhouse gas, carbon dioxide is also produced however the CO2 produced is insignificant when compared to emissions created by humans.Ocean current - The oceans are a major component of the climate system. Ocean currents move vast amounts of heat across the planet. Winds push horizontally against the sea surface and drive ocean current patterns. Interactions between the ocean and atmosphere can also produce phenomena such as El Niño which occur every 2 to 6 years. Deep ocean circulation of cold water from the poles towards the equator and movement of warm water from the equator back towards the poles. Without this movement the poles would be colder and the equator warmer. The oceans play an important role in determining the atmospheric concentration of CO2. Changes in ocean circulation may affect the climate through the movement of CO2 into or out of the atmosphere.
Earth orbital changes - The earth makes one full orbit around the sun each year. It is tilted at an angle of 23.5° to the perpendicular plane of its orbital path. Changes in the tilt of the earth can lead to small but climatically important changes in the strength of the seasons, more tilt means warmer summers and colder winters; less tilt means cooler summers and milder winters. Slow changes in the Earth’s orbit lead to small but climatically important changes in the strength of the seasons over tens of thousands of years. Climate feedbacks amplify these small changes, thereby producing ice ages.

Solar variations - The Sun is the source of energy for the Earth’s climate system. Although the Sun’s energy output appears constant from an everyday point of view, small changes over an extended period of time can lead to climate changes. Some scientists suspect that a portion of the warming in the first half of the 20th century was due to an increase in the output of solar energy. As the sun is the fundamental source of energy that is instrumental in our climate system it would be reasonable to assume that changes in the sun's energy output would cause the climate to change. Scientific studies demonstrate that solar variations have performed a role in past climate changes. For instance a decrease in solar activity was thought to have triggered the Little Ice Age between approximately 1650 and 1850, when Greenland was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.

Current global warming however cannot be explained by solar variations. Some examples are evidenced such as since 1750, the average amount of energy coming from the Sun either remained constant or increased slightly.
If global warming was caused by a more active sun, then scientists would expect to see warmer temperatures in all layers of the atmosphere. They have only observed a cooling in the upper atmosphere, a warming at the surface and in the lower parts of the atmosphere. This is due to greenhouse gasses capturing heat in the lower atmosphere. Also climate models that include solar irradiance changes cannot reproduce last century's observed temperature trend without including a rise in greenhouse gases.

The causes of climate change continued
Increase in global temperatures - Inter-government Panel

The most recent assessment report from the Intergovernmental Panel on Climate Change (IPCC) says that the earth’s average temperature has risen by 0.74 degrees in the period from 1906 to 2005, and that the average temperature will continue to rise.

The greenhouse effect is a natural mechanism that retains the heat emitted from the earth’s surface. The earth’s average temperature is at the moment around 14 degrees celsius (57 degrees fahrenheit). If the natural greenhouse effect did not exist, the average temperature would be around minus 19 degrees celsius (minus 2 degrees fahrenheit).

The greenhouse effect is caused by a range of different gases in the earth’s atmosphere. Water vapour makes the most significant contribution to the greenhouse effect, followed by CO2. The atmospheric content of greenhouse gases – in particular CO2 – and the consequences for the climate are being discussed because the content of these gases in the atmosphere has risen precipitously in a period covering approximately the latest 250 years, and especially the last 50.

At present the concentration of CO2 in the atmosphere is about 385 ppm (parts per million). Before industrialization it was about 280 ppm. Analyses of air contained in ice from the Antarctic ice cap show that there is far more CO2 in the air today than at any time in the last 650,000 years.

The consequence is that the greenhouse effect is becoming stronger, and therefore the earth is becoming warmer. How much warmer has, however, been a matter of dispute. The most recent assessment report from the IPCC is from 2007. It concludes that the earth’s average temperature has risen by 0.74 degrees in the period from 1906 to 2005. The warming is stronger over land areas than over the sea, and accordingly it is strongest in the northern hemisphere. At the same time occurrences of heat waves and violent downpours have also increased, the oceans have risen, and the ice at the world’s poles and on its mountains has begun to melt. All of these effects are predictable in the event of global warming.

Notes: Chemistry In The Community

Kinetic Molecular Theory
The experimental observations about the behavior of gases discussed so far can be explained with a simple theoretical model known as the kinetic molecular theory. This theory is based on the following postulates, or assumptions.
Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion.
These particles move in a straight line until they collide with another particle or the walls of the container.
These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space.
There is no force of attraction between gas particles or between the particles and the walls of the container.
Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container.
The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.
The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules), all of which are in constant, random motion. The rapidly moving particles constantly collide with each other and with the walls of the container. Kinetic theory explains macroscopic properties of gases, such as pressure, temperature, or volume, by considering their molecular composition and motion. Essentially, the theory posits that pressure is due not to static repulsion between molecules, as was Isaac Newton's conjecture, but due to collisions between molecules moving at different velocities.
While the particles making up a gas are too small to be visible, the jittering motion of pollen grains or dust particles which can be seen under a microscope, known as Brownian motion results directly from collisions between the particle and gas molecules. As pointed out by Albert Einstein in 1905, this experimental evidence for kinetic theory is generally seen as having confirmed the existence of atoms and molecules.
Boyle's Law
 (sometimes referred to as the Boyle-Mariotte law) is one of many gas laws and a special case of the ideal gas law . Boyle's law describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system. A law stating that the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature.
Boyle's law explains an inverse relationship between the volume and pressure of a gas. For example, if the volume of a gas doubled, the pressure it exerted would be cut by half. If the volume tripled, the pressure would be a third of what it was before.
Boyle's law is used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas. The before and after volumes and pressures of the fixed amount of gas, where the before and after temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:

Charles's law (also known as the law of volumes) is an experimental gas law which describes how gases tend to expand when heated the volume V of given mass of a gas is directly proportional to its absolute temperature.Charles studied the compressibility of gases nearly a century after Boyle. In his experiments he observed "At a fixed pressure, the volume of a gas is proportional to the temperature of the gas." Charles' Law describes the direct relationship of temperature and volume of a gas. Assuming that pressure does not change, a doubling in absolute tempature of a gas causes a doubling of the volume of that gas. A drop of absolute temperature sees a proportional drop in volume.The law can also be usefully expressed as follows:

The expression Gay-Lussac's law which concern the properties of gases, though it is more usually applied to his law of combining volumes, the first listed here. One law relates to volumes before and after a chemical reaction while the other concerns the pressure and temperature relationship for a sample of gas.
The law of combining volumes states that, when gases react together to form other gases, and all volumes are measured at the same temperature and pressure:The ratio between the volumes of the reactant gases and the products can be expressed in simple whole numbers.