Human influences on climate change: Anthropogenic factors are more influenced by human activities that can lead to changes in the environment and influence climate. In some cases the chain of causality is direct and unambiguous, while in others it is less clear. Various hypotheses for human-induced climate change have been researched and debated for many years, though it is important to note that the scientific debate has moved on from skepticism, to belief and scientific consensus that human activities beyond  doubt have contributed to the current rapid changes in the Earth's climate.
The biggest factor is the increase in carbon dioxide levels in the atmosphere due to burning of fossil fuels (oil, coal, natural gas). Other factors, which impacts climate are land use, ozone depletion, animal agriculture and deforestation.

What causes climate change?

Several gases in the atmosphere act to trap the energy from the sun, thereby warming the earth. These gases are called greenhouse gases and the process is called greenhouse effect. Without Earth's natural greenhouse effect there would be no life on earth. However what we are experiencing right now is called enhanced greenhouse effect which is happening largely due to the human activities over the last 150 - 200 years, particularly the burning of fossil fuels and deforestation, all of which has  dramatically increased the concentration of greenhouse gases in our atmosphere which in turn leads to the warming up of earth's surface.

What is Greenhouse Effect?
In nature Greenhouse effect is extremely useful as it is responsible for regulating Earth's temperature and thereby help maintaining earth's temperature at a level which can sustain life.
This phenomena works similar to the glass in a greenhouse which keeps heat in the greenhouse. Our atmosphere also traps the sun’s heat near earth’s surface, primarily through heat-trapping properties of certain “greenhouse gases”.
Earth is heated by sunlight. Most of the sun's energy passes through the atmosphere, to warm the earth's surface, oceans and atmosphere. However, in order to keep the atmosphere's energy in balance, the warmed earth also emits heat energy back to space as infrared radiation.
As this energy radiates upward, most is absorbed by clouds and molecules of
greenhouse gases in the lower atmosphere. These re-radiate the energy in all directions, some back towards the surface and some upward, where other molecules higher up can absorb the energy again. This process of absorption and re-emission is repeated until, finally, the energy does escape from the atmosphere to space.
However, because much of the energy has been recycled downward, surface
temperatures become much warmer then if the greenhouse gases were absent from the atmosphere. This natural process is known as the greenhouse effect.
Without greenhouse gases, Earth's average temperature would be -19°C instead of +14°C, or 33°C colder.
Over the past 10,000 years, the amount of greenhouse gases in our atmosphere has been relatively stable. Then a few centuries ago, their concentrations began to increase due to the increasing demand for energy caused by industrialization and rising populations, and due to changing land use and human settlement patterns.  

What are Greenhouse gases?
Water vapors is the most common greenhouse gas. But others that are very important too.  Some greenhouse gases such as CO2 or Carbon dioxide occur naturally and are emitted to the atmosphere through natural processes and human activities.

Carbon Dioxide or CO2 is the most significant greenhouse gas released by human activities, mostly through the burning of fossil fuels. It is the main contributor to climate change. Carbon dioxide enters the atmosphere through the burning of fossil fuels such as oil, natural gas, and coal solid waste, trees and wood products, and also as a result of of manufacture of cement. As the Co2 level rises in the atmosphere it directly results in increase in global temperature ( See Fig. Below).

Methane is produced when vegetation is burned, digested or rotted with no oxygen present. Garbage dumps, rice paddies, and grazing cows and other livestock release lots of methane
 

Nitrous oxide can be found naturally in the environment but human activities are increasing the amounts. Nitrous oxide is released when chemical fertilizers and manure are used in agriculture.
 

Halocarbons are a family of chemicals that include CFCs (which also damage the ozone layer), and other human-made chemicals that contain chlorine and fluorine.

What should we do to slow the process?

The greenhouse effect can be reversed by two ways (1) Forestation (2) Reduction of greenhouse gases. Forestation will help in more more absorption and cleaning of Co2 by trees. (2) Reduce fossil fuel usage and embrace new environmental friendly technologies such as solar energy wind energy and battery operated automobiles etc. Push our governments to sign and implement  kyoto protocol.

What would be the real impact of climate change remains uncertain, and exact consequences of climate change to all living species and environments across the world are also largely unknown. However in order to learn about some estimated effects Click here.