Also termed as Climate change, the phenomena revolves around rising temperatures and unnatural disasters caused as a result. Earth is in ever in a state of evolution due internal geological and external atmospheric changes, these by all means are slow and study. The effect appears after passing of millions of years which may not be much as per historical timescale but is significant whence human history is concerned. 

But the geological changes are in no way related to climate change vis a vis human activities. The factors that affect climate on Earth and fetch about unwarranted changes are all man made. The unwarranted changes are rising temperatures, drought, deluge, rise in sea levels, desertification, extreme weather, melting of ice in the polar regions and disasters that bring about harrowing misery. These happenings are some how related to widespread disease prevalence among the young, occurence of rare virus disease, physical deformities  and so on. Global warming may also result in species extinction.  Hydro-meteorological disasters result in famine and hunger giving rise to poverty.         

The impact of this change differs from region to region, and it is not universal. Earth practically exists in a state of equilibrium where composition of air, water, climate, geography and resources make life sustainable. In return life also sustains abiotic elements in order to assist in maintaining an equilibrium. This is a complex web which humans have to understand and respect in order to survive on this planet.  We gauge the environment on the basis of it's support to life. This means stable conditions should exist without any untimely disruption such that life may flourish.

Some of the external forcings out of human purview are changes in solar luminosity, high volcanic activities, disastrous meteoric activities. changes in atmospheric composition brought about by the emission of greenhouse gases can also effect sustainability of life on Earth.   

Since the industrial revolutions in most part of the World, the emission of greenhouse gases like Co2, Ozone, vapours and methane has rising dramatically and continues to do so.  It is essential to repeat this in the article that Fossil Fuels and deforestation are two major factors responsible for this anomaly in the Earth's systems. But there are certain non fuel chemical process responsible for climate change as well albeit to a lesser scale.   

United Nations Framework Convention on Climate Change (UNFCCC) is an organization that is supported by many countries with the objective of mitigating or preventing anthropogenic climate changes.  

Reduction in harmful emissions brought about resorting to fossil fuels, prevention of destruction of forests and other natural lands is important in order to fetch stability in the climate. The use of alternative energy although in a nascent stage can also assist by reducing dependency on fossil fuels and thereby reducing emissions. Sustainable use of natural resource help us leave a better carbon footprint profile. We as responsible citizens can aid tremendously here by conserving energy.     

Increase in industrial production and unchecked population growth are factors responsible for high levels of C02 emissions. These are the factors we can control. 

As technology advances hopefully greater impetus will be accorded to prevent disastrous climatic changes on Earth.  

For extensive reading visit Wikipedia Article on Global Warming.