Climate change can be defined as a change in climate variables, especially temperature and rainfall that occur gradually in a long period of time between 50 to 100 years. Besides it should be understood that the changes caused by human activity (anthropogenic), especially those related to fossil fuel consumption and over-land.
So the changes caused by natural factors, such as additional aerosols from volcanic eruptions, are not accounted for in terms of climate change. So the natural phenomena that lead to extreme climatic conditions such as cyclones can occur in a year (inter-annual) and El-Nino and La Nina, which can happen in ten years (inter-decade) can not be classified into global climate change.
Human activity in question is the activities that have led to an increase in atmospheric concentrations, especially in the form of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The gases then determines the temperature increase, because it is like glass, which can forward to short-wave radiation which is not hot, but hold long-wave radiation that is heat. As a result the earth’s atmosphere heats up.
The impact of climate change:
Agricultural sector will be affected through the reduction of food productivity caused by the increase in cereal sterility, reduction in area can be irrigated and decrease the effectiveness of nutrient absorption and spread of pests and diseases.
In some places in the developed (high latitudes) increase in CO2 concentration will increase productivity because of increased assimilation, but in the tropics that most developing countries, an increase of assimilation was not significant compared with respiration which is also increased. On the whole, if adaptation is not done, the world will experience a decline in food production to 7 percent.
However, with continued levels of adaptation, meaning high costs, food production can be stabilized. In other words, stabilization of food production on climate change will cost very high, for example by improving irrigation facilities, provision of inputs (seeds, fertilizers, insecticides / pesticides) added.
In Indonesia, the scenario of CO2 concentrations double from current rice plant production will increase to 2.3 percent if irrigation can be maintained. But if the irrigation system did not experience improvements in rice plant production will decline to 4.4 percent (Matthews et al., 1995).
Warmer temperatures will cause a shift in vegetation species and ecosystems. Mountain areas will lose many species of original vegetation and replaced by lowland vegetation species. Along with that the condition of water resources from the mountains will also be susceptible to interference. Furthermore the stability of land in mountainous areas is also disrupted and hard to keep the original vegetation. This impact is not so apparent in the low latitude areas or low elevation area. If more and more forest fires are common in Indonesia, it was difficult to connect the incident with climate change, because most (if not all) incidents of forest fires caused by human activities associated with land clearing.
That happened in conjunction with the El-Nino events because of this phenomenon provides dry weather conditions that facilitate the occurrence of fire. However, as described above El-Nino is phenomenon of nature which associated with extreme climate events in climate variability, not climate change in the meaning as described above. Increasing of population makes pressure on water supply, especially in urban areas.
At this moment there are lots of urban residents who have difficulty getting clean water, especially those who are low- income and low-educated or unskilled. The impact of climate change which causes changes in temperature and rainfall will have an impact on the availability of water from the surface runoff, groundwater and other reservoir shapes. In the year 2080 there will be 2 – 3.5 billion people will experience water shortages.