Climate model can be constructed by using the law of physics for the atmosphere i.e.: The Navier-Stokes equation, the conservation of mass, the conservation of energy, the equations of states and we have to include schemes for cloud formations, carbon and sulfur cycle, interactions between atmosphere and land surface, oceans, cryosphere, and biosphere, furthermore we have to include forcing by volcanic eruptions, the solar activity and galactic cosmic rays.
Researchers from LAPAN using GCM and DARLAM [Ratag, 2002] have reported some results of climate prediction for Indonesian regions. Under a scenario that CO2 concentration doubled in 100 years then the temperature in Indonesian regions will increase on the average about 0.03 degrees Celsius per year. This research showed that the result of prediction of rainfall in these regions is still poor (the correlations on the average are below 0.5) and need some modification on cloud formation scheme.
The second approach can use soft computing methods with the following considerations. The relative positions of the sun in the sky during the seasons, as well as the cycles of solar activity influence the weather and climate throughout the Indonesian archipelago. Solar irradiance and ultraviolet intensity increases with higher solar activity. This in turn will be followed by coronal mass ejection (CME) that increases the charged particles emitted by the sun which could alter the interplanetary magnetic field, and hence the intensity of galactic cosmic rays reaching the earth. The galactic cosmic ray intensity reaching the earth decreases with higher solar activity. Thus the solar activity is often considered as the dominant factor that determines the dynamics of climate [Svensmark, 2007; Landscheidt, 1988]. The dynamics of earth’s atmosphere and oceans, evaporation, clouds formation and rainfall, are influenced by the solar energy entering the earth. Several studies indicate that strong correlations exist between the cloud cover and the intensity of galactic cosmic ray reaching the earth [Carlslaw, 2002].
During 1645 – 1715 exceptionally low solar activity (also known as the Maunder minimum) which means high intensity of galactic cosmic ray reached the earth increased cloud cover that led to low temperatures causing what is known as the little ice age.
The present study shows that there is a strong correlation between rainfall in the middle Indonesian region and solar activity and the relation of solar activity and rainfall of other regions. Using this fact we can predict the climate in Indonesian regions by predicting the sunspot numbers (solar activity). It can be shown that to get a good accuracy of predicting a quasi periodic time series as sunspot numbers is possible.
The possibility of reducing the negative effect of climate using weather modification methods is also considered.