**2. Factors governing the climate change**

Over thousands or millions of years, global climate change typically occurred very slowly. But today, by contrast, our environment is changing fast. There are many factors that govern the climate change around the world. The most important factors are discussed below:

#### **2.1 The sun and the cosmic rays**

Climate change is influenced by natural changes like the amount of solar energy reaching the Earth. The rate of energy emitted by the Sun varies slightly from day to day. Over many millennia the relationship between Earth and Sun can change the geographic distribution of the energy of the sun throughout the earth's surface. The orbit of Earth around the Sun is an ellipse and when it changes in shapes, the Earth moves nearer to the Sun which makes our climate much warmer. *Climate Change and Its Potential Impacts on Insect-Plant Interactions DOI: http://dx.doi.org/10.5772/intechopen.98203*

The orientation of earth's axis can also affect the amount of sunlight reaching the earth's surface [4]. The angle of rotation of the earth's axis varies over time and it shifts from 22.1o to 24.5<sup>o</sup> and back again for around 41,000 years. With increase in the angle the summers become warmer and the winters turn colder. The Sun also emits particle radiation, primarily protons and electrons, which comprise the solar wind. These particles come near to the earth, but the earth's magnetic field averts them from reaching the surface. The earth's atmosphere reaches more intense executions, known as solar cosmic rays. Cosmic solar rays cannot be reaching the earth's surface, but are extremely energetic, collide with atoms at the top of the atmosphere, causing major magnetic field perturbations to disrupt power lines and electrical equipment [5]. It has been suggested that changes in solar output might affect our climate-both directly, by changing the rate of solar heating of the Earth and atmosphere, and indirectly, by changing cloud forming processes. The increase in absorption of solar radiation results in rise in temperatures which in turn results in upsurge of CO2 levels. Shrivastava [6] suggested that rise of 1°C will result in the release of 30 petagrams of carbon from the soils, which is almost twice the amount emitted due to human activities annually.

#### **2.2 The greenhouse effect**

Greenhouse gases are the molecules that are capable of absorbing infrared radiation released from the surface of the Earth and re-radiating it back, thereby leading to the greenhouse effect phenomenon. During the history of the Earth, greenhouse gases concentrations such as water vapour, carbon dioxide, methane, nitrous oxide, ozone and certain artificial chemicals like Chloro Fluoro Carbons (CFCs) have varied considerably, and these fluctuations have triggered major climate changes at a wide range of timescales. Human activities, particularly the combustion of fossil fuels (coal, oil and natural gas), agriculture and land clearing, are responsible for rising concentrations of greenhouse gases. This has intensified the greenhouse effect, leading to earth's warming.

#### **2.3 Human influence**

The factors above mentioned affect the climate naturally. However, we could not forget the effect of human activities on the changes in climate. Early in history, influence of human on the climate would have been quite small. Since, the beginning of the Industrial Revolution, at the end of 19th Century in the atmosphere there was a rise in the emission of the amount of greenhouse gases. The number of trees being cut down by humans has also increased, resulting in reduced uptake of carbon dioxide by the forests. Black carbon (BC), a solid particle or aerosol that is not a gas, leads to atmospheric warming. Unlike GHGs, in addition to absorbing infrared radiation, BC can also directly absorb incoming and reflected sunlight. It may also settle on the snow and ice, darkening the surface and thereby increasing the snow's absorption of sunlight and accelerating the melting process. Sulphates, organic carbon, and other aerosols might cause cooling by reflecting sunlight. Clouds can interact with warming and cooling aerosols, alters a number of properties of cloud like the rate of formation, dissipation, reflectivity, and precipitation. They may contribute to cooling, by reflecting sunlight and warmth and by trapping the outgoing heat.

True insights about climate change can be provided by factors such as temperature, precipitation (amount, frequency and timing), humidity, wind (velocity, timing), gaseous concentration etc.

