The Earth tilt is a natural factor that affects the seasonal changes to the environment. The Earth rotates around an axis tilted at an angle of 23.4°. This angle is directly perpendicular to the orbit of the Earth around the sun. The rotation of the Earth around the sun causes parts of the Earth to face the sun at certain times in the year, while other parts face away. Consequently, the hottest season -- summer -- occurs in the northern hemisphere when the northern parts of the Earth face the sun. Spring, autumn and winter occur as the northern part faces farther away from the sun. During winter in the north, it is summer in the southern hemisphere, as this part of the Earth directly faces the sun.
Global warming is the increase in global temperatures as a result of an increase in greenhouse gas emissions to the atmosphere. This is also known as the greenhouse effect. The increase in these greenhouse gases, such as carbon dioxide and methane, is largely a result of human activities -- for example, industrialization. But the rise in global temperature has resulted in rising sea levels and melting of ice caps. This has resulted in increasingly unpredictable seasons and weather patterns in all parts of the world.
The sun's intensity changes over time. The activities inside the sun affect the intensity of radiation that reaches Earth. A reduction in the sun's intensity causes more cooling on Earth and can therefore result in colder winters and changes to plant cover. Higher solar intensity may result in hotter winters, droughts and a loss of plants that require cooler temperatures to survive.
Environmental degradation through increased human population affects environmental seasonality in multiple ways. An increase in human population puts pressure on the numerous ecosystems on Earth. For example, an increased demand for land expedites deforestation. Deforestation means a loss of forest cover, which affects evaporation patterns and reduces the absorption of greenhouse gases. Rain patterns also change over time. An increase in population also means greater demand for water. This not only affects sea life but also changes to the water patterns (decrease in water) in large water bodies.