11.2.2. Causes of Climate Change

The causes for climate change are many. They can be grouped into astronomical and terrestrial causes. The astronomical causes are the changes in solar output associated with sunspot activities. Sunspots are dark and cooler patches on the sun which increase and decrease in a cyclical manner. According to some meteorologists, when the number of sunspots increases, cooler and wetter weather and greater storminess occur. A decrease in sunspot numbers is associated with warm and drier conditions. Yet, these findings are not statistically significant.

Astronomical causes of climate change refer to factors linked to the Earth's position and relationship with the sun. Changes in solar output, particularly sunspot activities, are crucial. Sunspots can influence Earth's weather; an increase in their number tends to be linked with cooler, stormier weather, whereas fewer sunspots suggest warmer and drier conditions. However, the relationship isn't strong enough to be statistically significant, meaning that other factors also play important roles in climate changes over time.

Think of sunspots like seasonal changes in weather: just as certain winter months can be colder due to patterns in weather, sunspots can influence larger climate patterns, even if their effects are subtle. Just like we can't predict a cold winter solely based on a previous chilly month, we shouldn't rely solely on sunspot activity to understand climate change.

Another astronomical theory is Milankovitch oscillations, which infer cycles in the variations in the earth’s orbital characteristics around the sun, the wobbling of the earth and the changes in the earth’s axial tilt. All these alter the amount of insolation received from the sun, which in turn, might have a bearing on the climate.

Milankovitch oscillations involve three main factors: the Earth's orbit around the sun, the wobbling movement of the Earth, and changes in its axial tilt. These changes happen over thousands of years and impact the distribution and intensity of sunlight received by the Earth. As the orbit shifts and the tilt alters, it can lead to significant climate changes, such as the onset and retreat of ice ages. Thus, these oscillations are critical to understanding long-term climate patterns.

Imagine turning a flashlight on and off while moving it closer or farther from an object. The way the light hits the object changes, simulating how the Earth’s changing position and tilt affect sunlight and, consequently, our climate over long periods. Just like adjusting a flashlight can brighten or dim your view of an object, the Earth's orbit and tilt change how sunlight warms different parts of the planet.

Volcanism is considered as another cause for climate change. Volcanic eruptions throw up lots of aerosols into the atmosphere. These aerosols remain in the atmosphere for a considerable period of time reducing the sun’s radiation reaching the Earth’s surface. After the recent Pinatubo and El Chichón volcanic eruptions, the average temperature of the earth fell to some extent for some years.

When volcanoes erupt, they release a variety of particles, including aerosols, which are tiny particles or droplets that can stay in the atmosphere for years. These aerosols block sunlight and can lead to a temporary cooling of the Earth's surface. For instance, after significant eruptions like those of Mount Pinatubo and El Chichón, the global temperatures dropped noticeably due to the ash and sulfur dioxide particles spreading in the atmosphere, reflecting sunlight away from Earth.

Consider how a brief mainly cloudy day makes things cooler compared to a clear, sunny day. In a similar way, volcanic eruptions can create a 'cloud' of particles in the atmosphere that blocks sunlight, leading to cooler temperatures for some time. Just as trees or buildings can block sunlight, the aerosols after an eruption can 'shade' the Earth from the sun.

The most important anthropogenic effect on the climate is the increasing trend in the concentration of greenhouse gases in the atmosphere which is likely to cause global warming.

Human activities, particularly the burning of fossil fuels, deforestation, and industrial activities, have led to a significant increase in greenhouse gases (GHGs) like carbon dioxide, methane, and others in the atmosphere. These gases trap heat, creating a 'greenhouse effect,' which leads to global warming—a rise in average Earth's temperature. This warming can result in severe weather patterns, rising sea levels, and other adverse changes in climate.

Think of Earth as a giant greenhouse. Just as a greenhouse keeps plants warm inside by trapping heat from the sun, the increased greenhouse gases around our planet are trapping more heat, making the Earth warmer. It's like wearing a thick winter coat in the summer—eventually, it becomes too hot to handle, just like Earth is experiencing due to these gases.

--