Concentrations of greenhouse gases in the atmosphere are increasing at an alarming rate. Majority of the world’s climate scientists agree that human activities are indeed the main reason behind climate change. This high degree of agreement among climate scientists has been established because of compelling evidences which show that the climate is indeed changing because of anthropogenic causes.
However, climate change is also linked to a few natural causes such as:
The change in energy output of the sun brings changes in climate. This idea is reasonable as the sun is the fundamental energy source that supports our climate system.
Solar energy can influence the abundance of atmospheric greenhouse gases and heats our climate system.
For example, the Little Ice Age that occurred between 1650 and 1850 has been linked to decrease in solar irradiance. However, it has been established that solar irradiance is not accountable for global warming.
When volcanoes erupt, thousands of tons of sulfur dioxide is released into the atmosphere. Sulfate aerosols have the property of absorbing and scattering solar radiation which cause cooling and warming of the earth respectively.
For example, when Mount Pinatubo in Philippines erupted in 1991, it subsequently decreased the global temperature by 0.9⁰F for almost three years.
Tectonic plates rearrange the topography of the earth over the course of time. This brings changes in the circulation of oceans and subsequently changes the patterns of the global climate.
For example, the Isthmus of Panama, which formed 5 million years ago, separated the Atlantic and Pacific Oceans. This changed the ocean dynamics of the Gulf Stream and has been linked to the formation of ice cover in the Northern Hemisphere.
Variations in the Earth’s Orbit
Variations in the orbit of the planet bring changes in seasonal distribution of the light from the sun. There are three types of variations; variations in axial tilt, variations in eccentricity and variations in precession.
These variations also lead to changes in the geographical distribution of sunlight that affects the global climate. They combine to form Milankovitch cycles which is based on the theory that changes in the movement of the earth brings changes upon the climate.