Natural Causes of Climate Change

Instructor: Meredith Mikell
Climate change is a complex occurrence with many possible causes. Here we will discuss the natural factors that affect climate change. At the end, you can test your knowledge with a brief quiz.

What is Climate?

The Earth's climate is a dynamic thing. In some parts of the world, it is consistently hot and dry. In other places, it's hot and humid. Still other regions are cold and dry or even cold and humid. The variations in climate depend on location and the amount of land or water in a given place. Even land formations can even have an impact on climate! So what does the term 'climate' really mean?

Climate is the average weather and temperature conditions for a given place. This is not the same as weather, which is day-to-day changes in temperature, cloud cover, and air pressure. The weather in Denver, Colorado today might be unusually hot and rainy, but the overall climate for Denver is relatively cool and dry.

The world has many different climate types.
global climates

Specific regions have their own climates, but we also refer to Earth's overall climate as the average set of conditions across the planet. Global climate change is a change in those conditions, and it typically happens gradually, at least from our perspective. Climate change has happened many times during Earth's history due to natural causes. The climate change we are currently experiencing is due to a combination of natural causes and human causes. Let's take a look at the natural causes.

There are several factors that contribute to our current climate change, some man-made and some natural.
climate change causes

Greenhouse Gases

Greenhouse gases are gases in our atmosphere that cause a greenhouse effect, where heat from the sun is trapped in the atmosphere, causing the climate to warm. This is the same effect that you experience if you get into your car on a hot day to find that it is much hotter inside the car than it is outside. Not all atmospheric gases are greenhouse gases; oxygen and nitrogen, for example, have no bearing on the greenhouse effect. The biggest greenhouse gases are carbon dioxide, water vapor, and methane. Throughout Earth's history, the levels of these gases have changed, and so the amount of heat trapped in the atmosphere has also changed.

Plant Power

Plants and algae have actually played a pretty huge role in the history of Earth's climate. Because they undergo photosynthesis, or the process of turning carbon dioxide and water into oxygen and glucose, they have helped to shape Earth's atmosphere. Back before plants and algae evolved, Earth's atmosphere was high in carbon dioxide and low in oxygen. The climate was much warmer than it is today, since the greenhouse effect was stronger, trapping more of the sun's heat. As plants evolved, they turned more carbon dioxide into oxygen, slowly decreasing the greenhouse effect and cooling the planet. If there were suddenly no more plants or algae on Earth's surface, the amount of carbon dioxide would skyrocket and Earth's climate would rapidly heat up!

Volcano Venting

Another way for greenhouse gases to get into the atmosphere is through volcanic activity. Volcanoes vent huge amounts of water vapor and carbon dioxide when they erupt. Considering how small volcanoes are compared to the size of Earth, this activity doesn't have a very large impact on the climate, though that wasn't always the case. If we go back four billion years, when Earth was still young, hot, and devoid of life, there was significantly more tectonic activity (the movement of Earth's plates), resulting in constant earthquakes and volcanic action. This level of activity had a much bigger impact on climate then than it does today.

The Sun's Heat

So Earth's atmosphere traps a lot of heat, which determines our climate. Where does that heat originate? The sun! Our sun is the ultimate source of the heat in our atmosphere. Though it may not seem like it, the sun goes through cycles of its own, phases where it puts out more heat or less heat. These cycles are due largely to the presence of sunspots, which are essentially cool patches on the sun's surface that appear darker when observed and last about 11 years. We have measured how much the sun's heat output changes during these cycles, though it seems to have a fairly small impact on Earth's climate.

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