Natural Events That Change Climate

By the end of this lesson, you will be able to use scientific evidence to explain how natural events change Earth's climate.

Climate is the pattern of temperature, rainfall, and other weather conditions in a place averaged over many years, so it is different from the weather you see outside today. Several natural events can nudge that long-term pattern warmer or cooler, and scientists find proof of these changes in ice cores, tree rings, rock layers, and ocean temperature records.

Think about getting into a car that has been parked in a Texas parking lot in July. Sunlight passes through the windows, the seats soak it up, and the heat gets trapped inside. Greenhouse gases, which are gases like carbon dioxide and water vapor that trap heat in the atmosphere, act like those car windows for the whole planet. Volcanic eruptions, decaying plants, and the ocean all release these gases, while oceans and growing forests absorb them. When more gas is released than absorbed, Earth warms.

Some natural events cool the planet instead. A huge volcanic eruption blasts ash and tiny droplets high into the atmosphere, where they reflect sunlight back to space for a year or two. Tree rings from those years are thin, showing cooler, shorter growing seasons. A large meteor impact can throw up so much dust and soot that sunlight is blocked for much longer, which is one reason many species died out long ago.

Ocean currents matter too, because they move enormous amounts of warm and cold water around the globe. When a current shifts abruptly, rainfall patterns and temperatures on nearby continents can change within a few years, and sediment layers on the seafloor record those shifts.

Try it: If a giant volcano erupted this year and filled the upper atmosphere with reflective ash, would you expect next summer's average temperature to be warmer or cooler, and why?