Chapter 26. Chapter 26: Climate Change

What natural and anthropogenic factors affect climate...?

Why You Should Care

The Earth’s climate is a complex web of interactions between sun, air, land, and water. The temperature of the Earth has changed over time—just 10,000 years ago, the Earth was emerging from an ice age. The Earth’s temperature is kept warmer by gases that absorb sunlight and heat radiated by the Earth’s surfaces: This is the greenhouse effect.

The greenhouse effect is affected positively and negatively by both natural and anthropogenic factors. Positive factors increase warming by building on themselves and negative factors decrease warming by damping themselves down. Our recent focus on the planet shows us that there are natural cycles (called Milankovitch cycles) that vary over long periods and depend on the Earth’s orbit and tilt on its axis. These cycles can either warm or cool the Earth depending on where they are in the cycle. More recently, we have discovered that anthropogenic (human-caused) factors can affect the greenhouse effect (positively, by increasing greenhouse gas emissions), albedo (negatively, by releasing air pollution to create more clouds), and carbon storage (positively, by deforestation).

Today, the fact is that humans are emitting more greenhouse gases and changing both positive and negative forcers. Both natural and anthropogenic factors are changing, and scientists are working to understand each of these factors in more detail but the net value of the forcers is positive and growing.