Climate Change: Can We Blame Nature?

Before humans, climate changes were caused entirely by natural factors that affect how much solar energy reaches earth.  More solar energy increases temperatures. Less solar energy decreases temperatures. Factors include:

• Variations in Earth’s orbit over the span of tens of hundreds of thousands of years. These changes probably caused past cycles of ice ages.
• Small ups and downs in the sun’s intensity occur in cycles.
• Aerosols ejected by volcanic eruptions and meteor strikes can block sunlight, causing cooling.
• Variations in the levels of greenhouse gases in the atmosphere.

Scientists have found no evidence that natural factors alone could have caused recent climate change.

Photo Credits: temperature graph: US-EPA, CO2 graph: NASA