Climate Change and Natural Forces: Lecture Notes

Introduction

• Common misconception: "Climate changes naturally" (e.g., ice ages, palm trees in Antarctica)
• Importance of understanding unique levels of education and experience
• Opportunity to educate and debunk misconceptions

Natural Forces and Climate Change

• Natural forces influence climate change throughout Earth's history
• Climate scientists study these natural cycles to understand human-caused climate change
• Climate models factor in natural forces; human impact is necessary to explain current changes

Big Picture of Earth's Climate

• Focus on temperature as a measure of climate
• Temperature relates to atomic movement (more jiggliness = higher temperature)
• Heat is energy in motion; energy transfer impacts climate

Energy from the Sun

• Sun as the primary energy source for Earth
• About one-third of solar energy is reflected back into space
• Absorbed energy heats air, water, and land, leading to thermal infrared radiation energy

Greenhouse Effect

• Greenhouse gases (e.g., CO2, methane) absorb and re-radiate energy, warming the atmosphere
• The greenhouse effect is necessary for life but can lead to excessive warming
• Current levels of greenhouse gases lead to a significant increase in temperature

Energy Budget of Earth

• Earth's energy budget: balance of incoming solar energy and outgoing energy
• Positive energy budget leads to warming
• Every square meter of Earth's surface has absorbed approximately 0.57 joules of energy per second since 1971
• Total excess energy accumulation equates to massive heating effects

Climate Forcing

• Climate forcing: the difference between incoming and outgoing energy
• Positive forcing leads to warming, while negative forcing leads to cooling

Natural Climate Influences

• Solar Cycles:
  • Sun's brightness varies over time; average brightness has been steady, not causing current warming
• Volcanoes:
  • Volcanic eruptions affect energy balance; typically have a cooling effect due to ash and sulfur
  • Eruptions can release CO2 but human emissions far exceed volcanic emissions
• Orbital Changes (Milankovitch Cycles):
  • Earth's orbit changes affect solar radiation and climate over long periods
  • Not sufficient to explain current warming trends

Other Factors Affecting Climate

• Reflectivity of surfaces (e.g., ice caps' albedo)
• Forest clearing impacts on heat absorption

Conclusion

• Climate scientists account for natural cycles and factors in climate models
• Human activities primarily responsible for current climate change
• Importance of recognizing human impact on climate and potential for solutions
• Understanding natural cycles should not lead to complacency in the face of human-caused climate change

Call to Action

• Awareness of climate change as a real and pressing issue
• Acknowledgment of the potential for human resolution of climate problems

Additional Resources

• PBS show: America Outdoors Understory with Baratunde Thurston
• Importance of curiosity and continued education on climate issues