Earth's Energy Balance and Climate Change

Earth's Energy Balance and Climate Change

• Earth's temperature is determined by the balance of incoming and outgoing energy.
• Incoming solar energy is absorbed, warming Earth.
• Energy released back into space cools Earth.
• Natural and human factors affect Earth's energy balance.

Historical Climate Data

• Scientists study indirect climate measures (ice cores, tree rings, etc.) to understand past climate.
• Ice cores provide thousands of years of atmospheric gas data, revealing past temperatures and climate factors.
• Earth's climate naturally fluctuates between warm and cold periods (e.g., ice ages).
• Before the Industrial Revolution, natural factors (volcanoes, solar activity) explained temperature variations.

Greenhouse Effect and GHGs

• Sunlight reaching Earth is either reflected or absorbed.
• Absorbed energy is released as heat (infrared radiation).
• Greenhouse gases (GHGs) absorb and re-emit infrared radiation, trapping heat and warming the planet.
• Key GHGs: water vapor, carbon dioxide, methane, nitrous oxide, fluorinated gases.
• Human activities have increased GHG levels since the Industrial Revolution.
• CO2 is the primary GHG contributing to recent climate change, despite lower global warming potential, higher abundance makes it significant.
• Human activities (e.g., burning fossil fuels, deforestation) significantly increase atmospheric CO2.
• CO2 levels have increased from ~280 ppm to ~410 ppm since the 18th century, exceeding levels in at least 800,000 years.
• Human CO2 emissions exceed volcanic emissions by more than 135 times.
• Methane (CH4) has a much higher global warming potential than CO2, but lower relative warming effect due to lower concentrations.
• Methane sources include wetlands and livestock.
• Nitrous oxide (N2O) has a higher global warming potential than CO2, but lower relative warming effect due to low atmospheric concentration.
• Agriculture & fertilizers are major sources of N2O.

Other Causes of Climate Change

• Solar activity affects the intensity of sunlight reaching Earth. Short-term solar variations have minimal effect on recent warming trends.
• Earth's orbit, axial tilt, and position affect sunlight over long timescales, not recently.
• Changes in reflectivity (albedo), influenced by surfaces and aerosols, affect climate.
• Aerosols (e.g., volcanic ash) can cool the planet by reflecting sunlight, while others (e.g., black carbon) warm it.
• Deforestation, urbanization, etc., affect regional albedo but have less global impact.
• Volcanic activity can briefly cool the planet.

Future Climate Change

• GHGs will continue to increase unless emissions decrease substantially; future warming expected.
• Ocean temperatures take time to respond, leading to future warming even if emissions stabilize.
• Climate change impacts various sectors, including food, water, infrastructure, and health.
• Factors influencing future climate change: GHG concentrations, solar activity, natural emissions.

Future Temperature, Precipitation, Ice & Sea Level Changes

• Climate models project continued warming, reduced ice extent, and rising sea levels.
• Sea ice is declining, glaciers shrinking, permafrost melting.
• Significant sea-level rise expected in the next century, influenced by thermal expansion and ice melt.
• Precipitation patterns will shift regionally—some regions will experience more or less precipitation, heavier rainfall expected.
• Rising ocean temperatures will influence ocean acidification.

Future Ocean Acidification & Disease Spread

• Ocean absorbs atmospheric CO2, leading to ocean acidification.
• Ocean acidification harms marine life, especially those that rely on calcium carbonate.
• Warmer temperatures expand disease vectors, potentially increasing infectious disease risk and range.

Climate Justice

• Climate change disproportionately affects developing nations.
• Historically stable climates are altered by warming, impacting global societies.
• Developed nations are argued to shoulder greater responsibility for addressing climate change impacts on developing nations.
• Individual actions are valuable but insufficient; government policies are crucial.