In-Depth Notes on Climate Change and Greenhouse Effect

Solar Radiation:
- Sun emits solar radiation primarily as visible light.
- Earth absorbs solar radiation, converting it into heat (infrared radiation).
Heat Emission:
- Heat is radiated upwards towards the atmosphere, which contains greenhouse gases (less than 1% of the atmosphere).
- Main Greenhouse Gases:
- H2O vapor (water vapor)
- CO2 (carbon dioxide)
- CH4 (methane)
- N2O (nitrous oxide)
Heat Dynamics:
- Some heat escapes into space, while some is absorbed by greenhouse gases, warming them.
- Some heat is reflected back to Earth, contributing to warming.
- The longer heat remains in the troposphere, the warmer the Earth’s surface becomes.
Historical Context:
- The greenhouse effect theory was established in 1896 and has been extensively studied in atmospheric science.

Solar Energy Absorption and Reflection:
- Solar energy absorbed at the surface generates longwave radiation.
- Different forms of radiation are generated:
- Ultra violet (UV)
- Visible light
- Infrared radiation
- Micro-waves and radio waves
Energy Cycle:
- Loss of some longwave radiation to space occurs.
- Surface continues to gain heat and emit longwave radiation repeatedly.

Establishment:
- Formed in 1988 by the U.N. and World Meteorological Society.
Mission:
- Document past climates and predict future climates.
- Comprises over 2,500 scientists from over 130 countries.
Key Findings (2007 Report):
- 90-99% likelihood that the lower atmosphere is warming due to human activities.
- This conclusion has been consistent in subsequent reports.

Temperature Increases:
- Average global surface temperature rose by 1.1°C (1.9°F) since 1880, most significantly since 1980.
Carbon Dioxide (CO2) Emissions:
- Increased by approximately 230% since 1970 (14.9 billion metric tons in 1970 to 34.8 billion metric tons in 2020).
Historical CO2 Levels:
- CO2 concentrations are at their highest in ~650,000 years.
Warmest Years:
- The 10 warmest years on record have all occurred since 2010.
Arctic Warming:
- Arctic temperatures rising twice as fast as the global average in the past 50 years.
Melting Glaciers and Rising Sea Levels:
- Increased melting of glaciers and ice sheets; global sea level rose 4-8 inches last century, mainly due to melting ice (1/3) and thermal expansion (2/3).

Industrial Revolution Impact:
- Since the industrial revolution (~275 years ago), greenhouse gas emissions have substantially increased proportionally with human activities (agriculture, industry, transportation).
Current CO2 Levels:
- Increased from 280 ppm 265 years ago to 418 ppm in 2022; primary driver of global warming.
Atmospheric Lifetime of CO2:
- Ranges from 300-1,000 years with 450 ppm being a tipping point for major irreversible climate changes.

Top Five Emitters:
- China, U.S., India, Russia, Japan.
Comparative Emissions:
- China produces over twice as much CO2 as the U.S.; a significant portion of its emissions (25%) comes from goods exported to the U.S. and E.U.
Per Capita Emissions:
- U.S. has over twice the per capita CO2 emissions of China, and over eight times that of India.

Methane Emissions:
- Increased by 60% in the last 275 years; significant contributor to warming (25x more potent than CO2).
- Emissions expected to rise again due to thawing permafrost and methane hydrate releases.
- Methane's atmospheric lifetime is ~12 years.
Nitrous Oxide (N2O) Emissions:
- Increased 20% in the last 275 years, predominantly from agricultural nitrogen fertilizers.
- Approximately 300x stronger than CO2; atmospheric lifetime is ~100 years.

CO2 Absorption:
- Oceans absorb half of the CO2 produced since the industrial revolution; moderate temperature by absorbing around 30% of human-emitted CO2.
Impact of Ocean Temperature:
- Warming of oceans reduces their ability to store CO2; rising temperatures could reverse this beneficial absorption effect, creating a positive feedback loop.
Ocean Acidity:
- Increased CO2 leads to higher acidity levels; pH decreased from 8.15 in 1950 to 8.05 in 2020, affecting marine life (e.g., corals, mollusks).

Temperature Rise:
- Rapid temperature change is concerning as previous natural changes occurred over much longer timescales (10,000s - 100,000s of years).
Projected Temperature Effects:
- 2°C warming leads to adverse impacts such as more frequent droughts and severe weather, affecting biodiversity and human habitats.

Global Cooperation:
- Tackling climate change demands a global cooperative effort and recognition of the long-term impacts of emissions.
Reduction Strategies:
- Focus on reducing emissions and preparing for unavoidable climate changes through sustainable practices, improved energy efficiency, and shifts to non-carbon energy sources.

Kyoto Protocol (1997):
- Required developed countries to reduce emissions by 5.2% below 1990 levels by 2012; exempted developing countries from strict reductions to support their economic growth.
Paris Agreement (2016):
- Aims for global greenhouse gas emission reductions, with as strong yet achievable goals.

Prepare for Climate Change:
- Implement adaptation measures such as crop modifications, infrastructure designed to withstand extreme weather, and sustainable land management.
Wildlife Conservation:
- Enhance biodiversity protection through wildlife corridors and habitat conservation in response to changing ecosystems.

Global Sunscreen:
- The ozone layer in the lower stratosphere protects Earth from harmful UV radiation; declining due to chlorofluorocarbons (CFCs).
Montreal Protocol:
- Efforts to phase out ozone-depleting substances successfully reduced CFC emissions, but full recovery of the ozone layer will take decades due to the persistence of existing chemicals.

Unified Global Response Required:
- Addressing climate change is a complex and multifaceted challenge that requires coordinated global policies, investments in sustainable technologies, and commitment to reducing greenhouse gas emissions to ensure a stable climate for future generations.