DL PPT6 Evidence supporting enhanced greenhouse effect

Changes in climate can span thousands of years.
Current climate change is driven by the enhanced greenhouse effect, which releases extra greenhouse gases into the atmosphere, trapping more solar energy.
Disruption in Earth’s climate equilibrium has led to a significant increase in global average surface temperature.
Scientific modeling indicates human activities are the primary cause of global warming.

The natural greenhouse effect is essential for sustaining life on Earth.
Solar energy penetrates the atmosphere and warms the Earth's surface.
The atmosphere's low density prevents significant heating before solar energy reaches the surface.
The Earth re-radiates energy (infra-red part of the spectrum) back into space, where greenhouse gases trap some of it, maintaining temperature.

Without the greenhouse gases, nighttime temperatures could drop to approximately -100℃ while daytime temperatures could rise to about 80℃.
Key greenhouse gases: carbon dioxide (CO2), water vapor (H2O), methane (CH4), nitrous oxide (N2O), and ozone (O3).
Greenhouse gas levels have surged since the Industrial Revolution, heightening the greenhouse effect.

Atmospheric concentrations of CO2 have significantly changed over the past centuries.
Current CO2 levels are 421 ppm (0.04%) as of May 2022, a 50% increase since the mid-18th century.
Methane concentration is 1911.8 ppb as of May 2022, with over a doubling effect, impacting global temperature significantly.

Carbon dioxide is the main greenhouse gas of concern.
Major source: burning fossil fuels (coal, petrol, oil, natural gas) produces CO2 and other pollutants.

Deforestation for agriculture and urban development increases atmospheric CO2 by releasing carbon stored in trees.
Trees help anchor soil; their removal allows soil erosion, contributing to carbon release.
Forests play a critical role in absorbing CO2 through photosynthesis; losing them exacerbates the greenhouse effect.
Increased deforestation disrupts evaporation, leading to dry air, low humidity, and decreased precipitation, creating drought-prone conditions.

Natural methane sources: organic decay in wetlands, termites, ocean emissions, and thawing methane hydrates in permafrost.
Human contributions include energy production, livestock emissions, biomass burning, and landfill decomposition.

Oceans act as carbon sinks, absorbing carbon and up to 90% of solar radiation.
Warmer oceans absorb less solar radiation and accelerate sea ice melting.
Melting sea ice reduces the reflection of solar radiation and increases water heat absorption, raising global temperatures further.

Permafrost consists of frozen ground storing carbon from previous plant material.
Regions with permafrost include high mountains and polar areas (Russia, Canada, Alaska).
The carbon stored in permafrost is double that present in the atmosphere, making its thawing a severe climate change threat.
Melting permafrost may release trapped bacteria and viruses, raising ecological concerns.

Global warming affects sea levels via:
- Melting glaciers and ice sheets.
- Thermal expansion of ocean water.
Average sea level rise is about 3mm per year (2mm from melting and 1mm from thermal expansion).