D4.3.1 Anthropogenic causes of climate change Notes

Anthropogenic Causes of Climate Change

1. Climate change is driven by both natural and anthropogenic (human-caused) factors.
2. In recent times, the anthropogenic causes of climate change have become a primary focus, particularly those related to the release of greenhouse gases such as carbon dioxide (CO₂) and methane (CH₄) into the atmosphere.
   1. Human activities have significantly increased the concentrations of carbon dioxide (CO₂) and methane (CH₄) in the atmosphere.
   2. These gases trap heat, amplifying the greenhouse effect and driving global warming.

Anthropogenic Increase in Carbon Dioxide (CO2)

1. Burning of Fossil Fuels

1. One of the primary anthropogenic sources of carbon dioxide is the burning of fossil fuels, including coal, oil, and natural gas.
2. These fuels are used in energy production, transportation, and industrial activities.
3. When fossil fuels are burned, the carbon stored in them is released into the atmosphere as carbon dioxide.

2. Deforestation

1. Another significant contributor to CO2 emissions is deforestation.
2. Trees naturally absorb CO2 during photosynthesis, and when forests are cleared for agriculture, urban development, or logging, this carbon is released back into the atmosphere.
3. Additionally, the loss of trees reduces the Earth's ability to absorb CO2, compounding the problem.

3. Industrial Processes

1. Certain industrial processes, such as cement production and the manufacture of steel, release CO2 as part of their chemical reactions.
2. In cement production, limestone (CaCO3) is heated to produce lime (CaO), releasing CO2 as a by-product.

Anthropogenic Increase in Methane (CH4)

1. Agriculture

1. Agricultural activities are the largest source of anthropogenic methane emissions.
2. Methane is released during the digestive processes of ruminant animals (like cows, sheep, and goats) through enteric fermentation.
3. Methane is also produced in manure management and rice paddies.

2. Landfills

1. Landfills, where organic waste such as food, paper, and yard clippings decompose, are another significant source of methane.
2. As waste breaks down anaerobically (without oxygen) in landfills, methane is produced and can escape into the atmosphere if not properly managed.

3. Fossil Fuel Extraction and Transport

1. Methane is also released during the extraction, processing, and transportation of natural gas and oil.
2. This occurs through leaks in infrastructure or the flaring of gas during extraction processes.

Correlation vs. Causation

1. While data from Antarctic ice cores show a positive correlation between global temperatures and atmospheric CO₂ concentrations over hundreds of thousands of years, it is important to recognize the difference between correlation and causation.
2. The fact that these two variables have moved in tandem does not necessarily mean that one causes the other.
3. However, a growing body of evidence from multiple sources, such as laboratory studies and climate models, supports the causal link between increasing CO₂ concentrations and global warming.
   1. Positive correlation: The increase in atmospheric CO₂ has closely followed the rise in global temperatures over the past century, which is an observed pattern.
   2. Causation: Other scientific evidence, such as radiative forcing calculations and global climate models, demonstrates that the increase in CO₂ due to human activity is a major driver of the current warming trend.

Feedback Loops: Amplifying the Impact

1. Melting Permafrost: Thawing permafrost releases stored methane, further enhancing warming.
2. Deforestation: Loss of forests reduces the Earth's capacity to absorb $CO_2$, creating a cycle where more $CO_2$ remains in the atmosphere.

Addressing the Challenge

1. Reducing Emissions: Transitioning to renewable energy sources (solar, wind) can significantly cut $CO_2$ emissions.
2. Carbon Sequestration: Reforestation and the restoration of peatlands can capture and store carbon.
3. Methane Management: Improving waste management and reducing methane leaks from fossil fuel infrastructure are critical steps.