ENVR101 Climate Change and Greenhouse Gases

New Zealand Carbon Emissions (2020 Data)

  • Primary source of carbon dioxide: vehicles.
  • Methane is a critical greenhouse gas primarily from agriculture (90% from livestock).
  • Methane's impact reflects its potency as a greenhouse gas.

Global Methane Budget

  • Natural sources: wetlands (167 million tons), volcanoes, lakes, permafrost (64 million tons).
  • Human sources: fossil fuels (106 million tons), agriculture and waste (188 million tons).
  • Total emissions exceed intake, leading to an annual increase of methane in the atmosphere.

Methane as a Greenhouse Gas

  • Higher efficiency compared to carbon dioxide.
  • Global Warming Potential (GWP): Carbon dioxide = 1, Methane = 86 (initially), 34 (after 100 years).
  • Methane reacts with oxygen, producing carbon dioxide and volatile organics (carcinogens).
  • Methane levels measured in parts per billion (ppb), showing a steady upward trend.

Sources of Methane

  • Agriculture: Cows (ruminant animals) produce methane due to bacteria in their gut.
  • Rice: Rice paddies produce methane in low-oxygen water environments.
  • High Arctic: Melting permafrost releases trapped methane, posing a significant risk.

New Zealand's Greenhouse Gas Emissions

  • Significant agricultural emissions of methane, primarily from dairy farming.
  • Challenges in reducing methane emissions from agriculture due to economic reliance on the dairy industry.
  • Need to address methane emissions from agriculture and carbon dioxide emissions from vehicles.

Global Carbon Dioxide Levels

  • Measurements from Mauna Loa in Hawaii show a steady increase since 1960 (from 310 ppm to 427 ppm).
  • Seasonal variations: Carbon dioxide levels drop during spring and summer due to deciduous trees in the Northern Hemisphere.

Ice Core Data

  • Ice cores from Greenland and Antarctica contain air bubbles that reveal past atmospheric composition.
  • Carbon dioxide and temperature are correlated over glacial-interglacial cycles.
  • Current carbon dioxide levels are off the scale compared to the past 400,000 years.

Future Climate Expectations

  • Global temperatures are expected to increase by more than 3 degrees Celsius.
  • Radiative forcing scenarios (RCPs) model potential temperature increases based on added energy in the atmosphere.
  • Paris Agreement goals: keep warming well below 2 degrees Celsius, efforts to limit to 1.5 degrees Celsius.

Ocean Impacts

  • Oceans absorb 70% of carbon and 50% of the expected heating.
  • Absorption of carbon dioxide leads to ocean acidification.
  • Increase in free hydrogen lowers the pH, causing more acidic conditions.