Anthropogenic Climate Change PP

By the end of this section, you will be able to do the following:
- Define global climate change
- Summarize the effects of the Industrial Revolution on global atmospheric carbon dioxide concentration
- Describe three natural factors affecting long-term global climate
- List two or more greenhouse gases and describe their role in the greenhouse effect

Biomes and Climate:
- All biomes are affected by global conditions such as climate, which shapes each biome’s environment.
- Scientists studying climate have noted significant changes over the last sixty years.
Definition of Global Climate Change:
- Global climate change refers to altered global weather patterns, particularly a worldwide increase in temperature, primarily due to rising levels of atmospheric carbon dioxide.

Common Misconception:
- A specific weather event (e.g., a cool week in June) does not provide evidence of global climate change, as it is a short-term phenomenon and not indicative of long-term climate trends.
Definitions:
- Climate:
- Refers to the long-term, predictable atmospheric conditions of a specific area.
- Characterized by consistent seasonal temperature and rainfall ranges.
- Represents “average” weather over many years.
- Weather:
- Refers to short-term atmospheric conditions, typically forecasted over 48-hour cycles with some long-range forecasts.
Example to Understand Climate vs. Weather:
- Planning an outdoor event:
- You would consider climate (long-term averages) when planning for summer rather than winter due to predictable weather patterns.
- Specific weather predictions on a given day are less reliable.

Three Areas of Study for Climate Change:
- Evidence of current and past global climate change
- Drivers of global climate change
- Documented results of climate change
Importance of Separating these Aspects in Media Reports:
- Reports often confuse changes in data with the drivers of climate change, requiring clarity in interpretation.

Indirect Measurement of Climate Variables:
- Scientists cannot directly measure past climatic variables but rely on indirect evidence like historical data.
Antarctic Ice Cores:
- Obtained through drilling into ice sheets or glaciers, deeper samples correlate with earlier time periods.
- Contains air bubbles and biological evidence that reveal temperature and carbon dioxide data.
- Estimates Earth’s temperature over the past 400,000 years.
- The graph reflecting temperature anomalies illustrates periodic cycles of increasing and decreasing temperature.
- The atmospheric concentration of carbon dioxide has historically cycled between 180 and 300 parts per million (ppm).
Notable Temperature Anomalies:
- Medieval Climate Anomaly (900-1300 AD):
- Slightly warmer conditions (0.10 °C – 0.20 °C above normal) allowed Vikings to colonize Greenland.
- Little Ice Age (1550-1850 AD):
- Cooling of less than 1 °C, resulting in harsh winters and impacting the climate.
- Industrial Era Anomaly:
- Coincides with significant changes due to the Industrial Revolution starting around 1750.

Indirect Evidence Methods:
- Ice cores, boreholes, tree rings, glacier lengths, pollen, and ocean sediments clarify factors driving climate change.
Natural Drivers of Climate Change (Pre-Industrial Era):
- Milankovitch Cycles:
- Effects of Earth's orbital changes on climate; cycles range from 19,000 to 100,000 years.
- Solar Intensity Variations:
- Amount of solar energy emitted by the sun; correlated with Earth's temperature changes.
- Volcanic Eruptions:
- Release gases and solids have been impacting the climate for years.
- Generally results in cooling, exemplified by the cooling following the 1783 Iceland eruptions (haze-effect cooling).

Greenhouse Effect:
- Greenhouse gases trap heat similar to greenhouse panes.
- Key greenhouse gases include:
- Carbon Dioxide (CO2)
- Methane (CH4)
- Water Vapor
- Nitrous Oxide
- Ozone
- About half of the solar radiation passes through these gases and is converted into thermal (infrared) energy, with greenhouse gases reflecting much of this thermal energy to Earth.
Historical Atmospheric CO2 Levels:
- CO2 levels naturally cycled; current concentrations exceed historical limits due to human activity.
- From 1950 to 2011, CO2 levels increased from approximately 280 ppm to 392 ppm.

Key Contributions to Carbon Emissions:
- Burning of fossil fuels: gasoline, coal, and natural gas.
- Deforestation, cement production, agricultural practices, and land clearing significantly release CO2.
Methane Emission Sources:
- Produced through anaerobic decomposition in conditions with organic matter underwater or in animal intestines, also released from natural gas fields and landfills.
- Clathrate melting increasingly contributes to methane release.
Positive Feedback Loop:
- Warming oceans accelerate clathrate melting; the release of methane further accelerates global warming.

Historical Extinction Events:
- Example: The Permian Extinction (around 251 million years ago), where approximately 70% of terrestrial species and 84% of marine species went extinct due to climate changes.
Current Climate Change Effects:
- Geological evidence shows the present-day effects of climate change:
- Glacier recession observed in Glacier National Park, where glacial numbers dropped from 150 (in 1850) to 24 (by 2010).
- Mass loss from Greenland and Antarctic ice sheets.
Sea Level Rise:
- Global sea level is rising on average at 1.8 mm per year; rates between 1993 and 2010 increased to 2.9-3.4 mm per year.
Biological Effects of Climate Change:
- Organisms are affected by temperature and precipitation changes influencing distribution and life cycles.
- Example: 385 plant species in Great Britain flower 4.5 days sooner than recorded earlier in the last 40 years.
- Mismatches between the timing of plant flowering and pollinator emergence threaten ecosystem balance.