Climate Change Chapter UNR1601

Study Notes

Refers to variations in the average state and statistics of the climate over time, beyond individual weather events.
Variability can be attributed to natural internal processes (internal variability) or changes due to natural or human external forces (external variability).

Involves alterations in weather patterns and related changes in oceans, land surfaces, and ice sheets, manifesting locally, regionally, or globally over decades or longer.

Earth's temperature is influenced by the balance between energy received from the Sun and energy released to space.
Formula: Earth's stored energy = Solar energy received - Energy released to space.

Greenhouse gases (water vapor, CO2, methane, and nitrous oxide) absorb and re-radiate heat, warming the Earth's surface and lower atmosphere.
Increased greenhouse gas concentrations enhance the warming effect.

Any activities affecting the global energy balance (GEP) that lead to climate change are termed climate forcing processes.
Classified into:
- Internal Climate Forcing Processes: Operate from within the Earth.
- External Climate Forcing Processes: Originate outside the Earth.

Internal factors include oceans, continental drift, atmosphere, water cycle, clouds, ice and snow, land surfaces, volcanic eruptions, and human activity.
External factors primarily involve solar energy variation and Earth's orbital changes.

Oceans: Key role in moisture regulation and heat storage/redistribution; significant carbon dioxide absorption.
Continental Drift: Slow movement impacts climate by altering landmass positions and ocean currents.
Atmosphere: Stores heat from solar energy; greenhouse gases and aerosols significantly influence climate regulation.
Water Cycle: Increases in temperature elevate evaporation and ice melting, with water vapor being a potent greenhouse gas.
Clouds: Reflect solar energy and trap heat; their variability can significantly influence climate patterns.
Ice and Snow: Reflect heat, cooling the earth; ice melting contributes to heat absorption by oceans.
Land Surfaces: Affects precipitation and heat absorption; deforestation can transform carbon sinks into greenhouse gas sources.
Volcanic Eruptions: Release aerosols and gases that can lead to cooling by reflecting sunlight.
Anthropogenic Factors: Include greenhouse gas emissions from activities like coal mining and deforestation.

Global average temperatures show a sustained warming trend, with significant data from land and ocean measurements since 1850.
Arctic sea ice extent and June snow cover in the Northern Hemisphere have dramatically decreased.
Average sea levels have risen approximately 16 cm since the late 19th century, with recent rates at about 3.6 mm per year.
Atmospheric CO2 concentrations measured at remote sites have steadily risen since 1958, reflecting human influence.
Paleoclimatology data extends climatic records back millions of years through various natural sources.
Ocean acidification observed with increased atmospheric CO2 correlating with decreasing seawater pH.