Climate Science Overview

Climate Variability

• Climate variability describes changes in the average state and other statistics, like extreme weather events, of the climate. These changes occur over various temporal and spatial scales greater than individual weather events.
• Variability can result from internal processes within the climate system (internal variability) or changes in natural or human-induced external factors (external variability).

What is Climate Change?

• Climate change is a shift in the pattern of weather, including changes in oceans, land surfaces, and ice sheets. These changes define Earth's local, regional, and global climates over decades or more.

Energy Balance

• Earth's temperature is regulated by a balance between incoming solar energy and outgoing energy.
• Global Energy Balance (GEB) considers Earth's stored energy: incoming solar energy versus energy released back into space.

The Greenhouse Effect

• Greenhouse gases (water vapor, carbon dioxide, methane, nitrous oxide) absorb and re-emit infrared radiation, which warms Earth's surface and lower atmosphere.
• Adding more greenhouse gases intensifies this effect, leading to a warmer planet.

Climate Forcing

• Climate forcing refers to any process influencing Earth's stored energy, either increasing or decreasing it. This leads to climate change.
• These forces can be external (e.g., variations in solar energy) or internal (e.g., ocean currents). A climate forcing can cause an imbalance in energy at the top of Earth's atmosphere, either due to external factors (e.g., natural changes in the sun's energy) or to human activities.

Climate Forcing Processes

• Internal climate processes operate within Earth (e.g., ocean currents, atmospheric circulations, water cycle)
• External climate processes operate from outside Earth (e.g., changes in solar energy, Earth's orbit)

Climate Change

• Climate change encompasses both natural (e.g., variations in solar energy, volcanic eruptions) and human-induced (e.g., greenhouse gas emissions) climate forcing processes.

External Climate Forcing Processes

• Variations in solar energy received from the sun.
• Changes in Earth's orbit around the sun.

Internal Climate Forcing Processes

• Oceans (influence moisture, heat distribution, CO2 absorption).
• Continental Drift (changing landmasses, ocean currents, wind patterns).
• Atmosphere (greenhouse gases, aerosols, temperature regulation).
• Water Cycle (evaporation, precipitation, temperature).
• Clouds (reflecting sunlight, trapping heat).
• Ice and Snow (reflecting heat, melting and sea levels).
• Land Surfaces (affecting cloud cover, water runoff, greenhouse gas exchange).
• Volcanic Eruptions (releasing particles, cooling the planet).
• Human Causes (anthropogenic activities influencing atmospheric composition and energy transfer).

Evidence of Climate Change

• Average global sea levels have risen approximately 16 cm since the late 19th century.
• Sea level rise is now accelerating, with estimates ranging from the last decade centred around 3.6 mm per year.
• Sea level uncertainty has decreased with more data collecting points.

Consequences of Climate Change

• Melting glaciers and ice sheets.
• Rising sea levels.
• Increased frequency of extreme weather events: heavy rainfall, drought, hurricanes.
• Decline in crop productivity.
• Ecosystem changes.
• Increased global temperatures
• Acidification of seawater.