Global climate change refers to altered global weather patterns, especially a worldwide increase in temperature, and resulting changes in climate due mainly to rising levels of atmospheric carbon dioxide.
It's crucial to understand the difference between climate and weather.
Climate
Climate refers to long-term, predictable atmospheric conditions of a specific area or biome.
It is characterized by consistent seasonal temperature and rainfall ranges.
Climate does NOT address specific, short-term weather events (e.g., rain on a particular day).
Examples:
Desert climate: Associated with hot temperatures.
Tropical rainforest: Associated with wet and humid conditions.
Weather
Weather refers to the conditions of the atmosphere during a short period of time.
Weather forecasts are typically 48-hour cycles.
Long-range forecasts are less reliable.
Weather is temperamental and can vary significantly even in areas with a consistent climate.
Example: Deserts can experience cold weeks despite being typically hot.
Climate Change Impact
Climate change is causing shifts in the expected climate of biomes.
Deserts are getting colder, while cold areas are warming up.
This occurs over a long period and is associated with temperature changes and rising water levels (streams, lakes, oceans), which serves as evidence.
Evidence for Climate Change
Scientists cannot directly measure past climate variables.
Indirect measurements are used, such as Antarctic ice cores.
Ice cores are samples of polar ice drilled from ice sheets or high mountain glaciers.
Younger ice is near the top, older ice near the bottom.
Air bubbles and biological evidence trapped in the ice reveal temperature and carbon dioxide data.
Antarctic ice cores have been analyzed to estimate Earth's temperature over the past 400,000 years.
The amount of carbon dioxide gas trapped in the core indicates the carbon dioxide levels present in the atmosphere at that time.
Ice Core Data Interpretation
Graphs from ice core data show temperature changes over Earth's history.
0∘C refers to long-term average temperatures.
Temperatures > 0∘C exceed Earth's long-term average, while temperatures < 0∘C are below average.
Before the late 1800s, Earth has been as much as −9∘C cooler and 3∘C warmer.
There is a direct correlation between CO2 concentrations and temperature.
Vostok Station Data
Ice at the Russian Vostok Station in East Antarctica was laid down over 420,000 years, reaching a depth of over 3,000 meters.
CO2 trapped in ice reveals past atmospheric CO2 concentrations.
Temperatures were determined from the amount of deuterium (non-radioactive isotope of hydrogen) present.
When analyzing graphs, examine the axes (temperature, years, CO2 concentration) to understand the information presented.
Temperature Anomalies
Two significant temperature anomalies in the last 2,000 years: the Medieval Climate Anomaly and the Little Ice Age.
The third temperature anomaly aligns with the Industrial Era.
Medieval Climate Anomaly
Occurred between 900-1300 AD.
Slightly warmer conditions prevailed (0.1-0.2°C above the norm).
This seemingly small change allowed Vikings to colonize Greenland due to reduced ice.
Little Ice Age
Occurred between 1550-1850 AD.
Slight cooling of less than 1°C was observed in North America, Europe, and other areas.
Resulted in harsh winters with much snow and frost.
Industrial Era
Began around 1750.
Characterized by advances in agriculture, new technologies, and increased use of fossil fuels (especially coal).
Burning fossil fuels releases carbon dioxide, leading to rising atmospheric CO2 levels.
Milankovitch Cycles
Milankovitch cycles describe the effects of slight changes in Earth's orbit on Earth's climate.
Cycle lengths range between 19,000 and 100,000 years.
These cycles involve:
Changes in Earth's tilt.
Variations in Earth's orbit (more oval or circular).
Changes in how the distance to the sun matches the seasons.
These changes affect amount of sunlight received
Indirect Evidence of Climate Change
Includes carbon dioxide levels in ice cores, boreholes, tree rings, glacier lengths, pollen remains, and ocean sediments.
Drivers of Climate Change
Pre-industrial era drivers (before the 1780s) unrelated to human activity:
Milankovitch cycles
Solar intensity changes
Volcanic eruptions
Volcanic Eruptions
Release solids and gases that can influence climate for a few years.
Gases and solids released include carbon dioxide, water vapor, sulfur dioxide, hydrogen sulfide, hydrogen, and carbon monoxide.
Volcanic eruptions generally cool the climate.
The haze effect (dust and ash blocking sunlight) can trigger lower global temperatures.
Example: 1783 Iceland eruption caused haze effect cooling in Europe and North America.
Greenhouse Gases
Trap heat, creating a "blanket" around the Earth.
Maintaining a stable body temperature is crucial (e.g., 98.6°F for humans).
Even slight deviations can have significant effects.
Past Climate Change and Extinction Events
The Permian extinction event (250 million years ago) was associated with global warming.
Approximately 70% of terrestrial plant and animal species and 84% of marine species became extinct.
Organisms adapted to wet and warm conditions may not have survived the changes.
Present Climate Change Effects
Glacier recession in Glacier National Park (Montana).
Decreasing mass of ice sheets in Greenland and Antarctica, resulting in rising sea levels. Greenland lost a 50 to 200 kilometers of ice per year.
Changes in abiotic conditions (temperature, precipitation) affecting plant and animal distributions and behaviors.