Year 9 Climate Change Exam Revision
Core Definitions in Climate Science
Global Warming: The long-term heating of Earth's climate system observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere.
Climate Change: A long-term shift in global or regional climate patterns. Often climate change refers specifically to the rise in global temperatures from the mid-20th century to present.
Greenhouse Effect (GHE): The natural process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere. This is essential for maintaining life on Earth.
Enhanced Greenhouse Effect: The concept that the natural greenhouse effect has been intensified by increased atmospheric concentrations of greenhouse gases emitted as a result of human activities. These added gases cause the Earth to warm beyond its natural state.
Natural Climate Change and Historical Periods
Historical Timeline: Natural climate change has been occurring over hundreds of thousands of years, characterized by distinct periods of temperature fluctuation.
Interglacials: These are periods of ice retreat associated with rising temperatures and increased emissions.
Glacials: These are periods of ice advance associated with falling temperatures.
Mechanism: Natural cycles involve the movement between these two states, but current trends show a significant departure from these historical natural cycles.
The Greenhouse Effect vs. The Enhanced Greenhouse Effect
The Greenhouse Effect (GHE): A natural phenomenon that keeps the Earth habitable. It involves the atmosphere trapping heat to maintain a stable temperature.
Enhanced Greenhouse Effect (Human-Induced): This occurs when human activity adds extra greenhouse gases to the atmosphere, trapping more heat than necessary and leading to global warming.
Reflectivity and Albedo: Different surfaces on Earth reflect varying amounts of radiation. Surfaces with high reflectivity (like ice and snow) have a high albedo, whereas darker surfaces (like oceans or forests) absorb more heat.
Causes and Sources of Greenhouse Gases
Mechanism of EGE: Increased atmospheric concentrations of gases such as and methane, resulting from human activity, trap more heat and drive global temperature increases.
Major Greenhouse Gases and Their Sources: - (Nitrous Oxide): Primarily produced by combustion engines in cars. - (Water Vapor): Resulting from evaporation from the oceans; while natural, it acts as a significant greenhouse gas as temperatures rise. - (Methane): Sourced from paddy fields (rice cultivation), landfill sites, and the digestive processes of livestock (cows). - (Carbon Dioxide): Produced by the burning of fossil fuels, specifically coal, oil, and gas.
Evidence for Rising Global Air Temperatures
Instrumental Readings (Post-1850): - Reliable global thermometer coverage began around 1850. - Data suggests a clear warming trend over the last 150 years. - Inaccuracy Factors: Scientists acknowledge potential inaccuracies at certain measurement sites due to the overgrowth of vegetation and increasing urbanisation (the Urban Heat Island effect).
Glacier Retreat: - Significant photographic evidence exists showing glaciers retreating over the last 50 to 100 years. - 2001 World Glacier Monitoring Service Report: Documented a significant retreat of glaciers since 1980. - Projections: It is estimated that of mountain glaciers will have disappeared by 2050, though recent data suggests this may happen much sooner. - Nuance: Retreat can also be caused by a reduction in snowfall rather than just warming; some global warming models even predict increased snowfall in specific regions.
Arctic Ice Cover: - Over the last 30 years, Arctic ice thickness has decreased to nearly half its original size. - Summer ice cover has reduced dramatically, allowing ships to cross the Arctic Ocean in summer—an impossible feat until recently. - Consequences: There is a risk that Arctic ice could disappear completely in summer, which would remove a major reflective surface, thereby increasing the amount of energy absorbed by the Polar region.
Ice Core Analysis: - Snowfall builds up annual records over thousands of years, similar to tree rings. - Scientists at the Antarctic Survey in Cambridge analyze water and air molecules trapped in the ice to get precise readings of air temperatures from the time the snow fell. - This data provides clear evidence of rapidly rising air temperatures in recent decades compared to historical norms.
Historical and Phenological Records: - Seasonal Shifts: In the last 30 years, Spring has been arriving approximately three weeks earlier than in the past, evidenced by earlier bird nesting and bulb growth. - Winter Severity: Winters have become less severe on average, with fewer frost days and reduced snow cover. - Economic Impact: The ski industry has been forced to introduce artificial snow to keep slopes operational due to the lack of natural snow.
Climate Change Response: Mitigation vs. Adaptation
Adaptation: Actions taken to respond to the effects of climate change. The goal is to adjust to the new conditions to minimize harm. - Examples of Adaptation: - Changing agricultural systems to suit new climates. - Managing water supplies more efficiently. - Reducing risks associated with rising sea levels (e.g., coastal defenses).
Mitigation: Actions taken to reduce or eliminate the causes of climate change. This focuses on reducing the source of greenhouse gases. - Examples of Mitigation: - Alternative energy production (renewables). - Carbon capture and storage technology. - Afforestation (planting trees to absorb ). - International agreements to set emission targets.
International Agreements: Two major examples of global policy efforts to address climate change include: - The Kyoto Protocol. - COP21 (The Paris Agreement).