Climatic Environments (Leaving Cert Geography): Revision Notes
Global warming
What is global warming?
Global warming describes the long-term increase in Earth's average surface temperature. This rise is primarily caused by human activities that boost concentrations of greenhouse gases in the atmosphere. It represents a direct result of the enhanced greenhouse effect - a human-driven intensification of the natural greenhouse effect.
The Intergovernmental Panel on Climate Change (IPCC) provides clear evidence for this warming trend. Global average surface temperature has risen by approximately 1.1°C since the Industrial Era (1850-1900). The period from 2011-2020 was the warmest decade on record, with 2020 ranking as one of the three warmest years ever recorded.
Evidence of warming
Rising carbon dioxide levels
Atmospheric CO₂ concentrations have reached unprecedented levels. In 2021, CO₂ levels surpassed 410 parts per million (ppm), representing a dramatic increase from pre-industrial levels of about 280 ppm. This rise directly correlates with increasing global temperatures, as shown by decades of climate data.
This represents a 46% increase in atmospheric CO₂ concentrations compared to pre-industrial levels - a change that has occurred in just over 150 years, which is extremely rapid in geological terms.
Human influence confirmed
Climate models demonstrate that natural processes alone cannot explain the warming observed over the past century. Only when scientists include the effects of human-generated greenhouse gas emissions can climate models accurately explain current temperature trends. This provides strong evidence that human activities are the primary driver of recent climate change.
Impacts of global warming
Melting ice and snow
Rising temperatures have triggered widespread melting of glaciers and ice caps worldwide. The Arctic Sea Ice extent has been declining by approximately 13% per decade since satellite records began in 1979. Contributing to rising sea levels, the Arctic Sea Ice reached its lowest summer coverage in recent years, with 2020 being one of the years with the smallest recorded ice extent.
The Antarctic ice sheet has lost over 3,000 gigatons of ice since 1992, with the rate of loss accelerating over time. Glaciers worldwide, from the Himalayas to the Andes, are retreating at an accelerated pace. Scientists estimate that the average thickness loss of glaciers worldwide has been about 1 metre per year over recent decades.
Extreme weather events
Global warming has increased both the frequency and severity of extreme weather events including heatwaves, hurricanes and heavy rainfall. The number of record-breaking rainfall events globally has increased significantly over the past two decades.
Real-World Example: The 2023 European Heatwave
The European heatwave of 2023 provides a stark example of these intensifying extremes:
- Ranked among the hottest summers on record
- Caused over 61,672 deaths across Europe
- Temperatures in Valencia, Spain soared to a record 46.8°C
- Research indicates that such heatwaves have become more likely due to climate change
Other notable extreme events include:
- The 2020 monsoon floods in South Asia affected over 17 million people
- Germany and Belgium faced devastating floods in July 2021 from unusually heavy rainfall
- The 2017 Atlantic hurricane season was exceptionally severe, with hurricanes such as Irma and Maria causing widespread destruction
How warming intensifies weather extremes
The enhanced greenhouse effect alters atmospheric conditions, fundamentally changing weather patterns. Warmer temperatures increase evaporation rates and boost the atmosphere's capacity to hold moisture. This leads to more intense rainfall and increased flooding risk in some regions. Conversely, disrupted weather patterns can cause prolonged droughts in other areas. Warmer sea-surface temperatures fuel the intensity of tropical storms and hurricanes.
Ecosystem disruptions
Rising temperatures significantly affect ecosystems and biodiversity. Coral-bleaching events, driven by warmer ocean temperatures, have become more frequent and severe. These changes threaten marine ecosystems and the communities that depend on them.
Marine ecosystems are particularly vulnerable because oceans absorb approximately 30% of human-produced CO₂, leading to ocean acidification alongside warming temperatures. This double impact creates severe stress on marine life.
Impact on human health and livelihoods
Global warming affects human health through multiple pathways including extreme heat, worsened air pollution, and increased spread of vector-borne diseases. Climate change also threatens livelihoods, particularly in vulnerable communities, through impacts on agriculture and water resources.
Future projections
Sea level rise
The melting of ice caps and glaciers contributes significantly to rising sea levels, posing threats to coastal communities worldwide. The IPCC estimates that global sea levels could rise by 0.6 to 1 metre by 2100 if current trends continue. This rise threatens increased coastal flooding, erosion, and can impact freshwater systems and ecosystems.
Even a 1-metre sea level rise would displace millions of people living in coastal areas and could make entire island nations uninhabitable. The impacts would be irreversible on human timescales.
Economic consequences
Extreme weather events create substantial economic impacts, affecting economies, ecosystems and communities globally. They pose major challenges to agriculture, infrastructure and human health. The economic costs of extreme weather events are substantial, with billions spent annually on recovery and adaptation efforts.
Key Points to Remember:
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Global warming refers to the 1.1°C temperature rise since the Industrial Era, primarily caused by human activities increasing greenhouse gases
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CO₂ levels have risen from 280 ppm (pre-industrial) to over 410 ppm (2021), directly correlating with temperature increases
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Major impacts include accelerating ice loss (Arctic sea ice declining 13% per decade), more frequent extreme weather events, and ecosystem disruptions
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Human influence is confirmed - climate models show natural factors alone cannot explain observed warming
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Future projections indicate continued sea level rise (0.6-1 metre by 2100) and intensifying climate impacts without action