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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Global Warming Consequences
Global warming is causing significant changes to our planet's systems. These changes affect everything from polar ice caps to tropical rainforests and from ocean currents to weather patterns. Understanding these consequences helps us appreciate why climate action is so urgent.
Key Definitions:
The greenhouse effect is a natural process that warms Earth's surface. When the Sun's energy reaches Earth, some is reflected back to space and the rest is absorbed. The absorbed energy warms the planet and is then re-emitted as infrared radiation. Greenhouse gases in the atmosphere trap some of this heat, keeping Earth warm enough to support life. Human activities have increased greenhouse gas concentrations, enhancing this effect and causing global warming.
The main human activities contributing to global warming include:
One of the most significant consequences of global warming is rising sea levels. This happens through two main mechanisms:
As ocean water warms, it expands, taking up more space. This thermal expansion is responsible for about one-third of observed sea level rise.
When land-based ice like glaciers and ice sheets melt, the water flows into the oceans, raising sea levels. The melting of the Greenland and Antarctic ice sheets is particularly concerning.
Sea level rise threatens coastal communities, infrastructure and ecosystems. Low-lying islands and coastal cities face increased flooding, erosion and saltwater intrusion into freshwater supplies. By 2100, global sea levels could rise by 0.3-1.1 metres, depending on greenhouse gas emissions.
Global warming is making extreme weather events more frequent and severe:
Longer, more intense and more frequent heatwaves are occurring worldwide, causing health problems and increased mortality.
Warmer oceans provide more energy for storms, potentially increasing the intensity of hurricanes, cyclones and typhoons.
Changes in precipitation patterns lead to more intense rainfall in some areas (causing floods) and drought in others.
In 2022, Pakistan experienced catastrophic flooding that submerged one-third of the country. The floods affected 33 million people, damaged 1.7 million homes and caused nearly 1,500 deaths. Scientists found that climate change likely intensified the rainfall that led to these floods. Warmer air holds more moisture and Pakistan's proximity to the heated Arabian Sea contributed to the extreme rainfall. This disaster highlights how climate change can amplify existing weather patterns with devastating consequences.
Global warming is having profound effects on the world's ecosystems and the species that inhabit them:
Rising temperatures and changing precipitation patterns are altering or destroying habitats. Arctic sea ice loss is threatening polar bears, while coral reefs are dying due to ocean warming and acidification.
Species are responding to climate change in three main ways:
Scientists predict that if global warming exceeds 1.5°C above pre-industrial levels, 20-30% of plant and animal species could face increased risk of extinction. Some ecosystems, like coral reefs and Arctic systems, are particularly vulnerable.
Global warming affects food production in complex ways:
Overall, the negative impacts of global warming on agriculture are expected to outweigh the positive ones, especially in developing countries near the equator. Food security is threatened as populations grow while crop yields become less reliable.
The oceans absorb about 30% of the CO₂ released into the atmosphere. When CO₂ dissolves in seawater, it forms carbonic acid, making the ocean more acidic. This process, called ocean acidification, has serious consequences:
Australia's Great Barrier Reef, the world's largest coral reef system, has experienced several mass bleaching events in recent years (2016, 2017, 2020 and 2022). Bleaching occurs when corals expel their symbiotic algae due to stress from high water temperatures. Without these algae, corals lose their main food source and often die. The 2016 and 2017 bleaching events killed about half of the reef's corals. This case demonstrates how global warming can rapidly damage even the largest ecosystems. The reef's decline threatens thousands of marine species and the tourism industry that depends on it.
Global warming affects human health in numerous ways:
More frequent and intense heatwaves increase heat-related illnesses and deaths, especially among vulnerable populations like the elderly.
Warming temperatures expand the range of disease vectors like mosquitoes, potentially increasing the spread of malaria, dengue fever and other diseases.
Higher temperatures can worsen air pollution and increase pollen production, exacerbating respiratory conditions like asthma.
Addressing the consequences of global warming requires both mitigation (reducing greenhouse gas emissions) and adaptation (adjusting to unavoidable changes). Key strategies include:
Individual actions matter too. Reducing your carbon footprint by using public transport, eating less meat, conserving energy and supporting climate-friendly policies all contribute to the solution.
The Paris Agreement aims to limit global warming to well below 2°C, preferably 1.5°C, compared to pre-industrial levels. The difference between 1.5°C and 2°C of warming is significant:
Every fraction of a degree matters in limiting the consequences of global warming.
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