Global climate change: describe briefly four potential effects of global climate change

The idea

Global climate change is the long-term shift in average weather patterns, driven mainly by increased greenhouse gases such as carbon dioxide and methane. Its effects are wide-ranging and interconnected. Four commonly described effects are: rising sea levels, as land ice melts and ocean water expands when warmed; more frequent and severe extreme weather, including heatwaves, droughts, storms and heavy rainfall; changes to ecosystems and species distribution, as organisms migrate or decline when their habitats become unsuitable; and impacts on human agriculture and water supply, as changing rainfall and temperatures reduce crop yields and freshwater availability. These effects are potential because the exact scale depends on future emission pathways, but the direction of change is well supported by evidence.

What earns the marks

• Rising sea levels caused by melting land ice and thermal expansion of ocean water, threatening low-lying coasts and islands.
• More frequent or intense extreme weather, such as heatwaves, droughts, storms and heavy rainfall, affecting people and infrastructure.
• Changes to ecosystems and species distribution, including migration, reduced biodiversity and possible extinction where organisms cannot adapt or move.
• Reduced agricultural productivity and water availability, leading to food and water insecurity in some regions.
• Additional valid effects such as ocean acidification, spread of disease vectors, or damage to coral reefs, if briefly described.

Common mistakes and how to put them right

• Confusing weather with climate.

  Put it right: Describe effects as long-term changes in average conditions or patterns.

• Claiming that all effects are certain and identical everywhere.

  Put it right: Describe them as potential effects whose severity depends on future emissions and local conditions.

• Listing a cause rather than an effect, such as 'burning fossil fuels releases carbon dioxide'.

  Put it right: State the consequence, for example 'sea levels rise as ice melts'.

Exam tips

• Read the command word 'describe briefly' and give four distinct effects, each with a short explanation of how it arises.
• Use precise terms such as 'thermal expansion', 'biodiversity' and 'food security' to show secure understanding.
• Link each effect to a mechanism where possible, for example melting ice and thermal expansion both raise sea level.
• Keep each point concise; four clear effects are better than one long, detailed paragraph.