Global controls on climate — Eduqas A-Level Geography

Global controls on climate refer to the large-scale factors that determine the Earth's climate patterns, including latitude, atmospheric circulation, ocean currents, and the distribution of land and sea. These controls operate at a global scale and interact to create the diverse climates experienced across the planet. Understanding these controls is fundamental to explaining why some regions are hot and wet while others are cold and dry, and how climate varies over time.

This topic is crucial for A-Level Geography as it provides the foundation for understanding more complex issues such as climate change, weather hazards, and biomes. By mastering global controls, students can analyse how natural factors like the Coriolis effect, the Hadley cell, and ocean currents like the Gulf Stream shape climate. This knowledge is also essential for evaluating human impacts on climate and predicting future climate scenarios.

Within the WJEC A-Level specification, 'Global controls on climate' sits within the 'Climate Change' theme, linking to both physical geography and human geography. It connects to topics such as the carbon cycle, climate change mitigation, and the impacts on ecosystems and societies. A strong grasp of these controls allows students to critically assess evidence for climate change and evaluate responses at different scales.

• →Latitude: The primary control on climate due to variations in solar energy receipt. Low latitudes receive more direct sunlight, leading to higher temperatures, while high latitudes receive less intense sunlight, resulting in colder climates.
• →Atmospheric circulation: The global system of pressure belts and wind patterns, including the Hadley, Ferrel, and Polar cells, driven by differential heating and the Coriolis effect. This redistributes heat and moisture around the planet.
• →Ocean currents: Large-scale movements of seawater, such as the Gulf Stream and the Labrador Current, which transport heat from the equator towards the poles, influencing coastal climates. Warm currents bring milder, wetter conditions, while cold currents can cause aridity.
• →Continentality: The effect of landmasses on climate. Inland areas experience greater temperature extremes (hot summers, cold winters) and lower precipitation compared to coastal areas, which have more moderate climates due to the thermal properties of water.
• →Albedo: The reflectivity of the Earth's surface. Surfaces with high albedo (e.g., ice, snow) reflect more solar radiation, leading to cooler temperatures, while low albedo surfaces (e.g., forests, oceans) absorb more heat, contributing to warming.

• Structure of the atmosphere and its role in climate regulation
• Atmospheric heat budget
• Processes of global atmospheric circulation (tricellular model)
• Distribution of high and low pressure belts and planetary surface winds
• Oceanic circulation and its impact on climate
• Regional impacts of continentality and altitude on climate

• 💡Use specific examples: When explaining global controls, always refer to real-world locations. For instance, mention how the UK's climate is influenced by the North Atlantic Drift and prevailing westerlies, or how the Atacama Desert is dry due to the cold Humboldt Current and the rain shadow effect of the Andes. This shows depth of knowledge.
• 💡Link to climate change: In exams, you may be asked to discuss how global controls might be altered by climate change. For example, melting Arctic ice reduces albedo, leading to further warming (positive feedback). Or, changes in ocean currents could disrupt heat distribution. Demonstrating these links can earn higher marks.
• 💡Use diagrams: When describing atmospheric circulation or ocean currents, sketch a simple diagram in your answer. This helps illustrate your understanding and can be a quick way to show the examiner you know the patterns. Label key features like pressure belts and cell names.

• Misconception: The Coriolis effect determines the direction of ocean currents. Correction: While the Coriolis effect influences the direction of surface currents (deflecting them to the right in the Northern Hemisphere and left in the Southern Hemisphere), the primary drivers of ocean currents are wind patterns and differences in water density (thermohaline circulation).
• Misconception: The Gulf Stream makes the UK warm because it brings warm water from the Gulf of Mexico. Correction: The Gulf Stream is part of the North Atlantic Drift, which does bring warm water across the Atlantic. However, the UK's mild climate is also significantly influenced by the prevailing westerly winds that carry warm, moist air from the ocean over the land. The ocean current alone is not sufficient.
• Misconception: The equator is always hot and wet. Correction: While the equator generally experiences high temperatures and high rainfall due to intense solar heating and rising air (ITCZ), some equatorial regions, like the highlands of East Africa, have cooler temperatures due to altitude. Additionally, areas like the Galapagos Islands can be surprisingly dry due to cold ocean currents.