Global atmospheric circulation, the formation, structure and distribution of tropical storms, the effects of and responses to a named tropical storm, UK extreme weather, and evidence, causes, effects and management of climate change.

What this dot point is asking

This is AQA GCSE Geography (8035) Paper 1, Section A (3.1.1 The challenge of natural hazards). AQA expects you to describe global atmospheric circulation and how it controls weather, explain how tropical storms form and are distributed, use a named tropical storm to explain primary and secondary effects and responses, give an example of a UK extreme weather event, and evaluate the evidence, natural and human causes, effects and management strategies for climate change.

Global atmospheric circulation

The atmosphere moves in giant loops called cells that transfer heat from the equator towards the poles. At the equator, intense heating causes air to rise (low pressure, heavy rain), then it sinks at around 30 degrees latitude (high pressure, deserts). The three cells in each hemisphere are the Hadley, Ferrel and Polar cells, and the spinning Earth deflects winds to create the trade winds and westerlies.

Tropical storms

A tropical storm has a clear structure: a calm central eye of sinking air with clear skies and light winds, surrounded by the eyewall where the most powerful winds and torrential rain occur, and spiralling rain bands further out. The storm moves with the trade winds, drawing energy from the warm sea, and weakens (dissipates) when it moves over land or cooler water and loses its energy source. As the climate warms, the area of ocean above 27 degrees Celsius grows and stays warm for longer, so storms may become more intense, carry more rainfall and affect a wider area, even if they do not necessarily become more frequent.

Named example: Typhoon Haiyan, 2013

Typhoon Haiyan struck the Philippines in November 2013 as one of the strongest tropical storms on record. Primary effects (immediate, from the storm itself): over 6,000 deaths, around 90 percent of the city of Tacloban destroyed by winds over 300 km per hour and a storm surge of around 5 metres, and power and communications cut. Secondary effects (knock-on consequences): flooding contaminated water and spread disease, food and shelter shortages led to looting, and the loss of crops, livestock and fishing boats destroyed livelihoods. Immediate responses included international aid, evacuation of survivors and emergency food and water. Long-term responses included rebuilding homes, replanting mangroves as natural defences, and the government's "Build Back Better" programme to make reconstruction more resilient.

UK extreme weather and climate change

The UK increasingly experiences extreme weather such as the Somerset Levels floods (2014) and heatwaves. Evidence for climate change includes ice cores, tree rings, global temperature records and rising sea levels.

• Natural causes: orbital (Milankovitch) changes, sunspot activity and volcanic eruptions.
• Human causes: burning fossil fuels, deforestation, farming (methane) all add greenhouse gases.
• Management: mitigation (renewable energy, carbon capture and storage, planting trees, international agreements such as the Paris Agreement) reduces the causes by cutting greenhouse-gas emissions; adaptation (flood defences, drought-resistant crops, managing water supply, changing agriculture) reduces the effects by helping people cope.

The greenhouse effect explains the mechanism: gases such as carbon dioxide and methane trap outgoing heat in the atmosphere, and adding more of them by human activity strengthens this effect (the enhanced greenhouse effect), raising global temperatures. Effects of climate change include rising sea levels (threatening low-lying land and coral islands), more extreme weather, shifting climate belts affecting farming, and loss of habitats and species.

Try this

Q1. State the minimum sea surface temperature needed for a tropical storm to form. [1 mark]

• Cue. 27 degrees Celsius.

Q2. Explain the difference between mitigation and adaptation in managing climate change. [2 marks]

• Cue. Mitigation cuts greenhouse-gas emissions to reduce causes; adaptation changes how we live to cope with the effects.