A tropical cyclone is a machine that runs on warm seawater. Understand how it fuels itself and the climate change link writes itself — warmer oceans mean more fuel, and more fuel means stronger storms.
📘 What you need to know
Tropical cyclones are large, rapidly rotating storm systems forming over warm tropical oceans.
They have a low-pressure centre (the eye), strong winds, heavy rainfall and thunderstorms.
Once sustained winds exceed 119 km/h they are called hurricanes, typhoons or cyclones depending on region.
They need ocean water above 26.5 degrees C; the energy comes from evaporation.
Rising moist air condenses, releasing latent heat, which drives the storm further.
The Coriolis effect makes the storm rotate and form its spiral structure.
Warming oceans increase intensity; the number of intense storms has risen even where total numbers have not.
Same storm, three names
Name
Region
Hurricane
Atlantic and eastern Pacific, including the Gulf of Mexico, Caribbean Sea and west coast of Mexico
Typhoon
South China Sea and western Pacific
Cyclone
Indian Ocean and South Pacific, including the Bay of Bengal and northern Australia
They are the same phenomenon. Only the location changes the name.
How a cyclone fuels itself
The key idea is that this is a self-reinforcing loop. Each stage makes the next stage stronger, which is why a tropical cyclone can intensify so rapidly once it gets going.
The loop only runs over warm water. Once a cyclone moves over land or cooler sea it loses its energy supply and weakens quickly.
Written out as a sequence:
Water evaporates from ocean above 26.5 degrees C, so the air above is warm and moist.
That air rises, and the water vapour condenses into clouds and rain, releasing huge amounts of latent heat energy.
The released latent heat warms the surrounding air, causing it to rise further and reducing pressure at the surface.
The low pressure at the centre pulls in more warm, moist air, continuing the cycle of evaporation, condensation and heat release.
This continuous cycle intensifies the storm into a tropical cyclone.
The Coriolis effect, caused by the Earth’s rotation, makes the storm rotate and develop its characteristic spiral structure.
If a question asks how a cyclone forms, do not just list ingredients. Show the loop — evaporation, condensation, latent heat, falling pressure, more air drawn in. It is the feedback that turns a rainstorm into a cyclone.
What climate change is doing
Ocean warming and intensity
Global warming is warming the oceans, which provides more energy for tropical cyclones. Warmer water allows greater evaporation, so storm systems become stronger and more sustained. As sea surface temperatures rise, cyclone intensity increases, giving:
Stronger winds, causing severe damage to infrastructure and ecosystems
Heavier rainfall, leading to more flooding in coastal and inland areas
Frequency and duration
Some studies suggest that while the total number of tropical cyclones may not increase, the frequency of the most intense storms (categories 4 and 5) has risen. The Atlantic hurricane season has seen an increase in major hurricanes in recent decades.
Rising sea levels caused by global warming also contribute to higher storm surges, worsening coastal flooding during a cyclone.
Get this distinction right. The claim is not “climate change causes more hurricanes”. It is that the storms which do form are more intense, and that sea level rise makes their storm surges more damaging. Precision here is worth marks.
Evidence
Event
What happened
Climate link
Typhoon Haiyan, 2013
One of the strongest tropical cyclones ever recorded, with wind speeds exceeding 315 km/h
Scientists believe warmer sea temperatures increased its intensity
Hurricane Harvey, 2017
Record rainfall causing catastrophic flooding in Texas
Warmer waters in the Gulf of Mexico supplied the extra moisture
Long-term trend
Research indicates around a 40% increase in the likelihood of storms reaching category 3 or above since the 1980s
Consistent with rising sea surface temperatures
WORKED EXAMPLE
Explain why a tropical cyclone weakens rapidly once it moves over land.
Step 1: Identify the energy sourceThe storm runs on evaporation from ocean water above 26.5 degrees CStep 2: What changes over landno warm ocean surface, so evaporation stopsStep 3: Break the loopLess condensation means less latent heat released, so the pressure at the centre rises and the feedback stopsThe storm loses its fuel supply and dissipates
WORKED EXAMPLE
A student writes: “Climate change is causing more hurricanes every year.” Evaluate this statement.
Step 1: What the evidence supportsWarmer oceans give more energy, so intensity has risen and category 4 and 5 storms are more frequentStep 2: What it does not supporttotal number may not be increasingStep 3: Correct the statementAdd that sea level rise worsens storm surges, increasing damage independently of storm countPartly right: storms are more intense, not necessarily more numerous
💡 Exam tip
Quote the threshold: ocean above 26.5 degrees C, sustained winds above 119 km/h.
Use the term latent heat — it is the mechanism, not just a detail.
Describe formation as a loop, not a list.
Distinguish intensity from frequency in every climate change answer.
Name a case study. Haiyan 2013 or Harvey 2017 both work.
⚠ Common mix-up
Treating hurricanes, typhoons and cyclones as different storms. Same phenomenon, different regions.
Saying climate change simply causes more storms. The clearer evidence is for greater intensity.
Leaving out latent heat. Without it the storm has no engine.
Forgetting the Coriolis effect. It is why the storm spins and why cyclones do not form at the equator.
Ignoring storm surge. Sea level rise makes coastal flooding worse even for a storm of unchanged strength.
That completes Topic 2 — energy and biomass, biogeochemical cycles, and climate and biomes. Go back to Following Energy Through an Ecosystem if you want to see how the whole chain fits together.
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