Show Notes

How can climate change mean bigger floods and worse droughts?

In this episode, Graham and Belle explore how a warmer atmosphere acts like a bigger sponge - holding more water, releasing heavier rain, and also drying land out faster. They also look at “sponge cities”: places designed to soak up, store and slowly release rainwater using green roofs, rain gardens, permeable surfaces and wetlands.

Belle's Question

“If climate change means more water in the air... why can it also mean worse droughts?”

If you remember one thing...

Climate change is intensifying the water cycle. Warmer air can hold about 7% more water vapour for every 1C of warming, which can make heavy rainfall more intense - but warmer conditions can also dry out soils, plants, rivers and lakes faster.

Key Ideas From This Episode

• 1. A warmer sky is like a bigger sponge

The atmosphere’s moisture-holding capacity rises by about 7% per 1C of warming.

• 2. The world is already much warmer than before

Long-term global warming is currently estimated at about 1.34-1.41C above the 1850-1900

baseline.

• 3. A faster water cycle means stronger swings

Climate change does not create a new water cycle - it speeds up the one we already have,

increasing the risk of heavier rain in some situations and worse drying in others.

• 4. Dry regions can get drier

Warmer air causes more evaporation and can hold more water vapour before condensation,

helping explain why heat can worsen drought conditions.

• 5. Some deserts sit under Earth’s dry air belts

Many major dry zones are linked to global circulation patterns around 30° north and 30° south.

One Bright Thing - Sponge Cities

Sponge cities are designed to absorb, store and slowly release rainwater using permeable pavements, rain gardens, green infrastructure and stormwater storage. Chinese sponge-city

programmes have included places such as Shanghai and Wuhan.

Classroom discussion

• Why might a warmer world bring both heavier rain and worse droughts? Discuss how a sky sponge and a faster water cycle can mean more intensive downpours in some places, while hotter conditions, dry soils, plants, rivers in others.

• What is a sponge city? Can pupils spot places in their school or neighbourhood that could be redesigned to act more like a sponge? Examples, green roofs, rain gardens, permeable pavements, wetlands and parks that double as flood basins

Sources & Further Reading

• IPCC AR6 WG1 Chapter 8: Water Cycle Changes

• WMO State of the Global Climate 2024 / March 2025 update• NOAA water cycle and drought explainers

• World Bank materials on sponge cities and urban flood resilience

Have a question you'd like Belle to ask? Send it in at theclimateclassroom.org. with "the" at the start.