Are ‘heat spikes’ becoming more common?

How fast temperatures rise depends not only on how hot the air is, but also on how dry the soil and atmosphere are.

Dry ground heats up faster than moist ground because less energy is used for evaporation and more goes directly to raising the temperature.

There is strong evidence that UK summer soils are becoming drier as the climate warms; Met Office forecasts show seasonal drying is coming earlier and droughts are more frequent, particularly in southern and eastern England.

The same principle applies higher above the ground. Large, slow-moving areas of high pressure, often called blocking highs or heat domes, are large areas of sinking air.

The downward movement dries the air, just like squeezing a sponge, and when you add the compression of the air to this, the heating of the air increases.

Although blocking altitudes doesn’t happen more often, research shows that when it does, the heat and dryness they bring are more intense than in the past.

As climate scientist Professor Sarah Perkins‑Kirkpatrick from the Australian National University puts it: “The membranes are loaded so that it heats up faster… when high pressure systems are activated, boom, the temperature rises.”