Thunderstorms were the costliest peril for insurers last year, driven by high-severity severe convective storms in the US, according to Aon’s annual Climate and Catastrophe Insight.

The report finds global economic losses from natural catastrophes totalled $US260 billion ($368 billion), the lowest sum since 2015. But insured losses were $US127 billion ($180 billion) – 27% above the century average.

Insured losses were mostly driven by major events in the US, which has high penetration.

Australia and New Zealand recorded $US3.4 billion ($4.8 billion) of insured losses due to Cyclone Alfred and the November storms in Queensland and NSW.

Aon says the impact of severe storms is expected to rise.

Insurance affordability and access remain important issues in Australia, according to Aon head of climate analytics for Asia-Pacific Tom Mortlock.

“Even in a softer market, where risk is not well differentiated, communities and businesses can still face a widening gap between economic losses and what is actually insured due to a combination of both climate and non-climate factors.”

He says urbanisation in increasingly hazardous areas is a significant driver of the loss trend.

There were 30 billion-dollar (US currency) events last year, compared with an annual average of 17.

Losses from severe convective storms were the third-highest on record at $US61 billion ($86 billion).

The report notes that although the global protection gap is narrowing, with insurers covering 49% of losses, it persists in developing markets.