Global extreme events - Heavy rainfall
Determining the likelihood and severity of extreme events for the past, present and future.
Reference: IPCC AR5
Extreme weather events such as heatwaves and floods impact all levels of society and can lead to large economic costs, population displacement and loss of life. This page outlines the latest research on whether we’re experiencing more heavy rainfall events globally, whether they’re due to climate change and what we can expect in the future.
Are heavy rainfall and flooding events increasing in frequency or intensity globally?
IPCC AR5 concluded it is likely (>66% probability) that since 1950 the number of heavy precipitation events over land has increased in more regions globally than it has decreased, with confidence highest for North America and Europe. For example, it is very likely (>90% probability) there is a trend towards heavier precipitation events in central North America.
Are these changes due to human activity?
There is medium confidence in a human contribution to global scale changes in precipitation patterns over land since 1950, including increases in the northern hemisphere mid to high latitudes.
Of the studies to look at heavy rainfall and flooding, about half have found that human activity has made the event more likely or more severe – a smaller proportion compared to studies that looked at heatwaves. This could be due to a number of reasons, for example limited data might make it difficult to detect a clear “signal” of climate change above the “noise” of weather considered normal for a particular region. In other cases, an inconclusive result could reflect the fact that rainfall and flooding events are inherently more complex than heatwaves, with many ways for natural variability to play a role. Human factors, such as land use and drainage, also play a part in whether heavy rain leads to flooding.
Are heavy rainfall and flood events set to increase in future?
Globally, for short-duration precipitation events, a shift to more intense individual storms and fewer weak storms is likely as temperatures increase. Over most of the mid-latitude land-masses and over wet tropical regions, extreme precipitation events will very likely be more intense and more frequent in a warmer world.