August saw dramatic instances of flooding across South Asia and the continental United States, with extreme weather events including Hurricane Harvey striking Houston, Texas, and unusually devastating floods during the monsoon season in northern India, Nepal and Bangladesh.
What has the impact been?
There has been significant damage to buildings and infrastructure. Save the Children estimates that 18,000 schools have been damaged or destroyed, affecting 1.8 million children.
The effects of US Tropical Storm Harvey, which began life as a hurricane in the Gulf of Mexico, have been less lethal, with a death toll thus far of 37 people, according to CNN.
However, its impact on the region has been devastating, with an estimated one million people displaced and cities engulfed by floodwater.
Does climate change play a part?
Yes and no. As the Earth’s atmosphere is a chaotic system in which numerous complex factors interact, it’s impossible to attribute any individual weather event to climate change.
“One must always remember that whether a hurricane occurs, whether there’s going to be a heavy hurricane season or a heavy monsoon season also depends on the atmospheric circulation of the winds and those are at the mercy of natural variations,” explains professor Adam Scaife from the Met Office.
However, climate change can contribute to the rainfall from weather patterns as a whole. Warm air is capable of holding a greater amount of moisture than cold air, as described by the Clausius-Clapeyron equation for water vapour under typical atmospheric conditions, which indicates that the atmosphere can carry approximate seven per cent more water for every one degree Celsius increase in temperature.
The globe’s warming average temperature has increased by about one degree Celsius since the industrial revolution, which means that more moisture is stored in the air, although other factors such as slowing atmospheric circulation – global air movement or winds – also resulting from increasing temperatures mean that, in practice, the atmosphere’s moisture-bearing capacity has increased by less than seven per cent.
Professor Scaife says an increase of about half of that is a reasonable estimate for rainfall, and that it’s nonetheless enough to have an impact on weather events around the world.
“Although we can’t say that either event is definitely due to climate change, there’s a pretty strong argument for the amount of rainfall coming from weather events today being significantly more than from events a hundred years ago,” he says.