Will global warming lead to more floods?

World over, the frequency of extreme floods is on the increase. Is global warming and climate change responsible for this?

Let us briefly look at the theory first: Because warmer air can hold more water, a warmer atmosphere has the potential to hold more more water molecules, and hence, when these condense, could result in higher rainfall.

What this means for the risk of flooding, however, will vary widely from location to location depending on local climatic changes that at present are difficult to predict with confidence.

• Floods can be caused either by an excess of rainfall leading to greater surface runoff or by storm surges raising the sea level. In a situation of excess rainfall, soils and groundwater reservoirs can become saturated, which can leads to flooding as additional rain runs off the land surface. The floods in Pakistan in 2010, for example, could belong to this category.
• Human activity can increase the risks of floods. For instance, paving over areas which were previously covered by vegetation reduces the capacity of the land to absorb rainfall, causing it to run off more quickly.
• Planning decisions – such whether to build houses in flood plains or position caravans next to the sea – can also affect society’s vulnerability to floods.
• Recent results with state-of-the-art climate models have raised the possibility that climate change may more severely affect the circulation patterns such as jet stream than scientists previously expected, making floods more likely in some regions. Flash flooding could also become more frequent as extreme rainfall events are consistently predicted to become more severe.
• The risk of coastal flooding is influenced by the frequency and intensity of storms, and by the local sea level. Although in most areas it is not possible to predict the effect of climate change on storms with certainty, we can say with confidence that the sea level is rising and this will increase the risk of coastal flooding in many areas.

So, all in all, it is highly likely that increased global warming will result in increased frequency and intensity of floods.