How will climate change affect rainfall?

Will climate change and global warming increase or decrease rainfall?

An interesting question, but there’s no straight answer.

A warmer world intuitively seems to suggest reduced rainfall, but as we will see in this post, it is not necessarily so, and it could be quite the opposite!

So far, any impact that climate change may have had generally on regional rainfall cannot be distinguished from natural variations. However, for specific cases, some trends and signals are starting to emerge.

Let’s look at theory first. A warmer atmosphere can hold more moisture. In fact, water vapour globally increases by 7% for every degree centigrade of warming.  However, how this will translate into changes in global precipitation is less clear.

Some estimates suggest that the total volume of precipitation is likely to increase by 1-2% per degree of warming. This may cause more intense rainfalls and snow events. On lines of the above reasoning, there’s some evidence that some regions that are already wet are getting wetter.

On the other hand, warmer air can also more quickly evaporate water from surfaces. This means that areas with less precipitation could see a faster drying out, resulting in droughts! Thus, this line of reasoning suggests that wet regions could get wetter, and dry regions could become more dry.

But, this might not be the entire picture. It could also so happen that the same region could experience both more drought and more flooding, just that these two will not be at the same time! The dry spells could be longer and with faster evaporation causing dryness in soils. But, when the rains fall, they come in heavy downpours potentially leading to more floods. In fact, the 2017 recent flooding in California – which followed a very intense and prolonged drought – provides a great example of such a cycle.

So, coming back to the question “Will global warming and climate change affect rainfall?” an objective answer will be: Quite likely, and anecdotal evidence seem to suggest that global warming will lead to both floods and droughts, but it is early days still to find decisive correlations.