The Earth is warming – and that changes the water cycle. More water evaporates, the air contains more water vapor, and that ultimately leads to more intense precipitation. According to climate models, for each degree of warming, the amount of water vapor in the atmosphere increases by about 7 percent, while precipitation and evaporation each rise by about 2 percent. This results in less frequent but more intense rainfall. The changes we have observed so far are consistent with this.

Precipitation and Evaporation in Balance 

On a global average, the amount of evaporation is almost equal to precipitation. This is because the amount of water vapor in the air is relatively small: if you were to let all the water vapor rain out, it would only yield a layer of 2.5 cm. In comparison, an average of 1 meter of rain falls each year. At that intensity, the atmosphere would be completely emptied in just 9 to 10 days. 

In a warmer world, the amount of water vapor increases more than the amount of precipitation. As a result, water vapor remains in the atmosphere longer (more than 10 days) and travels greater distances before it rains out. The areas where a lot of evaporation occurs and where a lot of rain falls generally do not coincide. The transport of water vapor between these areas is increasing. 

Less Frequent Rain, But Harder 

More water vapor in the air means that showers become more intense: it rains less often worldwide, but when it does rain, more water falls in a short period. At the same time, the increased evaporation raises the likelihood of longer dry periods and drought. These trends are already visible in the Netherlands as well.