Hot air ballooning is a unique form of aviation, where one is completely dependent on the natural conditions in the atmosphere. Unlike powered aviation, the weather not only plays a role in balloon flights; it determines whether a flight can take place at all. Balloonists are accustomed to the variable conditions in our temperate maritime climate with its changeable weather. However, the warming of the Netherlands is accompanied by changes in the weather that can be both favorable and unfavorable for ballooning in the Netherlands.

Higher temperatures lead to less lift and shorter flights  

The average temperature in the Netherlands has risen by nearly 2 degrees Celsius since the start of measurements in 1901. This warming leads to lower air density. For hot air balloons, this means that more heat is needed to generate the same lift. This has several consequences: 

• Higher fuel consumption. 
• Shorter flights to limit material load. 
• More cancellations of flights or fewer people on board during heatwaves due to reduced lift capacity. 

Inversions complicate ascent and descent 

An inversion occurs when the temperature increases with height, rather than decreases (which is normally the case). Inversions often occur in descending air masses that warm up due to compression as they descend. This layer acts as a lid on the atmosphere, preventing air masses from mixing. Balloons can therefore have difficulty ascending or descending through the layer. Climate change enhances the presence and duration of these inversions, especially in the summer half-year due to an increase in descending air movements. 

Convergence lines cause unexpected ascents and course changes  

Balloons are not steerable in the classical sense; they drift with the wind. By varying in height, pilots can take advantage of different wind directions and speeds. 

An invisible danger in the lower regions of the atmosphere are convergence lines. Convergence lines occur when air flows towards each other from different directions. Often, it involves a sea breeze front moving inland, sometimes up to 100 kilometers inland. This causes rising air and can lead to local showers, wind shifts, and turbulence. However, very often only clouds form on the convergence line and no showers, as shown in the situation in image 1. And sometimes there is even no cloud formation (extra dangerous, as it is invisible to the balloonist). Due to the higher temperatures in the Netherlands, these lines occur more frequently and actively. For balloonists, this means a risk of course changes, difficulty descending, or landing.