Why are nights getting warmer faster? That's exactly what researchers are looking into. They've found that over the past 50 years, nights have been getting a lot warmer a lot more quickly.
In recent decades, there's been more rapid warming at night compared to the day. While in the past researchers have pointed to possible increases in cloud cover, precipitation or soil moisture as possible causes, this latest study instead focuses on the climate system.
In this latest study, the researchers analyzed the causes of these changes from observations and model reconstructions of the climate.
Our atmosphere can be divided into many different layers with different names. The layer that exists just above the ground is known as the boundary-layer. At night, this particular layer is extremely thin at only a few hundred meters. During the day, though, it expands to a few kilometers.
As carbon dioxide enters the atmosphere, it increases both nighttime and daytime temperatures. However, at night there's a much smaller volume of air. In this case, the researchers found that it's this small volume that explains why nighttime temperatures are far more sensitive to climate warming. This, according to the researchers, explains why nights are getting warmer faster than days.
Unfortunately, it's difficult for climate models to calculate this faster warming at night. This is largely because they have a difficult time representing the boundary-layer. This means that creating a correct representation of this boundary-layer in computer simulations could be huge for future temperature and climate predictions.
"An improvement of the boundary-layer physics in climate models would very likely reduce our uncertainty in projections of temperature change," said Richard Davy, one of the researchers. "This is true for both global projections related to climate sensitivity, and regional projections on local temperature change. It is my expectation that by addressing this problem we can reduce this current uncertainty in how global mean temperature will change in response to increased carbon dioxide in the atmosphere."
The findings, published in the International Journal of Climatology, could help researchers better predict the changing climate in the future. In order for this to occur, though, the next step is to focus on accurately representing this night-time boundary-layer.
