Global Circulation and Climate

Global warming is thought to accelerate the upwelling of air masses in the UTLS region, i.e. the upper troposphere and lower stratosphere. This circulation change influences the thermal structure of the UTLS both directly and indirectly via changes in ozone and water vapour. All these changes would feed back on the warming and affect climate sensitivity. We try to better quantify the magnitude of these effects.

Another aspect we are investigating is that not only greenhouse gases but also aerosol forcing, for instance from volcanic eruptions, can affect global temperature. It is assumed, however, that the forcing from volcanic aerosols does this less effectively. We try to understand if and why this is the case, and how this may be related to the spatial structure of forcings and feedbacks.

A curiosity of Earth’s atmosphere is that the planet reflects as much solar radiation in the Northern as in the Southern hemisphere, despite the surface being brighter in the North. Clouds compensate for this surface difference, but it is unclear if this happens by accident or if the compensation is due to a physical mechanism. That is the reason why we investigate what defines Earth’s albedo.