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Disputation: Sigmund Guttu

Doctoral candidate Sigmund Guttu at the Department of Geosciences, Faculty of Mathematics and Natural Sciences, is defending the thesis Forcing from the 11-year Solar Cycle and relevance for inter-annual to decadal climate variability for the degree of Philosophiae Doctor.

Photo: Sigmund Guttu. Photo: Private

Sigmund Guttu. Photo: Private

The PhD defence and trial lecture are fully digital and streamed using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation. It is possible to be present at the disputation in auditorium 1.

Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants -> Raise hand'. 

Trial lecture

As a recording:

Shifts in Northern European climate associated with global warming

Conferral summary (in Norwegian)

Kunnskap om naturlige klimavariasjoner har stor betydning for å forstå dagens og framtidens klima. I avhandlingen er det brukt klimamodeller for å øke forståelsen av 11-års solsyklusens innvirkning på klimavariasjoner over korte tidsskalaer i Nord-Atlanteren og Det nordlige Stillehavet. Studien viser at solens variasjoner i stråling og geomagnetisk aktivitet gir liten effekt på klimaet, men et viktig funn er at solens påvirkning over Stillehavet er relativt stor når det permanente lavtrykket over Auletene, en øyrekke i det nordlige Stillehavet, er svakere enn normalt. 

Main research findings

Popular scientific article about Guttu’s dissertation:

The role of natural climate variability is an important research topic for predictions of future climate on various time scales

The 11-year solar cycle is one out of many climate drivers, acting on inter-annual to decadal time scales. This climate forcing from the sun component involves variations in incoming radiation and energetic particle precipitation. Although the atmospheric fingerprints are mostly observed in the stratosphere and mesosphere, related changes in wind and temperatures may connect to the tropospheric circulation during winter.

This doctoral thesis performs idealized climate model experiments to improve our understanding of the solar cycle impact on stratospheric and surface climate variability, with a focus on the North Atlantic and North Pacific during winter. The novelty has been to include both radiative and state-of-the-art particle precipitation forcings.

The results show that changes in stratospheric winds induced by solar variations are affecting the tropospheric circulation in extratropical regions. We find a characteristic radiative solar signal in the North Atlantic albeit its amplitude is weak, but no clear dynamical signatures from particle precipitation. On the Pacific side, the results suggest that the effect of the solar forcing is modulated by the background state of the coupled atmosphere-ocean system, with a relatively strong solar signal in the negative phase of the Pacific Decadal Oscillation.

Photo and other information:

Press photo: Sigmund Guttu, portrait; 600px. Photo: Private

Published Sep. 30, 2021 11:23 AM - Last modified Oct. 12, 2021 2:11 PM