The PhD defence will be held in Auditorium 1, and trial lecture in Auditorium 2 in The Geology Building. In some cases, it will be possible to attend the trial lecture and dissertation digitally, in that case a link to Zoom will be posted.
Trial lecture
Tuesday 25 November, 10:15-11:00, Aud 2, The Geology Building:
Understanding Aerosol Interactions in the Earth System: Progress and Challenges in Model Simulations at different scale
Conferral summary (in Norwegian)
Vindavblåst sand virker avkjølende på klimaet ved å reflektere solinnstråling, og ved å modifisere skyenes egenskaper. I sin avhandling har Ove Haugvaldstad brukt atmosfære- og klimamodeller til å vurdere hvordan økte støvmengder har påvirket klimaet de siste 150 årene. Studien bekrefter at endringer i sandstøv kan ha viktige effekter på jordsystemet, men at dagens modeller har store usikkerheter i fremstillingen av sandstøvets fysiske egenskaper, noe som gir varierende estimater av klimaeffekten. Ved å utelate historiske økninger i sandstøv fra beregningene, skaper det større usikkerhet knyttet til om dagens klimamodeller tilskriver temperaturendringer de riktige årsakene.
Main research findings
Popular scientific article about Haugvaldstad’s dissertation:
Drivers and impacts of windblown dust in a changing climate
Windblown mineral dust (sand) is a key component of the climate system, affecting the Earth’s energy balance, cloud properties, atmospheric chemistry, and biogeochemical cycles. It is important that climate models represent past changes in dust emissions consistent with reconstructions and accurately simulate the climatic effects of those changes. Reconstructions based on natural dust archives indicate large increases in global dust burden of about 55 ± 30% relative to the preindustrial era. However, current climate models do not reproduce these historical emission changes.
In his doctoral work, Ove Haugvaldstad addresses this discrepancy by (1) examining the role of natural variability in atmospheric circulation as a driver of the dust cycle (emission, transport, deposition) in East Asia; (2) quantifying the climate impact of historical dust emission changes using an ensemble of climate models forced with the reconstructed emissions; and (3) evaluating how models simulate dust’s direct and indirect climate effects.
The principal finding in the study is that prescribing the reconstructed increase in dust emissions produces surface cooling of a magnitude comparable to the cooling from anthropogenic air pollutant aerosols. This result implies that models may be compensating warming and cooling with incorrect attributions, raising the possibility that the climate system’s sensitivity to greenhouse gas forcing could be underestimated.
Photo and other information:
Press photo: Ove Haugvaldstad, portrait; 1500px. Photo: Private
Other photo material: Figure with description and credit as specified in the article above, size 1500px.
