500-year simulation reveals natural drivers of North Atlantic Oscillation shift

Much remains unknown about what causes the North Atlantic Oscillation (NAO), a significant climate phenomenon in the Northern Hemisphere, to move east and west of Iceland. To date, there are several hypotheses suggesting that this process known to the international scientific community may be related to the effects of greenhouse gases on the Earth.

The study, published in the academic journal NPJ Climate and Atmospheric Science, shows that changes in the NAO may be the result of natural fluctuations in the atmospheric system, rather than human-induced influences altering global climatology. It makes one thing clear. The new study is led by experts María Santralía Autin and Javier García Serrano from the Physics Department and Meteorology Group of the University of Barcelona.

Why does NAO move vertically?

NAO was first identified in the early 20th century, but its effects were known to people in Northern Europe much earlier. The NAO is one of the most studied climate change phenomena in the scientific community. However, many aspects of the dynamics and processes controlling its variation, both temporally and spatially, are still unknown, and evidence of its past and expected future trends is still debated.

“The atmosphere is a fluid system with highly chaotic and unpredictable behavior,” said Garcia Serrano, a professor in the UB Department of Applied Physics. “We have made it clear that legal coercion can be excluded.” Factors that may help understand these changes in the NAO, such as the effects of greenhouse gases or interactions with the ocean. However, more studies are needed to confirm these hypotheses. ”

On a global scale, the impact of this change in the NAO is likely to be small, but it could impact changes in Arctic sea ice and, by extension, other remote regions of the planet. According to the study, this process will not change the trend of anthropogenic global warming.

The NAO explains about half of the climate change in continental Europe and the Mediterranean region, so regional-scale effects will be more important. “However, the impact on future projections and predictions will primarily be to adjust the trends in climate change over a given time period,” Garcia-Serrano said.

In this context, the UB team used global climate models to run and analyze 500-year simulations. “By applying this innovative methodology, we are able to separate the effects of radiative forcing and ocean coupling, which cannot be reached using observational data alone,” said Santralia Autin, postdoctoral researcher and lead author of the study. We were able to reach a conclusion.” ”

The NAO is considered one of the most influential patterns of low-frequency fluctuations (teleconnections) in the Northern Hemisphere climate. In this challenging scenario, the UB team continues to expand its research to understand what factors control changes in the NAO and its remote effects from the perspective of global climatology.