Progress in Solar Cycle Predictions: Sunspot Cycles 24-25 in Perspective

TL;DR

This paper reviews and assesses various predictions for solar sunspot cycles 24 and 25, highlighting progress in physics-based forecasting methods and the consensus on a weak cycle 25, reflecting advances in understanding solar cycle predictability.

Contribution

It provides a critical assessment of solar cycle predictions, emphasizing the convergence of physics-based models and progress in understanding solar cycle predictability.

Findings

Predictions for cycle 25 indicate a weak sunspot cycle.

Physics-based models have become more consistent in recent forecasts.

Understanding of solar cycle predictability has improved significantly.

Abstract

The dynamic activity of the Sun -- sustained by a magnetohydrodynamic dynamo mechanism working in its interior -- modulates the electromagnetic, particulate and radiative environment in space. While solar activity variations on short timescale create space weather, slow long-term modulation forms the basis of space climate. Space weather impacts diverse space-reliant technologies while space climate influences planetary atmospheres and climate. Having prior knowledge of the Sun's activity is important in these contexts. However, forecasting solar-stellar magnetic activity has remained an outstanding challenge. In this review, predictions for sunspot cycle 24 and the upcoming cycle 25 are summarized, and critically assessed. The analysis demonstrates that while predictions based on diverse techniques disagree across solar cycles 24--25, physics-based predictions for solar cycle 25 have converged and indicates a weak sunspot cycle 25. It is argued that this convergence in physics-based predictions is indicative of progress in the fundamental understanding of solar cycle predictability. Based on this understanding, resolutions to several outstanding questions related to solar cycle predictions are discussed.