Modes of Climate Variability

The chapter highlights the growing interest in how modes of climate variability influence temperature extremes and heatwaves and explores the relationship between climate variability and the occurrence of heatwaves. It begins by defining modes of climate variability as quasi-periodic variations in ocean and atmospheric circulation patterns and outlines what is meant by climate teleconnections. The Chapter adopts a probabilistic frame. It posits that certain atmospheric and oceanic circulation patterns may tip the balance of probability towards heatwave occurrence or non-occurrence because the associated atmospheric, ocean and land surface conditions either enhance or diminish the probability of extreme heat events in different regions. Several key modes of climate variability are discussed, including the El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Madden Julian Oscillation (MJO), Indian Ocean Dipole (IOD), Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). Each mode’s characteristics, geographical impacts, and their potential to influence heatwave occurrences are examined. The chapter underscores the complexity of the association between modes of climate variability and heatwave occurrence, especially as multiple modes may amplify or dampen the likelihood of heatwave occurrence and calls for a deeper understanding of the physical mechanisms that underlie the cascade of processes that link modes of climate variability with atmospheric and marine heatwave occurrence.