Final answer:
The El Niño phase of the ENSO cycle has become more dominant since the late 1970s, characterized by warmer sea surface temperatures in the central and east-central equatorial Pacific and associated with global climatic changes.
Step-by-step explanation:
Since the late 1970s, the El Niño phase has become more dominant in the El Niño Southern Oscillation (ENSO). The El Niño is characterized by a band of warmer-than-average sea surface temperatures that extend across the central and east-central equatorial Pacific Ocean. This phase is marked by low air pressure in the eastern Pacific and high air pressure in the western Pacific, which leads to significant global changes in temperature and rainfall patterns. Studies, like the one conducted by Timmermann et al. (1999), suggest that increased El Niño frequency could be a consequence of future greenhouse warming, highlighting the impact of climate change on ENSO cycles.