Final answer:
The question refers to the natural climate variability and cyclical patterns such as the Pacific Decadal Oscillation, Arctic Oscillation/North Atlantic Oscillation, and El Niño Southern Oscillation, including the El Niño and La Niña phases that lead to global changes in weather patterns.
Step-by-step explanation:
The phenomena of the late 1970s that is evident when examining time series of Pacific Decadal Oscillation (PDO), Arctic Oscillation/North Atlantic Oscillation (AO/NAO), and El Niño Southern Oscillation (ENSO) likely refers to the natural climate variability and the periodic warming and cooling cycles of the earth's ocean-atmosphere systems.
These oscillations contribute to significant changes in global weather patterns, affecting temperatures and precipitation. For instance, El Niño is a warm phase of ENSO characterized by warm ocean water in the central and east-central equatorial Pacific, leading to high air pressure in the western Pacific and low air pressure in the eastern Pacific, which can cause global changes in weather.
Conversely, La Niña, the cool phase of ENSO, is associated with below-average SST in the eastern Pacific and changes in air pressure that are complementary to those of El Niño. Additionally, historical climate anomalies such as the Medieval Climate Anomaly and the Little Ice Age were periods of significant temperature deviations, with natural drivers including Milankovitch cycles, changes in solar activity, and volcanic eruptions. These natural fluctuations have long-term impacts on earth's climate patterns and are essential for understanding the historical context of contemporary climate changes.