Time Lag in Changes in Global Temperature and CO<sub>2</sub> Concentration Following Changes in the Oceanic Niño Index

Satellite measurements of global temperature began in 1979. According to the results of these measurements, the correlation between the global temperature and ocean temperature is very good, with a correlation coefficient of 0.99. The global temperature is controlled by the ocean temperature. The ocean temperature is not always constant but changes periodically, with high and low temperatures occurring repeatedly. This phenomenon is known as the El Niño or La Niña phenomenon. El Niño and La Niña phenomena are monitored by temperature changes in a specific area of the equator in the Pacific Ocean and are called the Oceanic Niño Index (ONI). When the ONI fluctuates significantly, El Niño and La Niña phenomena occur. A comparison of the ONI data from the National Oceanic and Atmospheric Administration (NOAA) and the global temperature data reveals that the temperature change throughout the entire Earth occurred approximately five months after the ONI change. At the western end of the Pacific Ocean, the direction of the warm current changes, and a warm current flows northward via the coast of the Japanese Islands. Even in such a unique location, the temperature change during the El Niño phenomenon changed five months later than did the change in the ONI value. Measurements of atmospheric CO2 concentrations at the Mauna Loa Observatory in Hawaii began in 1958. We compared these CO2 concentration changes with the above global temperature changes via NOAA data. As a result, we found that changes in global CO2 concentrations appeared approximately four months after global temperature changes. The CO2 concentration increases with increasing temperature. El Niño and La Niña phenomena are observed as small fluctuations in atmospheric CO2 concentrations. This is mainly due to increased plant respiration and accelerated decomposition of organic matter in soils due to rising temperatures. CO2 emissions from the ocean are also thought to have a significant impact, but quantitative investigations are a future task. On the other hand, compared with the global CO2 balance, CO2 emissions from anthropogenic activities are low. Our recent research results revealed that temperature and CO2 changes are correlated, but CO2 changes are the result of temperature changes, and we have not found that CO2 changes cause temperature changes.