Assessment of the role of the Pacific Ocean in present climate changes

Abstract

Hydrothermodynamic processes in the atmosphere–ocean system played in favour of global warming slowdown in 1998–2014 were studied in this work. On the base of remote sensing and reanalysis data, close relationships between total global and regional column water vapour, terrestrial wind speed and temperature anomalies of upper layer water in tropical Pacific region were revealed. Increase of the wind speed in tropical Pacific has been observed since 1980 (linear trend ratio is –0.017 m · s–1/year). The most significant wind speed increase was in 1992–2013 (–0.025 m · s–1/year). During this period, the following phenomena were also observed: water temperature rise in upper layers of central and east equatorial Pacific regions by 0.024 K/year and accumulation of heat in the deeper layers of western Pacific north of the equator. These tendencies contributed to decrease in evaporation from the surface of the Pacific, which exerts considerable influence on the global mean water vapour content in the atmosphere with nearly 1-year lag (correlation coefficient is 0.88). Thus, average total column water vapour had been decreasing with average rate 0.12 mm/year until 2014. Atmospheric radiation transfer model calculations showed that decrease of water vapour content in atmospheric during 2001–2014 reduced the incoming part of Earth’s surface radiation balance by 0.93 W/m², which exceeds CO2-related increase in greenhouse warming by 11 times. Such behaviour of greenhouse gases concentrations could be the reason of decrease of winter temperature in Northern hemisphere. Summer temperatures continued to grow due to decrease in cloud optical depth in 35°N–70°N latitude zone and following radiation heating of the land surface.