The Hot Spot in Climate Systems project will impact on the broader understanding of the Earth’s climate, with convincing evidence that the mid-latitude ocean, especially, an intense warm current along the extreme western portion of each ocean basin such as the Gulf Stream or Kuroshio, can exert thermodynamic forces on the atmosphere. Merging with a cold current, the eastward extension of the warm current forms an oceanic frontal zone characterized by sharp gradient of sea surface temperature (SST). The variability of the frontal zone yield strong persistent SST anomalies and thereby modify heat/moisture release as thermodynamic forcing on the atmosphere. The warm western boundary currents and associated mid-latitude frontal zones, which we call climatic ‘hot spots’ in mid-latitude ocean basins, can therefore be significant in shaping the tropospheric circulation and its variability, which is obviously contrary to the established notion that the extratropical ocean is passive to atmospheric variability. The project has re-discovered the climatic signficance of the mid-latitude ocean, by highliting the impacts of the ‘hot spots’ on the mean status and varianility of the extratropical climate, for example, by organizing convective cloud/precipitation systems and also organizing 'storm tracks`through favoring recurrent development of extratropical cyclones and anticyclones and thereby forcing basin-scale/hemispheric-scale westerly jets, including their variability. The project involves hundered of scientsts/graduate students across Japan, working collaborative studies between in situ observations and analysis of high resolution satellite observations and model outputs. Our findings urge the international community of climate studies to enhance high resolution modelling of the ocean to resolve narrow mid-latitude climatic hot spots.