[1] Atmospheric climate models are subjected to the observed sea ice conditions during 2007 to estimate the regionality, seasonality, and vertical pattern of temperature responses to recent Arctic sea ice loss. It is shown that anomalous sea ice conditions accounted for virtually all of the estimated Arctic amplification in surface-based warming over the Arctic Ocean, and furthermore they accounted for a large fraction of Arctic amplification occurring over the high-latitude land between 60°N and the Arctic Ocean. Sea ice loss did not appreciably contribute to observed 2007 land temperature warmth equatorward of 60°N. Likewise, the observed warming of the free atmosphere attributable to sea ice loss is confined to Arctic latitudes, and is vertically confined to the lowest 1000 m. The results further highlight a strong seasonality of the temperature response to the 2007 sea ice loss. A weak signal of Arctic amplification in surface based warming is found during boreal summer, whereas a dramatically stronger signal is shown to develop during early autumn that persisted through December even as sea ice coverage approached its climatological values in response to the polar night. Citation:

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The differences in tropical air-sea interactions and global climate connection as well as the hindcast skills for the warm pool (WP) and cold tongue (CT) El Niños are investigated based on observed, (re)analyzed, and model hindcast data. The robustness of observed global climate connection is established from the model simulations. Lastly, variations of atmosphere and ocean conditions in the recent decades, and their possible connection with the frequency increase of the WP El Niño are discussed. Consistent with previous results, our individual case study and composite results suggest that stronger (weaker) and more eastward extended (westward confined) westerly wind along the equatorial Pacific in early months of a year is associated with active (suppressed) air-sea interaction over the cold tongue/the Intertropical Convergence Zone complex, as well as more (less) intensive oceanic thermocline feedback, favoring the CT (WP) El Niño development. The preceding westerly wind signal and air-sea interaction differences may be responsible for the predication skill difference with higher (lower) overall hindcast skill for the CT (WP) El Niño in the Climate Forecast System of National Centers for Environmental Prediction.Our model experiments show that, in addition to the tropics, the eastern Pacific, North America and North Atlantic are the major regions having robust climate differences between the CT and WP El Niños. Nevertheless, the climate contrasts seem not robust over the Eurasian continent. Also, the frequency increase of the WP El Niño in the recent decades may not be directly connected with the linear trend of the tropical climate.