Arctic Ocean precludes evaluation of the full spectrum of internal variability, recent model- based estimates of signal-to-noise ratios indicate that the time of emergence of the greenhouse warming (signal-to-noise > 1) over the Arctic Ocean is the present decade for the cold season and the 2020s for the warm season (Hawkins and Sutton, 2012, Fig. 3). Moreover, climate model experiments show that the likelihood of an increase of Arctic sea ice over any particular 10-year period is about 30% (Kay 2011). For example, the et al., CCSM climate model simulates a hiatus in sea ice loss and Arctic warming over an entire decade in the mid-21st century (Vavrus 2012). Therefore, if models successfully et al., capture the key Arctic feedback processes and their timescales, it would not be surprising if there is pause or a temporary reprieve from the Arctic warming and sea ice loss over several years or a decade. By the second half of the century, however, an ice-diminished Arctic (relative to the present) should become the norm. Over the past decade, the Arctic has moved from the backwaters to the forefront of climate change research. The challenges listed above, including a narrowing of the uncertainty in the rate of future sea ice loss and mid-latitude impacts, are daunting. However, the potential consequences of Arctic change, together with the momentum of the research efforts summarized here, ensure that the Arctic will remain at the forefront of climate research and that it will be increasingly prominent in broader discussions of climate changes and impacts on middle latitudes. Acknowledgments. Preparation of this paper was supported by the Arctic National Science Foundation’s Research Program through Grant ARC-1023131. The manuscript is based on a keynote address at the Third International Symposium on Arctic Research in Tokyo, Japan, in
Arctic Ocean precludes evaluation of the full spectrum of internal variability, recent model- based estimates of signal-to-noise ratios indicate that the time of emergence of the greenhouse warming (signal-to-noise > 1) over the Arctic Ocean is the present decade for the cold season and the 2020s for the warm season (Hawkins and Sutton, 2012, Fig. 3). Moreover, climate model experiments show that the likelihood of an increase of Arctic sea ice over any particular 10-year period is about 30% (Kay et al., 2011). For example, the CCSM climate model simulates a hiatus in sea ice loss and Arctic warming over an entire decade in the mid-21st century (Vavrus et al., 2012). Therefore, if models successfully capture the key Arctic feedback processes and their timescales, it would not be surprising if there is pause or a temporary reprieve from the Arctic warming and sea ice loss over several years or a decade. By the second half of the century, however, an ice-diminished Arctic (relative to the present) should become the norm. Over the past decade, the Arctic has moved from the backwaters to the forefront of climate change research. The challenges listed above, including a narrowing of the uncertainty in the rate of future sea ice loss and mid-latitude impacts, are daunting. However, the potential consequences of Arctic change, together with the momentum of the research efforts summarized here, ensure that the Arctic will remain at the forefront of climate research and that it will be increasingly prominent in broader discussions of climate changes and impacts on middle latitudes. Acknowledgments. Preparation of this paper was supported by the National Science Foundation’s Arctic Research Program through Grant ARC-1023131. The manuscript is based on a keynote address at the Third International Symposium on Arctic Research in Tokyo, Japan, in