This talk will review the observations of Arctic climate warming and sea ice retreat, from space-based, surface, and submarine platforms. I will also review the history of global climate model predictions of Arctic warming, their consistency with observations, and their predictions for rest of the century. We now recognize several anthropogenic factors influencing Arctic climate change. Not only do ice-albedo and cloud-radiative feedbacks change the energy budget, but the Northern Annular Mode is manifesting in an accelerated outflow of sea ice from the central Arctic Ocean. I will give particular attention to one of the most recently discovered and most subtle anthropogenic influences: indirect effects of aerosols on Arctic clouds. The Arctic is polluted during winter, spring, and early summer, by pervasive aerosol burden having mainly Eurasian industrial origins. This aerosol burden, known as the "Arctic haze", has existed for nearly a century. The Arctic radiation budget is strongly influenced by pervasive low stratiform cloud cover, and with low sun elevations throughout most of the year, the longwave radiative effects of clouds predominate over the shortwave. Arctic haze particles entrained in clouds serve as cloud condensation nuclei, decreasing the cloud effective droplet size for a given cloud liquid water content. The resulting increase in cloud emissivity enhances the surface downwelling longwave radiation by up to 8 Watts per square meter, comparable to the effect of trace gas increases. This Arctic manifestation of the aerosol indirect effect contrasts with the usual shortwave manifestation observed at mid-latitudes. This longwave aerosol indirect effect was detected using multisensor data from the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program North Slope of Alaska site, and the unique potential for the advanced ARM instrumentation to advance Arctic atmospheric science will also be reviewed.