Abstract
<title>Abstract</title> <p>The Arctic has warmed considerably faster than the global average, with consequences for sea ice, permafrost and mid-latitude weather, yet the radiative feedback mechanisms behind the warming amplification remain poorly constrained by observations. Determining feedback magnitudes from radiation flux measurements is difficult because they blend the effects of many factors including atmospheric temperature, moisture, clouds and greenhouse gases. Here we apply a spectral fingerprinting method to long-term measurements of spectrally resolved downwelling longwave radiance at the North Slope of Alaska, isolating individual longwave forcings and feedbacks using their distinct spectral signatures. We find a positive surface longwave cloud feedback of 1.10 ± 0.93 W m-2 per decade, which strongly amplifies surface warming at this Arctic site and contrasts starkly with the negative feedback documented at mid-latitudes. These findings identify cloud feedback as an important amplifier of Arctic surface warming, suggesting a fundamental asymmetry in cloud feedbacks between high and mid latitudes that many climate models fail to capture.</p>