An 800 year volcanic record is constructed from high-resolution chemical analysis of recently obtained West Antarctica and central Greenland ice cores. The high accuracy and precision of the ice core chronologies are a result of dating by annual ice layer counting. Nineteen bipolar volcanic signals in this record represent large, explosive eruptions in the tropics with probable climatic impact. One of the two bipolar volcanic signals dated at 1453 and 1459 is probably left by the eruption of the submarine volcano Kuwae in the tropical Pacific, one of the largest volcanic eruptions in the last millennium. The discovery of the two signals in the 1450s casts doubt on the eruption year of 1452 or 1453 for Kuwae based on previous ice core records. The volcanic sulfate deposition patterns in this bipolar record suggest that the later signal is likely from the Kuwae eruption in 1458, although a firm attribution is not possible. Sulfur isotope composition in the volcanic sulfate in the central Greenland cores indicates that both eruptions in the 1450s injected sulfur gases into the stratosphere with probable impact on the global climate. These results are in agreement with tree ring records showing two short cold episodes during that decade. The bipolar volcanic record supports the hypothesis that unusually active volcanism in the thirteenth century contributed to the onset of the Little Ice Age and another active period in the mid fifteenth century may have helped to sustain the Little Ice Age.