A region of the northern Atlantic–sometimes called the “cold blob”–has cooled since the 19th Century while the rest of the world has warmed. It is particularly the ocean which has cooled there. Scientists have been discussing whether this is because ocean currents bring less heat into this region, or because more heat is being lost through the sea surface there. An analysis of temperature data sets based on measurements show it is the former–changing ocean heat transport–which dominates heat content changes in the “cold blob.” This is of concern because a further weakening of Atlantic heat transport in future climate change could lead to serious impacts on climate and weather conditions in Europe and other parts of the world.