Scientists have been concerned about a gap in satellite data that was being used to monitor mass balance changes of the world's glaciers. Using alternative data, a new study has helped to fill the gap, creating a continuous record of rates of glacier retreat around the world since 2002 until present. It is important to monitor changes in mass balance—the net changes in a glacier's mass, after accounting for gains from snowfall and losses from melting and iceberg calving—in order to generate robust predictions of sea level rise.