evidence: Global mean sea level is the average height of the world’s oceans. It has been steadily increasing over the past century, primarily due to two major factors: the thermal expansion of ocean water as it warms and the addition of water from melting ice sheets and glaciers. This long-term rise is a clear indicator of ongoing climate change, driven by human activities that add greenhouse gases to the atmosphere. [...] At time periods slightly longer than seasons, naturally occurring climate variations can also cause changes in global mean sea level. For instance, El Niño and La Niña events can temporarily elevate or lower sea levels by affecting ocean temperatures and currents. During an El Niño event, the ocean temporarily warms on average and there is a net transfer of water from land and into the ocean due to shifting precipitation patterns. This leads to higher global mean sea level. The opposite happens during a La Niña and global mean sea level can actually drop.