The US Geological Survey has an interesting story about the utility of Florida corals to track long-term variations in regional climate. Similar to tree rings, coral growth patterns can be used as proxy data to study changes in ocean temperature over time. These patterns show that there are multi-decade oscillations in sea surface temperature that have been occurring at least back to 1720, before the current human-assisted warming. By knowing past cycles, scientists think they can say something about long-term patterns in future climate as well. Of course, this depends on the corals being alive to mark the oscillations, and this is a concern because higher water temperatures and more acidic water from absorption of carbon dioxide threatens coral growth and health. You can read the story at https://www.usgs.gov/news/florida-corals-tell-cold-spells-and-dust-bowls-past-foretell-weather-come.