The theme of the Observatory Open Day 2021 “The ocean, our climate and weather” aims to remind public that human activities have caused global warming, thereby affecting the ocean and the weather. To alleviate these situations, countries must pay closer attention to the sustainable development of the environment and act immediately to combat climate change with a view to slowing down the global warming. At individual level, we can contribute through continuously and actively adopting greener lifestyle, saving energy and reducing carbon emissions.