Professor Kim Sang-wook, a physicist, shares his perspective on environmental issues. He mentions that the Earth's climate has experienced dramatic changes throughout its history. The most significant event occurred approximately 55 million years ago, during a period known as the Paleocene-Eocene Thermal Maximum (PETM). During this time, the Earth's temperature increased by about 5 to 6 degrees Celsius over a span of 20,000 years. This period is also referred to as the "maximum hot" phase. Professor Kim highlights the importance of understanding the environment from a physicist's viewpoint and emphasizes the need for further research in this field.