Professor Yoshinori Iizuka cuts a slice from an ice core sample taken from a glacier in the Pamir mountain range in Tajikistan, at the Hokkaido University Institute of Low Temperature Science, in Sapporo, in northern Japan's Hokkaido prefecture on December 9, 2025. Dressed in an orange puffer jacket, Japanese glacier scientist Yoshinori Iizuka stepped into a storage freezer chilled to minus 50 Celcius to retrieve an ice core. (Photo by GREG BAKER / AFP via Getty Images) / TO GO WITH: Japan-Tajikistan-climate-science-environment-research, FOCUS by Hiroshi HIYAMA

Researchers examine an ice core sample taken from a glacier in the Pamir mountain range in Tajikistan, at the Hokkaido University Institute of Low Temperature Science, in Sapporo, in northern Japan's Hokkaido prefecture on December 9, 2025. Dressed in an orange puffer jacket, Japanese glacier scientist Yoshinori Iizuka stepped into a storage freezer chilled to minus 50 Celcius to retrieve an ice core. (Photo by GREG BAKER / AFP via Getty Images) / TO GO WITH: Japan-Tajikistan-climate-science-environment-research, FOCUS by Hiroshi HIYAMA

Sketches and descriptions of an ice core sample taken from a glacier in the Pamir mountain range in Tajikistan, are seen on a sheet at the Hokkaido University Institute of Low Temperature Science, in Sapporo, in northern Japan's Hokkaido prefecture on December 9, 2025. Dressed in an orange puffer jacket, Japanese glacier scientist Yoshinori Iizuka stepped into a storage freezer chilled to minus 50 Celcius to retrieve an ice core. (Photo by GREG BAKER / AFP via Getty Images) / TO GO WITH: Japan-Tajikistan-climate-science-environment-research, FOCUS by Hiroshi HIYAMA

Researchers examine an ice core sample taken from a glacier in the Pamir mountain range in Tajikistan, at the Hokkaido University Institute of Low Temperature Science, in Sapporo, in northern Japan's Hokkaido prefecture on December 9, 2025. Dressed in an orange puffer jacket, Japanese glacier scientist Yoshinori Iizuka stepped into a storage freezer chilled to minus 50 Celcius to retrieve an ice core. (Photo by GREG BAKER / AFP via Getty Images) / TO GO WITH: Japan-Tajikistan-climate-science-environment-research, FOCUS by Hiroshi HIYAMA

A researcher prepares to take shavings from an ice core sample taken from a glacier in the Pamir mountain range in Tajikistan, at the Hokkaido University Institute of Low Temperature Science, in Sapporo, in northern Japan's Hokkaido prefecture on December 9, 2025. Dressed in an orange puffer jacket, Japanese glacier scientist Yoshinori Iizuka stepped into a storage freezer chilled to minus 50 Celcius to retrieve an ice core. (Photo by GREG BAKER / AFP via Getty Images) / TO GO WITH: Japan-Tajikistan-climate-science-environment-research, FOCUS by Hiroshi HIYAMA

A researcher cuts a slice from an ice core sample taken from a glacier in the Pamir mountain range in Tajikistan, at the Hokkaido University Institute of Low Temperature Science, in Sapporo, in northern Japan's Hokkaido prefecture on December 9, 2025. Dressed in an orange puffer jacket, Japanese glacier scientist Yoshinori Iizuka stepped into a storage freezer chilled to minus 50 Celcius to retrieve an ice core. (Photo by GREG BAKER / AFP via Getty Images) / TO GO WITH: Japan-Tajikistan-climate-science-environment-research, FOCUS by Hiroshi HIYAMA

Slices of ice from an ice core sample taken from a glacier in the Pamir mountain range in Tajikistan are seen in bottles at the Hokkaido University Institute of Low Temperature Science, in Sapporo, in northern Japan's Hokkaido prefecture on December 9, 2025. Dressed in an orange puffer jacket, Japanese glacier scientist Yoshinori Iizuka stepped into a storage freezer chilled to minus 50 Celcius to retrieve an ice core. (Photo by GREG BAKER / AFP via Getty Images) / TO GO WITH: Japan-Tajikistan-climate-science-environment-research, FOCUS by Hiroshi HIYAMA

A researcher drops slices of ice from an ice core sample taken from a glacier in the Pamir mountain range in Tajikistan into a bottle at the Hokkaido University Institute of Low Temperature Science, in Sapporo, in northern Japan's Hokkaido prefecture on December 9, 2025. Dressed in an orange puffer jacket, Japanese glacier scientist Yoshinori Iizuka stepped into a storage freezer chilled to minus 50 Celcius to retrieve an ice core. (Photo by GREG BAKER / AFP via Getty Images) / TO GO WITH: Japan-Tajikistan-climate-science-environment-research, FOCUS by Hiroshi HIYAMA