01 / The world before
Weather alone cannot reveal long-term climate trends.
02 / The discovery
Measurements from land, ocean and space form long-term records.
03 / The people
Climate scientists, instrument makers and observers worldwide.
04 / The obstacles
Interpretation requires calibration and independent evidence.
05 / The world after
Multiple records now help explain planetary change.
06 / Why it still matters
Reliable observation supports decisions and further research.