Q. Consider the following principles regarding the use of Oxygen-18 in Palaeoclimatology:

1. Oxygen-18 helps in measuring the average atmospheric temperature
2. Water molecules containing the heavier O-18 evaporate at a higher temperature
3. When temperature increases, the ratio of O-18 to O-16 will be higher

Which of the above principles is / are correct?
Answer: Only 2 & 3
Notes: Oxygen-18 (O-18) is utilized in palaeoclimatology due to its behavior during phase changes in the hydrological cycle. O-18–enriched water evaporates at higher temperatures and condenses differently than O-16, which is lighter. As temperatures increase, the O-18/O-16 ratio in precipitation or ice cores generally rises, providing a temperature proxy. Statement 1 is inaccurate, as O-18 does not directly measure temperature.