Question

select the event that marks the beginning of the instrumental period of climate history.

invention of the mercury thermometer by daniel fahrenheit in 1714
routine and widespread usage of thermometers starting in 1860
first temperature recording by an orbiting weather satellite in 1979
use of ocean - going vessels to measure marine air temperatures in 2000

Explanation:

The instrumental period of climate history begins when there is routine and widespread data collection using instruments. The invention of a thermometer (1714) is just the creation of the tool, not the start of systematic climate - data gathering. The first satellite temperature recording (1979) and ocean - going vessel measurements (2000) are much later. Routine and widespread usage of thermometers starting in 1860 marks the beginning of consistent instrumental climate data collection.

Answer:

routine and widespread usage of thermometers starting in 1860