Which tool is used to measure ambient temperature?

The thermometer is the appropriate tool for measuring ambient temperature. It operates on the principle of thermal expansion or contraction of liquids, usually mercury or alcohol, which provides a direct reading of temperature on a scale. Thermometers are specifically designed to gauge temperature across various ranges, making them ideal for assessing the warmth or chill of the surrounding environment.

Other tools mentioned serve different purposes. A barometer measures atmospheric pressure, which can help forecast weather but does not provide temperature readings. An altimeter measures altitude above sea level, often used in aviation and mountaineering, but it does not relate directly to temperature measurements. An anemometer is utilized to measure wind speed, giving insights into wind conditions but not atmospheric temperature. Thus, the thermometer stands out as the clear choice for measuring ambient temperature.