Air temperature

Surface air temperature refers to the temperature of the Earth’s surface, which is influenced by various factors such as solar radiation, greenhouse gases, and land use changes. Changes in air surface temperature influence many systems and sectors (USGCRP, 2017). More frequent and intense extreme heat events can lead to human health issues and agricultural damage. Warming temperatures, both during the day and at night, also lead to an increase in the use of energy needed to meet indoor cooling needs.

Surface temperature is a key measure of climate change. Observations come from meteorological stations, ships and buoys, and satellites (IPCC, 2021). Temperature is typically described in terms of maximum, minimum, and mean values. Other common indicators include the number of hot days and cool nights, as well as heat‑indices or wet‑bulb metrics which measure human comfort.

Because of the moderating influence of the ocean, Palau’s annual temperature range is small (on the order of 1°C; Miles et al., 2020). However, small changes in surface temperature matter in tropical islands: very hot days and warm nights increase heat stress and cooling needs, especially when humidity is high (USGCRP, 2017).

In this section we look at three indicators of surface temperature change. Using observations from the Koror meteorological station we will create plots that show changes in the mean surface temperature, minimum and maximum surface temperature, and the amount of hot days and cool nights. Hot days are defined as days above the 90th percentile for that same calendar day (e.g., January 15th) from the 1960–1990 period, while cold nights are defined as days below the 10th percentile for that same calendar day in the 1960–1990 period. We will also create a table that summarizes these results.