Wash the thermometer in soap and rinse with cool, clean water before and after you use it. Do not use hot water because the thermometer may break. After washing, it is best to soak the thermometer in alcohol for 20 minutes. You can use ethyl, isopropyl, or medical alcohol (ethanol).
1 In 2015, the average temperature across global land and ocean surfaces was 1.62Â°F (0.90Â°C) above the twentieth-century averageâthe hottest year in the 136-year record.  Since 1976, every year has been warrmer than the long-term average.
Despite the overall increase, global temperatures have not climbed steadily during the decades. The average global annual temperature hovered around 13.7 Â°C (56.7 Â°F) from the 1880s through the 1910s. During the 1920s to 1940s, temperatures climbed about 0.1 Â°C (0.18 Â°F) each decade. Mean global temperatures then stabilized at roughly 14.0Â°C (57.2 Â°F) until the 1980s.