Warming
The increase in the planet's average surface temperature of about 1 degree Celsius since the late 19th century has been driven largely by increased carbon dioxide emissions into the atmosphere and other human activities.
Most of that warming has occurred in the past 40 years. The years 2016 and 2020 are currently tied for the warmest year globally on record.
The roughly 2°F (1°C) increase in global average surface temperature that has occurred since the 2nd Industrial Revolution might seem small, but it corresponds to a significant increase in accumulated heat. It takes a massive amount of heat energy to raise Earth’s average yearly surface temperature by even a small amount.
Global Average Surface Temperature
This NOAA Climate.gov graph - from this page - shows yearly surface temperature compared to the average from 1880–2022. Blue bars indicate cooler-than-average years; red bars show warmer-than-average years.
Earth’s temperature has risen by an average of 0.14° Fahrenheit (0.08° Celsius) per decade since 1880, or about 2° F in total. The rate of warming since 1981 is more than twice as fast: 0.32° F (0.18° C) per decade.
This analysis generally matches independent analyses, such as that prepared by the Climatic Research Unit.
Average surface temperature
The concept of an average temperature for the entire globe may seem strange.
However, as this extract explains, given the wide variation in surface temperature of the globe at any time using a calculated average temperature provides a straightforward means of measuring changes in Earth's "energy budget".
April 2023: ‘Headed off the charts’: world’s ocean surface temperature hits record high
Climate scientists have reported that preliminary data from the National Oceanic and Atmospheric Administration (NOAA) have shown the average temperature at the ocean’s surface to be 21.1C since the start of April 2023. The previous high was 21C set in 2016.
Their findings are summarised in this article, which also shows how this apparently slight increase is a strong warning sign for increased extremes.
Research teams anticipate that the effects of warming ocean temperatures will increase in frequency, duration and intensity.