Couertsy: livescience.com

Global warming is the rise in average temperatures across the globe, which has been ongoing at least since record keeping began in 1880. 

Here are the bare numbers, according to the National Oceanic and Atmospheric Administration (NOAA)(opens in new tab): Between 1880 and 1980, the global annual temperature increased at a rate of 0.13 degrees Fahrenheit (0.07 degrees Celsius) per decade, on average. Since 1981, the rate of increase has sped up, to 0.32 F (0.18 C) per decade. This has led to an overall 3.6 F (2 C) increase in global average temperature today compared with the preindustrial era. So far, 2016 is the hottest year on record, but that record has been close to falling several times already. The years 2019 and 2020 both came within fractions of degrees of knocking 2016 off its perch. In 2020, the average global temperature over land and ocean was 1.76 F (0.98 C) warmer than the 20th-century average of 57.0 F (13.9 C). 

Modern global warming is caused by humans. The burning of fossil fuels has released greenhouse gases into the atmosphere, which trap warmth from the sun and drive up surface and air temperatures. Global warming is a synonym for climate change, though “climate change” has become the preferred term among scientists.