The rising average temperature of Earth's climate system, called global warming, is driving changes in rainfall patterns, extreme weather, arrivals of seasons, and more. Collectively, global warming and its effects are known as climate change.
The globe is heating up. Both land and oceans are warmer now than they were when record keeping began, in 1880, and temperatures are still ticking upward. This rise in heat is global warming, in a nutshell.
Here are the bare numbers, according to the National Oceanic and Atmospheric Administration (NOAA): 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 degrees F (0.18 degrees C) per decade. This has led to an overall 3.6 degrees F (2 degrees C) increase in global average temperature today compared to the preindustrial era. In 2019, the average global temperature over land and ocean was 1.75 degrees F (0.95 degrees C) above the 20th-century average. That made 2019 the second hottest year on record, trailing only 2016.
This rise in heat 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.
How the greenhouse effect plays a role
The main driver of today's warming is the combustion of fossil fuels. These hydrocarbons heat up the planet via the greenhouse effect, which is caused by the interaction between Earth's atmosphere and incoming radiation from the sun.
"The basic physics of the greenhouse effect were figured out more than a hundred years ago by a smart guy using only pencil and paper," Josef Werne, a professor of geology and environmental science at the University of Pittsburgh, told Live Science.
That "smart guy" was Svante Arrhenius, a Swedish scientist and eventual Nobel Prize winner. Simply put, solar radiation hits Earth's surface and then bounces back toward the atmosphere as heat. Gases in the atmosphere trap this heat, preventing it from escaping into the void of space (good news for life on the planet). In a paper presented in 1895, Arrhenius figured out that greenhouse gases such as carbon dioxide could trap heat close to the Earth's surface, and that small changes in the amount of those gases could make a big difference in how much heat was trapped.
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