What is the difference between the greenhouse effect, global warming, climate change, and the climate crisis? These terms are used interchangeably, so why use one term instead of another? For one, you can roughly date a text by which term it uses. Each comes from a different era, and each reflects what we knew at the time, and what we worried about. Mostly, the language followed the science. The language also has the fossil fuel industry’s fingerprints on it.
In technical terms, the greenhouse effect describes how greenhouse gases, including, famously, carbon dioxide, trap heat in the atmosphere. It’s actually quite easy to demonstrate by taking two sealed jars with thermometers and filling one with a greenhouse gas, before exposing both to a heat lamp for thirty minutes or an hour. The classic greenhouse gas to use is, of course, carbon dioxide, but I’ve heard that a glass of water works, too, and absorbs the heat significantly faster.
The greenhouse effect was discovered in the 19th century, so this term has been around the longest. The term is also slightly misleading, because that is not how a greenhouse works. A greenhouse works by trapping hot air and preventing it from mixing with cool air from shaded areas. Greenhouse gases work differently: sunlight passes through them mostly unhindered and warms the Earth’s surface. The surface then releases that energy back toward space as infrared radiation. This is what greenhouse gases absorb, trapping heat in the atmosphere that would otherwise escape to space.
If greenhouse gases trap heat, then adding more of them should raise global average temperatures. That is the second term: global warming.
Ironically, oil majors were deeply involved with the science on global warming, particularly in the late 1970s and early 1980s. Exxon in particular spent big on climate science and carried out data collection from one of its tankers to determine how much carbon dioxide the ocean would absorb (thereby lessening global warming). Exxon had remarkably accurate projections of global warming, yet swiftly abandoned these efforts in the 1980s and pivoted to climate denial (Supran, Rahmstorf, and Oreskes 2023).
In the 1980s, the public discourse on global warming picked up, particularly in 1988, when NASA’s James Hansen delivered his landmark testimony on global warming to the U.S. Senate. (Hansen also used the term “greenhouse effect” quite a bit.) In the mid-1990s, scientists formally confirmed that greenhouse gas emissions had already led to a measurable increase in global mean temperatures.
But rising temperatures come with knock-on effects. Around the same time, the scientific literature began cataloguing the other impacts of global warming, and the most important of these, we know today, is an increase in extreme weather. Hot air can absorb (and later release) more moisture, so downpours intensify; a destabilized climate can also deliver weeks of extreme cold, even as the Arctic warms faster than anywhere else. The average temperature rises modestly; the extremes shift much more. That’s what the term climate change captures.
By the time the Earth Summit was held in Rio de Janeiro in 1992, climate change had become the dominant language.
Another reason why global warming has mostly disappeared from public discourse may be strategic communication by American conservatives in the early 2000s (when global warming was still more commonly used in public discourse, such as newspapers). The 2002 “Luntz memo” lays out the plan to use the language of climate change to take some of the edge off, because “climate change” had polled with focus groups as sounding less alarming (Schuldt, Enns, and Cavaliere 2017).
In the second half of the 2010s, when climate change really began to show its ugly face and it became clear that the international community would not do anything about it (Stoddard et al. 2021), the term climate crisis finally began to catch on.
The term should be pretty straightforward to explain. Climate change is no longer a phenomenon to observe; it constitutes an ongoing crisis. The language was popularized by climate activist groups, such as Extinction Rebellion, but also driven by climate scientists, whose warnings had fallen on deaf ears for years (there is actually some overlap between the groups, in organizations like Scientist Rebellion). The language has caught on in declarations of emergency in many constituencies, often local or sub-national.