Words matter – especially with a topic as complex and critical as climate change. Language can be used to motivate or demotivate people, to clarify a threat or to cloud it. Moreover, when it comes to our human-altered climate, there’s a perennial tug-of-war between scientists’ desire for precision and nuance and the need to make key points understandable to policymakers and the public.

Below is a short history of a few terms and phrases that are helping fill the ever-more-crowded linguistic toolbox of climate change.

The problem emerges

Climate science wasn’t always front-page news. In fact, British climatologist Hubert Lamb once summarized a long-held view of his discipline as “the dry-as-dust bookkeeping branch of meteorology.” Scientists began to unravel the history of ice ages as far back as the early 1800s, but well into the 20th century, it was widely assumed that contemporary climate was more or less stable.

Long-term concern about greenhouse gases began to increase after regular monitoring of carbon dioxide was launched at Mauna Loa, Hawaii, in 1957. Global temperatures weren’t yet climbing in a sustained way, though. On the contrary, sun-blocking aerosols being spewed out in the industrial boom after World War II were actually cooling much of the Northern Hemisphere.

By the 1970s, more scientists were analyzing both of these warming and cooling factors, typically under the broad heading of climatic change. The first prominent appearance of the term global warming was in a 1975 Science paper by Columbia University scientist Wallace Broecker entitled “Climatic change: Are we on the brink of a pronounced global warming?”

Attention swung hard toward greenhouse gases as global temperatures began a sharp rise in the 1980s. By this point, environmental regulations were tamping down on sunlight-blocking aerosols, while allowing carbon dioxide and other invisible greenhouse gases to increase unconstrained.

Global warming became front-page U.S. news in 1988, when a major congressional hearing coincided with devastating wildfires in the West. Journalists of the day typically referred to the problem at hand as either global warming or the greenhouse effect. Scientists were already starting to favor climate change – a more versatile term that could embrace past, present, and future events, whether natural (such as ice ages) or human-caused.

The launch of the Intergovernmental Panel on Climate Change (IPCC) in late 1988, and its first major assessment in 1990-91, further solidified the use of “climate change” in scientific parlance.

Meanwhile, “global warming” remained – and still remains – in wide popular use as shorthand. It’s an accurate term as far as it goes, but too narrow to convey all the threats that go beyond higher temperatures. Some scientists and activists have advocated for the term global heating, a label that subtly implies human activity is behind what’s going on.

Politics enter the picture

Virtually all of the world’s nations, including the United States, signed on to the United Nations Framework Convention on Climate Change (UNFCCC), a treaty finalized at the 1992 Earth Summit in Rio de Janeiro. The treaty’s objective – “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system” – still guides all UNFCCC activities. These include the annual Conference of the Parties (COP) meetings that have included COP15 (Copenhagen, 2009), COP21 (Paris, 2015), and COP26 (Glasgow, 2021).

Some of the many signatures by participants at the 1992 Earth Summit in Rio de Janeiro who signed the Earth Pledge, promising to “help make the Earth a secure and hospitable home for present and future generations”. (Image credit: UN Photo / Michos Tzovaras)

Given that the UN had successfully addressed ozone depletion with the Montreal Protocol in 1987, hopes were high that the Rio agreement could help do the same for climate change. However, pushing in the other direction were the world’s massive fossil fuel companies, politicians allied with them, and a contingent of think tanks, often peppered with a few iconoclastic scientists.

These naysayers were typically referred to as climate-change skeptics, a phrase that rankled many researchers who saw skepticism as an inherent part of all science. Alternative labels such as contrarians soon popped up. Yet some observers, especially climate hawks (activist-oriented stakeholders, including some scientists), felt these terms did not go far enough to convey how far the naysayers were positioned from the ever-strengthening mainstream of climate science.

News stories in the 1990s often paired quotes from a mainstream scientist with those from a skeptic – a distorted “both sides” approach that obscured the larger asymmetry. This type of pseudo-balanced reporting has now largely evaporated, according to a 2021 study.

Taking a page from the use of “Holocaust denier” for those who make the incredulous claim that the Holocaust never happened, the term climate denier got increasing traction in the 2010s. Since climate itself isn’t being denied, a more precise variant is climate-change denier.

Climate-change denial is highlighted in this protestor’s sign from the March for Science in Washington, D.C., on April 14, 2018. (Image credit: Adam Fagen / CC BY-NC-SA 2.0)

Mainstream media outlets (for example, the Associated Press) have often veered away from the climate-denier label, perhaps in part because there are multiple modes of climate science rejection and opposition. Occasionally, for instance, ​some ​scientists on the fringe of the debate have claimed​ ​that carbon dioxide doesn’t cause global warming at all – a clear case of denying established science. Others accept some of the basic precepts of greenhouse-gas warming but assert that the amount of warming would be on the reassuringly low side, or that various feedbacks (sometimes unspecified) would “balance out” greenhouse warming, or that human adaptation would make the whole thing a minor concern.

Many of the most outspoken and highly visible climate-change contrarians of the 1990s have passed on or aged out of the debate. And the relentless advance of climate change itself has worked to defang some of the most fervent naysayers. Yet there’s still huge financial incentive for those invested in fossil fuels (financially, emotionally, and/or politically) to downplay or dismiss climate-change science.

The fraught topic of geoengineering – what many consider to be the last-ditch form of climate action – has its own lingo. The term gained prominence in the 2000s and 2010s as a catch-all for two types of activities: solar radiation management, or SRM (i.e., blocking sunlight to cool Earth), and carbon dioxide removal, or CDR (i.e. pulling carbon from the air, either through natural means or artificial devices).

Over the past few years, the term climate intervention strategies has gained popularity as an alternative term for these activities. It’s also becoming more common to see SRM described as solar geoengineering and CDR simply as carbon removal.

The linguistic revolution

How climate change is discussed in traditional and social media has arguably changed more since 2018 than in any period since the topic first surged in the late 1980s.

One huge impetus was the blockbuster IPCC report issued in 2018 that laid out the potential consequences of 1.5 degrees Celsius of warming over preindustrial temperatures. The report stressed the need to cut global carbon dioxide emissions by nearly half by 2030, compared to 2010 values, in order to preserve a two-thirds chance of keeping long-term warming to no more than 1.5°C above pre-industrial values (with the potential for some brief overshoot above that threshold in some scenarios). Staying within that range, in turn, would reduce the odds of some of the worst consequences of climate change, such as the destabilization of Antarctic ice sheets and other potential tipping points with dire global implications.

It’s the 2030 framing used in this report that has fostered widespread adoption of the “ten years to act” concept.

From the 1990s into the 2000s, it was widely assumed by diplomatic bodies that 2°C of warming was a suitable and reasonably practical target. In fact, the 2°C goal was central to the nonbinding Copenhagen Accord in 2009. However, leaders and activists from developing countries, including some of the world’s most vulnerable small island states – their very existence threatened by sea level rise they had no role in creating – were already pushing for a more stringent target, 1.5°C.

The 2015 Paris Agreement aimed for a compromise, calling to “limit global warming to well below 2, and preferably to 1.5 degrees Celsius, compared to pre-industrial levels.” The IPCC’s subsequent report lent immense momentum to the 1.5°F goal (even though the planet’s nation-by-nation emission-reduction goals continue to fall short of the mark).

The 2018 IPCC report also galvanized many scientists and activists and prompted the spread of newly dire terminology, including climate crisis, climate emergency, and climate breakdown. Two other terms, both famously employed by United Nations secretary general António Guterres, have also gained currency: existential threat (2018) and Code Red for humanity (2021).

UN Secretary-General António Guterres addresses a virtual ministerial plenary meeting on September 30, 2021, in advance of that November’s COP26 meeting in Glasgow. (Image credit: UN Photo / Mark Garten)

The Guardian, one of the world’s most widely read legacy-media websites, drew global notice in 2019 with its decision to favor the new terms:

The Guardian has updated its style guide to introduce terms that more accurately describe the environmental crises facing the world. Instead of “climate change” the preferred terms are “climate emergency, crisis or breakdown” and “global heating” is favoured over “global warming,” although the original terms are not banned.

Editor-in-chief Katharine Viner explained: “We want to ensure that we are being scientifically precise, while also communicating clearly with readers on this very important issue … The phrase ‘climate change,’ for example, sounds rather passive and gentle when what scientists are talking about is a catastrophe for humanity.”

In a 2020 style guide revision, the Associated Press added the terms but made them optional rather than mandatory:

The terms climate crisis and climate emergency are used by some scientists, policymakers and others, and are acceptable.

Declaring human-caused climate change to be an emergency might seem odd given that it’s been under way for decades (a lumbering emergency if ever there were one). However, the designation has a practical side: It implies that a response is needed, and soon. Cities, states, and nations that formally declare a climate emergency can leverage that designation in support of a variety of actions.

While several cities had declared climate emergencies up to 2018, momentum surged in 2019 and 2020, when Argentina, Canada, Japan, and the European Union followed suit. By October 2021, more than 2,000 jurisdictions in 35 countries, representing more than a billion people, had declared a climate emergency. Meanwhile, more than 11,000 scientists signed on to a 2019 paper in BioScience asserting “clearly and unequivocally that planet Earth is facing a climate emergency.”

Demands to declare climate emergencies, as in this photo from Melbourne, Australia, were a major part of a student-oriented climate strike held on March 15, 2019. (Image credit: Takver via Wikimedia Commons, CC BY-SA 2.0)

As for “climate breakdown,” the climate itself doesn’t break down like a washing machine or a bicycle might – but the phrase does bring to mind a metaphorical monkey wrench of human-produced greenhouse gases torquing the finely tuned mechanisms that preserve the climatic envelope to which people and ecosystems have adapted for centuries.

The phrase “existential threat” can be interpreted in a wide range of ways. Does it mean everyone would literally cease to exist? Or is the threat instead to civilization “as we know it,” a terrifying but not identical concept? The possibility that high-end climate scenarios might someday trigger a mass extinction event can’t be entirely ruled out, as noted by the MIT Climate Portal. Much more likely is an existential threat to particular cultures, such as those of the indigenous peoples of small island states or polar regions, together with major disruption to myriad aspects of other societies.

When should one best use each of these terms? There’s no rulebook, of course: the terms are so fresh that their usage is still being worked out in the marketplace of language.

Protestors outside the COP15 meeting in Copenhagen on December 12, 2009. (Image credit: Bob Henson)

Considering each term’s origin and usage, one might argue that the physical manifestations of climate change (observed and predicted) have prompted a global climate crisis and led to local, regional, and global climate emergencies.

Ultimately, the toolbox of terms we use to discuss climate change is just that: a set of tools. Swedish climate action advocate Greta Thunberg made this point vividly when she addressed the UN’s 2021 general assembly in September:


“Build back better. Blah, blah, blah. Green economy. Blah blah blah. Net zero by 2050. Blah, blah, blah … Words that sound great but so far have not led to action. Our hopes and ambitions drown in their empty promises.”

In short, words indeed matter – but actions matter even more when it comes to addressing the calamities of a human-warmed atmosphere.

Bob Henson

Bob Henson is a meteorologist and journalist based in Boulder, Colorado. He has written on weather and climate for the National Center for Atmospheric Research, Weather Underground, and many freelance...