The most interesting thing about climate change is not how long we have known about it. It is how long it took for that knowledge to feel like ours. The physics has been on the table for two hundred years. The measurements have been unambiguous for seventy. And yet, if you had asked most people in Britain or the United States in the 1970s whether the air outside was quietly warming because of what we burn, they would have looked at you as if you had wandered in from a novel.
This is not a story about villains, though there are some. It is mostly a story about the slow, human process of a fact becoming common knowledge. It is worth sitting with, because it explains where we are now.
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The science was quiet long before it was loud
The idea that the atmosphere holds heat is older than the internal combustion engine. In the 1820s, the French mathematician Joseph Fourier calculated that a planet the size of Earth, at Earth's distance from the sun, ought to be considerably colder than it is. He proposed that the atmosphere itself must be doing some of the work of keeping the surface warm, a suggestion that is now recognised as the first description of what we call the greenhouse effect.
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Thirty-odd years later, in a laboratory at the Royal Institution in London, the Irish physicist John Tyndall began the experiments that turned that idea into evidence. In May 1859, he demonstrated that certain gases in the atmosphere, including carbon dioxide, methane and water vapour, strongly absorb infrared radiation. That is what allows the atmosphere to trap the heat that would otherwise leave the surface at night. His notebook entry for 18 May reads, quite simply, "the subject is completely in my hands" (NASA Earth Observatory).
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By 1896, the Swedish chemist Svante Arrhenius had gone further, calculating that a doubling of atmospheric carbon dioxide would raise average temperatures by several degrees. His figures were not exact, but the direction of travel was correct, and the paper is still in print as one of the founding documents of climate science.
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There is a lovely British footnote to this. In 1938, a steam engineer named Guy Stewart Callendar, working from his home in West Sussex and using data from 147 weather stations, published a paper in the Quarterly Journal of the Royal Meteorological Society showing that global land temperatures had risen by around 0.3°C over the previous fifty years, and proposing that fossil fuel combustion was the cause ( Callendar, 1938). It became known for a time as the Callendar Effect. He was working on this in his spare time. The paper attracted almost no attention.
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Then came Mauna Loa. In March 1958, a young American scientist named Charles David Keeling installed an infrared analyser at an observatory on a Hawaiian volcano and began taking continuous measurements of the carbon dioxide in the atmosphere. His first reading was 313 parts per million ( Scripps Institution of Oceanography). Every year since, the number has climbed. The Keeling Curve is now the longest uninterrupted instrumental record of atmospheric CO2 in the world, and by 2024 the reading had passed 425 ppm ( Britannica).
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So by the early 1960s, three things were true. The greenhouse effect was a well-established physical principle. Global temperatures were known to have risen. And carbon dioxide in the air was measurably increasing, in real time
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Almost no one outside a few laboratories and government committees had heard about any of it.
By the early 1960s almost no one outside a few laboratories and government committees had heard about any of it.
When the warning finally reached the public
There is usually a moment when a specialist subject crosses over into ordinary conversation. For climate change, that moment was 23 June 1988.
That day, in a hearing room in Washington during a punishing American heatwave, a NASA scientist named James Hansen told the United States Senate three things. The Earth was warmer in 1988 than at any point in the history of instrumental measurements. The warming was now large enough to attribute, with high confidence, to the greenhouse effect. And computer models suggested the effect was already beginning to influence the probability of extreme events such as heatwaves (Hansen Senate Testimony, 1988).
The testimony was carried on the front page of the New York Times the next morning. Within two years, the Intergovernmental Panel on Climate Change had published its First Assessment Report, concluding that global mean surface temperatures had risen by 0.3 to 0.6°C over the previous century and that this was "broadly consistent with the predictions of climate models forced by increasing concentrations of greenhouse gases."
The public, in both Britain and the United States, was paying attention for the first time.
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What the polls actually show
Public opinion data on climate does not go back very far. The first serious tracker in the United States was Gallup's global warming series, which began in 1989. In that year, 63% of Americans said they worried "a great deal" or "a fair amount" about the issue (NSF, National Science Board; Gallup, 2015).
Since then the American line has moved less than you might expect. Concern rose to a peak of 72% in 2000, fell to 50% in 1997, and by 2024 sat at 63%, with 44% worrying "a great deal", one of the highest readings in the trend's history (Gallup, 2024). The share of Americans who attribute warming mainly to human activity has climbed more clearly, from around 50% in 2010 to 64% in 2024.
Britain's story is different in shape. When Ipsos first began tracking climate concern here in 2005, 82% of Britons already reported being concerned. That figure drifted down to 60% by 2013, then climbed again after the extraordinary summer of 2018, reaching 85% by 2019, with a majority saying they were "very concerned" for the first time (Ipsos, 2019).
The British Social Attitudes survey, which has run since 1983, tells a compatible story. By 2017, 93% of British adults believed the world's climate was probably or definitely changing, and 95% accepted that human activity played at least some role in it (British Social Attitudes 35). By 2021, 60% believed climate change was mostly caused by human activity, up from a much lower baseline a decade earlier (British Social Attitudes 39).
The most recent official UK figures, from the DESNZ Public Attitudes Tracker published in October 2025, show 79% of the British public concerned about climate change, down from a peak of 85% in Autumn 2021 but consistent with a settled, long-running majority.
Two things are worth noticing here.
First, the British public has, on the whole, arrived at a higher and more stable level of climate acceptance than the American public. In the most recent Gallup tracking, only 61% of Americans express even "a fair amount" of concern, and only 64% attribute warming primarily to human activity, roughly the same as it was in 2016 (Gallup, 2024).
Second, both trend lines fell in the early 2010s and rose again by the late 2010s. That U-shape is not an accident. Something specific happened in those years, and it is worth being honest about it.
The pattern of manufactured doubt
If the science was clear from the 1960s onwards, and the warning was public from 1988, why did belief take another two or three decades to settle?
Part of the answer is that scientific knowledge takes time to spread through a population, particularly when the subject is invisible, gradual and global. Most people learn about climate the way they learn about medicine or economics: piecemeal, second-hand, mixed in with other things.
But part of the answer is that a well-documented effort was made to keep the public unsure.
We now have unusually good evidence about this, because internal documents from within the fossil fuel industry itself have been examined by historians of science. A study published in Science in January 2023 by researchers at Harvard University and the Potsdam Institute for Climate Impact Research analysed thirty-two internal industry documents produced between 1977 and 2002, alongside seventy-two peer-reviewed papers by industry scientists between 1982 and 2014.
They found that industry scientists' own climate projections from the late 1970s onward matched subsequently observed warming with accuracy comparable to independent academic and government models. Between 63% and 83% of the industry's private projections were, on statistical analysis, correct.
The public communications from those same organisations, over the same decades, expressed doubt.
Historians who have studied the wider pattern, most notably Naomi Oreskes and Erik Conway in their 2010 book Merchants of Doubt, have shown that the strategy did not begin with climate. Similar tactics had been used, decades earlier, in response to the science on tobacco. A now-famous 1969 internal memo from within the tobacco industry put the approach with startling honesty: "doubt is our product since it is the best means of competing with the 'body of fact' that exists in the mind of the general public." The document, known as the Smoking and Health Proposal, is archived by UCSF.
The pattern, as historians describe it, has five recurring moves. Fund parallel research to create what looks like a competing scientific view. Elevate a small number of credentialed contrarians so that they appear to balance the field. Argue that more research is needed, indefinitely. Frame the mainstream position as alarmist, politically motivated or economically damaging. And press journalists, in the name of balance, to give equal weight to both sides even when the evidence is not evenly weighted.
None of this required most people to consciously choose to disbelieve. It only required them to hear enough uncertainty in the background to feel that the science was not yet settled, and therefore that action could reasonably wait. That is why the polling numbers wobble in the years they do. It is why belief in human causation was lower in the United States in 2010 than in 2007. It is why "the seriousness of climate change is exaggerated" was a view held by around a third of the British public in the early 2010s (Attitudes to climate change risk, PLOS One via PMC).
Understanding this history is not about assigning blame. It is about recognising that when a person says they have felt confused about climate for a long time, they are not being irrational. They were, to a real extent, given something to be confused about.
What has actually shifted
The last decade has quietly closed a lot of that gap.
By the late 2010s, the scientific consensus had become one of the most heavily documented in modern science, with major bodies including the IPCC, the Met Office, NASA and the Royal Society converging on the same conclusions. The proportion of British adults who believe climate change is at least partly caused by human activity is now 95%, according to the British Social Attitudes series. The proportion of Americans who say the effects of global warming have already begun has hovered around 60% since 2016, up from far lower figures in the previous decade (Gallup, 2024).
There has also been a change in what people notice around them. The most recent Ipsos Earth4All research found that two in three British adults now agree that human activity is pushing the planet close to environmental tipping points. In ONS Opinions and Lifestyle Survey data from October 2024, 83% of adults expected to be affected by climate change in at least one specific way over the next ten years. Increased temperatures, more flooding and stronger winds top that list.
That is not confidence in a comfortable future. It is something more useful: a settled sense that the subject is real, and a widely shared willingness to take it seriously.
The doubt that did not go away, it just changed shape
It would be neat to end there. The physics won, the polls caught up, the argument moved on. The picture is more honest, and more interesting, than that.
Researchers now distinguish between two kinds of climate denial. "Old denial" argues the science itself is wrong: the climate is not really changing, it is not caused by people, the warming has stopped. "New denial" accepts the science but attacks the response: net zero will not work, action here does not matter if other countries emit more, the solutions are unaffordable, personal effort is pointless. The Center for Countering Digital Hate, developed by academic researchers, analysed 4,458 hours of YouTube content from 96 channels and found that old-denial claims fell from 65% of climate denial content in 2018 to 30% in 2023, while new-denial claims rose from 35% to 70% over the same five years. A 2025 paper in Cambridge's Global Sustainability journal documents the same shift in the peer-reviewed literature.
That shift shows up in the UK's own official tracker too, though in quieter numbers. In the DESNZ Public Attitudes Tracker, Summer 2025, the proportion of British adults agreeing that they personally have the ability to make changes to help reduce climate change fell from 76% in Summer 2022 to 69% in Summer 2025.
Disagreement with the statement "it is not worth doing things to help climate change if others do not do the same" fell from 58% to 49% over the same three years. Belief in the science has held. Belief in the point of acting on it has softened.
The reasons for that softening are contested, and the evidence is still developing. Peer-reviewed work in Nature Communications Earth and Environment has shown that engagement-driven platform algorithms tend to surface higher volumes of climate misinformation than a neutral feed would produce. A 2024 Nature Scientific Reports paper mapped the online climate-denial network in the United States and identified the president at the time, Donald Trump, as its single most influential node. In the United Kingdom, the Grantham Research Institute at the LSE has documented the return of new-denial arguments in mainstream British politics, and specifically the recurrent claim that British action on net zero "will make zero difference" to the climate, which the Institute assesses as factually incorrect on the evidence.
What all this suggests is that the argument has moved rather than ended. The old fight was about whether climate change is real. That fight is essentially over. The current fight is about whether the response is worth making. That fight is live, and it is being fought partly on the same platforms where much of the public now gets its information.
CNB's view: no believers and no deniers
If there is one thing this history should protect us from, it is the temptation to sort the world into believers and deniers. Most people are neither. They are trying to work out, in the middle of the rest of their lives, what to trust and what to do next.
That is why, at CNB, we do not treat climate action as a moral test with a pass and fail mark. We treat it as a practical question that deserves clearer answers.
Two of those answers matter here.
Reducing emissions and financing verified climate action are not sequential steps. They belong together. Reducing what a business emits today changes the emissions still to come. Financing high-integrity carbon removals and reductions helps address the cumulative carbon we have already added to the atmosphere. Presenting these as an either-or choice is one of the small ways in which the older habit of manufactured doubt still lingers in the debate.
And scrutiny of climate finance is not a reason to walk away from it. It is a reason to demand better of it: better methodologies, better verification, clearer registry evidence, a documented audit trail. Businesses that ask those questions do more good than businesses that do not ask them.
A quieter kind of hope
Two hundred years is a long time for a scientific idea to travel from a page to a public. It is also, in the arc of human understanding, not that long at all.
The most striking fact about the belief numbers we have looked at is not the drops or the political splits. It is the fact that, in Britain today, four in five adults are concerned about climate change, nine in ten accept the science, and a majority believe the effects are already here. That is not a country that has failed to notice. It is a country that has finally caught up with what its own scientists were telling it decades ago.
There is no useful satisfaction to be taken in how long it took. There is, though, a quiet form of encouragement to be drawn from the fact that we got here at all. The physics that Fourier proposed, that Tyndall measured, that Callendar wrote up in a spare room in Sussex, and that Keeling patiently recorded on a Hawaiian volcano, is now the common ground of a serious public conversation.
The work now is to keep that ground clear.
If you are interested in the underlying science that sits behind all of this, you may find CNB's companion piece Is Climate Change Real? What 2026 Science Says a useful next read. It sets out, in plain terms, what today's evidence actually shows.
