History of Climate Change

I — Deep Time

The Paleoclimatic Baseline

To comprehend the magnitude, velocity, and danger of anthropogenic climate change, it is first necessary to establish the baseline of the Earth's natural climate variability. Paleoclimatology — the study of past climates — relies on proxy data from ice cores, seafloor sediments, coral reefs, cave speleothems, and ancient tree rings, allowing scientists to reconstruct planetary conditions over millions of years.

10×

The Rate Anomaly — Natural vs. Anthropogenic Warming

Global warming at the end of an ice age was an exceedingly gradual process, unfolding over approximately 5,000 years. The modern anthropogenic warming rate is roughly ten times faster — an order of magnitude that starkly highlights the unprecedented and artificial nature of present-day climate forcing. This single comparison is among the most important in all of climate science.

Ice Cores Milankovitch Cycles PETM +14°C 180 ppm at LGM Orbital Eccentricity Albedo Feedback Mid-Pliocene Analog

Major Climate States in Earth History

Period	Timeframe	Climate State	Relevance to Today
Huronian Glaciation	2.4–2.1 Bya	Extreme glaciation — possibly global ice cover	Earliest evidence of large-scale glaciation
Mid-Cretaceous	90–120 Mya	Extreme warmth — dinosaurs at high latitudes	Analogue for a very high-CO₂ world
PETM "Hothouse"	56–47 Mya	+14°C above modern average	Deep-time analogue for rapid CO₂ injection
Mid-Pliocene	3–5 Mya	CO₂ levels similar to today; higher seas	Closest analogue to present atmospheric CO₂
Last Glacial Maximum	~21,000 ya	180 ppm CO₂; ice sheets to NYC and Stockholm	Demonstrates GHG sensitivity at planetary scale

Milankovitch Cycles: Cyclical variations in Earth's orbital eccentricity (100,000-year cycle), axial obliquity, and precession alter the seasonal distribution of solar radiation — initiating or ending ice ages. But orbital forcing alone cannot explain the full magnitude of glacial temperature swings. Greenhouse gases operate as powerful amplifying feedbacks, a mechanism that makes their current manipulation by human industry so consequential.

II — The Pioneers

19th-Century Thermodynamics and the Greenhouse Effect

The physical mechanics of global climate change were not theorized until the nineteenth century — a period that ran exactly parallel to the First Industrial Revolution, when coal combustion and steam power began emitting greenhouse gases on a scale never before seen in human history.

1824 — 1827

Joseph Fourier

Theoretical Framework

Proposed that the Earth's atmosphere acts as an insulator — formulating the initial conceptual framework of the "greenhouse effect." Could not identify the specific gases responsible, lacking advanced spectrometry.

1859 — 1861

John Tyndall

Experimental Proof

Using a custom spectrophotometer, proved that CO₂ and H₂O vapor are highly opaque to infrared radiation. Delivered his landmark Bakerian Lecture at the Royal Society in 1861 — the first physical mechanism for glacial cycles.

1896

Svante Arrhenius

First Climate Model

Published the first calculation of global warming from human emissions. Calculated that doubling atmospheric CO₂ would raise surface temperature 5–6°C — remarkably close to modern supercomputer upper bounds after 130 years.

"Humanity is performing a large-scale geophysical experiment — extracting and returning millions of years' worth of stored organic carbon to the atmosphere within a few short generations."

Roger Revelle & Hans Suess, 1957 — Framing the Modern Climate Crisis

1824

1824 — Fourier

The Insulating Atmosphere Hypothesis

Fourier calculates that Earth should be much colder than it is at its distance from the Sun and hypothesises that the atmosphere traps heat. The intellectual foundation of climate science is laid.

1859

1859 — Tyndall

CO₂ Identified as the Heat-Trapping Gas

Experimental proof that CO₂ and water vapour absorb infrared radiation. Tyndall notes that even minute changes in these trace gases could bring about vast planetary climate changes.

1896

1896 — Arrhenius

First Quantitative Climate Sensitivity Calculation

CO₂ doubling → +5–6°C. Arrhenius estimates it will take 3,000 years at 1890s emission rates. By 1908, observing accelerating fuel use, he revises to "hundreds of years." Counterintuitively, he views the warming as beneficial.

1912

March 1912

First Global Public Awareness — Popular Mechanics

Francis Molina's article in Popular Mechanics describes the greenhouse effect for a lay audience. Widely syndicated globally, including in New Zealand's Rodney and Otamatea Times — an early, optimistic public reckoning with fossil fuel emissions.

1938

1938 — Callendar

Empirical Proof: Temperatures Already Rising

Amateur meteorologist Guy Stewart Callendar compiles historical weather records and demonstrates global temperatures had risen 0.3°C over 50 years — directly linked to a 10% increase in atmospheric CO₂ from fossil fuels. Met with intense skepticism, but proved entirely correct.

1957

1957 — Revelle & Suess

Oceans Cannot Absorb the Carbon

A critical paradigm shift: complex seawater chemistry prevents rapid CO₂ absorption. Revelle hires young geochemist Charles Keeling to begin continuous atmospheric monitoring at Mauna Loa.

1958

1958 → Present

The Keeling Curve — 315 ppm to 420+ ppm

Charles Keeling begins continuous CO₂ monitoring at Mauna Loa. His data becomes the world's longest continuous greenhouse gas record — rising without interruption from 315 ppm in 1958 to over 420 ppm today. Undeniable, irreversible proof of accumulating atmospheric CO₂.

IV — The Architecture of the Anthropocene

Emissions and Energy Transitions

The history of greenhouse gas emissions is intrinsically linked to the history of human industrialisation, population growth, and global energy transitions. In 1850, global CO₂ emissions were 204 million tonnes. By 2022, they had reached 37.1 billion tonnes — 182 times higher.

Year	Global CO₂ Emissions	Relative Increase (vs 1850)	Key Historical Driver
1850	204 Mt	1×	First Industrial Revolution (Coal)
1893	1,440 Mt	7×	Second Industrial Revolution
1936	4,540 Mt	22×	Interwar period; rise of oil
1950	6,000 Mt	~29×	Post-WWII economic boom
1979	20,500 Mt	100×	Mass motorisation; global trade
2022	37,100 Mt	182×	Asian economic expansion; persistent fossil reliance

Historical Responsibility: Cumulative Emissions 1850–2021

Rank	Country	Historical Share	Notes
1	United States	20% (>509 GtCO₂)	Dominant early industrialiser; highest per capita among top emitters
2	China	11%	Rapid escalation post-1990; currently largest annual emitter
3	Russia	7%	Heavy industrial and fossil fuel extraction history
4	Brazil	5%	High ranking driven primarily by land-use change and deforestation
5	Indonesia	4%	Land-use changes and peatland destruction

The Core Climate Justice Tension: Developed nations achieved immense wealth and high living standards through unrestricted historical carbon pollution. Per capita emissions in the U.S. are double those of China and 8 times those of India. Developing nations argue they are now being penalised with severe carbon constraints before achieving similar developmental parity — a geopolitical friction that sits at the heart of every international climate negotiation.

V — The Scientific Consensus

The IPCC and the Consolidation of Certainty

In 1988 — a watershed year of record heatwaves and NASA scientist James Hansen's historic congressional testimony publicly declaring the greenhouse effect was already changing the climate — the WMO and UNEP jointly established the Intergovernmental Panel on Climate Change. The evolution of its Assessment Reports tracks the exponential growth in scientific certainty.

FAR · 1990

First Assessment Report

Identified greenhouse effect; insufficient data to definitively attribute observed warming to human activity.

Possible

SAR · 1995

Second Assessment Report

"The balance of evidence suggests a discernible human influence on global climate."

Discernible

TAR · 2001

Third Assessment Report

"New and stronger evidence" that most warming over the previous 50 years was attributable to human activities.

Likely

AR4 · 2007

Fourth Assessment Report

Warming of the climate system is "unequivocal" and "very likely" caused by human activity. Nobel Peace Prize awarded.

Very Likely (>90%)

AR5 · 2013–14

Fifth Assessment Report

"Extremely likely" (95–100%) that human influence has been the dominant cause of warming since the mid-20th century.

Extremely Likely (95–100%)

AR6 · 2021–23

Sixth Assessment Report

Human activities have unequivocally warmed the atmosphere, ocean, and land. The science is no longer debatable.

Unequivocal

2024

Warmest Year on Record — +1.35°C above Pre-Industrial Baseline

The 10 warmest years in the historical record have all occurred in the past decade (2015–2024). Earth's temperature has risen at an average of 0.06°C per decade since 1850 — but since 1982 the rate has more than tripled to 0.20°C per decade. The acceleration is non-linear and ongoing.

VI — Global Climate Policy

From Stockholm to Paris

As scientific consensus solidified during the late twentieth century, climate change transitioned from esoteric science into the preeminent geopolitical challenge of the modern era — catalysed by the rise of the environmental movement and a succession of international frameworks with progressively binding ambitions.

1962

1962 — Rachel Carson

Silent Spring — The Environmental Movement is Born

Publication of Silent Spring galvanises environmental consciousness. The 1970s sees the creation of the EPA, NOAA, Friends of the Earth (1969), and Greenpeace (1971). Earth Day 1970 marks a cultural turning point.

1972

Stockholm 1972

First UN Conference on the Human Environment

Institutionalisation of global environmental policy begins. Climate change is a footnote — overshadowed by smog and acid rain — but the conference creates UNEP and establishes the framework for international environmental coordination.

1992

Rio de Janeiro 1992

Earth Summit — UNFCCC Adopted

197 nations adopt the UN Framework Convention on Climate Change. Goal: stabilise GHG concentrations to prevent dangerous anthropogenic interference. A foundational framework without binding targets — the architecture for all future negotiations.

1997

Kyoto 1997

Kyoto Protocol — Binding Targets for Developed Nations

Legally binds Annex I (developed) nations to specific emission reduction targets. The U.S. Senate passes Byrd-Hagel Resolution 95-0, pre-empting ratification. Without U.S. participation, the protocol's effectiveness is severely crippled.

2015

Paris 2015

The Paris Agreement — Universal, Voluntary, NDCs

Adopted by 196 parties. All nations submit voluntary Nationally Determined Contributions. Central aim: limit warming to "well below 2°C," pursuing 1.5°C. USD 100 billion annual climate finance floor. Despite its universality, current NDC pledges remain vastly insufficient to meet the 1.5°C target.

Kyoto Protocol (1997)

Top-down, legally binding
Annex I nations only — developed countries
Developing nations exempted
U.S. refused to ratify (Senate 95-0)
Canada withdrew in 2011
First period: 2008–2012

Paris Agreement (2015)

Bottom-up, voluntary NDCs
All 196 parties equally included
Developed/developing divide dissolved
$100B/yr climate finance target
Ratchet mechanism for ambition
Current pledges: still insufficient

VII — The Countermovement

The Manufacture of Uncertainty

The persistent inadequacy of the global policy response cannot be attributed solely to diplomatic friction or energy system inertia. It is heavily rooted in a decades-long, heavily financed campaign of climate science denial led primarily by the fossil fuel industry — an industry that knew exactly what it was doing.

$30M+

ExxonMobil alone — directed to climate denial think tanks (1998–2014)

Internal corporate documents unsealed through litigation and FOIA requests reveal that as early as 1968, scientists from the Stanford Research Institute warned the American Petroleum Institute that significant global temperature changes were "almost certain" by 2000. ExxonMobil's own researchers confirmed the greenhouse effect in peer-reviewed publications — while its paid advertorials in major newspapers simultaneously promoted public doubt.

The Four Tactical Pillars of Denial

Strategy 1

Obscuring Science

Pseudo-Science

Producing pseudo-scientific "backgrounders" for lawmakers emphasising model uncertainty while ignoring vast areas of agreement. A 1988 Exxon memo explicitly ordered executives to "emphasise the uncertainty in scientific conclusions."

Strategy 2

Economic Alarmism

Biased Economics

Commissioning and utilising biased economic studies to amplify arguments that greenhouse gas regulations would devastate industrial economies and cause catastrophic job losses.

Strategy 3

Astroturfing

PR Campaigns

Funding fake grassroots organisations, massive PR campaigns, and secretly funding contrarian scientists to create the illusion of an ongoing, robust scientific debate where none existed.

Strategy 4

Aggressive Lobbying

Political Action

Sending delegations to all major international climate conventions, heavily lobbying political elites in Washington, and donating millions to politicians who deny climate change to successfully stall federal action.

Early Industry Knowledge: By 1959, an internal Shell paper titled "The Earth's Carbon Cycle" explicitly acknowledged that burning fossil fuels "might conceivably change the climate." Exxon was raising the decks of offshore drilling platforms to account for projected sea-level rise as early as 1981 — while publicly funding denial. The parallel to the tobacco industry's concealment of cancer risks is explicit and documented.

VIII — Political Polarization & FAQ

Ideological Science Rejection

Climate change was not intrinsically partisan in the late 1980s — major U.S. environmental legislation enjoyed broad bipartisan support, and the Senate approved the UNFCCC 100-0 under Republican President George H.W. Bush. But following the Kyoto Protocol collapse and decades of fossil fuel lobbying aligned with conservative ideology, the issue became one of the most polarized in American politics.

84% of Democrats

Accept scientific consensus on climate
94% of liberal Democrats see it as major threat
Support regulatory action and green transition
Treat climate as a top-tier policy priority

43% of Republicans

Accept scientific consensus on climate
Only 19% of conservative Republicans see it as major threat
Oppose binding regulatory frameworks
Economic protectionism over climate action

Key Questions on Science, Policy, and Denial

What is the Keeling Curve and why does it matter? ▼

The Keeling Curve is the longest continuous instrumental record of atmospheric CO₂ concentration, begun by Charles David Keeling at Mauna Loa Observatory, Hawaii, in 1958. When measurements began, CO₂ stood at 315 ppm. By the 2020s it had surpassed 420 ppm — levels not seen since the Mid-Pliocene epoch millions of years ago. The curve rises relentlessly every year with no sign of deceleration in absolute terms. Its characteristic sawtooth shape (from seasonal vegetation cycles) superimposed on an upward trend visualises, with brutal clarity, the continuous addition of fossil carbon to the atmosphere. It is the fundamental empirical spine of modern climate science and makes the hypothesis that CO₂ is not rising essentially impossible to maintain.

Why did Arrhenius think global warming would be beneficial? ▼

Svante Arrhenius viewed global warming through the geopolitical and agricultural lens of a late-19th-century Northern European. At the very low emission rates of 1896, he estimated it would take 3,000 years for atmospheric CO₂ to double. He genuinely believed that gradual warming would be beneficial — preventing future ice ages and increasing agricultural yields in colder northern climates like Sweden's. By 1908, watching the rapid acceleration of global fuel use, he revised his timeline to hundreds of years and remained optimistic. Neither Arrhenius nor any 19th-century scientist could have foreseen the exponential industrial growth of the 20th century that would compress his 3,000-year timeline into roughly 150.

How did the Byrd-Hagel Resolution kill the Kyoto Protocol? ▼

In July 1997, as Kyoto negotiations neared completion, the U.S. Senate unanimously passed the Byrd-Hagel Resolution 95-0 — declaring that the U.S. should not sign any climate treaty that mandated new commitments for developed nations unless developing nations like China and India faced identical binding limits in the same period. The Clinton administration had shaped much of the treaty text but never sent it to the Senate for ratification, knowing it would fail. The unanimous vote demonstrated that at this critical moment, resistance to climate action was entirely bipartisan — driven by economic protectionism and fears of competitive disadvantage, not yet by science denial. The subsequent U.S. non-participation crippled the protocol's effectiveness and initiated a prolonged period of diplomatic stagnation.

What is the "Six Americas" framework? ▼

The "Six Americas" is a public opinion research framework developed by Yale and George Mason universities to map the nuanced spectrum of American beliefs about climate change — far more granular than a simple believer/denier binary. The six groups range from Alarmed (deeply concerned, highly motivated) through Concerned, Cautious, Disengaged, and Doubtful to Dismissive (convinced it's not real and actively opposed to action). Each group requires distinct communication strategies. The framework reveals that a majority of Americans accept climate science but vary enormously in perceived urgency, personal relevance, and political priority — making broad coalition-building for climate legislation extremely difficult.

Why does the 2024 EU renewables milestone not solve the global problem? ▼

In 2024, the EU's power sector emissions fell almost 10% year-on-year, with renewables (wind and solar) reaching a record 28% share — surpassing the combined share of coal and gas for the first time. This is a genuine and significant achievement. However, these localized reductions were completely offset globally: coal emissions rose 0.9% globally, driven by China, India, and Southeast Asia; oil emissions rose 0.8%, driven by aviation (up 5.5%) and petrochemical demand. The core problem is that climate change operates on cumulative global atmospheric concentrations, not regional performance metrics. Until absolute global emissions fall — not just the rate of growth — the atmospheric CO₂ concentration continues to rise, and the warming commitment continues to increase.

What is the Paris Agreement's most significant structural weakness? ▼

The Paris Agreement's central architectural innovation — replacing Kyoto's legally binding top-down emission targets with voluntary bottom-up "Nationally Determined Contributions" — was both its diplomatic masterstroke (achieving universal adoption) and its Achilles' heel. Because NDCs are self-submitted, non-binding, and not subject to external enforcement, states may pledge ambitious targets but face no legal consequence for missing them. Subsequent analyses from the IPCC and UN Environmental Programme consistently demonstrate that even if all current NDC pledges are fully met (which they are not on track to be), the world is still heading toward approximately 2.5–3°C of warming by 2100 — far above the 1.5°C target and in the range of severe, widespread, and potentially catastrophic climate impacts.

The Historical Trajectory of CLIMATE CHANGE Science · Emissions · Global Policy