Climate Change
The most thoroughly documented phenomenon in the history of science is also the most politically contested — and the gap between what we know and what we've done about it may define the century.
The short version
- Earth has warmed approximately 1.2°C above pre-industrial levels, driven overwhelmingly by human emissions of CO2, methane, and other greenhouse gases.
- The IPCC's 2021 report stated it is 'unequivocal' that human influence has warmed the climate — the strongest language the body has ever used.
- Fossil fuel companies knew about the warming effects of their products as early as the 1970s and funded decades of organized doubt to delay regulation.
- Limiting warming to 1.5°C — the threshold beyond which cascading, irreversible changes accelerate — requires cutting global emissions roughly in half by 2030.
What it is
Climate change refers to long-term shifts in global temperatures and weather patterns. While some natural variation has always existed, the term as used today describes the rapid, human-driven warming of Earth's surface and oceans since the Industrial Revolution. The mechanism is the greenhouse effect: certain gases — primarily carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) — absorb outgoing infrared radiation from Earth's surface and re-emit it back downward, trapping heat in the lower atmosphere. This effect is not speculative; it was first described mathematically by physicist Eunice Newton Foote in 1856 and elaborated by Svante Arrhenius in 1896, who calculated that doubling atmospheric CO2 would raise global temperatures by roughly 5°C.
Since 1750, atmospheric CO2 has risen from approximately 280 parts per million (ppm) to over 422 ppm as of 2024 — a level not seen in at least 3 million years, according to ice core and sediment records. This increase is directly attributable to burning fossil fuels, deforestation, and cement production. We know this in part through isotopic analysis: fossil carbon has a distinct isotopic signature (depleted in carbon-14 and carbon-13) that allows scientists to fingerprint the source of the rising CO2 in the atmosphere. The signal is unambiguous.
The observable consequences are extensive and accelerating. Global average surface temperature has risen approximately 1.2°C above the 1850–1900 baseline. Arctic sea ice extent has declined roughly 13% per decade since satellite records began in 1979. Sea levels are rising at an accelerating rate — currently about 3.7 mm per year — driven by both thermal expansion of warming water and melting of land-based ice sheets. The Greenland ice sheet is losing mass at a rate six times faster than it did in the 1990s. Heat waves, droughts, and extreme precipitation events have all intensified in frequency and severity in patterns consistent with model predictions.
The IPCC — the Intergovernmental Panel on Climate Change, which synthesizes thousands of peer-reviewed studies — concluded in its Sixth Assessment Report (2021) that it is 'unequivocal that human influence has warmed the atmosphere, ocean and land.' That word — unequivocal — represents the highest confidence level the body uses. It reflects a scientific consensus broader and more robust than that behind the germ theory of disease or the link between smoking and cancer at the time those were established.
Why it matters
The 1.5°C threshold — enshrined in the 2015 Paris Agreement as the preferred ceiling for warming — is not a political number. It represents the point beyond which a cluster of self-reinforcing feedback loops becomes substantially more likely to activate: permafrost thaw releasing stored methane, ice-albedo loss accelerating Arctic warming, Amazon dieback reducing the rainforest's capacity to absorb CO2. Beyond 1.5°C, coral reef systems — which support roughly 25% of all marine species — face near-total collapse. At 2°C, hundreds of millions of people in South Asia and Sub-Saharan Africa face conditions of extreme heat stress incompatible with outdoor labor. At 3°C and beyond, projections include sea level rise that would submerge coastal cities home to hundreds of millions of people, widespread crop failure, and the destabilization of the Greenland and West Antarctic ice sheets on timescales of centuries.
The denial machine is as important to understand as the science itself. Beginning in the late 1980s, fossil fuel companies — including ExxonMobil, BP, Shell, and the American Petroleum Institute — funded a coordinated disinformation campaign modeled explicitly on the tobacco industry's strategy of manufacturing doubt. Internal documents, first surfaced through investigative journalism and later confirmed in legal proceedings, show that Exxon's own scientists accurately predicted the trajectory of warming as early as 1977. The company's public communications contradicted those findings for decades. The result was the loss of at least 30 years of potential policy action, during which global emissions continued to climb.
The economics of inaction are increasingly legible. The Stern Review (2006) estimated that unmitigated climate change would cost 5–20% of global GDP permanently; more recent modeling incorporating non-linear damage functions pushes this higher. Conversely, the cost of the energy transition has fallen precipitously: solar electricity has dropped over 90% in cost since 2010, and wind is now the cheapest source of new electricity generation in most of the world. The International Energy Agency concluded in 2024 that the transition to clean energy is already underway and is creating more jobs than fossil fuel industries are losing — the economic case against action has largely collapsed.
What remains is a governance problem. Emissions are a global externality: the costs of burning are diffuse and delayed, while the profits are immediate and private. The nations most responsible for historical emissions are not the ones facing the worst near-term consequences, creating a structural inequity that complicates international negotiations. The window to limit warming to 1.5°C required emissions to peak by around 2025. Whether that window has already closed or remains barely open is now the central empirical and political question of the coming decade.
Sources & Further Reading
- Climate Change 2021: The Physical Science Basis (AR6 WGI)
- Global Surface Temperature | NASA Global Climate Change
- Exxon Knew about Climate Change almost 40 years ago
- Carbon dioxide now more than 50% higher than pre-industrial levels
- Net Zero by 2050: A Roadmap for the Global Energy Sector
- The Stern Review on the Economics of Climate Change