What is climate change
Executive summary
Climate change is the long-term alteration of Earth’s average climate driven increasingly by human activities that raise greenhouse gas concentrations, causing global temperatures, ocean heat content and extreme weather to rise; Earth's surface has warmed about 2°F (≈1.1°C) since 1850 and greenhouse gases and ocean heat reached record levels in 2024–25 [1] [2]. International bodies warn we are not on track to meet the Paris 1.5°C goal — current policies and pledges imply warming closer to about 3°C by century’s end absent stronger action [3] [4].
1. What climate change is — a clear definition
Climate change describes long-term changes in temperature, precipitation and other climate patterns at global and regional scales, produced by natural processes and human-caused changes in the atmosphere, land use and ocean systems; contemporary concern centers on human-driven warming from greenhouse gas emissions [5] [6]. The United Nations frames this as a global emergency requiring cross-border cooperation and systemic shifts to a low-carbon economy [7].
2. The physical evidence — planets’ “vital signs” flashing red
Multiple monitoring programs report consistent trends: rising global surface temperatures, record-high greenhouse gas concentrations, steadily increasing ocean heat content, and retreating ice and glaciers — all recorded into 2024–25 [2] [1] [8]. Scientific syntheses describe abrupt shifts in indicators (for example, expanded wildfire area in the EU and Canada) and link many extreme events to the influence of anthropogenic warming [8] [1].
3. Causes — why scientists point to human activity
Scientists identify greenhouse gas emissions from burning fossil fuels, land-use change and other industrial activities as the dominant drivers of recent climate trends; reductions of these emissions are the central lever to slow warming [2] [3]. International reporting emphasizes methane as the second-largest near-term driver after CO2 and notes that cutting methane can quickly reduce near-term warming risk [2].
4. The scale of the problem — targets, gaps and projections
The Paris Agreement aims to hold warming “well below” 2°C and pursue efforts to limit it to 1.5°C; authoritative trackers find current policies and announced targets fall far short. UN and independent analyses in 2025 showed pledged emission pathways could at best reduce emissions modestly (e.g., projected emissions fall of ~10–12% by 2035 under certain assumptions) but still remain far below the ~60% cut some pathways indicate is needed for 1.5°C [9] [3]. Some compilations project warming near ~3.2°C by 2100 if present trajectories continue [4].
5. Impacts already being felt — weather, economies and people
Climate-driven changes are producing more frequent and intense heatwaves, heavy precipitation, wildfires, glacier melt and sea-level rise, with direct consequences for food security, displacement, and economic losses; recent disasters — such as costly wildfires — illustrate escalating financial impacts [6] [8]. UN assessments link climate extremes to risks for older populations, potential release of ancient pathogens from melting glaciers, and cascading disaster and economic shocks [2].
6. International response — COPs, coalitions and contested politics
Global negotiations continue: COP30 in Belém, Brazil (November 2025) reflected progress and friction — nations discussed emissions caps, carbon markets and adaptation finance, while analysts noted political tensions and uneven participation by major powers [9] [10]. UN officials framed the talks as evidence that “climate cooperation is alive,” even as analysts and civil society described outcomes as insufficient to lock in 1.5°C [11] [12].
7. Disagreements, limits and competing framings in the reporting
Sources agree on the physical trends and the human role, but they differ on the feasibility of 1.5°C: some institutions stress that stronger policies could still alter trajectories (UN/UNFCCC reporting), while trackers and analysts warn that current pledges are inadequate and likely produce substantially higher warming [9] [3]. Projections such as “~3.2°C by century-end” are scenario-dependent and hinge on assumptions about policy and technology deployment [4] [3].
8. What the reporting does not say (and what remains open)
Available sources document the scientific trends, policy talks and projections, but they do not provide a single, universally agreed forecast for every sector or region; regional impacts and the detailed costs of every adaptation option are not fully described across these summaries (not found in current reporting). Also, the precise mix of technologies and finance that would reliably deliver a <1.5°C outcome remains contested among experts [3].
9. Bottom line for readers
Climate change is a scientifically established, human-driven alteration of Earth’s climate with measurable warming, rising ocean heat and intensifying extremes; current national pledges and policies fall short of Paris targets and leave the world facing substantially higher warming unless stronger, rapid mitigation and adaptation measures are implemented [1] [2] [3].