Is climate change real?

Yes, climate change is real. It is supported by overwhelming scientific evidence from multiple independent lines of observation, and there is a near-unanimous consensus among climate scientists that the recent warming is primarily driven by human activities.[1]

Scientific Consensus

Multiple studies of peer-reviewed literature and surveys of climate experts show extremely high agreement:

•Around 97% (and in more recent analyses, greater than 99%) of actively publishing climate scientists agree that humans are causing global warming and climate change.[2]

•Leading scientific organizations worldwide—including NASA, NOAA, the Intergovernmental Panel on Climate Change (IPCC), the U.S. National Academies of Sciences, the American Association for the Advancement of Science (AAAS), the American Geophysical Union, and numerous national science academies—have issued statements affirming this.[3]

•The IPCC states it is unequivocal that human influence has warmed the atmosphere, ocean, and land.[4]

This consensus is based on decades of data, not opinion or models alone. Dissenting views exist but represent a tiny fraction of the literature and are not supported by the broader evidence base.

Key Evidence That Earth Is Warming

Multiple independent datasets and observations confirm rapid warming:

•Global surface temperatures have risen by about 1.0–1.3°C (roughly 1.8–2.3°F) since the late 19th century/pre-industrial period (around 1850–1900), with most of the warming in recent decades. The past decade (and individual recent years like 2023 and others) ranks among the warmest on record since systematic measurements began around 1880. Independent analyses from NASA GISS, NOAA, the UK Hadley Centre, and Berkeley Earth all show the same long-term upward trend.[5]

•Oceans are absorbing most of the excess heat (about 90%), with the upper ocean warming significantly. Sea levels are rising (about 20 cm / 8 inches over the last century, with the rate accelerating) due to thermal expansion and melting ice.[6]

•Cryosphere (ice) changes: Arctic sea ice extent and thickness have declined rapidly; Greenland and Antarctic ice sheets are losing mass (hundreds of billions of tons per year); glaciers are retreating nearly worldwide; Northern Hemisphere spring snow cover is decreasing.[6]

•Other indicators: Increasing frequency of extreme heat events, changes in precipitation patterns, ocean acidification (from absorbed CO₂), and shifts in ecosystems and species ranges.

Paleoclimate records (ice cores, tree rings, sediments, etc.) show that the current rate of warming is unprecedented in at least thousands of years—roughly 10 times faster than typical post-ice-age warming.[7]

Evidence That Humans Are the Primary Cause

•Greenhouse gases: Atmospheric CO₂ has risen from about 280 parts per million (ppm) pre-industrial to over 420 ppm recently (e.g., global averages around 422–427 ppm in recent years, with 2025 figures reported near 427 ppm), a level higher than at any time in at least the last 800,000–2 million years. Methane and nitrous oxide have also increased substantially. More than half the CO₂ rise has occurred since 1970.[8]

•The isotopic “fingerprint” of the added carbon matches fossil fuel burning (not natural sources like volcanoes or the ocean). Human emissions of CO₂ from fossil fuels and industry far exceed natural fluxes that could explain the rise.[5]

•Basic physics established since the 19th century shows that CO₂ and other greenhouse gases trap heat. Satellite and surface measurements confirm less infrared radiation escaping to space at CO₂ wavelengths, and the planet’s energy imbalance (more heat in than out).

•Climate models and attribution studies that include only natural factors (solar variability, volcanoes, orbital changes) cannot explain the observed warming since the mid-20th century. When human greenhouse gas emissions and other forcings are included, they match the observations closely. Natural factors alone would have produced little net warming or even slight cooling in recent decades.[9]

In short, the climate has always varied naturally, but the speed, magnitude, and pattern of current changes—and their clear link to human-emitted greenhouse gases—make this period distinct. The evidence comes from direct measurements, satellites, ice cores, ocean data, and more, cross-validated by independent research groups and agencies worldwide.

For primary sources, see NASA’s climate pages, NOAA Climate.gov, IPCC Assessment Reports, and the Royal Society’s summaries on evidence and causes. The reality of warming and its human cause is as well-established as other major scientific conclusions, such as the link between smoking and cancer or the role of gravity.

Citations (9)

1archive.isData and tools
https://archive.is/2025.02.12-121037/https://science.nasa.gov/climate-change/faq/do-scientists-agree-on-climate-change/
Backs: “It is supported by overwhelming scientific evidence from multiple independent lines of observation, and there is a near-unanimous consensus among climate scientists that the recent warming is primarily driven by human activities.”
2iop.orgAcademic
https://iopscience.iop.org/article/10.1088/1748-9326/ac2966
Backs: “Around 97% (and in more recent analyses, greater than 99%) of actively publishing climate scientists agree that humans are causing global warming and climate change.”
3nasa.govGovernment
https://science.nasa.gov/climate-change/scientific-consensus/
Backs: “National Academies of Sciences, the American Association for the Advancement of Science (AAAS), the American Geophysical Union, and numerous national science academies—have issued statements affirming this.”
4climate.govGovernment
https://www.climate.gov/news-features/climate-qa/isnt-there-lot-disagreement-among-climate-scientists-about-global-warming
Backs: “The IPCC states it is unequivocal that human influence has warmed the atmosphere, ocean, and land.”
5archive.mdData and tools
https://archive.md/2024.11.07-200429/https://www.climate.gov/news-features/climate-qa/what-evidence-exists-earth-warming-and-humans-are-main-cause
Backs: “Independent analyses from NASA GISS, NOAA, the UK Hadley Centre, and Berkeley Earth all show the same long-term upward trend.”
6nasa.govGovernment
https://science.nasa.gov/climate-change/evidence/
Backs: “Sea levels are rising (about 20 cm / 8 inches over the last century, with the rate accelerating) due to thermal expansion and melting ice.”
7archive.phData and tools
https://archive.ph/2024.10.06-154745/https://science.nasa.gov/climate-change/evidence/
Backs: “Paleoclimate records (ice cores, tree rings, sediments, etc.) show that the current rate of warming is unprecedented in at least thousands of years—roughly 10 times faster than typical post-ice-age warming.”
8climate.govGovernment
https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide
Backs: “Methane and nitrous oxide have also increased substantially. More than half the CO₂ rise has occurred since 1970.”
9ipcc.chGovernment
https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-3
Backs: “Natural factors alone would have produced little net warming or even slight cooling in recent decades.”