Originally published June 30, 2010. Updated September 16, 2026.
Yes, and 2024 was the hottest year ever measured, at 1.29°C above the 20th-century average. The Intergovernmental Panel on Climate Change calls the human influence behind that heat “unequivocal”. 2025 came in close behind as the third warmest year in 176 years of NOAA data. Scientists don’t stop at watching that number climb. They can point to a specific gas building up in the atmosphere and a chemical signature in the air that only burning fossil fuels leave behind.
The scientific consensus is about as strong as it gets
The Intergovernmental Panel on Climate Change isn’t one scientist’s opinion. It’s built from the peer-reviewed climate literature, written by researchers from dozens of countries and checked line by line by governments before publication. Its 2021 assessment states plainly that human influence has “warmed the atmosphere, ocean and land,” and that the scale of change now underway is unprecedented over many centuries to many thousands of years. Neither line hedges with words like probably or likely. The rest of the evidence in this piece sits underneath that conclusion, starting with the temperature record itself.
How much the planet has warmed so far
Every major temperature record agrees on the direction, even when the exact numbers differ by dataset. NOAA measured 2024 at 1.29°C above its 20th-century average, its warmest year on record. NASA’s independent analysis, which uses a 1951 to 1980 baseline instead, put the same year at 1.28°C above that average. Copernicus, which measures against the pre-industrial period, recorded 1.60°C for 2024, making it the first calendar year on record to cross 1.5°C above pre-industrial levels. The baselines differ, but the direction doesn’t.
2025 cooled slightly but stayed extreme, ranking as the third-warmest year in NOAA’s 176-year record at 1.17°C above the 20th-century average. The World Meteorological Organization’s consolidated estimate, which averages eight independent datasets, put 2025 at 1.44°C above pre-industrial levels, ranking it second in two of those datasets and third in the other six. Copernicus’s own tally ranked 2025 third-warmest as well, 0.01°C behind 2023 and 0.13°C behind 2024. Put the last three years together and 2023 through 2025 is now the first three-year period on record to average above 1.5°C. The ten warmest years ever measured have all happened since 2015.
The major trackers compare like this for the same two years:
| Tracker | Year | Anomaly | Baseline |
|---|---|---|---|
| NOAA | 2024 | 1.29°C | 20th-century average |
| NOAA | 2025 | 1.17°C | 20th-century average |
| NASA GISS | 2024 | 1.28°C | 1951 to 1980 average |
| Copernicus | 2024 | 1.60°C | Pre-industrial (1850 to 1900) |
| Copernicus | 2025 | 1.47°C | Pre-industrial (1850 to 1900) |
| WMO (8-dataset average) | 2025 | 1.44°C | Pre-industrial (1850 to 1900) |
Source: NOAA NCEI, NASA GISS, Copernicus/C3S 2024, Copernicus/C3S 2025, WMO. All read September 2026.
Carbon dioxide is at the highest level in recorded history
Before industrialization took hold, the atmosphere held roughly 280 parts per million of carbon dioxide. By full-year 2024, that had climbed to 422.8 parts per million, after the largest annual jump ever recorded, up 3.75 ppm in a single year. The most recent reading from NOAA’s Mauna Loa Observatory, taken in August 2026, put CO2 at 427.55 parts per million, up from 425.48 ppm the same month a year earlier. That rate of increase is 100 to 200 times faster than anything that happened naturally at the end of the last ice age. If you’re wondering where that extra carbon comes from, the buildup traces back to burning fossil fuels.
The fingerprints that rule out the sun and natural cycles
If you’ve heard the argument that this is only the sun or a natural cycle, the physical evidence says otherwise. Carbon in the atmosphere carries a chemical signature that reveals where it came from. Fossil fuel CO2 has no measurable carbon-14, and the ratio of carbon-13 to carbon-12 in the atmosphere has been falling since large-scale fossil fuel burning began, a signature that only ancient, buried carbon can produce. The atmosphere is also cooling exactly where greenhouse-driven warming predicts it should. A team led by Santer, publishing in PNAS in 2023, found the mid to upper stratosphere cooled by 1.8 to 2.2°C from greenhouse gases between 1986 and 2022, compared to natural cooling of no more than 0.15°C over the same stretch, a gap of 12 to 15 times.
Who has emitted the most carbon, historically
Add up all the carbon dioxide humanity has put into the atmosphere from fossil fuels and industry since 1750, and the running total is lopsided. The United States accounts for 24% of that cumulative total, more than any other country. China follows at 15%. Russia has emitted 6.7% of the total and Germany 5.2%. Further down the list, the United Kingdom accounts for 4.4%, Japan 3.8%, France 2.2%, Canada 1.9%, and Ukraine 1.7%. Those nine countries together account for well over half of everything humanity has ever put into the atmosphere, using the Global Carbon Project’s accounting through 2023. China’s own historical share is smaller than the United States’, but it’s now the world’s largest annual emitter, a reminder that the cumulative ranking above and the current pace of emissions are two different measures.
Is this storm caused by climate change
When an unusually intense heat wave hits close to home, or a dust storm makes national news, you’ll often hear people ask whether climate change caused it. That’s not a fair yes-or-no question for a single event. Weather is what happens on a given day. Climate is the pattern measured over decades, which is what the temperature and CO2 records above track. Blaming climate change for one storm, or pointing to one cold snap as proof it isn’t happening, both miss the same distinction. The ten warmest years ever measured have all happened since 2015, and no single week of weather changes that.
What would change this finding
The case for human-caused warming doesn’t rest on one data point that a single new study could overturn. A rival explanation would have to account for the warming record and the rising CO2 measurements. It would also have to explain away the isotopic and stratospheric fingerprints that point specifically at burning fossil fuels. Nothing currently on the table does either.
What’s worth watching now is the pace of change. The direction itself isn’t in question anymore. NOAA’s Mauna Loa Observatory updates its CO2 readings every month, so the newest figure is the fastest way to check whether emissions are still accelerating. The 1.5°C figure in the Paris Agreement is judged against decades-long averages, so a single hot year doesn’t settle it on its own, and 2023 through 2025 is already the first three-year stretch on record to average above that line. Whether that becomes a permanent, multi-decade pattern or eases back down is the number worth watching if you want to know where this is headed next.
