The big facts page

133 climate change facts, all checked

Every fact on this site in one place, each linked to the Met Office, NASA, NOAA, the United Nations or Encyclopaedia Britannica. Our build checks each one against the source text; see the sources page.

What climate change is

1 Climate change is a large-scale, long-term shift in the planet’s weather patterns and average temperatures. Met Office: What is climate change?
2 NASA describes climate change as a long-term change in the average weather patterns that define Earth’s local, regional and global climates. NASA Science: What is climate change?
3 Global warming means the long-term heating of Earth’s surface seen since the pre-industrial period (1850 to 1900), caused mainly by burning fossil fuels. NASA Science: What is climate change?
4 NASA points out that “climate change” and “global warming” are often swapped around but do not mean quite the same thing. NASA Science: What is climate change?
5 The signs scientists track include warmer land and oceans, rising seas, ice loss at the poles and in mountain glaciers, and changes in extreme weather. NASA Science: What is climate change?
6 Scientists study climate change with observations from the ground, the air and space, plus computer models. NASA Science: What is climate change?
7 In the 11,000 years before the Industrial Revolution, the world’s average temperature held steady at around 14 °C. Met Office: What is climate change?
8 The Met Office dates the start of the problem to the mid-1800s, when people began burning coal, oil and gas for fuel on a large scale. Met Office: What is climate change?
9 Burning fossil fuels releases greenhouse gases such as carbon dioxide, methane and nitrous oxide. Met Office: What is climate change?
10 The Intergovernmental Panel on Climate Change (IPCC) was set up in 1988 to give governments the information they need to tackle climate change. Met Office: What is climate change?
11 The IPCC’s 2021 report says human activity is unequivocally the cause of climate change. Met Office: What is climate change?
12 Scientists have ruled out natural causes such as volcanoes, changes in the Sun and natural sources of carbon dioxide as the main driver. Met Office: What is climate change?
13 Since the Industrial Revolution the planet’s average temperature has risen by around 1.1 °C (IPCC Sixth Assessment Report). Met Office: What is climate change?
14 For 2024, the World Meteorological Organization’s estimates of the current warming level ranged from 1.34 °C to 1.41 °C. Met Office: What is climate change?
15 Greenhouse gases can stay in the air for tens or hundreds of years, so some further warming can’t be avoided even if all emissions stopped today. Met Office: What is climate change?
16 If fossil fuel burning and forest clearing carry on at the same rate, the planet could warm by more than 4 °C by 2100. Met Office: What is climate change?
17 The IPCC’s Sixth Assessment Report found 64% of human-made greenhouse gas emissions come from fossil fuels and industry, and 11% from land use and forestry. Met Office: What is climate change?
18 Aeroplanes and cement-making add carbon dioxide too. Met Office: What is climate change?

The greenhouse effect

19 Greenhouse gases act like a blanket round the Earth: sunlight passes through, the ground warms and gives off infrared heat, and some of that heat is caught and sent back down. Met Office: What is climate change?
20 The greenhouse effect itself is vital: without it the Earth would be bitterly cold and people could not survive. Met Office: What is climate change?
21 Adding extra greenhouse gases makes the blanket thicker. The Met Office calls this the enhanced greenhouse effect, and it is the main cause of climate change. Met Office: Causes of climate change
22 Without greenhouse gases, Earth would be about 30 degrees colder than it is today. Met Office: Causes of climate change
23 Britannica puts Earth’s average surface temperature without the greenhouse effect at only about −18 °C. Encyclopaedia Britannica: greenhouse effect
24 Water vapour is the greenhouse gas with the largest effect. Encyclopaedia Britannica: greenhouse effect
25 Some greenhouse gases occur naturally, like carbon dioxide, methane and nitrous oxide. Others, such as CFCs, are made only by people. Met Office: Causes of climate change
26 On Venus, a thick carbon dioxide atmosphere causes an extreme greenhouse effect, with surface temperatures as high as 450 °C. Encyclopaedia Britannica: greenhouse effect
27 Despite the name, the greenhouse effect works differently from a glass greenhouse, which keeps heat in mainly by trapping warmed air. Encyclopaedia Britannica: greenhouse effect
28 Joseph Fourier is sometimes credited with the idea, after comparing the atmosphere in 1824 to an insulated glass-lidded “hotbox”, though he never used the term greenhouse effect. Encyclopaedia Britannica: greenhouse effect
29 Svante Arrhenius is credited with the origins of the term, through the climate model he published in 1896. Encyclopaedia Britannica: greenhouse effect
30 Carbon dioxide alone is responsible for about 80% of the total heating influence of all human-produced greenhouse gases since 1990 (NOAA). NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide

The causes

31 The Met Office says the evidence is clear: the main cause of climate change is burning fossil fuels such as oil, gas and coal. Met Office: Causes of climate change
32 Earth’s climate has been changing since the planet formed 4.5 billion years ago. Until recently, natural factors drove those changes. Met Office: Causes of climate change
33 Over the past million years, cold glacials and warmer interglacials have come round roughly every 100,000 years, driven by changes in Earth’s orbit. Met Office: Causes of climate change
34 There is more carbon dioxide in the air today than at any time in at least the past 2 million years. Met Office: Causes of climate change
35 During the 20th and 21st centuries the level of carbon dioxide rose by 40%. Met Office: Causes of climate change
36 Forests take in and store carbon dioxide, so cutting them down lets it build up faster, and burning the trees releases the carbon they stored. Met Office: Causes of climate change
37 The Met Office says methane from farm animals is 30 times more powerful than carbon dioxide as a greenhouse gas, and nitrous oxide nearly 300 times. Met Office: Causes of climate change
38 Making cement causes 2% of all carbon dioxide emissions. Met Office: Causes of climate change
39 Milankovitch cycles, small changes in Earth’s path and tilt, alter how much sunlight reaches us, but they work over tens or hundreds of thousands of years. Met Office: Causes of climate change
40 El Niño years warm the globe and La Niña years cool it, but only for months or years. They can’t explain the steady warming. Met Office: Causes of climate change
41 If extra energy from the Sun were the cause, the whole atmosphere would warm, but only the bottom layer is warming. Met Office: Causes of climate change
42 Volcanoes give out 50 times less carbon dioxide than people do, and their main effect is actually cooling. Met Office: Causes of climate change
43 Plants and the ocean soak up about half the carbon dioxide people release from fossil fuels. The rest stays in the air. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
44 Yearly carbon dioxide emissions from fossil fuels rose from about 11 billion tons in the 1960s to an estimated 37.4 billion tons in 2024. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide

The evidence

45 Global average carbon dioxide reached 422.8 parts per million in 2024, a new record. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
46 The rise during 2024 was 3.75 ppm, the largest one-year increase on record. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
47 Carbon dioxide is now 50% higher than before the Industrial Revolution. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
48 Air bubbles in ice cores show carbon dioxide never went above 300 ppm in the ice-age cycles of the past million years or so, and it was 280 ppm or less before the Industrial Revolution. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
49 Over the past 60 years carbon dioxide has risen 100 to 200 times faster than at the end of the last ice age. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
50 The yearly rise was about 0.8 ppm in the 1960s and has sped up to 2.6 ppm a year in 2015–2024. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
51 At Mauna Loa the highest reading each year comes in May, because Northern Hemisphere plants take in carbon dioxide as they grow in summer and release it as they decay in winter. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
52 The yearly average at Mauna Loa Observatory, Hawaii, was 424.61 ppm in 2024. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
53 “Parts per million” means the number of carbon dioxide molecules in every million molecules of dry air. NASA: Carbon dioxide (vital sign)
54 Ice cores from Antarctica hold tiny bubbles of ancient air, extending the carbon dioxide record back through Earth’s last three glacial cycles. NASA: Carbon dioxide (vital sign)
55 The Keeling Curve, devised by Charles David Keeling of the Scripps Institution of Oceanography, charts carbon dioxide at Mauna Loa since 1958. Encyclopaedia Britannica: Keeling Curve
56 It is the longest unbroken instrument record of carbon dioxide in the world. Encyclopaedia Britannica: Keeling Curve
57 Keeling chose Mauna Loa and the South Pole because they were far from big carbon dioxide sources such as cities. Encyclopaedia Britannica: Keeling Curve
58 Measurements at Mauna Loa paused briefly in spring 1964 because of funding problems, and in 2022 because of the Mauna Loa eruption. Encyclopaedia Britannica: Keeling Curve
59 The shape of the curve shows that about 57% of carbon dioxide emissions stay in the atmosphere from year to year. Encyclopaedia Britannica: Keeling Curve
60 NOAA’s yearly averages for Mauna Loa run from 315.98 ppm in 1959 to 427.35 ppm in 2025. NOAA Global Monitoring Laboratory: Mauna Loa CO2 annual mean data (text file)
61 The 10 most recent years are the warmest on record (NASA). NASA: Global temperature (vital sign)
62 Since record-keeping began in 1880, the hottest year in NASA’s record is 2024. NASA: Global temperature (vital sign)
63 In 2025 the global surface temperature was 1.19 °C above the 1951–1980 average, slightly cooler than 2024. NASA: Global temperature (vital sign)
64 NASA’s analysis uses more than 25,000 weather stations, plus ship and buoy readings of sea temperature and Antarctic research stations. NASA: Global temperature (vital sign)
65 In NASA’s GISTEMP data, 2024 stands 1.28 °C above the 1951–1980 average, the highest yearly value since 1880. NASA GISS: GISTEMP v4 global annual mean data (CSV file)
66 NOAA says Earth has warmed by about 0.06 °C a decade on average since 1850, and more than three times as fast, 0.20 °C a decade, since 1982. NOAA Climate.gov (archived June 2025): Global temperature
67 By 2024 it had been 48 years since Earth last had a cooler-than-average year in NOAA’s record. NOAA Climate.gov (archived June 2025): Global temperature
68 When 2005 set a new record it was the first of the new century to do so. It now ranks only 13th-warmest. NOAA Climate.gov (archived June 2025): Global temperature
69 Clues from ice cores, tree rings and ocean sediments show today’s warming is roughly 10 times faster than the average warming after an ice age. NASA Science: Evidence
70 Carbon dioxide from human activities is rising about 250 times faster than it did from natural sources after the last ice age. NASA Science: Evidence
71 In just the last 800,000 years there have been eight cycles of ice ages and warmer periods. The last ice age ended about 11,700 years ago. NASA Science: Evidence
72 Scientists showed in the mid-19th century that carbon dioxide and other gases trap heat. NASA Science: Evidence

The effects

73 Climate change is already having visible effects: the Earth is warming, rainfall patterns are changing and sea levels are rising. Met Office: Effects of climate change
74 Some changes can’t now be prevented, but the sooner emissions are cut, the smaller the changes will be. Met Office: Effects of climate change
75 The oceans take up 90% of the extra heat caused by people. Met Office: Effects of climate change
76 NOAA estimates the ocean is storing about 91% of the excess heat trapped by extra greenhouse gases. NOAA Climate.gov (archived June 2025): Ocean heat content
77 Seawater expands as it warms, so a warmer ocean takes up more room and the sea rises. Meltwater from ice on land adds more. Met Office: Effects of climate change
78 Between 1901 and 2018 the global average sea level rose by around 20 centimetres. Met Office: Effects of climate change
79 NOAA puts the rise since 1880 at 21–24 centimetres. NOAA Climate.gov (archived June 2025): Global sea level
80 Sea level rise is speeding up: from 1.4 mm a year through most of the 20th century to 3.6 mm a year in 2006–2015. NOAA Climate.gov (archived June 2025): Global sea level
81 In 2023 global average sea level set a record, 101.4 mm above 1993 levels. NOAA Climate.gov (archived June 2025): Global sea level
82 The poles warm faster than other places: less ice means less sunlight reflected back to space, so the area heats up and more ice melts. Met Office: Effects of climate change
83 Arctic ice is already 65% thinner than it was in 1975. Met Office: Effects of climate change
84 Late-summer Arctic sea ice is the smallest it has been in at least 1,000 years. Met Office: Effects of climate change
85 Without soon cutting emissions, the Arctic could have ice-free summers by the middle of this century. Met Office: Effects of climate change
86 Arctic sea ice is at its largest in March and its smallest in September. NOAA Climate.gov (archived June 2025): Arctic sea ice
87 Between 1979 and 2024, end-of-summer Arctic sea ice shrank by 12.1% per decade compared with the 1981–2010 average. NOAA Climate.gov (archived June 2025): Arctic sea ice
88 Ice more than four years old, the thick ice, is now only 5% of what there was in the 1980s. NOAA Climate.gov (archived June 2025): Arctic sea ice
89 In September 2024 Arctic sea ice covered 4.38 million square kilometres, sixth lowest in the satellite record. NOAA Climate.gov (archived June 2025): Arctic sea ice
90 The oceans also take up around 25% of the carbon dioxide people release, which makes the water more acidic. Met Office: Effects of climate change
91 Since the Industrial Revolution the pH of the ocean’s surface has dropped from 8.21 to 8.10, making it harder for sea creatures to build shells and skeletons. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
92 The reference glaciers watched by the World Glacier Monitoring Service lost ice for the 37th year in a row in 2023/24. NOAA Climate.gov (archived June 2025): Mountain glaciers
93 Since 1970 those glaciers have lost the same as slicing about 30 metres of ice off the top of each one. NOAA Climate.gov (archived June 2025): Mountain glaciers
94 Melting glaciers and ice sheets are the biggest cause of sea level rise in recent decades. NOAA Climate.gov (archived June 2025): Mountain glaciers
95 Spring snow is melting earlier: late-spring snow cover has been above average only 5 times in the past 25 years. NOAA Climate.gov (archived June 2025): Snow cover
96 Warmer air holds more water, so rainfall is increasing on average across the world, though some places get less. Met Office: Effects of climate change
97 Plants and animals are shifting where they live, river and lake ice breaks up earlier, and plants and trees are flowering sooner. NASA Science: Effects
98 Nearly 4 in 10 people (39%) live within 100 kilometres of a shoreline. Met Office: Effects of climate change
99 2015, 2016, 2017, 2018, 2019 and 2020 were among the hottest years ever recorded, and heatwaves have become more likely as the planet warms. Met Office: Effects of climate change
100 The IPCC expects the global average temperature to reach or pass 1.5 °C within the next few decades. NASA Science: Effects

The UK

101 The UK has a temperate maritime climate: cool and mild, with changeable weather. Met Office: Climate change in the UK
102 In future the UK can expect warmer, wetter winters, hotter, drier summers, and more frequent and intense weather extremes. Met Office: Climate change in the UK
103 Compared with 1990, by 2070 on a high-emissions path, UK winters could be 1–4.5 °C warmer and up to 30% wetter, and summers 1–6 °C warmer and up to 60% drier. Met Office: Climate change in the UK
104 Hot summer days could be 4–7 °C warmer by 2070 in that scenario. Met Office: Climate change in the UK
105 Over the southern UK, two days or more above 30 °C become sixteen times more frequent by 2070. Met Office: Climate change in the UK
106 UK warm spells have already increased and cold spells decreased, and both are linked to climate change. Met Office: Effects of climate change
107 The Met Office’s UK Climate Projections (UKCP) show how the UK climate may change. Met Office: Climate change in the UK

How we found out

108 Irish physicist John Tyndall (1820–1893) found that water vapour and carbon dioxide absorb much more radiant heat than the other gases of the air. Encyclopaedia Britannica: John Tyndall
109 Tyndall became professor of natural philosophy at the Royal Institution in London in 1853 and was a friend of Michael Faraday. Encyclopaedia Britannica: John Tyndall
110 Tyndall also showed that the sky is blue because molecules in the air scatter the Sun’s rays. Encyclopaedia Britannica: John Tyndall
111 He was a daring mountaineer. Encyclopaedia Britannica: John Tyndall
112 Swedish scientist Svante Arrhenius built the first climate model of the effect of carbon dioxide, published in 1896. Encyclopaedia Britannica: Svante Arrhenius
113 He came to it through debates about what caused the ice ages. Encyclopaedia Britannica: Svante Arrhenius
114 Arrhenius predicted that fossil fuel burning alone would take 500 years to double carbon dioxide, and that doubling it would warm Earth by 3 to 4 °C. Encyclopaedia Britannica: Svante Arrhenius
115 Arrhenius won the Nobel Prize for Chemistry in 1903. Encyclopaedia Britannica: Svante Arrhenius
116 The IPCC was set up in 1988 by the UN Environment Programme and the World Meteorological Organization, and is based in Geneva. Encyclopaedia Britannica: Intergovernmental Panel on Climate Change
117 The IPCC does no research of its own: it gathers and assesses work by hundreds of scientists from around the world. Encyclopaedia Britannica: Intergovernmental Panel on Climate Change
118 In 2007 the IPCC shared the Nobel Peace Prize. Encyclopaedia Britannica: Intergovernmental Panel on Climate Change
119 Between 1990 and 2021 the IPCC released six main assessment reports. Encyclopaedia Britannica: Intergovernmental Panel on Climate Change

Kyoto, Paris and the agreements

120 The Kyoto Protocol, adopted in Kyoto, Japan, in December 1997, aimed to cut emissions of six greenhouse gases. Encyclopaedia Britannica: Kyoto Protocol
121 It came into force in February 2005. Encyclopaedia Britannica: Kyoto Protocol
122 It asked 41 countries plus the European Union to cut those gases to 5.2% below 1990 levels in 2008–12. Encyclopaedia Britannica: Kyoto Protocol
123 The Paris Agreement was adopted in Paris in December 2015, and was meant to improve on and replace the Kyoto Protocol. Encyclopaedia Britannica: Paris Agreement
124 France hosted representatives from 196 countries at the conference, from 30 November to 11 December 2015. Encyclopaedia Britannica: Paris Agreement
125 The Paris Agreement came into force on 4 November 2016 and is a legally binding international treaty. United Nations: The Paris Agreement
126 Its goal is to keep warming well below 2 °C above pre-industrial levels, and to try to limit it to 1.5 °C. United Nations: The Paris Agreement
127 195 Parties (194 States plus the European Union) have joined the Paris Agreement. United Nations: The Paris Agreement
128 Every five years each country is expected to send an updated climate plan, called a Nationally Determined Contribution (NDC). United Nations: The Paris Agreement
129 The first “global stocktake” of progress finished at COP28 in 2023, with a call to speed up the move from fossil fuels to renewables such as wind and solar. United Nations: The Paris Agreement
130 The detailed rules, nicknamed the Paris Rulebook, were agreed at COP24 in Katowice, Poland, in 2018 and finished at COP26 in Glasgow in 2021. United Nations: The Paris Agreement
131 The process goes back to the 1992 Earth Summit in Rio de Janeiro, where countries joined the UN Framework Convention on Climate Change. Encyclopaedia Britannica: Paris Agreement
132 In 2015 almost every country in the world signed up to cut greenhouse gas emissions, aiming for 2 °C and, if possible, 1.5 °C. Met Office: What is climate change?
133 The IPCC has said 1.5 °C was likely to be reached sometime between 2030 and 2052 if emissions carried on at the rate of its 2018 report. Encyclopaedia Britannica: Intergovernmental Panel on Climate Change