Is the Warming Caused by Humans?

Mostly. The CO2 rise is fossil by its isotopes and by the carbon bookkeeping, the sun's measured output has been flat since 1978, and cosmic rays change clouds too little. The other causes CMI names are human, regional or small, and cleaner air implies a higher sensitivity, not a lower one.

By AI (Claude Opus 5.5, thinking level unavailable) Draft:  October 2026

Summary

Most of it.  Carbon dioxide stayed between 272 and 284 parts per million for the 1,800 years before 1800 in the Law Dome ice core, a span that fits inside a young-earth chronology, and is now 427.1  The sun's output has been flat since satellites began measuring it in 1978.2  The ocean is gaining heat, which a natural reshuffling of heat from ocean to air cannot do.  The IPCC's best estimate is that humans caused 1.07 °C of the 1.06 °C observed to 2010–2019, with natural causes adding close to nothing.3

Don Batten's climate article for Creation Ministries International (CMI), the fullest young-earth treatment of the subject,4 offers several alternatives, and each fails as a natural explanation of the warming.  The warming early in the twentieth century, before most emissions, is real, but temperature follows the sum of all heating and cooling influences, not yearly emissions, and the warming that began in 1975 has now lasted fifty years.  The sun's 11-year cycle is real and has no upward trend.  The cosmic-ray route to cloud formation was tested in a chamber at CERN and found too weak to matter, and the sun's trends that would drive it ran the wrong way.  The ozone-depleting gases CMI names are man-made.  Cleaner air has added real warming, but only by unmasking greenhouse warming that pollution had been hiding, which points to a higher sensitivity, not a lower one.

Other young-earth writers already accept the main point.  Jake Hebert, the Institute for Creation Research's physicist, treats the human cause of the CO2 rise as settled, and the skeptical climatologist Roy Spencer lists the opposite claim among the arguments skeptics should drop.  Whether the earth is warming at all is argued in Is the Earth Warming?, and how much warming the added CO2 brings in How Much Warming Does More CO2 Cause?.

Part 1: Where the CO2 comes from

This article takes CMI's alternatives one at a time:  that the CO2 rise is not ours, that the timing of the warming does not fit CO2, that the sun or cosmic rays did it, and that other factors deserve more of the credit.

The CO2 is ours

CMI does not quite say that the CO2 rise is natural, but it lists "volcanoes, the weathering of rocks, the release of carbon dioxide from the oceans" as other sources and leaves the question open.4  Hebert does not leave it open:  "even scientists skeptical of global warming alarmism tend to think that human activity is indeed the cause of this increase."5  Spencer puts "WARMING CAUSES CO2 TO RISE, NOT THE OTHER WAY AROUND" on his "Top 10 list of stupid skeptic arguments".6  Three lines of measurement settle it.

  1. The ice record. Air bubbles in the Law Dome ice core in Antarctica, dated to within a few years, show CO2 between 272 and 284 parts per million for the 1,800 years before 1800.1 The core's youngest air overlaps the air sampled from the snowpack above it and the instrument record at Cape Grim, Tasmania, so the ice and the instruments are checked against each other.1 Mauna Loa recorded 316 ppm in 1959 and 427 in 2025.7 All of this fits inside a young-earth chronology. Nothing about it depends on the deep ice cores.
  2. The bookkeeping. In 2023 humans released 11.1 billion tonnes of carbon from fossil fuels, cement and land clearing. The atmosphere gained 5.9 billion tonnes, the oceans absorbed 2.9 and land plants 2.3.8 The air gained about half of what was burned. Nature as a whole took up carbon, not released it. If the oceans were the source, they would be losing carbon and growing less acidic. They are gaining carbon and growing more acidic, which CMI itself discusses as a possible harm.4
  3. The fingerprint. Fossil fuels are made from ancient plants, so they carry less carbon-13 than the air and no carbon-14 at all. Burning them should dilute both isotopes in the atmosphere, an effect named for Hans Suess, who first measured it in 1955. It is there. Carbon-13 in the air fell by 1.8 parts per thousand between 1850 and 2015, and carbon-14 fell by about 20 parts per thousand between 1850 and 1950, before nuclear bomb tests swamped the signal.9 The same dilution is why radiocarbon dates of recent samples need correcting, a point the radiocarbon article takes up.

The "12 %" claim

One skeptic argument, though not one CMI makes, holds that only 12 % of the CO2 in the air comes from fossil fuels.  It comes from a 2022 paper by Kenneth Skrable and colleagues in the journal Health Physics, which concluded that "the percentage of the total CO2 due to the use of fossil fuels from 1750 to 2018 increased from 0% in 1750 to 12% in 2018, much too low to be the cause of global warming."10  Stephen Schwartz, Ralph Keeling, Harro Meijer and Jocelyn Turnbull replied that the paper's historical carbon-14 values are "completely at odds with the measurements" and that it "should be retracted in its entirety".11  The underlying confusion is between atoms and causes.  Carbon atoms trade places constantly between the air, the ocean surface and plants, so fossil carbon atoms do not stay in the air;  they are swapped for others.  What matters is the size of the stock, and the bookkeeping above shows that the air gains about half the carbon humans emit each year, while the ocean and land take up the rest.8

Part 2: Does the timing fit?

The timing

CMI's strongest-looking argument is that warming and emissions do not track each other.  "The planet has warmed by about 0.8°C since 1880 and half of this warming occurred before there was any significant change in the CO2."4  It quotes Phil Jones, director of the University of East Anglia's Climatic Research Unit, who agreed in 2010 that the rates of warming from 1860–1880, 1910–1940 and 1975–1998 "are similar and not statistically significantly different from each other", although emissions were "about 60 times greater for the latter period".4

The quotation is accurate.  Jones's own answer gave the trends:  0.163, 0.15 and 0.166 °C per decade, and 0.161 for 1975–2009.12  It also said what CMI leaves out.  The 1860–1880 data "are more uncertain, because of sparser coverage", and that period "is also only 21 years in length."  In the same interview Jones was asked about natural causes of the 1975–1998 warming and answered that "Solar influence was about flat over this period," and that volcanoes would have cooled it:  "Combining only these two natural influences, therefore, we might have expected some cooling over this period."12

Three further points answer the argument.

  1. The numbers have moved. The total warming is now about 1.3 °C, not 0.8, and the warming up to the 1940s was about 0.3 °C, a quarter of the total, not half.13
  2. The physics does not predict that temperature tracks emissions. It predicts that temperature tracks forcing, the sum of all heating and cooling influences. CO2's forcing grows with the logarithm of its concentration, not with yearly emissions, and part of it has been offset by sulphate pollution, which cools.3 Natural factors also played a part early on: even Lockwood and Fröhlich, who rule out the sun for recent warming, write that "the Sun may well have been a factor in post-industrial climate change in the first half of the last century."14 That is not in dispute.
  3. The recent warming has lasted. The bursts of 1860–1880 and 1910–1940 lasted twenty to thirty years and then stopped or reversed. The warming that began in 1975 has now run fifty years at about 0.21 °C per decade, and since 2000 at about 0.25.13 The 1975–1998 window in the question put to Jones ended a quarter of a century ago.

Part 3: The natural alternatives

The sun

CMI writes that "The sun is, rather obviously, a major driver of climate on Earth," and adds:  "We have recently moved into an exceptionally quiet period of solar activity. ... Maybe the normal 11-year cycle will resume, but maybe not."4  The sun is indeed the climate's energy source, and its 11-year cycle shows up in global temperature:  Charles Camp and Ka Kit Tung found "a global warming signal of almost 0.2°K attributable to the 11-year solar cycle", the figure CMI quotes.15  That is a cycle, up and down, not a trend.  Satellites have measured the sun's output since 1978, and it has not risen.  The NOAA record of total solar irradiance is flat from 1980 to 2025, with a trend of 0.003 W/m² per decade and every yearly value between 1361.2 and 1362.6 W/m².2  The IPCC's best estimate of the sun's forcing from 1750 to 2019 is 0.01 W/m², against 2.72 for human influences.16  And the cycle did resume.  The yearly mean sunspot number fell to 3.6 in 2019 and rose to 154.7 in 2024.17  The sun cannot be the cause of a warming that its measured output did not follow.

Cosmic rays

Henrik Svensmark proposed in 1997 that cosmic rays help form clouds, so that a strong sun, which shields the earth from cosmic rays, means fewer clouds and a warmer earth.18  Brian Tinsley, Hebert's doctoral adviser, proposed a different route through the atmosphere's electric current.  CMI cites both.4  The idea was tested directly in the CLOUD chamber at CERN.  Eimear Dunne and 58 colleagues found that ion-produced particles are common, but that "variations in cosmic ray intensity do not significantly affect climate via nucleation in the present-day atmosphere."  Over a solar cycle, the change in the particles on which cloud droplets form is "only 0.1% ... with local changes of no more than 1%."19  That test covers Svensmark's route, not Tinsley's.  But both depend on the sun, and Mike Lockwood and Claus Fröhlich showed that "over the past 20 years, all the trends in the Sun that could have had an influence on the Earth's climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures."14  Hebert's own 2013 paper lists "a number of apparent difficulties" with the mechanism he favours.20

The other factors CMI names

CMI is right that CO2 is not the only influence on climate, and several of the factors it names are real.  But each turns out to be either human, regional, or small.

  1. Ozone-depleting gases. CMI quotes a study as saying these gases "could be responsible for up to half of the effects of climate change observed in the Arctic from 1955 to 2005."4 That sentence is not in the paper's summary or in Columbia University's press release; the closest wording found is in a news report.21 The paper itself, by Lorenzo Polvani and colleagues, found in model runs that "when ODS are kept fixed, forced Arctic surface warming and forced sea-ice loss are only half as large as when ODS are allowed to increase."22 Columbia University's press release put their share of global warming from 1955 to 2005 at "about a third".23 Either way, CFCs and their relatives are man-made greenhouse gases. This is a human cause, banned by the Montreal Protocol, not a natural alternative.
  2. Arctic "Atlantification". Tommaso Tesi and colleagues found from Svalbard sediments that warm Atlantic water began pushing into the Arctic around 1900, and CMI quotes their statement accurately: climate models "fail to reproduce the post-LIA Atlantification documented in our reconstructions."4 That is a fair point against the models for one region. CMI does not mention that the same paper says "During the modern period, anthropogenic-derived forcing (ANTROP) intensified the progressive Atlantification that commenced in the early 20th century."24
  3. Cleaner air. CMI notes that air-pollution controls let more sunlight through: Martin Wild's team measured an 8 % rise in clear-sky transmission in central Europe, which they attribute to "aerosol pollutants as likely major drivers".25 The 2020 cut in sulphur in ships' fuel had a global effect that Tianle Yuan and colleagues put at "+0.2 ± 0.11 Wm−2" over the oceans, which "translates to around 0.16 K of warming with a timescale of 7 years".26 A decline in desert dust added a forcing of "+0.02 ± 0.05 watts per square meter".27 These are real, and the shipping effect is not small. But they cut against CMI's argument. Sulphate pollution is man-made and cools. If removing it warms the earth, then for decades it was hiding part of the warming from greenhouse gases. The more cooling pollution hid, the more sensitive the climate must be to explain the warming observed. CMI cannot use cleaner air to explain recent warming and also argue for a sensitivity of 0.5 °C.

Objections and responses

"Natural ocean cycles caused the warming."  Ocean cycles move heat between the ocean and the air.  If they had warmed the surface by drawing heat out of the ocean, the ocean would be losing heat.  It is gaining heat at about 0.7 W/m² over the whole earth, and the planet's net heat gain has risen (Is the Earth Warming?;  How Much Warming Does More CO2 Cause?).

Issues and unanswered questions

  1. Sources not read in full. The full paper by Polvani and colleagues was read only in its summary, and the source of CMI's "up to half" wording on ozone-depleting gases was not traced beyond a news report.

Verdict

Most of the warming is human.  The CO2 rise is fossil carbon:  the ice and the instruments agree on its size, the carbon bookkeeping shows nature taking carbon up rather than giving it off, and the isotopes carry the signature of burned fossil fuel.  The sun's measured output has not risen since satellites began watching it, so the sun cannot explain a warming its output did not follow.  The other influences CMI names are real, and some of them, such as Atlantic water in the Arctic and cleaner shipping fuel, are worth knowing about.  But each is human, regional or small, and none is a natural cause large enough to replace CO2.  CMI's timing argument rests on numbers that have since moved and on the idea that temperature should track yearly emissions, which the physics does not predict.

Sources

  1. 1.

    Etheridge, David M. et al.  “Law Dome Ice Core 2000-Year CO2, CH4, and N2O Data.”  IGBP PAGES/World Data Center for Paleoclimatology, Data Contribution Series 2010-070.  2010.  The Australian Antarctic record of greenhouse gases from air trapped in Law Dome ice and snow, AD 1 to 2004, joined to direct air measurements at Cape Grim, Tasmania, with smoothed curves and dating uncertainties.  The original paper is MacFarling Meure and others, Geophysical Research Letters, 2006.

    1. 1a.

      Tables CO2 spline, column 6:  The smoothed CO2 curve gives 276.8 ppm for 1750, 286.1 for 1860, 296.1 for 1900, 310.5 for 1940 and 315.7 for 1959.  From AD 1 to 1799 it stays between 271.6 and 283.9 ppm. ↩ ↩

    2. 1b.

      Section Abstract, MacFarling Meure et al. 2006:  “Firn air measurements span the past 65 years and overlap with the ice core and direct atmospheric observations.”  Section Description:  “DE08 and DE08-2 ice core air dating uncertainty is less than +/- 3 years.” ↩

  2. 2.

    Coddington, Odele et al.  “NOAA Climate Data Record of total solar irradiance, version 3, annual.”  NOAA National Centers for Environmental Information.  2026.  NOAA's yearly record of the sun's total output at the earth, measured by satellites since 1978 and reconstructed from sunspots before then.

    1. 2a.

      Annual values 1980–2025 lie between 1361.17 and 1362.56 W/m².  Least-squares trend 1980–2025:  0.003 W/m² per decade.  Means:  1980–1990, 1361.76;  2008–2019, 1361.50;  2015–2025, 1361.77. ↩ ↩

  3. 3.

    Intergovernmental Panel on Climate Change.  “Summary for Policymakers.”  Climate Change 2021:  The Physical Science Basis, Contribution of Working Group I to the Sixth Assessment Report, 3–32.  Cambridge University Press.  2021.  The summary of the IPCC's 2021 physical-science assessment, approved line by line by government delegates.  It states the consensus position on observed warming, its causes, and climate sensitivity.

    1. 3a.

      Section A.1.3, page 5:  “The likely range of total human-caused global surface temperature increase from 1850–1900 to 2010–2019”.  “is 0.8°C to 1.3°C, with a best estimate of 1.07°C.”  “other human drivers (principally aerosols) contributed a cooling of 0.0°C to 0.8°C, natural drivers changed global surface temperature by –0.1°C to +0.1°C, and internal variability changed it by –0.2°C to +0.2°C.”  Its footnote 11 gives the observed warming to 2010–2019 as 1.06 [0.88 to 1.21] °C. ↩ ↩

  4. 4.

    Batten, Don.  “Climate Change:  A biblical and scientific approach to Anthropogenic Global Warming.”  Creation Ministries International.  Feb 17, 2026 (edition of 2020).  CMI's main statement on modern climate, a long essay by its scientist Don Batten, a former research horticulturalist with the New South Wales Department of Agriculture, written with colleagues.  It sets out a biblical history of climate, a critique of the climate movement, a scientific case for low climate sensitivity and against the temperature records, and a policy section.  This article tests every factual claim in it. ↩

    1. 4a.

      Section The raw data:  “Other sources include changes in land use (e.g., deforestation), volcanoes, the weathering of rocks, the release of carbon dioxide from the oceans (any warming of the oceans results in CO2 being less soluble and therefore it is released into the atmosphere), the breakdown of organic remains (dead wood in forests), etc.” ↩

    2. 4b.

      Section Ocean acidification:  “When the atmospheric CO2 increases, more dissolves in the ocean.” ↩

    3. 4c.

      Section The raw data:  “The planet has warmed by about 0.8°C since 1880”.  “and half of this warming occurred before there was any significant change in the CO2”.  CMI's note numbers 23 and 24 fall between the two parts of the sentence. ↩

    4. 4d.

      Section The surface temperature record and CO2 rise:  “A prominent member of the climate establishment, Dr Phil Jones, admitted that the rates of global warming from 1860–1880, 1910–1940, and 1975–1998 (the red lines in Fig. 1) “are similar and not statistically significantly different from each other”.”  “Indeed, the rate of rise in temperature 1860–1880 is similar to the recent rise, and yet the amount of human-generated CO2 is about 60 times greater for the latter period.” ↩

    5. 4e.

      Section The sun:  “The sun is, rather obviously, a major driver of climate on Earth.”  “We have recently moved into an exceptionally quiet period of solar activity. For the first time since the 1600s we have had several recent years with no sunspots. Maybe the normal 11-year cycle will resume, but maybe not.” ↩

    6. 4f.

      Section The sun:  “In the 1990s, Danish physicist Henrik Svensmark and colleagues began publishing on the effect of cosmic rays on cloud formation, which would affect global warming/cooling.”  “Dr Brian Tinsley, professor emeritus at the University of Texas, Dallas, proposed an alternative model wherein cosmic rays make clouds last longer, thus cooling the earth.” ↩

    7. 4g.

      Section Other factors causing climate change on planet Earth:  “A study published in 2020 attributed a substantial amount of the warming in the Arctic to the rise in ozone-depleting substances in the second half of the 20th century.”  “The authors wrote, “Gases that deplete the ozone layer could be responsible for up to half of the effects of climate change observed in the Arctic from 1955 to 2005.”” ↩

    8. 4h.

      Section Other factors causing climate change on planet Earth:  “The authors acknowledge, “Currently, the latest CMIP6 historical climate experiments … fail to reproduce the post-LIA [Little Ice Age] Atlantification documented in our reconstructions.”” ↩

  5. 5.

    Hebert, Jake.  “Shutdown:  Chance to Test Climate Change Assumption.”  Institute for Creation Research.  May 2, 2020.  A short ICR article on whether the 2020 lockdowns would show up in the CO2 record.  It is useful mainly for its list of what Hebert regards as not in dispute.

    1. 5a.

      Paragraph on the Mauna Loa record:  “However, even scientists skeptical of global warming alarmism tend to think that human activity is indeed the cause of this increase.”  “Remember, the global warming debate is ultimately not about whether atmospheric CO 2  is increasing. Nor is it really a debate about whether or not humans are primarily responsible for the increased CO 2 . Nor is it even a debate about whether or not an increase in atmospheric carbon dioxide would result in an eventual temperature increase. It would, but this increase would be very slight.” ↩

  6. 6.

    Spencer, Roy W.  “Skeptical Arguments that Don't Hold Water.”  Roy Spencer, PhD (blog).  Apr 25, 2014.  A short post by the UAH climatologist and prominent skeptic listing ten arguments he asks fellow skeptics to stop using, each with a one-paragraph reason.

    1. 6a.

      Section introduction and argument 7:  “So, here’s my Top 10 list of stupid skeptic arguments.”  “WARMING CAUSES CO2 TO RISE, NOT THE OTHER WAY AROUND The rate of rise in atmospheric CO2 is currently 2 ppm/yr, a rate which is 100 times as fast as any time in the 300,000 year Vostok ice core record.” ↩

  7. 7.

    NOAA Global Monitoring Laboratory.  Mauna Loa CO2 annual mean data.  2026.  The yearly averages of the continuous CO2 record begun by Charles David Keeling at Mauna Loa, Hawaii, in 1958.

    1. 7a.

      Annual means, ppm:  1959, 315.98;  2020, 414.21;  2024, 424.61;  2025, 427.35.  Average growth 0.86 ppm a year over 1959–1969 and 2.63 over 2015–2025. ↩

  8. 8.

    Friedlingstein, Pierre et al.  “Global Carbon Budget 2024.”  Earth System Science Data 17:965–1039.  2025.  The yearly accounting, by an international team of over a hundred carbon-cycle scientists, of how much CO2 humans emit and where it goes:  the air, the ocean and land plants, each measured or modelled independently, with the mismatch reported.

    1. 8a.

      Section Abstract, page 965:  “Also, for 2023, GATM was 5.9 ± 0.2 GtC yr−1 (2.79 ± 0.1 ppm yr−1 ; ppm denotes parts per million), SOCEAN was 2.9 ± 0.4 GtC yr−1 , and SLAND was 2.3 ± 1.0 GtC yr−1”.  The same abstract gives total human emissions for 2023, fossil fuels, cement and land-use change together, as 11.1 ± 0.9 GtC. ↩ ↩

  9. 9.

    Graven, Heather et al.  “Changes to Carbon Isotopes in Atmospheric CO2 Over the Industrial Era and Into the Future.”  Global Biogeochemical Cycles 34(11):e2019GB006170.  2020.  A review of how fossil-fuel burning and nuclear tests changed the carbon-13 and carbon-14 content of the air since 1850, and what those isotopes will do under future emission paths.  Mirror:  PMC

    1. 9a.

      Section 5, Atmospheric Changes Over the Industrial Period:  “From 1850 to 2015 atmospheric δ^13CO 2 decreased by 1.8‰”.  “Atmospheric Δ^14CO 2 decreased by approximately 20‰ between 1850 and 1950 as a result of fossil fuel emissions after the Industrial Revolution (Suess,  1955 )”. ↩

  10. 10.

    Skrable, Kenneth et al.  “World Atmospheric CO2, Its 14C Specific Activity, Non-fossil Component, Anthropogenic Fossil Component, and Emissions (1750–2018).”  Health Physics 122(2):291–305.  2022.  A paper in a radiation-protection journal estimating from carbon-14 dilution how much of the CO2 in the air consists of fossil carbon, and concluding that it is too little to cause warming.

    1. 10a.

      Section Abstract:  “Our results show that the percentage of the total CO2 due to the use of fossil fuels from 1750 to 2018 increased from 0% in 1750 to 12% in 2018, much too low to be the cause of global warming.” ↩

  11. 11.

    Schwartz, Stephen E. et al.  “Comment on "World Atmospheric CO2, Its 14C Specific Activity, Non-fossil Component, Anthropogenic Fossil Component, and Emissions (1750–2018)".”  Health Physics 122(6):717–719.  2022.  A reply by four atmospheric and radiocarbon scientists, among them Ralph Keeling, showing that Skrable's carbon-14 history contradicts the measurements.

    1. 11a.

      Page 717:  “the historical specific activity given by Skrable et al. is completely at odds with the measurements over virtually the entire record”.  “Skrable et al. should be retracted in its entirety.” ↩

  12. 12.

    Jones, Phil, and Roger (questions) Harrabin.  “Q&A:  Professor Phil Jones.”  BBC News.  Feb 13, 2010.  Written answers by the director of the University of East Anglia's Climatic Research Unit to questions gathered by the BBC's environment analyst, several from climate skeptics, three months after the leak of the unit's e-mails.

    1. 12a.

      Section answer A:  “Temperature data for the period 1860-1880 are more uncertain, because of sparser coverage, than for later periods in the 20th Century. The 1860-1880 period is also only 21 years in length.”  “So, in answer to the question, the warming rates for all 4 periods are similar and not statistically significantly different from each other.”  His table of trends in °C per decade:  1860–1880, 0.163;  1910–1940, 0.15;  1975–1998, 0.166;  1975–2009, 0.161. ↩

    2. 12b.

      Section answer D:  “Solar influence was about flat over this period. Combining only these two natural influences, therefore, we might have expected some cooling over this period.” ↩

  13. 13.

    Annual global means from HadCRUT5 version 5.2.0.0 28, Berkeley Earth 30 and GISTEMP v4 29, each re-expressed as the difference from its own 1850–1900 mean (1880–1900 for GISTEMP).  Means:  2011–2020, 1.12, 1.18, 1.05 °C;  2015–2024, 1.27, 1.33, 1.20;  1940–1949, 0.33, 0.33, 0.26;  2024, 1.55, 1.62, 1.50.  Least-squares trends in °C per decade:  1975–2025, 0.209, 0.208 (to 2024), 0.207;  2000–2025, 0.254, 0.257, 0.265;  1988–2006, 0.209, 0.209, 0.193;  1910–1940, 0.167, 0.130, 0.113;  1940–1975, −0.032, −0.017, −0.019;  1860–1880, 0.134 and 0.119 for HadCRUT5 and Berkeley. ↩ ↩

  14. 14.

    Lockwood, Mike, and Claus Fröhlich.  “Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature.”  Proceedings of the Royal Society A 463:2447–2460.  2007.  A comparison by two solar physicists of every solar quantity that might affect climate, sunspots, solar output and cosmic-ray flux, with global temperature since the mid-1980s.

    1. 14a.

      Section Abstract:  “There is considerable evidence for solar influence on the Earth's pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century.”  “Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth's climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.” ↩ ↩

  15. 15.

    Camp, Charles D., and Ka Kit Tung.  “Surface warming by the solar cycle as revealed by the composite mean difference projection.”  Geophysical Research Letters 34:L14703.  2007.  A statistical separation of the 11-year solar cycle's imprint on global surface temperature from about 50 years of data, finding a warming of almost 0.2 °C from solar minimum to solar maximum.

    1. 15a.

      Section Abstract:  “we obtain a global warming signal of almost 0.2°K attributable to the 11-year solar cycle.” ↩

  16. 16.

    Forster, Piers et al.  “The Earth's Energy Budget, Climate Feedbacks and Climate Sensitivity.”  Climate Change 2021:  The Physical Science Basis, Contribution of Working Group I to the Sixth Assessment Report of the IPCC, 923–1054.  Cambridge University Press.  2021.  Chapter 7 of the IPCC's 2021 assessment, the chapter on the earth's heat budget, the size of each feedback, and climate sensitivity.  It combines model, observational and ice-age evidence, and it sets out the energy-budget method and the "pattern effect" argument for why observed warming understates long-term sensitivity.

    1. 16a.

      Section 7.3.4.4, page 958:  “The best estimate solar ERF is assessed to be 0.01 W m–2, using the 14C reconstruction from SATIRE-M, with a likely range of –0.06 to +0.08 W m–2 (medium confidence).”  For 1750 to 2019. ↩

  17. 17.

    SILSO, Royal Observatory of Belgium.  Yearly mean total sunspot number.  2026.  The international reference series of sunspot numbers, kept in Brussels, from 1700.

    1. 17a.

      Yearly means:  2008, 4.2;  2014, 113.3;  2019, 3.6;  2020, 8.8;  2024, 154.7;  2025, 123.2. ↩

  18. 18.

    Svensmark, Henrik, and Eigil Friis-Christensen.  “Variation of cosmic ray flux and global cloud coverage — a missing link in solar-climate relationships.”  Journal of Atmospheric and Solar-Terrestrial Physics 59(11):1225–1232.  1997.  The Danish physicists' first paper proposing that cosmic rays, modulated by the sun, change global cloud cover, based on a correlation over one solar cycle.

    1. 18a.

      Section Abstract:  “We find that the observed variation of 3–4% of the global cloud cover during the recent solar cycle is strongly correlated with the cosmic ray flux.” ↩

  19. 19.

    Dunne, Eimear M. et al.  “Global atmospheric particle formation from CERN CLOUD measurements.”  Science 354(6316):1119–1124.  2016.  Results of the CLOUD experiment at CERN, in which 59 authors measured in a chamber how ions from cosmic rays help new particles form, then put the measured rates into a global model to see how much cosmic-ray changes over a solar cycle alter cloud-forming particles.

    1. 19a.

      Section Abstract:  “the relatively weak dependence on ion concentrations indicates that for the processes studied variations in cosmic ray intensity do not significantly affect climate via nucleation in the present-day atmosphere.”  Main text, the solar-cycle paragraph:  “Over the solar cycle, the global mean change in CCN at cloud base altitude (915 hPa, usually around 850 m above the surface) is only 0.1% (Fig. 4B) with local changes of no more than 1%.” ↩

  20. 20.

    Hebert, Jake.  “Apparent difficulties with a CMAS cosmic ray–weather/climate link.”  Journal of Creation 27(3):93–97.  2013.  A literature review in the young-earth technical journal listing the problems with the cosmic-ray cloud mechanism that its author otherwise favours.  It presents no new data.

    1. 20a.

      Page 93:  “there are a number of apparent difficulties with the CMAS mechanism, and these apparent weaknesses are now discussed.” ↩

  21. 21.

    ArcticToday.  Ozone-depleting gases may account for up to half of Arctic warming in the last 50 years.  Jan 2020.  A news report on the Polvani study.

    1. 21a.

      “could account for up to half of the temperature increase observed in the Arctic from 1955-2005”. ↩

  22. 22.

    Polvani, Lorenzo M. et al.  “Substantial twentieth-century Arctic warming caused by ozone-depleting substances.”  Nature Climate Change 10:130–133.  2020.  A climate-model study by Columbia University researchers comparing runs with and without the rise in CFCs and other ozone-depleting gases from 1955 to 2005, to measure their share of Arctic warming and sea-ice loss.

    1. 22a.

      Section Abstract:  “We show that, when ODS are kept fixed, forced Arctic surface warming and forced sea-ice loss are only half as large as when ODS are allowed to increase.” ↩

  23. 23.

    Columbia University.  Ozone-Depleting Substances Caused Half of Late 20th-Century Arctic Warming, Says Study.  Jan 20, 2020.  The university's press release on the Polvani study.

    1. 23a.

      “they caused about a third of all global warming from 1955 to 2005, and half of Arctic warming and sea ice loss during that period”. ↩

  24. 24.

    Tesi, Tommaso et al.  “Rapid Atlantification along the Fram Strait at the beginning of the 20th century.”  Science Advances 7(48):eabj2946.  Nov 24, 2021.  An 800-year reconstruction of water temperature and salinity from a sediment core in a Svalbard fjord, showing warm Atlantic water spreading into the Arctic from the early twentieth century, decades before instruments recorded it.

    1. 24a.

      Figures 3, caption, page 3:  “During the modern period, anthropogenic-derived forcing (ANTROP) intensified the progressive Atlantification that commenced in the early 20th century.” ↩

  25. 25.

    Wild, Martin et al.  “Evidence for clear-sky dimming and brightening in central Europe.”  Geophysical Research Letters 48:e2020GL092216.  2021.  A study of the 71-year solar-radiation record at Potsdam, Germany, 1947–2017, showing that clear-sky sunlight at the ground fell and then rose over decades as air pollution grew and was cleaned up.

    1. 25a.

      Section Abstract:  “suggests that these variations are anthropogenically forced rather than of natural origin, with aerosol pollutants as likely major drivers.”  Page 7:  “This increase is of similar magnitude as the observed increase in clear-sky atmospheric transmission from 0.64 to 0.69 shown in Figure 3, which corresponds to an increase of 8%.” ↩

  26. 26.

    Yuan, Tianle et al.  “Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming.”  Communications Earth & Environment 5:281.  2024.  A NASA-led estimate, from satellite cloud observations and models, of the extra sunlight reaching the ocean after the 2020 international rule cut sulphur in ships' fuel by about 80 %.

    1. 26a.

      Page 5:  “+ 0.2 ± 0.11 Wm−2”.  Page 3:  “0.2 W m−2 translates to around 0.16 K of warming with a timescale of 7 years.”  The forcing is averaged over the global ocean.  The authors say their warming estimate ignores heat uptake by the deep ocean over the first decade. ↩

  27. 27.

    Gupta, A. K. et al.  “A global decline in atmospheric dust during the 21st century.”  Science Advances 12:eaef5691.  2026.  A reconstruction of global dust in the air from 2003 to 2023, combining satellite records, reanalyses and ground stations in one statistical model.

    1. 27a.

      Section Abstract:  “This decline in atmospheric dust has exerted a positive effective radiative forcing of +0.02 ± 0.05 watts per square meter over 2003–2023, implying that declining atmospheric dust might have modestly contributed to the rapid warming of the past two decades.” ↩

  28. 28.

    Met Office Hadley Centre;  Climatic Research Unit, University of East Anglia.  HadCRUT5 analysis, global annual summary series, version 5.2.0.0.  2026.  The British global surface temperature record, combining land stations from the Climatic Research Unit with the Hadley Centre's sea-surface temperatures, 1850 to the present, as anomalies from 1961–1990 with uncertainty limits. ↩

  29. 29.

    NASA Goddard Institute for Space Studies.  GISTEMP v4, global land-ocean temperature index.  2026.  NASA's global surface temperature record from 1880, as monthly and annual anomalies from 1951–1980. ↩

  30. 30.

    Berkeley Earth.  Global land and ocean temperature, annual summary.  2026.  The independent Berkeley Earth global surface record from 1850, built with its own station selection and statistical method.  This file runs to 2024. ↩