How Much Warming Does More CO2 Cause?

Lewis, Nicholas, and Judith Curry.  “The Impact of Recent Forcing and Ocean Heat Uptake Data on Estimates of Climate Sensitivity.”  Journal of Climate 31(15):6051–6071.  2018.  The leading skeptical energy-budget estimate, by the independent researcher Nicholas Lewis and the climatologist Judith Curry, formerly of Georgia Tech.  It divides observed warming between 1869–1882 and 2007–2016 by the IPCC's forcing minus ocean heat uptake, and finds sensitivity at the low end of the IPCC range.

1. 1a.

   Page 6051:  “medians are derived for ECS of 1.50 K (5%–95% range: 1.05–2.45 K) and for TCR of 1.20 K (5%–95% range: 0.9–1.7 K).”  “Using infilled, globally complete temperature data give slightly higher estimates: a median of 1.66 K for ECS (5%–95% range: 1.15–2.7 K)”.  “Allowing for possible time-varying climate feedbacks increases the median ECS estimate to 1.76 K (5%–95% range: 1.2–3.1 K), using infilled temperature data.” ↩ ↩

Spencer, Roy W., and John R. Christy.  “Effective climate sensitivity distributions from a 1D model of global ocean and land temperature trends, 1970–2021.”  Theoretical and Applied Climatology 155:299–308.  2023.  A peer-reviewed estimate by the two UAH climatologists, fitting a simple heat-flow model of land and ocean to measured surface, deep-ocean and borehole warming trends for 1970–2021 under two forcing histories.  It finds sensitivity near the low end of the IPCC range and below 34 of 36 current models.

1. 2a.

   Paragraph abstract:  “EffCS is lower using the newer Shared Socioeconomic Pathways (SSP245, 1.86 °C global EffCS, ± 34% range 1.48–2.15 °C) than the older Representative Concentration Pathway forcing (RCP6, 2.49 °C global average EffCS, ± 34% range 2.04–2.87 °C).” ↩ ↩

2. 2b.

   Section 2, The 1D model and radiative forcing scenarios:  “The SSP245 effective radiative forcing values come from the tables in Annex III of IPCC ( 2021b ), and include the AR6 best estimates up to 2019”.  The IPCC's forcing tables include solar and volcanic forcing alongside the human ones. ↩

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. ↩

2. 3b.

   Section A.4.4, page 11:  “The AR6 assessed best estimate is 3°C with a likely range of 2.5°C to 4°C (high confidence), compared to 1.5°C to 4.5°C in AR5, which did not provide a best estimate.” ↩ ↩

The energy-budget relation is ΔT = ECS × (ΔF − ΔN) / F2×, with the IPCC's values for 1850–1900 to 2006–2019:  warming ΔT = 1.03 °C, forcing ΔF = 2.20 W/m², heat still entering the ocean ΔN = 0.59 W/m², and F2× = 3.93 W/m² for doubled CO2 ⁷.  At ECS = 0.5 °C the forcing gives 0.5 × 1.61 / 3.93 = 0.20 °C, a fifth of the warming observed.  Producing 1.03 °C at that sensitivity needs ΔF = 1.03 × 3.93 / 0.5 + 0.59 = 8.7 W/m², which is 6.5 W/m² more than the IPCC's estimate.  Solar forcing is about the change in the sun's output × (1 − 0.29 albedo) / 4, so 6.5 W/m² of forcing needs the sun to brighten by about 37 W/m², 2.7 % of its 1,361 W/m².  At Harde's 0.7 °C the gap is 4.2 W/m², a brightening of about 24 W/m².  Harde's own solar sensitivity, 0.17 °C per 0.1 % rise in the sun's output ²⁰, needs a 0.26 % rise, about 3.5 W/m², for his 0.44 °C of solar warming.  The measured output has stayed within 1361.2–1362.6 W/m² since 1980 ²⁵.  At Spencer and Christy's 1.86 °C, the equilibrium warming for the IPCC's 2.72 W/m² of human forcing from 1750 to 2019 is 1.86 × 2.72 / 3.93 = 1.29 °C. ↩ ↩ ↩ ↩

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. 5a.

   Section What we need to know:  “Van Wijngaarden and Happer show this, based on the infrared (‘heat’) spectral absorption curve for CO2.”  “This is not conjecture, but solid experimental physics and shows that 400 ppm CO2 contributes 30 W/m2 reduction in thermal radiation into space from Earth. Increasing the CO2 to 800 ppm contributes only a further 3 W/m2.”  “The IPCC in their 2001 report”.  “gave some acknowledgement to this decreasing effect, but their ‘forcing’ from doubling from 400 to 800 was around 4.5-5 W/m2, depending on the various formulas used, which is 50% or more greater than the 3 W/m2 figure based on the spectral absorption curves.” ↩

2. 5b.

   Section The raw data:  “Nearly all of this GHG effect is due to water vapour, and only about 3.3°C is due to CO2.”  “Yet, since water has a much greater greenhouse effect, the exclusion of water from the debate is inexcusable.” ↩

3. 5c.

   Section Does positive feedback (amplification) operate:  “Both the global balloon data and the satellite data show no such hot spot in the atmosphere (see Figure 4), which means that positive feedback is not operating, contrary to the models’ predictions.”  “However, satellite measurements show increased outgoing radiation, the opposite of IPCC models’ predictions.” ↩

4. 5d.

   Section What we need to know:  “Our opinion is that these sorts of values for the ECS are nothing to panic about. And the IPCC would seem to tacitly agree, because their target (based on the faulty models) is to limit the warming to 1.5°C. The bottom line is that we don’t have to take any drastic action to limit the warming due to human-generated CO2 to less than 1.5°C.” ↩

5. 5e.

   Section The raw data:  “The atmosphere is mostly nitrogen and oxygen, which have no greenhouse effect.” ↩

Hebert, Jake.  “Climate Alarmism and the Age of the Earth.”  Institute for Creation Research.  Mar 29, 2019.  ICR's clearest statement of its climate position, by its physicist Jake Hebert.  He argues that the whole dispute turns on climate sensitivity, that the models have run hot, and that the evidence for high sensitivity from past ice ages rests on dating he rejects.  He gives no sensitivity calculation of his own.

1. 6a.

   Section Climate Sensitivity:  “The real issue in the climate change debate is climate sensitivity.”  “If the amount of CO 2 in the atmosphere were to double while everything else stayed the same, the increase in global average surface temperatures would be small, only about 1°C (less than 2°F).” ↩

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. 7a.

   Page 945:  “The ERF from doubling CO2 (2×CO2) from the 1750 level (278 ppm; Section 2.2.3.3) is assessed to be 3.93 ± 0.47 W m–2 (high confidence).” ↩

2. 7b.

   Table 7.10, page 978:  AR6 assessed central estimates of the feedback parameters, in W m–2 °C–1:  Planck −3.22;  water vapour plus lapse rate +1.30;  surface albedo +0.35;  clouds +0.42 (very likely −0.10 to +0.94);  net −1.16 (very likely −1.81 to −0.51). ↩ ↩

3. 7c.

   Section 7.4.2.2, page 969:  “Atmospheric moistening has been detected in satellite records (Section 2.3.1.3.3), it is simulated by climate models (Section 3.3.2.2), and the estimates agree within model and observational uncertainty”.  “The estimate of this feedback inferred from satellite observations is αWV = 1.85 ± 0.32 W m–2 °C–1 (R. Liu et al., 2018). This is consistent with the value αWV = 1.77 ± 0.20 W m–2 °C–1 (one standard deviation) obtained with CMIP5 and CMIP6 models”. ↩

4. 7d.

   Section 7.4.2.2, page 969:  “Therefore, each of these two sums may simply be referred to as the ‘water-vapour plus lapse-rate’ feedback.”  The lapse-rate feedback alone is assessed at −0.50 ± 0.20 W m–2 °C–1, and the combined feedback at +1.30 in Table 7.10. ↩

5. 7e.

   Section 7.5.2.1, page 996:  “Employing these values within the traditional global energy balance framework described above (following the methods of Otto et al. (2013) and accounting for correlated uncertainties between ΔF and ΔF2×CO2) produces a TCR of 1.9 [1.3 to 2.7] °C and an effective ECS of 2.5 [1.6 to 4.8] °C.”  The inputs on the same page:  energy imbalance change ΔN = 0.59 ± 0.35 W m–2, warming ΔT = 1.03 ± 0.20 °C, forcing ΔF = 2.20 [1.53 to 2.91] W m–2, all between 1850–1900 and 2006–2019. ↩ ↩ ↩ ↩

6. 7f.

   Section 7.5.2.1, page 996:  “This arises because historical warming has been relatively larger in key negative feedback regions (e.g., western tropical Pacific Ocean) and relatively smaller in key positive feedback regions (e.g., eastern tropical Pacific Ocean and Southern Ocean) than is projected in the near-equilibrium response to CO2 forcing (Section 7.4.4.3; Held et al., 2010; Proistosescu and Huybers, 2017; Dong et al., 2019), implying that the true ECS will be larger than the effective ECS inferred from historical warming.” ↩

van Wijngaarden, William A., and William Happer.  “Dependence of Earth's Thermal Radiation on Five Most Abundant Greenhouse Gases.”  arXiv.  Jun 4, 2020.  A line-by-line radiation calculation by two physicists, Happer a well-known skeptic of climate alarm, of how water vapour, CO2, ozone, nitrous oxide and methane affect the heat the earth sends to space, using over 300,000 spectral lines and checked against satellite spectra.  It finds strong saturation per molecule, forcings close to mainstream codes, and a warming of 1.4 °C for doubled CO2 without water-vapour feedback and 2.2 to 2.3 °C with it.

1. 8a.

   Table 2, page 19:  Partial forcing increments for CO2, in W m−2:  removing all CO2, −44.6 at the tropopause (11 km) and −30.2 at the mesopause (86 km);  doubling CO2, +5.5 at the tropopause and +3.0 at the mesopause.  The text on page 13 gives the same doubling figure:  Page 13:  “Doubling the standard concentration of CO2 (from 400 to 800 ppm) would cause a forcing increase (the area between the black and red lines) of ∆F {i} = 3.0 W m−2”. ↩

2. 8b.

   Page 19:  “The forcing increments in Table 3 are comparable to those calculated by others.”  “Our values are fairly close to those of Collins et al.” ↩

3. 8c.

   Table 3, page 20:  Doubled CO2:  Collins et al., 5.5 W m−2 at the tropopause and 2.8 at the mesopause;  this work, 5.5 and 3.0. ↩

4. 8d.

   Page 18:  “This dependence of forcing increments on the logarithm of the CO2 column density was first pointed out by Arrhenius”. ↩

5. 8e.

   Page 34:  “For the case of fixed absolute humidity, the surface warms by 1.4 K which agrees very well with other work as shown in Table 5. The surface warming increases significantly for the case of water feedback assuming fixed relative humidity. Our result of 2.3 K is within 0.1 K of values obtained by two other groups”. ↩

Intergovernmental Panel on Climate Change.  Climate Change 2001:  The Scientific Basis.  Cambridge University Press.  Edited by J. T. Houghton, Y. Ding, D. J. Griggs, M. Noguer, P. J. van der Linden, X. Dai, K. Maskell and C. A. Johnson.  2001.  The IPCC's third assessment of the physical science, the report CMI cites for the CO2 forcing formulas and for its sentence on the chaotic climate system.

1. 9a.

   Table 6.2, page 358:  Three simplified expressions for CO2 forcing, C in ppm:  ΔF = 5.35 ln(C/C0);  ΔF = 4.841 ln(C/C0) + 0.0906(√C − √C0);  ΔF = 3.35[g(C) − g(C0)] with g(C) = ln(1 + 1.2C + 0.005C² + 1.4 × 10⁻⁶C³). ↩ ↩

The three formulas of the 2001 IPCC report's Table 6.2 ⁹, evaluated for 400 to 800 ppm, give 3.71, 4.11 and 4.25 W/m².  For 280 to 560 ppm they give 3.71, 3.98 and 3.97 W/m².  The first formula is Gunnar Myhre's 1998 expression ³¹, 5.35 × ln 2 = 3.71. ↩

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. 11a.

   Section arguments 1 and 5:  “THERE IS NO GREENHOUSE EFFECT.”  “ADDING CO2 TO THE ATMOSPHERE HAS NO EFFECT BECAUSE THE CO2 ABSORPTION BANDS ARE ALREADY 100% OPAQUE. First, no they are not, and that’s because of pressure broadening. Second, even if the atmosphere was 100% opaque, it doesn’t matter.” ↩

Harries, John E. et al.  “Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997.”  Nature 410:355–357.  Mar 15, 2001.  A comparison of the infrared spectrum of the heat leaving the earth, measured from satellites in 1970 and 1997.  The difference shows the fingerprints of added methane, CO2, ozone and CFCs, a direct observation that the greenhouse effect grew.

1. 12a.

   Page 355:  “increase in the Earth's greenhouse effect that is consistent with concerns over radiative forcing of climate.” ↩

Feldman, Daniel R. et al.  “Observational determination of surface radiative forcing by CO2 from 2000 to 2010.”  Nature 519:339–343.  Mar 19, 2015.  A decade of measured infrared spectra at two US Department of Energy sites, Oklahoma and northern Alaska, separating the CO2 signal from water vapour and temperature.  It measured the extra downward heat from rising CO2 directly at the surface.  Mirror:  Escholarship.org

1. 13a.

   Results, the paragraph on the two sites' time series:  “statistically significant trends of 0.2 W m−2 per decade”.  The period 2000 to 2010, during which CO2 rose 22 ppm. ↩

Coe, David et al.  “The Impact of CO2, H2O and Other "Greenhouse Gases" on Equilibrium Earth Temperatures.”  International Journal of Atmospheric and Oceanic Sciences 5(2):29–40.  2021.  A short paper by two retired industrial engineers and an electrical-engineering professor that fits a one-layer absorption model to the 33 °C greenhouse effect and extrapolates it to doubled CO2.  It was accepted nine days after submission.  CMI cites it for both its 3.3 °C share for CO2 and its 0.5 °C sensitivity.

1. 14a.

   Page 29:  “From this data it is concluded that H2O is responsible for 29.4K of the 33K warming, with CO2 contributing 3.3K and CH4 and N2O combined just 0.3K. Climate sensitivity to future increases in CO2 concentration is calculated to be 0.50K, including the positive feedback effects of H2O”. ↩ ↩

2. 14b.

   Section 1.4, The Impact of Retained Energy, page 30:  “Let “n” represent the “energy retention factor”, the fraction of the absorbed energy a∙R that is retained by the atmosphere/earth system”. ↩

Schmidt, Gavin A. et al.  “Attribution of the present-day total greenhouse effect.”  Journal of Geophysical Research 115:D20106.  2010.  A calculation with NASA's GISS radiation code of how much of today's greenhouse effect each absorber carries, allowing for overlaps between them.  It gives water vapour about half, clouds a quarter and CO2 a fifth.

1. 15a.

   Paragraph 1:  “The relative contributions of atmospheric long-wave absorbers to the present-day global greenhouse effect are among the most misquoted statistics in public discussions of climate change”.  “water vapor is the dominant contributor (∼50% of the effect), followed by clouds (∼25%) and then CO 2 with ∼20%.” ↩

Lindzen, Richard S., and Yong-Sang Choi.  “On the observational determination of climate sensitivity and its implications.”  Asia-Pacific Journal of Atmospheric Sciences 47(4):377–390.  2011.  A revised version of the MIT meteorologist Richard Lindzen's 2009 attempt to infer feedbacks from how outgoing radiation measured by satellites changed with tropical sea-surface temperature, concluding that feedback is negative and sensitivity low.

1. 16a.

   Page 377:  “The results imply that the models are exaggerating climate sensitivity.” ↩

Trenberth, Kevin E. et al.  “Relationships between tropical sea surface temperature and top-of-atmosphere radiation.”  Geophysical Research Letters 37:L03702.  2010.  A reanalysis of Lindzen and Choi's 2009 method by four atmospheric scientists, showing that its result depends on the choice of start and end dates and that it ignored the forcing in its regressions.

1. 17a.

   Page 2:  “A serious omission of LC09’s is that they did not consider the forcing F in equation (1) in their regressions, and this is an especially grievous error when the period following the large perturbation”. ↩

Dessler, Andrew E.  “Cloud variations and the Earth's energy budget.”  Geophysical Research Letters 38:L19701.  2011.  An energy-budget test, using 2000–2010 data, of whether clouds drive temperature changes, written in reply to Lindzen and Choi 2011 and Spencer and Braswell 2011.  It finds that clouds account for little of the observed variation.

1. 18a.

   Paragraph 5, page 1:  “LC11 choose the ratios of the standard deviations of the time series”.  The ratio Lindzen and Choi chose is about 2;  Spencer and Braswell chose about 0.5.  Dessler then estimates the ratio from data. ↩

Oard, Michael J.  “Human-Caused Global Warming Slight So Far.”  Answers in Genesis, Answers in Depth.  Sep 20, 2006.  Oard's longest piece on modern warming.  He estimates the human share of warming by assuming half of it is natural, then scales the result to a doubling of CO2 and concludes that the models are too sensitive.  It is the only young-earth piece that shows its sensitivity arithmetic.

1. 19a.

   Section the split between natural and human warming:  “I will assume that half of the 1.2°F (0.7°C) rise is caused by natural long-term climatic cycles and the other half is due to man-made global warming.”  Section How Much Warming after Carbon Dioxide Doubles?:  “This 60% rise in CO 2 and its equivalency units has resulted in approximately a 0.6°F (0.3°C) rise in temperature. At this rate, a doubling of CO 2 will produce only a 1°F temperature rise.” ↩

Harde, Hermann.  “Radiation Transfer Calculations and Assessment of Global Warming by CO2.”  International Journal of Atmospheric Sciences, 9251034.  2017.  A single-author paper by a laser physicist at the Helmut Schmidt University, Hamburg, combining line-by-line radiation calculations with a two-layer energy-balance model.  Its low sensitivity depends on taking a rising sun from one of the competing solar records and on attributing observed cloud changes to the sun.

1. 20a.

   Paragraph abstract:  “Including solar and cloud effects as well as all relevant feedback processes our simulations give an equilibrium climate sensitivity of C S = 0.7°C (temperature increase at doubled CO 2 ) and a solar sensitivity of S S = 0.17°C (at 0.1% increase of the total solar irradiance).” ↩ ↩

2. 20b.

   Section 4.3.7, Total Feedback:  “With these parameters we find a climate sensitivity of C S = 2.9°C, which is 10% smaller than the model mean of the CMIP5 AOGCMs”.  "These parameters" are the feedback values of the IPCC's 2013 report. ↩

Lewis, Nicholas.  “Objectively combining climate sensitivity evidence.”  Climate Dynamics 60:3139–3165.  2022.  A reanalysis of the multi-evidence assessment of Sherwood and colleagues, changing its statistical method and several inputs.  It finds a lower and narrower sensitivity than Sherwood or the IPCC.

1. 21a.

   Page 3139:  “The resulting estimates of long-term climate sensitivity are much lower and better constrained (median 2.16 °C, 17–83% range 1.75–2.7 °C, 5–95% range 1.55–3.2 °C) than in Sherwood et al. and in AR6 (central value 3 °C, very likely range 2.0–5.0 °C).” ↩

Sherwood, Steven C. et al.  “An assessment of Earth's climate sensitivity using multiple lines of evidence.”  Reviews of Geophysics 58(4):e2019RG000678.  2020.  A 25-author review that combines three lines of evidence, physical processes, the historical record and past climates, in one statistical framework.  It was the main input to the IPCC's 2021 sensitivity range.

1. 22a.

   Paragraph abstract:  “The 66% range is 2.6–3.9 K for our Baseline calculation”. ↩

Armour, Kyle C.  “Energy budget constraints on climate sensitivity in light of inconstant climate feedbacks.”  Nature Climate Change 7:331–335.  2017.  A study of climate models showing that the sensitivity inferred during warming is lower than the eventual value, and correcting energy-budget estimates for it.

1. 23a.

   Page 331:  “I find that the long-term value of climate sensitivity is, on average, 26% above that inferred during transient warming within global climate models, with a larger discrepancy when climate sensitivity is high.” ↩

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. 24a.

   Section Introduction:  “The change in the solar constant amounts to about 0.90”.  The sentence ends "Wm−2 for the last three cycles." ↩

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. 25a.

   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. ↩ ↩

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. ↩

Loeb, Norman G. et al.  “Satellite and Ocean Data Reveal Marked Increase in Earth's Heating Rate.”  Geophysical Research Letters 48:e2021GL093047.  2021.  A comparison of the earth's heat gain measured two independent ways, by the CERES satellites and by the ocean floats, over 2005–2019.  The two agree, and both show the gain rising.  The authors attribute the rise to fewer reflecting clouds and less sea ice as well as to greenhouse gases and water vapour.

1. 27a.

   Paragraph abstract:  “We show that independent satellite and in situ observations each yield statistically indistinguishable decadal increases in EEI from mid-2005 to mid-2019 of 0.50 ± 0.47 W m^−2 decade^−1 (5%–95% confidence interval).”

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. ↩

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. ↩

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. ↩

Myhre, Gunnar et al.  “New estimates of radiative forcing due to well mixed greenhouse gases.”  Geophysical Research Letters 25(14):2715–2718.  1998.  Radiative-transfer calculations by three independent models that gave the simplified CO2 forcing formula, 5.35 times the natural logarithm of the concentration ratio, used by the IPCC since 2001. ↩