Professor John Raine: Balancing the climate narrative - The science is not settled

The 23rd July 2025 USA Department of Energy (DoE) Report, “A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate” [1], authored by five eminent scientists, at last brings some balance back into official statements on climate change and humankind’s contribution to this. The USA DoE Report reviews the science around how anthropogenic carbon dioxide (CO2) and other greenhouse gas emissions have affected, or will affect, climate in the USA, extreme weather events, and selected metrics of societal wellbeing.

Why should we pay attention to this report? Goals set under the Paris Climate Agreement, (November 2016) included to “hold the increase in the global average temperature to well below 2°C above pre-industrial levels”.The UN Intergovernmental Panel on Climate Change (IPCC) indicates that, “Crossing the 1.5°C threshold risks unleashing far more severe climate change impacts, including more frequent and severe droughts, heatwaves and rainfall.” However, the USA DoE Report, and numerous scientific papers that validly critique climate science models, expose significant alarmism in such statements and present a far less apocalyptic view.

The USA DoE Report offers strong and reasoned counterfactual to the climate catastrophising and “the science is settled” thinking that has dominated the United Nations-led climate discussion and media for many years. There is outrage from some members of the science community, who show a fanatical adherence to the climate alarmist view while not addressing the scientific detail of the report [2]. One scientist commented, “This little report is basically designed to suppress science, not to enhance it or encourage it…..it’s awful.” On the contrary, the USA DoE Report aims to open up scientific discussion, not suppress it.

If scientists condemn without evidence others’ work, they are likely breaching their fundamental responsibility never to treat science as settled and closed to debate. Climate science has become the standout example of this in our generation, and associated research funding has rigidified the views of some scientists.

Greenhouse Gas Effects on Temperature

Papers on the atmospheric physics of CO2 are far too numerous to cover here. Berry [3] agrees with IPCC statements that anthropogenic CO2 is only 5% and natural CO2 is 95% of the CO2 inflow into the atmosphere. However, he draws attention to numerous errors in IPCC climate science models regarding the human contribution to long-term atmospheric CO2. These assert that anthropogenic CO2 is entirely responsible for the rise in CO2 from 280 ppm in pre-industrial times to 410 ppm at the time Berry’s paper was written (2019).

Berry’s physics analysis shows that both natural CO2 and anthropogenic CO2 must contribute to re-absorption through photosynthesis and land or oceanic absorption in proportion to their percentages in the atmosphere. i.e. CO2 does not accumulate forever in the atmosphere. Berry calculated that the balance level of anthropogenic CO2 was about 4.4%, and natural CO2 95.6%, not the 32% claimed by the IPCC. Anthropogenic CO2 is thus a small percentage of the long-term CO2 in the atmosphere, but it has influenced the increase.

Over geological time, global temperature rise has preceded a rise in the atmospheric CO2 level. This does not contradict the increase in temperature caused by the greenhouse gas (GHG) effect of additional CO2, which leads to increased photosynthesis activity, and greater oceanic and land vegetation release of CO2 through the Carbon Cycle. At a higher constant atmospheric CO2 input level, a new equilibrium is reached where CO2generation and absorption are once again in balance. The USA DoE Report [1] notes that there is evidence that scenarios frequently presented in the literature, “overstate observed and likely future emission trends…..Moreover, solar activity's contribution to the late 20th century warming might be underestimated.”

The USA DoE Report also emphasises that, “Elevated concentrations of CO2 directly enhance plant growth, globally contributing to “greening” the planet and increasing agricultural productivity.” Estimates of the extent of this regreening vary. Zhu et al [4] report a roughly 14 percent increase in green vegetation over 30 years. They note, “a persistent and widespread increase of growing season greening over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows browning.”

The world’s several dozen global climate models referred to by the IPCC vary substantially on how much the climate responds to higher CO2 levels, average surface warming under a doubling of the CO2 concentration ranging from 1.8°C to 5.7°C. The USA DoE Report notes, “Data-driven methods yield a lower and narrower range. Global climate models generally run “hot” in their description of the climate of the past few decades. The combination of overly sensitive models and implausible extreme scenarios for future emissions yields exaggerated projections of future warming.”

As an example of a lower CO2 impact model, the analysis of Coe et al [5] found that the temperature sensitivity to rising CO2 levels falls exponentially with further CO2 increases. They note:

· “The two main atmospheric greenhouse gases are water (H2O) and CO2,

· Climate sensitivity to future increases (a doubling) in CO2 concentration is calculated to be 0.50°C, including the positive feedback effects of H2O, while climate sensitivities to CH4 and N2O are almost undetectable at 0.06°C and 0.08°C respectively. This result strongly suggests that increasing levels of CO2 will not lead to significant changes in earth temperature and that increases in methane (CH4) and nitrous oxide (N2O) will have very little discernible impact.”

On this basis, we should not be damaging our animal farming industry through methane control measures.

The Coe et al analysis predicts lower temperature sensitivity to further CO2 increases than many models, but temperature increases at the higher end of the IPCC range appear to be extremely unlikely. CO2 is currently at about 430ppm or 0.043% of the Earth’s atmosphere and this is at the very low end of the range over geological time. CO2 appears to have been unjustly demonised. It is necessary for life and below 60 - 140ppm most plant life would cease.

Happer, Koonin and Lindzen [6] note, in their wide-ranging California Court evidence paper on climate change:

· “The climate is always changing; changes like those of the past half-century are common in the geologic record, driven by powerful natural phenomena.

· Human influences on the climate are a small (1%) perturbation to natural energy flows.

· It is not possible to tell how much of the modest recent warming can be ascribed to human influences.

· There have been no detrimental changes observed in the most salient climate variables and today’s projections of future changes are highly uncertain.”

Incoming solar radiation not reflected back to the atmosphere is about 240 W/m2 (watts per square metre) on average. A human contribution of 1% to natural energy flows equates to ~2.3 W/m2. While the later USA DoE Report places the human contribution at a little under 3 W/m2, this is still not much more than 1% of natural energy flows.

While our approach to future emissions must be prudent, the foregoing indicates that CO2 emissions will cause no more than modest temperature increases and will deliver benefits in global greening and in agricultural productivity. This view should always be subject to revision based on new evidence, but we could do well to follow the counsel of environmentalist and author, Michael Shellenberger [7], who argues persuasively against climate alarmism.

Extreme Weather Events

The USA DoE Report shows that, “Most extreme weather events in the U.S. do not show long-term trends. Claims of increased frequency or intensity of hurricanes, tornadoes, floods, and droughts are not supported by U.S. historical data. Additionally, forest management practices are often overlooked in assessing changes in wildfire activity. Global sea level has risen approximately 8 inches since 1900, but there are significant regional variations driven primarily by local land subsidence; U.S. tide gauge measurements in aggregate show no obvious acceleration in sea level rise beyond the historical average rate.”

Attribution of climate change or extreme weather events to human CO2 emissions is challenged by natural climate variability, data limitations, and inherent model deficiencies. Moreover, solar activity's contribution to the late 20th century warming might be underestimated.

Global scientific data indicate that extreme weather events have occurred periodically during the past 100 years and present times are not exceptional. Happer, Koonin and Lindzen [5] present significant data on this question.

Net Zero 2050 - Implications for New Zealand

New Zealand’s gross CO2 emissions in 2023 were 31,559.81 kilotonnes, with net CO2 emissions about 35% of this figure. The gross was approximately 0.088% of global anthropogenic CO2 emissions. If New Zealand manages GHG emissions to achieve Net Zero, the reduction in global atmospheric temperature would be negligible and probably unmeasurable.

This alone makes Net Zero 2050 unnecessary, but there is also the crippling cost to the economy. Professor Michael Kelly [8] analysed the cost for the UK to meet Net Zero 2050 at ~GBP 3 trillion. Kelly [9] also carried out a similar exercise for a presentation to Engineering New Zealand. Such exercises involve large uncertainty, but achieving Net Zero 2050 would cost New Zealand well over NZD 200 billion, an impractical figure.

Whether on a cost or global emissions basis, it would be crazy for our government to persist with a Net Zero 2050 goal. This issue also has direct implications for New Zealand’s future electrical energy strategy and may be addressed in a later article.

Final Word

This commentary does not claim scientific authority but asks that we never see science as settled. Scientists must always be willing to debate the available evidence and revise their view as appropriate. Decisions for the economic and environmental future of New Zealand should be based on the most comprehensive current science, and not on UN exhortations on climate change.

John Raine is an Emeritus Professor of Engineering and a former energy researcher. He has held positions as Pro Vice Chancellor or Deputy Vice Chancellor in three New Zealand universities.

References

1. John Christy, Ph.D., Judith Curry, Steven Koonin, Ross McKitrick, Roy Spencer, “A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate”, Report of the Climate Working Group to U.S. Energy Secretary Christopher Wright, USA Department of Energy, July 23, 2025

2. Jeff Tollefson, “Outrage over Trump team’s climate report spurs researchers to fight back” Nature, 7thAugust 2025 https://www.nature.com/articles/d41586-025-02505-x

3. Edwin X Berry, “Human CO2 Emissions Have Little Effect on Atmospheric CO2”, International Journal of Atmospheric and Oceanic Sciences. Vol. 3, No. 1, 2019, pp. 13-26. doi: 10.11648/j.ijaos.20190301.13, June 4, 2019

4. Zaichun Zhu, Shilong Piao, Ranga B. Myneni, Mengtian Huang, Zhenzhong Zeng, Josep G. Canadell, Philippe Ciais, Stephen Sitch, Pierre Friedlingstein, Almut Arneth, Chunxiang Cao, Lei Cheng, Etsushi Kato, Charles Koven, Yue Li, Xu Lian, Yongwen Liu, Ronggao Liu, Jiafu Mao, Yaozhong Pan, Shushi Peng, Josep Peñuelas, Benjamin Poulter, Thomas A. M. Pugh, Benjamin D. Stocker, Nicolas Viovy, Xuhui Wang, Yingping Wang, Zhiqiang Xiao, Hui Yang, Sönke Zaehle, Ning Zeng, “Greening of the Earth and its Drivers”. Nature Climate Change. volume 6, pages791–795 (2016)

5. David Coe, Walter Fabinski, Gerhard Wiegleb. “The Impact of CO2, H2O and Other “Greenhouse Gases” on Equilibrium Earth Temperatures.” International Journal of Atmospheric and Oceanic Sciences. Vol. 5, No. 2, 2021, pp. 29-40. doi: 10.11648/j.ijaos.20210502.12, August 23, 2021

6. William Happer, Steven E. Koonin, Richard S. Lindzen, Tutorial Submission on Global Warming and Climate Change to United States District Court Northern District of California San Francisco Division, Case No. C 17-06011 WHA, Case No. C 17-06012 WHA. Hearing Date: March 21, 2018.

7. Michael Shellenberger, “Apocalypse Never: Why Environmental Alarmism Hurts Us All”. Harper Collins, © Copyright 2020 Michael Shellenberger. ISBN 9780063074767 international edition; ISBN 9780063001701 e-book

8. Michael Kelly, “Achieving Net Zero: A report from a putative delivery agency”. Note 30 The Global Warming Policy Foundation © Copyright 2022, The Global Warming Policy Foundation, UK.

9. Michael Kelly, “An Assessment of the NZ Resources Needed for Carbon Zero”, a presentation to Engineering New Zealand, 1 December 2020, Auckland.