How much human-caused global warming should we expect?

By Andy May

OMG! The world is going to end, and we caused it. This story, in one form or another, goes back to biblical times. According to Genesis (6:9 to 9:17) God decided that humans had sinned too much and must be punished, so he called up a great flood to destroy the world. A similar story also appears in the earlier Epic of Gilgamesh. End of the world predictions are very popular and recur regularly in human history.

More recently, prognosticators have predicted climate change disasters that are due to human actions (sins?). During the Little Ice Age (see Figure 3 in the link), the European public blamed the cold weather on witches and Jews, over 50,000 “witches” and tens of thousands of Jews were killed because they supposedly caused the cold weather and glacial advances. Thus, the idea that humans somehow control climate change is very old. We have no more proof that this is the case today than people had in 800AD, which is about when Archbishop Agobard of Lyons, France said:

“In these parts nearly everyone – nobles and common folk, town and country, young and old – believe that human beings can bring about hail and thunder … We have seen and heard how most people are gripped by such nonsense, indeed possessed by such stupidity…” (Behringer 2010, p. 69)

Not much has changed since. It does seem odd that while old single women and Jews were killed, often in horrible ways, for supposedly causing the cold of the Little Ice Age, we are now facing demands from politicians and celebrities to “prevent” warming of 1.5 to 2.0°C above the same “preindustrial” temperatures. To emphasize the point that humans have always blamed other humans for bad weather, we show a 1486AD woodcut of a sorceress conjuring a hailstorm with the jawbone of an ass.

Figure 1. A woman conjuring up a hailstorm with a jawbone of an ass. Behringer’s caption reads: “Anthropogenic Climate Change.” Source: (Behringer 2010, p. 129).

In the 1960s human overpopulation would supposedly cause hundreds of millions to starve to death in the 1970s, according to Paul Ehrlich. In 2013, Sir David Attenborough said humans were a “plague on the Earth.” However, none of these predictions came true. Now, we are faced with the IPCC predictions that we are facing 1.5 to 2°C of warming in this century and that this will cause irreversible damage to the planet and humankind unless we act now. According to the IPCC, this warming is caused primarily by burning fossil fuels and, therefore, we must curtail or quit all fossil fuel use.

The United Nations Framework on Climate Change (UNFCCC) hosted the Paris Climate Convention in 2015 that agreed to keep the global average temperature increase to less than 2°C above preindustrial levels and to pursue efforts to limit the increase to 1.5°C. This agreement is often called the “Paris Agreement.” President Trump pulled the United States out of the agreement in November 2019 and the withdrawal will take effect in November 2020. As explained by Roger Pielke Jr. in 2005 the UNFCCC defines “climate change” as something caused by humans and totally ignores the possibility of natural climate change. This “misdefining” of climate change by the UNFCCC has hurt their credibility and undermines their arguments (Pielke 2005).

Connolly, Connolly, Carter and Soon have written a new paper (Connolly, et al. 2020) examining the IPCC predictions the UNFCCC used to construct the Paris Agreement. We will refer to their paper as “C3S20.” While the paper has just been published, it has been a work-in-progress for some time. Dr. Robert M. Carter passed away on January 19, 2016, but he did a considerable amount of work on an earlier version of the paper.

C3S20 asks, how much human-caused warming will occur if we do nothing, that is, continue “business-as-usual?” It’s unfortunate, but the IPCC, for all their work, do not adequately answer that question, their projections are all based on abstract “scenarios.” C3S20 break this overall question into five parts:

  1. What would greenhouse gas emissions (GHG) be, if we did nothing and continued normally?
  2. For each GHG, how do emissions relate to the change in atmospheric concentration?
  3. What would the global temperature be if GHG concentrations were at “preindustrial” levels?
  4. How sensitive are global temperatures to GHG concentrations?
  5. How much warming should we expect if we do nothing?

C3S20 tell us the Paris Agreement conclusion that we need to limit global warming to 2°C above preindustrial levels suffers from several unknowns.

  1. The preindustrial period is not formally defined. The preindustrial temperature and greenhouse gas level are not specified. In fact, several time periods, temperatures and GHG levels are used as “preindustrial” in the latest IPCC AR5 report.
  2. The assumptions that warming is bad and increasing levels of CO2 are bad, are not supported with any data. Numerous studies have concluded that some warming is good for humankind and additional CO2 is good for plants.
  3. The penultimate draft of AR5 identified the period 1850 to 1900 as the preindustrial baseline for CO2 and temperature. This was the end of the Little Ice Age, the coldest period in the last several thousand years. Why use that period as a baseline (Luning and Vahrenholt 2017)? This is not explained, and the final draft of the report removed the reference to the 1850 to 1900 baseline.
  4. If the UNFCC and the Paris Agreement assume “climate change” and “Human-caused Climate Change” are synonymous, how do they explain that climate has change much quicker and much more dramatically many times in the past 13,000 years before human civilization began and well before industrialization?

The first five questions are dealt with in C3S20. To answer question five, they adopt the UNFCCC assumption that all climate change is due to human activities. Or, perhaps a better way of saying this, is that they only considered the human-caused portion of global warming, using IPCC assumptions. Then they use various estimates of GHG climate sensitivity (ECS) to compute projected temperatures to 2100AD, as shown in Figure 2. ECS is defined as the temperature rise expected from a doubling of the atmospheric CO2 concentration, the other major greenhouse gases are assumed to increase in concert. Their estimates of the surface temperature in 2100 are similar to the IPCC estimates, shown in Figure 3, because they used similar assumptions. That is, they only considered human influences on climate and the human contribution was computed with the same or similar parameters. The projections differ in detail because the IPCC projections vary the human greenhouse emissions and C3S20 only vary the climate sensitivity to greenhouse gases. See the paper for the details of the C3S20 calculations and the IPCC AR5 report for the details of the IPCC calculations (IPCC 2014, Chap. 12). The AR4 (see Figure 10.4 in AR4) estimates are similar. Basically, the “magical” CMIP5 computer models don’t add much, the uncertainty in their projections is fully explained by the uncertainly in ECS. Further, ECS only applies to the human-caused component of global surface warming. It does not account for natural variability.

C3S20 do note that empirical estimates of ECS, in particular those by Lewis and Curry (Lewis and Curry 2018) and Lindzen and Choi (Lindzen and Choi 2011), are less than 2.5 and as low as 0.4. Soon, Connolly and Connolly computed an ECS of 0.44 using a correlation to solar variability and Shaviv (Shaviv 2012) calculated an implied ECS of 0.69 to 1.26°C. The estimates higher than 2.0°C/2xCO2 are nearly all model results from hypothetical IPCC “scenarios” and not based on measurements. The empirical results are greatly preferred. A reasonable data-based maximum ECS is around two degrees, and as you can see in Figure 2, this shows a maximum human-caused warming of less than two degrees by the year 2100AD while carrying on “business as usual.” Shaviv’s 2012 estimate for warming of between 1 and 1.5°C by 2100AD for a business-as-usual scenario (Shaviv 2012).

Figure 2. Human-caused warming, using IPCC assumptions and making no changes in greenhouse gas emissions. Source: (Connolly, et al. 2020).

Figure 3. The IPCC AR5 global surface warming predictions for 2100 are very similar to those in C3S20, since they are based on nearly the same parameters and assumptions. Source: (IPCC 2014, p. 1037).

The preindustrial period

Since the Paris Agreement does not define a preindustrial period, one can reasonably ask “1.5° to 2.0°C above what?” They often refer to the IPCC AR5 report, but unfortunately, there is no definition of “preindustrial” in that report either (Hawkins, et al. 2017). The whole purpose of the Paris Agreement is thus cast into doubt. Early AR5 drafts tried to define preindustrial as 1850 to 1900, but this definition was removed from the final draft of the report (Hawkins, et al. 2017). And, in fact, within the AR5 report, many different definitions of “preindustrial” are used. AR5 uses the difference between the average global temperature from 1850 to 1900 and the average from 1986 to 2005 (0.61°C) as their “observed” 20th century warming value. These periods are noted in Figure 4.

In C3S20, they do not even attempt to select a period to label as preindustrial, nor do they define a preindustrial temperature. They simply use the greenhouse gas levels from Antarctic ice cores to establish a baseline greenhouse gas concentration, then use that as a starting point for their greenhouse gas concentration warming trend, the trends are shown in Figure 2. They have no starting point, they simply show warming that can be attributed to greenhouse gases, using a set of simple assumptions, described in the paper. The vertical axis in Figure 2 is not a real temperature anomaly, it is more of an index of warming that might be attributable to human greenhouse emissions. The vertical axis bears no relationship to the real world; it incorporates no estimate of natural warming or climate oscillations, like the AMO or ENSO. If the assumptions are correct and it is understood to be only the greenhouse gas caused warming, only the “human-caused warming,” if you prefer, then maybe the estimates in Figure 2 tell us something useful. Figure 2 certainly highlights the oversimplification of climate change that is endemic in the IPCC and UNFCCC. But actual warming or cooling that we experience over the next century may be higher or lower, depending upon natural forces and the true value of ECS. The largest unknown is the impact of solar variability. For a more detailed look at solar variability and climate change see here.

The real problem is that the UNFCCC and the IPCC have conflated human-caused global warming with actual warming and so has much of the world. Human-caused warming may be occurring, it is probably one component of the warming that we are observing. But it is very poorly understood. As Figures 2 and 3 show, the estimates of the potential human component in 2020 spread over one degree Celsius, this is more warming than the world has seen (using the HadCRUT 4 record) since 1850. Thus, the error in one component (the human part) of our current warming is more than we have measured since 1850!

Figure 4. The HadCRUT 4 surface temperature record. Periods of warming and cooling are highlighted with color and trends. The early IPCC draft preindustrial period is identified as “A.” The average used to compute the modern warming baseline is identified as “C.” The difference, 0.61°C is the IPCC AR5 “modern warming.” “B” is the preindustrial baseline recommended by Luning and Vahrenholt (Luning and Vahrenholt 2017).

The reason the period 1850-1900 was dropped from the report is not known, but perhaps it was because many other “preindustrial” periods were used in the report, for example 1750AD was the preindustrial baseline for radiative forcing (Hawkins, et al. 2017). Hawkins et al. suggest that the IPCC adopt a consistent and precise preindustrial period and use the same period throughout the next report. The period they suggest is 1720-1800, however a robust global surface temperature estimate is not available for that period.

Luning and Vahrenholt (Luning and Vahrenholt 2017) suggest a reference period of 1940 to 1970 because this temperature (see Figure 4, average “B”) is closer to the average preindustrial temperature of the past two thousand years. This is in sharp contrast to the period 1850-1900, which is much colder than average for the preindustrial era, this is particularly true for the northern hemisphere.

We have seen that the impact of greenhouse gas concentrations on surface temperature (ECS) is poorly understood and decades of very expensive research has not narrowed the uncertainty The Charney Report (Charney, et al. 1979) estimated that ECS was between 1.5 and 4.5°C in 1979, which is exactly the range determined by the IPCC in AR5 in 2013. We are no closer in estimating the climatic impact of greenhouse gases today than we were in 1979, despite spending billions of dollars on research.

Finally, it is not clear why warming of two degrees, if it even occurs, will be a problem for humankind. Additional CO2 causes plants to grow larger and faster, it also improves crop yields. Warming disproportionately occurs at the poles, there is far less warming at the equator. Thus, warming has the effect of opening land for farming in the far north, especially in Northern Europe, Siberia and Canada, but it does not affect tropical countries much. Some claim that warming is accelerating and will “take off” and burn us all up, but the data shows warming has slowed in the last twenty years or so. This can be seen in Figure 4, especially if we ignore the strong El Nino in 2016. Accelerating warming is sometimes called “going runaway.” This is very unlikely to happen, especially since the Earth has oceans, as explained here. If you have heard the Earth may become like Venus, see here for why it will not happen. For more on ocean oscillations and global warming, see here.


As we see by reading C3S20, the 2.0°C limit idea in the UNFCCC Paris Agreement is very flawed. The agreement does not define the preindustrial starting point, either as a temperature or a greenhouse concentration. It is not even defined in time. The effect of human-emitted greenhouse gases is not known accurately enough. This is clearly seen in Figure 2. The error in warming estimates for 2020, is larger than the total surface warming since 1850. Finally, there have been no observed problems with warming or greenhouse gas emissions. The net impacts of warming and higher greenhouse gas concentrations have been positive to date according to the economists that have studied the issue. Further, the impacts are likely to remain positive for some time to come.

The 2.0°C limit is arbitrary and subjective (Mahony 2015) and has no starting point. There is no way to accurately project the effects of the emissions the UNFCCC seeks to control, and two degrees of warming is just as likely to be beneficial as harmful. Further, we have no idea how natural forces will affect future climate, will they contribute to warming or work in the opposite way? There are studies that point both ways. See here and here.

Given how little we know about future climate, it would seem wise to give up on the idea of revolutionary changes like eliminating or curtailing fossil fuel use. This sort of change will undoubtably cost more than it saves. The impacts of climate change, whether natural or human-made, are different for every location. A coastal city may be impacted by either local or general sea level change. Changes in precipitation may cause flooding in some areas and droughts in another. These problems are better fought on a local level, as they always have been in the past. People must choose to adapt or move; it should be their choice. A global change, so-called “mitigation,” will be extraordinarily expensive and will likely have serious and unpredictable side effects. See the discussion here for more details.

Adaptation is the way to go, because we do not know what will happen. Keep our energy sources, we may need them. Free our builders from the severe and often foolish environmental constraints that cause construction projects to be delayed for years. The Galveston Seawall, that protected the island for 97 years was completed in eleven years after the devastating 1900 Great Galveston Hurricane in 1900. It was not topped by a hurricane until Hurricane Ike in 2008. After Ike, an “Ike Dike” was proposed to improve the island’s protection, but it has been mired in politics and environmental surveys ever since. We need to get rid of most of the national regulations that strangle local solutions, the local communities know what must be done to protect their community, national and global “policies” simply get in the way.

Works Cited

Behringer, Wolfgang. 2010. A Cultural History of Climate. Cambridge: Polity Press.

Charney, J., A. Arakawa, D. Baker, B. Bolin, R. Dickinson, R. Goody, C. Leith, H. Stommel, and C. Wunsch. 1979. Carbon Dioxide and Climate: A Scientific Assessment. National Research Council, Washington DC: National Academies Press. doi:

Connolly, Ronan, Michael Connolly, Robert M. Carter, and Willis Soon. 2020. “How Much Human-Caused Global Warming Should We Expect with Business-As-Usual (BAU) Climate Policies? A Semi-Empirical Assessment.” Energies 13 (6).

Hawkins, Ed, Pablo Ortega, Emma Suckling, Andrew Schurer, Gabi Hegerl, Phil Jones, Manoj Joshi, Timothy J. Osborn, and Valerie Masson-Delmotte. 2017. “Estimating changes in global temperature since the pre-industrial period.” Bulletin of the American Meteorological Society 1841-1856.

IPCC. 2014. Fifth Assessment Report (AR5). 4 vols. Cambridge: Cambridge University Press.

Lacis, Andrew, Gavin Schmidt, David Rind, and Reto Ruedy. 2010. “Atmospheric CO2: Principle Control Knob Governing Earth’s Temperature.” Science 330: 356-359.

Lewis, Nic, and Judith Curry. 2018. “The impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity.” Journal of Climate.

Lindzen, Richard, and Yong-Sang Choi. 2011. “On the Observational Determination of Climate Sensitivity and Implications.” Asia-Pacific Journal of Atmospheric Sciences 47 (377).

Luning, Sebastian, and Fritz Vahrenholt. 2017. “Paleoclimatological Context and Reference Level of the 2 degree and 1.5 degree Paris Agreemnet Long-Term Temperature Limits.” Frontiers in Earth Science.

Mahony, Martin. 2015. “Climate change and the geographies of objectivity: the case of the IPCC’s burning embers diagram.” Transactions of the Institute of British Geographers.

Pielke, Roger. 2005. “Misdefining ”climate change”: consequences for science and action.” Environmental Science and Policy 8: 548-561.

Shaviv, N. J. 2012. “The Role of the Solar Forcing in the 20th century climate change.” Edited by A. Zichichi. International Seminar on Nuclear War and Planetary Emergencies. 279-286.

Ziskin, Shlomi, and Nir Shaviv. 2012. “Quantifying the role of solar radiative forcing over the 20th century.” Advances in Space Research 50: 762-776.


78 thoughts on “How much human-caused global warming should we expect?

  1. What are people’s thoughts on the latest C02 levels?

    Lets critically analyze and question it, especially the “man made” portion of this CO2 most up to date data…
    China (supposedly the biggest emitter) has been under full lockdown and at a complete stand still for 3 months and following on many other parts of the world…
    Well if humans were the biggest source of C02 (which they are not) – you would expect to see this signiture and perhaps even a downturn in the very lastest data – which is measured extremely accurately and down to .00 of the parts per million?
    I think one good consequence of this Coronavirus Crisis is that the CO2/global warming scam is being exposed…
    And the data is bearing out the we (humans) contribute very little to overall C02 levels – the vast majority of which is natural and is naturally regulated by the oceans and plant life as it has for millennia…
    It has to be noted that this data comes daily fro the Hawaiian observatory – Which when taking into account its geographical proximity to China with Pacific jet dream and prevailing trade winds you’d expect to see something by now???
    But completely normal!!!

    • Everyone pretty much knows that human emissions at any given time are a small fraction of natural emissions. For instance, sea surface temperature changes give rise to signals much greater than human emissions, especially on short time scales. Further, Chinese emissions are significant but are a fraction of total human emissions. Certainly lockdown will reduce emissions, but it will not eliminate them.

      It is not reasonable to expect to detect a drop in human signal change on this scale when natural noise is so much higher.

      • Why is this not seen in the latest figures – all of China under lockdown for 8 weeks – You’d think there would be a signature in these readings – I think with all these global lockdowns we have a unique opportunity to review raw data and prove that we have zero control over CO2 levels and that it is naturally regulated:

        • You just have to wait for ol’ Mosh to come in clutching his pure data…he will show you you’re wrong.

          Sometimes I wonder if he is like Tolkien’s Gollum referring to his data as “precious.”

      • Scissor
        The IPCC says “all of the increased CO2 in the atmosphere since the industrial age began is due to human emissions.” They claim the “air born” fraction is nearly 50%. I cannot square these statements with the idea that changes in our emissions are not detectable in the over all data. If we can’t see the changes we make ( )
        in the Mauna Loa record, how will changing our emissions “fix ” the problem. Your analysis is correct- Our emissions are lost in the noise and only account for about 3% of the total. The reasonable conclusion is: stopping our emissions will not be evident in the Mauna Loa data and as such can be pointed to as falsification of the base hypothesis that our emissions are driving the atmospheric content and thus any greenhouse warming.

        • Yes, even if they were right about the “air born” fraction being cumulatively 50% man made, even within a day the natural variation is about +/- 3 ppm.

        • Having now read the paper I see the brilliance of its concept in this controversy. Bob Carter’s often repeated warning to ‘Not be tied to the short view or one perspective” come through. This paper’s propose is not so much to compute and project human caused warming as to demonstrate the winding and necessarily controversial logic needed to get to that calculation and generate a reference list that addresses each necessary step.
          It is well worth reading the paper that lists several paradigms within the scientific community for each of four necessary steps to get to the calculation of the titled quantity. Often contradictory these paradigms must be sorted and studied to chose one of multiple possible paths to the calculation phase.
          C3S20 is a resounding refutation of the concept of “settled science”.

    • 1) While China is the largest single emitter of CO2, that doesn’t mean that their contribution is most of the CO2 being produced.
      2) Parts of China are on lock down, not the whole country.
      3) Even those parts that are on lock down are still producing CO2.

      • But no signature of that of any of the other lockdowns in the very latest CO2 figures – does this show once and for all that we have no control over them ?

  2. No worries. The world economy is one victim of the medical situation. Each nation’s economy is a victim. Each city’s economy, each town’s, each person’s economy. Factories will shut down. No bad CO2.

    Even if hydroxychloroquine works, our economy has taken a major hit already.

  3. Paper claims (Illegal, thanks China) CFC s caused 1/2 warming since 1980s. So CO2 not a problem. Charney sensitivity of less than 0.85 K anyone? As I estimated.

  4. No one seems to be aware ogf the revolutionary mlten salt nuclear technology which can easilly supplant all fossil fuels due to its competitive cost ad its ability to load follow, eliminating most needs for peak generation (usuallly fossil fueled). Electric cars are the obvious future simply on the basis of efficiency. Battery costs have or are about to be lower than $100 per Kwhr,which has always been cited as the price at whcih electric cars become cost competitive with gas powered cars in terms of purchase price,, the price of fueling and maintaning electrics being less that gas powered cars.
    Any estimates of future carbon emissions which does not take molten salt reactors into account is totally worthless.

    • Col,
      I think regular readers here probably are very well aware of the claims.
      They are mentioned here a bit more than occasionally!


    • Efficiency is not the only driver for vehicle choice. Most people cannot afford an electric vehicle as a daily driver for short haul trips to and from work, store, etc while also keeping a fossil fueled vehicle for long haul trips, e.g. vacations, etc. On long trips recharge vs refuel time also becomes a consideration. Fast charging of any kind of battery has large negative impacts on battery life while quick refuels of gasoline or diesel has none.

      If electric vehicles were the panacea many believe their sales would be much higher than they actually are.

      • Until they produce, at reasonable cost, a self powered electric vehicle to replace my grand caravan and 1 ton pickup I will remain aggressively antagonistic to their tinkertoy crap.

  5. “This story, in one form or another, goes back to biblical times. According to Genesis (6:9 to 9:17) God decided that humans had sinned too much and must be punished, so he called up a great flood to destroy the world. A similar story also appears in the earlier Epic of Gilamesh. End of the world predictions are very popular and recur regularly in human history”

    Yes sir. And I think that our obsession with the end of days derives from the Late Bronze Age Collapse. Pls see

  6. Logically, the whole idea of human-caused warming is irrelevant.

    IF warming is going to be catastrophic, and IF we can do something about it, such that expected benefits exceed expected costs, then we should take action. It does not matter if such warming is natural or caused by human activity.

    The emphasis on “human-caused” warming is because everyone knows intuitively that stopping a natural, global climate cycle is idiocy. We have no expectation of being able to stop natural forces and nobody will agree to more taxes in order to try.

  7. Great work, Andy. You provide the intellectual scaffolding to defuse the absolutism of a future no one can accurately see or understand. Thanks for the science lesson.

  8. OK, one more time, with feeling, climate changes constantly, humans are not causing it and can not stop it.

  9. The CMIP6 ensemble has 31 models. They mostly all give different predictions, leading to 30 odd different scenarios, from low (1.8C) to high (5.6C).

    Those models can not all be correct at the same time; at most only one can. Therefore, the odds that any model is correct are worse than 1 in 31. The odds that any model is wrong are 30 to 31 at least.

    With such odds against, the probability that in fact one of them is correct is 1-0.36, about 65% at best. Hence the probability that the ‘true’ model is in the range covered by the scenarios is at best 65%; the probability that the ‘true’ model, real world, is outside that range is at least 35%. Outside means most probably lower than 1.8C (and imho considerably much lower, more like 0.5-0.7C).

    Question for politicians: would you gamble the family silver on such odds? (of 65% being right).

  10. 2 to 10 million years ago (estimates vary) there were trees and beavers on Ellesmere Island, the most northerly island in Canada.

    This means the climate was substantially warmer than it is now.

    So how did life survive?

  11. The climate model forecasts, on which the entire Catastrophic Anthropogenic Global Warming meme rests, are structured with no regard to the natural 60+/- year and, more importantly, 1,000 year periodicities that are so obvious in the temperature record. The modelers approach is simply a scientific disaster and lacks even average commonsense. It is exactly like taking the temperature trend from, say, February to July and projecting it ahead linearly for 20 years beyond an inversion point. The models are generally back-tuned for less than 150 years when the relevant time scale is millennial. The radiative forcings used in the IPCC reports merely reflect the assumptions of the modelers The IPCC future temperature projections depend in addition on the Representative Concentration Pathways (RCPs) chosen for analysis. The RCPs depend on highly speculative scenarios, principally population and energy source and price forecasts, dreamt up by sundry sources. The cost/benefit analysis of actions taken to limit CO2 levels depends on the discount rate used and allowances made, if any, for the positive future positive economic effects of CO2 production on agriculture and of fossil fuel based energy production. The structural uncertainties inherent in this phase of the temperature projections are clearly so large, that the outcomes provide no basis for action or even rational discussion by government policymakers. The IPCC range of ECS estimates reflects merely the predilections of the modelers.
    My2017 paper “The coming cooling: usefully accurate climate forecasting for policy makers.” said:
    ” This paper argued that the methods used by the establishment climate science community are not fit for purpose and that a new forecasting paradigm should be adopted.”
    The reality is that Earth’s climate is the result of resonances and beats between various quasi-cyclic processes of varying wavelengths.
    It is not possible to forecast the future unless we have a good understanding of where the earth is in relation to the current phases of these different interacting natural quasi-periodicities which fall into two main categories.
    a) The orbital long wave Milankovitch eccentricity,obliquity and precessional cycles which are modulated by
    b) Solar “activity” cycles with possibly multi-millennial, millennial, centennial and decadal time scales.
    When analyzing complex systems with multiple interacting variables it is useful to note the advice of Enrico Fermi who reportedly said “never make something more accurate than absolutely necessary”. The 2017 paper proposed a simple heuristic approach to climate science which plausibly proposes that a Millennial Turning Point (MTP) and peak in solar activity was reached in 1991,that this turning point correlates with a temperature turning point in 2003/4, and that a general cooling trend will now follow until approximately 2650.
    The establishment’s dangerous global warming meme, the associated IPCC series of reports ,the entire UNFCCC circus, the recent hysterical IPCC SR1.5 proposals and Nordhaus’ recent Nobel prize are founded on therefore on two basic errors in scientific judgement. First – I reiterate that the sample size is too small. Most IPCC model studies retrofit from the present back for only 100 – 150 years when the currently most important climate controlling, largest amplitude, solar activity cycle is millennial. This means that all climate model temperature outcomes are too hot and likely fall outside of the real future world. (See Kahneman -. Thinking Fast and Slow p 118) Second – the models make the fundamental scientific error of forecasting straight ahead beyond the Millennial Turning Point (MTP) and peak in solar activity which was reached in 1991.These errors are compounded by confirmation bias and academic consensus group think.
    See the Energy and Environment paper The coming cooling: usefully accurate climate forecasting for policy makers.
    and an earlier blog version at See also

      • Andy -I say in the comment above that the AGW meme is based on 2 basic errors of scientific judgement. There is a third even more fundamental disconnect between the consensus climate science and reality. Here is an excerpt from a draft of a new paper I’m working on:
        “The composition of the atmosphere by weight is 75.52% nitrogen, 23.13% oxygen, 1.289% argon, 0.053% carbon dioxide,(only 3% of which is anthropogenic) 0.0013% neon, 0.0003% methane, 0.0003% krypton, 0.0007% helium, and 0.0000038 % hydrogen.H2O vapor is about 0.25 % by mass but varies widely. It is inconceivable because of the basic laws of thermodynamics that the effect on temperature of CO2 or of the rate of changing energy flows in 0.053 % of the whole atmosphere can even be measured let alone that it can be the main driver of global atmospheric temperatures.
        .Jelbring 2003 ( 6 )in “The “Greenhouse Effect” as a Function of Atmospheric Mass ” Abstract says
        “The main reason for claiming a scientific basis for “Anthropogenic Greenhouse Warming (AGW)” is related to the use of “radiative energy flux models” as a major tool for describing vertical energy fluxes within the atmosphere. ……… Here, using a different approach, it is shown that GE {Greenhouse Effect} can be explained as mainly being a consequence of known physical laws describing the behaviour of ideal gases in a gravity field. …………. The distinguishing premise is that the bulk part of a planetary GE depends on its atmospheric surface mass density. ….. A noteworthy implication is that the calculated values of AGW, accepted by many contemporary climate scientists, are thus irrelevant and probably quite insignificant (not detectable) in relation to natural processes causing climate change”

        • If IR had an effect on CO2 that caused warming then it would be mentioned in specific heat tables, the Shomate equation, and NIST page for CO2. Heck the specific heat of air has not been changed since it was at 300 ppm. It should be.

          The forcing equation is a failure as it does not account for mass change.

        • “It is inconceivable because of the basic laws of thermodynamics that the effect on temperature of CO2 or of the rate of changing energy flows in 0.053 % of the whole atmosphere can even be measured let alone that it can be the main driver of global atmospheric temperatures.”

          I love it!

          This quote should be used every time we get some alarmist attributing human activity to severe weather.

  12. “OMG! The world is going to end, and we caused it. This story, in one form or another, goes back to biblical times. According to Genesis (6:9 to 9:17) God decided that humans had sinned too much and must be punished, so he called up a great flood to destroy the world. A similar story also appears in the earlier Epic of Gilamesh. End of the world predictions are very popular and recur regularly in human history.”
    Wasn’t there a chap called Noah who was commanded by God to build an ark in which he and his family would live until the flood subsided? In which case God didn’t exactly intend to destroy the whole world. So that’s another ‘end of the world’ story washed away.

    • You seem to have a very pedantic view of ‘End of the World’.

      Noah, his wife, his 3 sons and their wives were, supposedly, the only people or animal left alive after the flood.

      It was certainly the end of the world for (x million – 8) people who lost their lives.

      If the World ends and there is no-one there to notice it, does it really end?

  13. “Climate change ” or climate lies, as I prefer has had it’s 15 minutes, good riddance. Let us now get on to solving actual problems- like the one we see before us now.
    And always keep your eye on the ball- it never was about CO2, that is well established- it is about causing an economic and social overthrow that is undesirable to the vast majority.

  14. “This was the end of the Little Ice Age, the coldest period in the last several thousand years. Why use that period as a baseline (Luning and Vahrenholt 2017)? This is not explained, and the final draft of the report removed the reference to the 1850 to 1900 baseline.”

    Mainly because all we have before that (apart from the CET), are proxies, which aren’t very reliable thermometers. I agree that it’s kind of a cherry pick, but not much choice available.

    • In science, if you don’t have good data, you go out and get good data.
      You don’t just, go with what you have because it’s the best you can find.

      In other words, you can’t do good science with bad data.
      All attempts to fix “bad data” merely adds to the uncertainty.

    • The temperature data we have from the 1850 to 1900 baseline has an uncertainty interval larger than the growth in temperature trying to be identified since then. Therefore that data is actually no better than the proxy data used for periods earlier than that.

  15. Love the Medieval wood-cut. It really sums up the modern, cutting-edge sciences of our day: the voodoo medium invoking the spirits of the gods with the ossified, toothless… hell, you can’t say it any better than the caption.

  16. This critique of the IPCC’s goal of limiting global temperature increase (to some arbitrarily assumed level, by way of dubious energy control strategies) is very welcome! This fear of a prophesied “tipping point” to a runaway situation where the Earth would supposedly become a lot like planet Venus, isn’t this more or less the ultimate scare story in the alarmists’ bag of tricks?

    The ‘Earth is not like Venus” link in the head posting, , is a very interesting analysis. The ‘Figure 2’ graph there would seem to confirm what I’ve always understood, that compared to the Earth, Venus has an enormously deep, near-linear temperature increase trend, starting from about 70 km altitude, where it is zero degrees C, and extending from there on down to the surface.

    Under the heading Conclusions, I see that Andy May states that,
    “this author leans toward a maximum additional greenhouse effect of 51°C and a density and phase change effect of 398°C or more, but this is very speculative.”

    So, the surface temperature on Venus is mostly pressure/density/PVT driven convection related, and the earth is never going to be like Venus at all.

    • David Blenkinsop, I’ve spent way too much time studying this issue and that is my opinion. There are people who disagree with me on this, but I do not believe the PVT law has been repealed and pressure makes a difference. The pressure on the surface of Venus is 92 atmospheres! That has to account for most of the increased temperature. Further, at that pressure CO2 is supercritical, it is not a gas, so the surface of Venus is an ocean of supercritical CO2, that makes a difference as well. And, there is no water on Venus and almost no water vapor. So, I stand by my, still unproven, opinion that only 51 degrees of the higher temperature on Venus is due to the extra greenhouse effect.

    • “This fear of a prophesied “tipping point” to a runaway situation where the Earth would supposedly become a lot like planet Venus, isn’t this more or less the ultimate scare story in the alarmists’ bag of tricks?”

      It is the ultimate scare story, the only problem with claiming human-caused CO2 will turn Earth into Venus is that the Earth has had much higher levels of CO2 in the past than we have at present, yet the Earth never went into a runaway Greenhouse effect during that time.

      If humans burnt every bit of fossil fuels we could get at one time, the human-caused CO2 would raise the level of CO2 in the atmosphere to no more than 1,000ppm total, when it has been up to 7,000ppm in the Earth’s atmosphere in the past with no runaway Greenhouse effect happening.

      We couldn’t turn Earth into Venus if we tried. Not by pumping out CO2, anyway.

  17. Dr. May,
    Thank you for this fine piece.

    I admit to being a little obsessive about spelling. In the first paragraph, the fifth sentence needs a “g” added to “Gilamesh” in order to appear correctly as “Epic of Gilgamesh.”

  18. What I find disturbing is that many of those who are a bit sceptical about ‘global warming’ are still firmly anti-human. They believe that the planet cannot stand even the present population – humans are a plague. Their targets for ‘necessary’ reduction vary from cutting to half to cutting to less than 1 billion. Just like with the climate freaks, when data such as that in Jan 2019 Lancet is pointed out, they are disbelieving. Anyone with more than 1 child is seen as a selfish sinner.

    What Lancet Jan 2019 found was that only 3 African countries have current birth rates above replacement, and all developed countries are well below. The conclusion was that urbanisation and education of women makes children an expense rather than an asset.

    • Not sure I have read many anti-human comments among us skeptics? Seems to me like almost everyone on here feels the earth is doing fine with the numbers we have. And yes I agree as people get richer they have less children, that it’s why it’s imperative to get good inexpensive carbon based fuels to all of the remaining poor, the opposite goal of the alarmists.

    • “What I find disturbing is that many of those who are a bit sceptical about ‘global warming’ are still firmly anti-human.”

      I think you have it exactly backwards, Fran. Skeptics generally do not display those traits that I have ever seen.

  19. Mr. May, thank you.

    I have been ttrying to make the point for a number of years that the current “climate crisis” mentality has its origins in prehistory and paganism.

    Natural disaster? Man must have ticked off the gods, either through comission or omission- an early, and largely untested, version of cause and effect.

    In other words, this is all about us, a narcissistic viewpoint that is, sadly, common to all of humanity.

    Now that we have entered an “Age of Atheism”, angering the gods is a less viable proposition (note to readers- I am not an atheist. I consider the arguments of Intelligent Design one of the major scientific controversies of our time!), so something must take the place of the gods… “Science” (or something like it) to “prove” that it is still all about US.

    I conclude that, to a very large extent, climate alarmism is merely superstition, power hunger, arrogance, and compounded by ignorance.

    And, of course, I am troubled by the lack of attention to the two claims by the “Global Warm-mongers” that 1) a warmer climate is bad, and 2) that increased CO2 is also bad. Both assumptions are unproven.

    • Kpar, Agreed. You can be sure a climate alarmist proclaiming “I believe in science” has no training in science. If they did they would know science is a process, not a “belief.”

    • It might be of interest to some of those here to know that the majority of Christians do not believe in AGW. There is an article on that subject here on WUWT that was produced within the last couple of years, but I haven’t been successful in locating it in the archives.

      God does not consider us a blight to be done away with. He loves us intensely.

      • “God does not consider us a blight to be done away with. He loves us intensely.”

        Assumes facts not in evidence.

  20. I make a prediction for the amount of human caused global warming. Damn all, approximately 0 Degrees Celsius.

  21. I see mention of the climate being warmer some millions of years ago, Yes, true, but one does not have to go back nearly that long ago to see a warmer climate; this during the Medieval Warm period that occurred just prior to the Little Ice Age. The eminent climatologist Hubert Lamb, cited a specific case of conditions in Greenland during the MWP as being significantly milder than the present. Dr. Lamb tells of Greenland settler having to rescue one of his sheep from an offshore island by swimming to the island to retrieve his sheep. Well, in the present day this man would have not been able to swim the distance required, as he would died from hypothermia. So was deduced by Dr. Lamb that the ocean water off the coast of Greenland was warmer, by at least three or four degrees Celsius. I have also seen a reference that some Chinese very early sailors circumnavigated Greenland about the same time as the sheep incident. I would also like to indicate that although the Carbon dioxide graphs can be made to look impressive (Mauna Loa record etc.), it is necessary to put this in perspective when you realize that the amounts of carbon dioxide in the atmosphere, is in parts per million. So 450 parts per million remains as an incredibly small amount.

    • I would not put it past the Chinese sailors to have feasted on yang rou (sheep), and they probably didn’t wash their hands either.

  22. “As explained by Roger Pielke Jr. in 2005 the UNFCCC defines “climate change” as something caused by humans and totally ignores the possibility of natural climate change. ”

    “If the UNFCC and the Paris Agreement assume “climate change” and “Human-caused Climate Change” are synonymous….”

    Gotta remember we’re shooting at moving targets. The UNFCC may have started by arbitrarily defining climate change as man-made, and may still have been doing so in 2005. But by 2012 the definition had quietly changed:

    Climate change
    A change in the state of the climate that can be identified (e.g., byusing statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.1

    Tempted to make a cynical remark about shell games, but in this case the change was a clear improvement.

    • Juan Slayton, Yes the IPCC considers both natural and human influences on climate, but then they assume that the natural changes average zero. The UNFCCC did not change their definition in 2012, they still assume it is all human-caused. They are separate organizations. The UNFCCC organized the Paris Conference and used the IPCC reports as their scientific basis.
      The image below shows the temperature influence of various sourcing according to the IPCC, “ANT” are anthropogenic GHGs”, “OA” is other anthropogenic “NAT” is natural and “Internal variability” are ocean oscillations like the AMO and ENSO. From page 66 of AR5 WG1.

      • Andy:
        Thanks for the organizational clarification. I think I’m in danger of developing acronym derangement syndrome.

      • It is true that over a long enough period natural climate change will average to zero.
        However, the IPCC hasn’t bothered to demonstrate that 50 years is a long enough period for this averaging to have occurred.

        NOTE: There is one natural climate change that isn’t cyclical. The sun is gradually warming up as it progresses through it’s life cycle. However this change operates on a scale of 100’s of millions of years and up. No need to consider it for this discussion.

        • The Milankovich cycles are 413,000 years, 100,000 years, 41,000 years and 21,000 years. The Bray cycle is 2400 years and Eddy cycle is 1000 years, and there are others. They all affect climate.

  23. So, it started as far back as 1486 AD and probably even earlier…and the jawbones of asses are still heard from, conjuring up ever more doom and gloom based on nothing but fake data and the desire to control others. Nowadays we call them “politicians” and “climatistas” and “warmistas”…but they still have the jawbones of asses.

  24. I’d be very wary about those figures for the numbers of witches and Jews killed during the period in question. It’s very difficult to get reliable data for such things. Also, with no widespread weather data available at the time, people only knew what was happening in their own area so it would be individual hail and lightning storms that individuals might get the blame for. Mass hysteria over climate change is a modern phenomenon!

  25. I will trumpet till I die that the mean temperature of the globe is a useless measurement. Means and averages tell you absolutely nothing about the extremes of the temperature envelope which is where climate impacts are actually felt. Impacts on mankind, including food supplies, are not driven by average temperatures but by maximum and minimum temperatures. If you don’t analyze the maximums and minimums of the temperature envelope then you have no chance of determining what is going to happen in the future.

    Climate models focused on “average” temperatures are basically useless. They tell us nothing. And the uncertainty intervals associated with the models only compound their uselessness.

    If you want to know the actual impacts on climate then the climate scientists should be studying heating and cooling degree-days, especially when calculated from an integral of all the local temperature envelopes at the measuring stations. I understand that this would require at least an order of magnitude increase in complication for data collection and analysis. That should not be used as an excuse for maintaining a useless method of analyzing climate.

  26. Here is the REAL surface temperatue profile of the Earth, the U.S. surface temperature chart (Hansen 1999):

    Compare this chart’s temperature profile to the HadCRUT 4 chart in Figure 4.

    As you can see, the two are entirely different. What if all the IPCC calculations were based on the U.S. surface temperature profile instead? Well, obviously the IPCC would have to disband because the U.S. surface temperature chart demonstrates that the Earth is not experiencing unprecedented warming, it was just as warm as today in the Early Twentieth Century.

    The reason I claim the (slightly) unmodified U.S. surfce temperature chart represents the real global surface temperature profile is because all other unmodified surface temperature charts from around the world resemble the U.S. chart in that they all show it was just as warm in the Early Twentieth Century as it is today.

    No unprecedented warming = No CAGW (Catastrophic Anthropogenic Global Warming)

    Here’s a chart of the AMO (Atlantic Multi-decadal Oscillation).

    Which one does the AMO resemble, the HadCRUT 4 chart, or the U.S. surface temperature chart? Obviously, it resembles the U.S. chart profile. As do all the other unmodified temperture charts around the world.

    None of the unmodified temperature charts from around the world look like the HadCRUT 4 chart (or any other of the bastardized Hockey Stick charts).

    So what does that tell you? It tells me that the IPCC is operating in a false reality of their own creation (Bogus Hockey Stick territory), that has no relation to the actual facts on the ground on in the air.

    We shouldn’t be spending TRILLIONS of dollars trying to fix this nonsense “problem”. There is no problem. Other than a bunch of dishonest Data Manipulators.

    This whole Human-caused Climate Change charade is based on made-up numbers. This article shows it is all based on nothing. The IPCC can’t even define a starting point. And then they use bastardized temperature data on which to base their opinions and projections.

    Human-Caused Climate Change via CO2 is the biggest scientific fraud in world history.

    • Tom,

      I have loaded four images of cooling degree-days over the past 36 months for four widely separated locations across the globe. go here:

      You’ll find images for Brazil, China, Australia, and the US.

      None of them show any increased cooling being required over the past 36 months. The peak cooling degree-day monthly average has remained pretty much constant. I integrated the three pulses for Kansas and got 1643 for 2017, 2008 for 2018, and 1698 for 2019. The 5 year annual average cooling degree-day total for Kansas is about 1800. Two of the past three years have been well under the five year average.

      I haven’t done heating degree-days for the northern hemisphere since we won’t have 3 full pulses for a couple more months. For Australia, however, the five year annual average heating degree-day total is 1824. For 2017 the total was 1793, for 2018 it was 1773, and for 2019 it was 1895. So it’s not obvious that Australia is seeing warmer temps during the winter, at least for the short term past.

      None of this data shows any kind of catastrophic changes over the past three years. I keep saying this kind of data is far more instructive about what the real world climate is actually doing than the “average” global temperature. offers far more historical data but requires a subscription of $30 per month to access it. Perhaps someone else can afford this. It would be interesting to see what 20 or 30 year past data shows.

      • Very interesting, Tim. This is another way to put the lie to the “hottest year evah!” meme, and another way to poke holes in the Human-caused Climate Change claims..

      • if you want to see my graphs the web site is My carrier intercepts regular web queries.

    • I agree, Tom. A few years ago I did an analysis on three or four stations that I believe have not been affected by the Urban Heat Island Effect, or any anthropogenic warming. These climate stations in two cases, are surrounded by oceans. Their records go back over one hundred years. My analysis that took me to a few years ago (five or six years), did not show any perceptible warming, whatsoever. I am almost positive that all calculations done by the weather services in all countries have included all climate stations, hence an obvious bias, the bias is a warming, I know as well, that the temperatures that ships take out at sea are also fraught with errors, that again bias the data to arrive at warmer values. No wonder the result is a warmer world every year!!!

  27. When someone figures out how to calculate, from first principles, the amount of extra heat retained in the atmosphere by each individual extra PPM of CO2, then we can all relax.

    No one has, no one can, so this is all Pseudo-Science. Estimates, let us destroy our economy for two reasons now, let us cause another Great Depression or actually worse, to save some lives of people in their declining years, and to ensure that Obama’s and Gore’s seaside mansions will be secure.


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