Guest essay by David Middleton and Andy May

The Geological Society of London recently published a statement on climate change:

Geological Society of London Scientific Statement: what the geological record tells us about our present and future climate

Geologists Andy May and David Middleton have spent the past few days reviewing the Geological Society of London Scientific Statement and have assembled a rebuttal to some of the more questionable items in the paper.

Interestingly, the paper includes this disclaimer:

Data availability
Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.

Geological Society of London Scientific Statement

The authors make many claims, but offer up little in the way of supporting material. It is rife with exaggerations and at least a few internal contradictions. It seems to entirely miss the concept of deep time and the loss of resolution in the geological record relative to modern instrumental observations.

Atmospheric CO2

Observations from the geological record show that atmospheric CO2 concentrations are now at their highest levels in at least the past 3 million years.

Geological Society of London Scientific Statement

This is quite possibly true. Atmospheric CO2 concentrations could be, even now, at their highest levels in at the past 12 million years.

Figure 1. Neogene-Quaternary temperature and carbon dioxide (older is toward the left). (WUWT)

The geological record of atmospheric CO2 is massively uncertain, and becomes less certain the further back in time we go. This passage from Evolution of the Earth (1976) is just as true today as when we were geology students way back in the Pleistocene…

Unfortunately we cannot estimate accurately changes of past CO2 content of either atmosphere or oceans, nor is there any firm quantitative basis for estimating the magnitude of drop in carbon dioxide content necessary to trigger glaciation.  Moreover the entire concept of an atmospheric greenhouse effect is controversial, for the rate of ocean-atmosphere equalization is uncertain.

Dott & Batten, 1976

While methods of estimating past atmospheric CO2 concentrations have improved since the 1970’s, we can’t even be certain that the atmospheric concentration of CO2 during the much warmer Mid-Miocene Climatic Optimum was significantly elevated relative to the extremely low values of the Quaternary Period.

Furthermore, the current speed of human-induced CO2 change and warming is nearly without precedent in the entire geological record, with the only known exception being the instantaneous, meteorite-induced event that caused the extinction of non-bird-like dinosaurs 66 million years ago.

Geological Society of London Scientific Statement

Jeffrey Severinghaus and colleagues would be very surprised to see this statement. They showed that, at the beginning of the Holocene, about 11,700 years ago, Northern Hemisphere temperatures rose “5 – 10ºC” in just a few decades (Severinghaus, Sowers, Brook, Alley, & Bender, 1998).

With regard to CO2, this is possible. There are no geological records of CO2 change that have sufficient resolution to make this claim with any degree of certainty. The only exception would be the Law Dome ice cores in Antarctica, which only go back about 2,000 years. The lack of resolution in pre-industrial era CO2 and temperature estimates greatly limit comparisons of geological history to modern times.

This composite ice core CO2 record (0-800 kyr BP) from Bereiter et al. (2014) appears to present a very convincing Hockey Stick.

Figure 2. Composite CO2 record (0-800 kyr BP) from Bereiter et al. (2014).

This is a composite of the following ice cores:

-51-1800 yr BP:’ Law Dome (Rubino et al., 2013)
1.8-2 kyr BP: Law Dome (MacFarling Meure et al., 2006)
2-11 kyr BP: Dome C (Monnin et al., 2001 + 2004)
11-22 kyr BP: WAIS (Marcott et al., 2014) minus 4 ppmv (see text)
22-40 kyr BP: Siple Dome (Ahn et al., 2014)
40-60 kyr BP: TALDICE (Bereiter et al., 2012)
60-115 kyr BP: EDML (Bereiter et al., 2012)
105-155 kyr BP: Dome C Sublimation (Schneider et al., 2013)
155-393 kyr BP: Vostok (Petit et al., 1999)
393-611 kyr BP: Dome C (Siegenthaler et al., 2005)
612-800 kyr BP: Dome C (Bereiter et al., 2014)

These ice cores are of vastly different resolutions.  Petit et al., 1999 indicate that the CO2 resolution for Vostok is 1,500 years. Lüthi et al., 2008 suggest a CO2 resolution of about 500 years for Dome C.  It appears that the high resolution Law Dome DE08 core was just spliced on to the lower frequency older ice cores.

If we apply smoothing filters to the DE08 ice core in order to match the resolution of the lower resolution ice cores, we get a considerably different picture.

Figure 3. A 500-yr smoothing filter totally removes the Hockey Stick’s blade.

The lower frequency ice cores are not capable of resolving century scale CO2 shifts.  As such, they cannot be used to rule out the possibility of short duration fluctuations comparable to the industrial era rise in atmospheric CO2 during the early Holocene and Pleistocene.  And thus do not contradict the conclusions of Wagner et al., 1999:

In contrast to conventional ice core estimates of 270 to 280 parts per million by volume (ppmv), the stomatal frequency signal suggests that early Holocene carbon dioxide concentrations were well above 300 ppmv.


Most of the Holocene ice core records from Antarctica do not have adequate temporal resolution.


Our results falsify the concept of relatively stabilized Holocene CO2 concentrations of 270 to 280 ppmv until the industrial revolution. SI [stomatal index]-based CO2 reconstructions may even suggest that, during the early Holocene, atmospheric CO2 concentrations that were 300 ppmv could have been the rule rather than the exception.

Wagner et al., 1999

Or Wagner et al., 2004:

The majority of the stomatal frequency-based estimates of CO2 for the Holocene do not support the widely accepted concept of comparably stable CO2 concentrations throughout the past 11,500 years. To address the critique that these stomatal frequency variations result from local environmental change or methodological insufficiencies, multiple stomatal frequency records were compared for three climatic key periods during the Holocene, namely the Preboreal oscillation, the 8.2 kyr cooling event and the Little Ice Age. The highly comparable fluctuations in the paleo-atmospheric CO2 records, which were obtained from different continents and plant species (deciduous angiosperms as well as conifers) using varying calibration approaches, provide strong evidence for the integrity of leaf-based CO2 quantification.

Wagner et al., 2004

The GSL authors also presented a stark contradiction.

In short, whilst atmospheric CO2 concentrations have varied dramatically during the geological past due to natural processes, and have often been higher than today, the current rate of CO2 (and therefore temperature) change is unprecedented in almost the entire geological past.

Geological Society of London Scientific Statement

They claim that “the current rate of CO2 (and therefore temperature) change is unprecedented in almost the entire geological past,” but then state the following:

Given the record of past climate change (Section 1), the magnitude of recent observed climate change is not unusual.

Geological Society of London Scientific Statement

Modern climate change is allegedly both unprecedented and “not unusual.” They appear to conflate CO2 and temperature. While they are related, they aren’t interchangeable.

CO2 and sea level

They also make the claim that the geological record depicts a relationship between CO2 and sea level.

The geological record is consistent with predictions that the long-term magnitude and rate of future sea-level rise will be highly sensitive to future CO2 emission scenarios and may include intervals of very rapid rise.

Geological Society of London Scientific Statement

However, there is no relationship between CO2 and sea level in the geological record.

Figure 4. Left to right: Generalized cross section along northern GOM region (Galloway et al., 2009), depositional phases are numbered. Relative sea level (Miller et al., 2005), atmospheric CO(Berner & Kothavala, 2001) and temperature anomalies (Royer et al., 2004). Click for image.

William Galloway, of the University of Texas Jackson School of Geosciences, summarized the depositional history of the Gulf Coast/Gulf or Mexico in this paper…

Depositional history can be generalized in seven phases: (1) Middle-Late Jurassic evaporite and carbonate deposition in a broad, shallow, restricted to open marine basin. (2) Latest Jurassic-Early Cretaceous sand-rich clastic progradation from the northern margins. (3) Late-Early Cretaceous development of a rimmed carbonate shelf. (4) Late Cretaceous mixed clastic and carbonate aggradation of the continental margins. (5) Resurgent Paleogene clastic progradation and filling centered in the NW basin. (6) Miocene progradation and basin filling centered in the central and NE Gulf. (7) Late Neogene climatically and eustatically influenced progradation along the central Gulf margin. In contrast to the broad, progradational sediment wedge of the northern Gulf, the Florida margin is a primarily aggradational carbonate platform.

Galloway, 2008.

Figure 4 clearly demonstrates the importance of climate, atmospheric CO2 and sea level cycles in the depositional history of the US Gulf Coast/Gulf of Mexico; but no correlation of CO2 and sea level. Note that most of the source rock formations were deposited when atmospheric CO2 was above 1,000 ppm and the Earth was considerably warmer than it is today, suggesting more plant life in the warmer, CO2 rich times.

The temperature and CO2 plots have 10 million year resolutions; they are highly smoothed. However, there is almost no relationship between CO2 and temperature on a geological time scale.

The modern warming period began at the nadir of the Little Ice Age (ca. 1600 AD), the coldest period in the Holocene Epoch. This was 300 years prior to atmospheric CO2 significantly exceeding the assumed normal preindustrial range.

Figure 5. Temperature reconstruction (Moberg et al., 2005) and Law Dome CO2 (MacFarling Meure et al., 2006)

The modern rise in sea level began at the end of neoglaciation. The sea level reconstruction of Jevrejeva et al., 2014 (J14) indicates that sea level was falling in the early 1800’s.

Figure 6. Sea level reconstruction from tide gauge data (Jevrejeva et al., 2014). Note rock pick added for scale.

Figure 7. Sea level compared to the CO2 record and temperature.

Climate sensitivity

“The IPCC (2014) gave a 66% probability that the ECS value was between 1.5 and 4.5°C. …

To estimate ECS from the geological record, quantitative paired records of atmospheric CO2 and global temperature from proxies are needed …

many studies of the geological past have provided support to the canonical range for ECS of 1.5–4.5°C”

Geological Society of London Scientific Statement

The first modern estimate of ECS, published in the Charney Report, in 1979, was 1.5 to 4.5 degrees C per doubling of CO2 (ECS). In other words, the “canonical range” has not changed in over 40 years. Modern empirical estimates of ECS, based on instrumental data, have ranged from 0.44 degrees C (Lindzen and Choi, 2011) to 1.6 (Lewis and Curry, 2018). These estimates have high resolution CO2 and temperature data. The geological estimates do not.

While geological estimates of ECS may be higher, the GSL says the geological estimates fall in the range of 2.6 to 3.9 degrees, we cannot be comfortable with the accuracy or precision of these estimates. The data, especially the CO2 data are too poor.

Furthermore, the authors present a cartoon, apparently depicting a strong correlation of CO2 and temperature over the Cenozoic Era.

Figure 8. GLS Cenozoic climate sensitivity (modified after Lear, et al., 2012). Click to enlarge.

The GSL cartoon indicates a climate sensitivity of nearly 7 °C per doubling of CO2. This would result in about 3.5 °C of warming since the mid-1800’s, which clearly did not occur. Modern high resolution instrumental measurements yield a much lower climate sensitivity.

Parallels in the geological record

The authors try to draw parallels to modern climate change from the geological record.

In the mid Pliocene (3.3–3.1 million years ago), atmospheric CO2 concentrations ranged from 389 (–8 to +38) ppm to 331 (–11 to +13) ppm (de la Vega et al. 2020), which is higher than pre-industrial levels of about c. 280 ppm and slightly lower than modern levels (c. 407.4  ±  0.1 ppm in 2018). Earth’s continental configurations, land elevations and ocean bathymetry were all similar to today (Haywood et al. 2016). The Pliocene was characterized by several intervals in which orbital forcing was similar to that of modern times and so it offers us a close analogue to the climate under modern CO2 concentrations (McClymont et al. 2020). During this interval, global temperatures were similar to those predicted for the year 2100 (+2.6 to 4.8°C compared with pre-industrial) under a business-as-usual scenario (i.e. with no attempt to mitigate emissions). Several lines of work suggest similarities between the model-predicted ocean circulation of the future and that of the mid-Pliocene warm period, with a weaker thermohaline circulation, related to upper-ocean warming and stratification, but also reduced ice sheets and sea ice, a poleward shift in terrestrial biomes and weaker atmospheric circulation (Haywood and Valdes 2004Cheng et al. 2013Corvec and Fletcher 2017Fischer et al. 2018). Pliocene sea-level may have reached 20 m above the present-day value and may have varied, on average, by 13 ± 5 m over Pliocene glacial–interglacial cycles, in association with fluctuations in the extent of the Antarctic ice sheet (Grant et al. 2019).

Geological Society of London Scientific Statement

While “Earth’s continental configurations, land elevations and ocean bathymetry were” more similar to today, during the Pliocene Epoch than they were during earlier time periods, the Mid-Pliocene was significantly warmer than today due to tectonic differences. The Panama Seaway was still open, enabling much more efficient ocean heat transport. Significant uplift episodes in the Rocky and Himalayan Mountains during the Pleistocene Epoch were also driving factors in the deep freeze that Earth has experienced over the past 2 million years.

The geological record informs us that the major climatic shifts of the Cenozoic Era were correlated with tectonic changes.

Figure 9. Cenozoic climate, tectonics and carbon isotope excursions. (Zachos et al., 2001)

The temperatures in Figure 9 are derived from δ18O in benthic foraminifera using a no sea ice model.  Salinity and ice volume have an effect on the conversion.  These temperatures are only applicable to the Lower Tertiary, hot-house climate.

This claim about the Pliocene as a precedent for modern climate change is patently ridiculous:

During this interval, global temperatures were similar to those predicted for the year 2100 (+2.6 to 4.8°C compared with pre-industrial) under a business-as-usual scenario (i.e. with no attempt to mitigate emissions).

Geological Society of London Scientific Statement

They are clearly considering RCP8.5 to be “business as usual”.

Figure 10. Climate model scenarios. (click to enlarge)

When the full range of model forecasts are considered, it is clear that the climate is behaving more like RCP4.5 than RCP8.5.

Figure 11. Models vs observations. (Climate Lab Book)

Even with an additional 0.5 to 1.0 °C of warming by the end of this century, the climate will still be in the range of Pleistocene interglacial stages, well below the Mid-Pliocene.

Figure 12. High latitude SST (°C) from benthic foram δ18O (Zachos, et al., 2001) and HadSST3 ( Hadley Centre / UEA CRU via plotted at same scale, tied at 1950 AD.

It all comes down to context and resolution

Bear in mind that the resolution of the δ18O temperature reconstruction is much lower than the instrumental record and would not resolve the HadSST signal. Again, the geological record provides a general picture of past climate change, but cannot be directly compared to high resolution instrumental records without explicitly putting it into context. The Modern Warming only appears anomalous due to the higher resolution of the instrumental record and its position at the tail-end of the time series.

Ljungqvist (2010) clearly explained the problem by directly comparing instrumental data to proxy reconstructions.

The amplitude of the reconstructed temperature variability on centennial time-scales exceeds 0.6°C. This reconstruction is the first to show a distinct Roman Warm Period c. AD 1-300, reaching up to the 1961-1990 mean temperature level, followed by the Dark Age Cold Period c. AD 300-800. The Medieval Warm Period is seen c. AD 800–1300 and the Little Ice Age is clearly visible c. AD 1300-1900, followed by a rapid temperature increase in the twentieth century. The highest average temperatures in the reconstruction are encountered in the mid to late tenth century and the lowest in the late seventeenth century. Decadal mean temperatures seem to have reached or exceeded the 1961-1990 mean temperature level during substantial parts of the Roman Warm Period and the Medieval Warm Period. The temperature of the last two decades, however, is possibly higher than during any previous time in the past two millennia, although this is only seen in the instrumental temperature data and not in the multi-proxy reconstruction itself.


The proxy reconstruction itself does not show such an unprecedented warming but we must consider that only a few records used in the reconstruction extend into the 1990s. Nevertheless, a very cautious interpretation of the level of warmth since AD 1990 compared to that of the peak warming during the Roman Warm Period and the Medieval Warm Period is strongly suggested.


The amplitude of the temperature variability on multi-decadal to centennial time-scales reconstructed here should presumably be considered to be the minimum of the true variability on those time-scales.

Ljungqvist, 2010

Direct comparisons of the modern instrumental record to the older proxy reconstructions are not robust because the proxy data are of much lower resolution. The proxy data indicate the “minimum of the true variability on those time-scales.” The instrumental data are depicting something closer to actual variability.

The proxy data lack the high frequency component of the signal.  When the high frequency component of a signal is filtered out, it attenuates the amplitude. This is basic signal theory.

Figure 13. Sine wave with 10-pt smoothing average applied. Note the reduction in amplitude due to filtering and  smoothing. (Wood for Trees) Older is toward the left.

The direct comparison of instrumental data to proxy data becomes even more problematic when the record length is extended beyond 2,000 years.

Figure 14. Holocene Climate Reconstruction, Andy May WUWT. Older is to the left.

The supposedly “four warmest years on record” have occurred only about 300 years after the coldest century of the past 100 centuries.  This could only be described as a “climate crisis” or “climate emergency” by someone who was unversed in the basic scientific principles of Quaternary geology and signal processing.

The longer the record length of the reconstruction, the more important the consistency of the temporal resolution becomes.

“Consistency of the temporal resolution” means that the resolution of the older proxies are consistent with the recent proxies. Temporal resolution is a function of the sampling interval…

We believe the greater source of error in these reconstructions is in the proxy selection. As documented in this series, some of the original 73 proxies are affected by resolution issues that hide significant climatic events and some are affected by local conditions that have no regional or global significance. Others cover short time spans that do not cover the two most important climatic features of the Holocene, the Little Ice Age and the Holocene Climatic Optimum.


We also avoided proxies with long sample intervals (greater than 130 years) because they tend to reduce the resolution of the reconstruction and they dampen (“average out”) important details. The smallest climate cycle is roughly 61 to 64 years, the so-called “stadium wave,” and we want to try and get close to seeing its influence. In this simple reconstruction, we have tried to address these issues.

Andy May WUWT.

For additional reading on resolution, see: Resolution and Hockey Sticks, Part 1.


While geological data is very helpful in studying climate, as the GSL says, interpreting the significance of modern climate change will probably not benefit from geological input. The warming over the 20th century is only about one degree and the warming since 1950, used as a benchmark by the IPCC, is only about 0.7 degrees. Geological timeframes are greater than 1,000 years, as the GSL paper states, and consequential warming and cooling events in the geological record are greater than five degrees. The geological data we have is very low resolution and unlikely to improve. The main problem is that recent warming is insignificant at a geological scale.

As described above, the CO2 data is lower resolution and less accurate than the temperature data. We have seen that comparing temperature proxy data over the past 2,000 years to modern instrumental data is inappropriate and it is even less appropriate to compare geological data to the modern instrumental record. Neither the magnitude of recent warming nor recent CO2 concentration changes are unusual over geological time periods.

Geoscientists have a responsibility to convey the geological context of climate change, rather than claiming that every observation not resolvable in the geological record is unprecedented and grounds for economically destructive government policies.  It should be sufficient to say that anthropogenic CO2 emissions  have probably been the cause of most of the rise from ~280-400 ppm over the past 200 years and that this has a net warming effect on the atmosphere.  Although just about every recent  observation-based estimate indicates that the warming effect is minimal.

While, there is no “climate emergency,” economically viable pathways exist to reduce the carbon intensity of our energy production and restrain the ultimate growth in atmospheric CO2 to ~600 ppm by the end of this century. This would keep us in the Cenozoic “noise level.”

Figure 15a. Marine pCO2 (foram boron δ11B, alkenone δ13C), atmospheric CO2 from plant stomata (green and yellow diamonds with red outlines), Mauna Loa instrumental CO2 (thick red line) and Cenozoic temperature change from benthic foram δ18O (light gray line).

Figure 15b. Legend for Figure 15a.

Rather than setting deadlines for “net-zero emissions” and other unattainable and arbitrary criteria, the focus should be on reducing the carbon intensity of energy production in an economically sustainable manner. The United States, largely through our private sector, has been doing this. U.S. CO2 emissions from electricity generation have fallen to 1980’s levels, mostly due to the replacement of coal-fired with natural gas-fired electricity generation.

Figure 16. Source: U.S. Energy Information Administration, Monthly Energy Review

Geoscientists will play a vital role in this process by continuing to find economically recoverable oil & gas reserves, improving methods of geological carbon capture & storage, leading the way in expanding our access to the vast array of mineral resources required for the expansion of “renewables” (wind & solar), battery and other storage technologies, promoting the safe geological disposal of nuclear waste products and doing all of this in the safest manner, with as little environmental impact as possible.   Economic geoscientists in the oil & gas and minerals sectors are particularly well-positioned to lead the way, due to our experience with project economics.

Energy, economics and environment are inextricably linked. Without affordable, reliable energy, a society cannot have the economic means to protect the environment.  Nothing more strongly correlates to human prosperity and a clean environment than cheap access to energy (May, Climate Catastrophe! Science or Science Fiction?, 2018, p. 7, 18). For a discussion on energy and poverty, see here.

Texas State Geologist and Director of the Bureau of Economic Geology Scott Tinker summed it up very well in this OEd on carbon pricing:

Aug 23, 2019
Carbon Pricing Is Not a Fix for Climate Change

By: Scott Tinker

There is much talk today about carbon pricing to reduce CO2 emissions and address climate change. Unlike many environmental pollutants that have a local or regional impact, carbon dioxide (CO2) is global — there is only one atmosphere. If actions taken to reduce atmospheric emissions in one region result in increased emissions elsewhere, then the one atmosphere suffers.

Some form of carbon pricing — carbon tax, carbon trading, carbon credits — is favored by many politicians, NGOs, academics and even some in industry. But the reality is that a price on carbon will not be imposed by developing and emerging economies because it makes their energy more expensive, and they are too busy trying to build their economies and lift themselves from poverty.

In the developed world, carbon pricing increases the cost of manufacturing and products, which in turn drives manufacturing to developing nations where it is more affordable because of lower labor costs and less stringent environmental regulations and emissions standards. Global emissions rise in the one atmosphere.

Said differently, the good intentions of carbon pricing have an unintended negative impact on climate change. This is not hypothetical. It is happening.

If carbon pricing won’t work, what will? Energy science tells us how to actually lower CO2 emissions into the one atmosphere in the time frame needed. Unfortunately, those who are the most passionate about addressing climate change seem to not like the answers from the energy experts.


So what options does energy science suggest will have a major impact on climate change?

Natural gas and nuclear replacing coal for power generation in major developing nations such as India, China and Vietnam would have a major impact. Carbon capture, utilization and storage; direct carbon capture from the atmosphere; and perhaps nature-based solutions such as increasing the size of forests would help, especially in fossil fuel producing regions such as the U.S., Russia, China and the Middle East.


These scientifically sound and economically underpinned energy solutions present a problem. Many are not favored by people who are the most concerned about climate change. Thus, politicians seeking climate votes continue to passionately promote programs and policies that won’t actually address climate change.

But we have a remarkable opportunity. The right can acknowledge the need to tackle climate change. The left can acknowledge the energy science needed to accomplish real global emissions reductions into the one atmosphere. And developing and emerging nations can continue to climb out of energy poverty.

Unfortunately, this appears to be far from happening. Climate politics seems to trump energy solutions in Europe and the U.S., and the developing world continues to burn coal.

Scott Tinker is the Allday Endowed Chair of Subsurface Geology and director of the Bureau of Economic Geology at The University of Texas at Austin.

UT News

To the extent that climate change is a problem, we can only tackle it, if we pursue economically viable pathways that preserve access to affordable, reliable energy and enable the further expansion of human prosperity. And the private sector is far better at doing this than any government.

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Andy May, now retired, was a petrophysicist for 42 years. He has worked on oil, gas and CO2 fields in the USA, Argentina, Brazil, Indonesia, Thailand, China, UK North Sea, Canada, Mexico, Venezuela and Russia. He specializes in fractured reservoirs, wireline and core image interpretation and capillary pressure analysis, besides conventional log analysis. He is proficient in Terrastation, Geolog and Powerlog software. His full resume can be found on linkedin or here: AndyMay