What are, in fact, the grounds for concern about global warming?
This is an answer to the Geological Society of London position statement on “Climate Change: evidence from the geological record,” published in November 2010, and the addendum published in December 2013. They can be found at:
This article was first written as a long comment contributing to a discussion over the Geological Society statement at the energy and climate blog Energy matters. Scientists of the Geological Society that authored the statements participated in the discussion to defend their views.
Climate change is a reality attested by past records. Concerns about preparing and adapting for climate change are real. However, the idea that we can prevent climate change from happening is dangerous and might be anti-adaptive. Certain energy policies that might have no effect on climate change could make us less able to adapt.
Physics shows that adding carbon dioxide leads to warming under laboratory conditions. It is generally assumed that a doubling of CO2 should produce a direct forcing of 3.7 W/m2 , that translates to a warming of 1°C (by differentiating the Stefan-Boltzmann equation) to 1.2°C (by models taking into account latitude and season). But that is a maximum value valid only if total energy outflow is the same as radiative outflow. As there is also conduction, convection, and evaporation, the final warming without feedbacks is probably less. Then we have the problem of feedbacks that we don’t know and cannot properly measure. For some of the feedbacks, like cloud cover we don’t even know the sign of their contribution. And they are huge, a 1% change in albedo has a radiative effect of 3.4 W/m2 , almost equivalent to a full doubling of CO2.
So, in essence we don’t know how much the Earth has warmed in response to the increase in CO2 for the past 67 years, and how much for other causes. That is the reason why, after expending billions on the question of climate sensitivity to CO2, we have not been able to reduce the range of possible values, 1.5°C to 4.5° C, a factor of 3, in the 39 years that have passed since the Charney Report was published . A clear scientific failure.
Climate is a very complex system and adding CO2 to the atmosphere in great amounts since 1950 led first to cooling, then to warming, and lately to a stilling of temperatures until the 2014-16 El Niño. A different explanation is required for every period when the expected warming doesn’t take place, an approach that leaves Occam’s beard unshaved.
A very big assumption underlies the 2010 Statement and 2013 Addendum by the Geological Society of London. And in science assumptions are very dangerous, because they are not subjected to the scientific method. The big ugly assumption in these reports is that past changes in CO2 were responsible for planetary temperature changes. At most, what we can extract from past data is a correlation between both, and even that correlation is tentative, as the quality and nature of the data makes any conclusions in the statement and addendum questionable.
We do know that temperature affects CO2 levels, as an increase in temperature leads to a release of CO2 by the oceans, due to the gas solubility dependence on temperature. So, the causality is confusing. Is the CO2 mainly the result of temperature changes or is the temperature mainly the result of CO2 changes? We don’t know. The proposed positive feedback where each one enhances the other must be very limited, if they were significant, we wouldn’t be here. The extraordinary claims by the authors of the Geological Society statements are not accompanied by extraordinary evidence. Quite the contrary.
We believe that over hundreds of millions of years CO2 levels have been decreasing dramatically in the Earth’s atmosphere. We also believe that over that time Earth’s temperature has been kept within a very narrow range compatible with life. So, a clear relationship between both does not exist. Some evidence suggests ice ages are compatible with high CO2 values.
“The last (and thus best known) Late Ordovician Saharan ice sheet formed during a time of high (16 × the modern value) atmospheric CO2. The ice sheet may have been comparable in size to the last North American Laurentide Ice Sheet (∼36×106 km3) and expanded eastward from North Africa onto the Arabian platform.” .
Using the Paleocene-Eocene Thermal Maximum (PETM) as an analog is misleading. We don’t know what caused it, although hypotheses have been proposed. However, we must consider that the PETM took place during a warm (hothouse) period of the planet, while currently we are in a cold (icehouse) period, as attested by the massive ice sheets over Antarctica and Greenland. The long-term real danger for humankind is a return to the average glacial conditions of the Late Pleistocene, as our interglacial is already long in the tooth. The report final paragraph: “the massive injection of carbon into the atmosphere 55 million years ago that led to the major PETM warming event,” shows the authors’ overreaching assumption. They simply lack the evidence to say that CO2 caused the PETM, or even to say how much of the warming was caused by the increase in CO2.
The authors also talk about more recent abrupt shifts in climate during the last glacial stage (100,000 – 11,500 years ago), known as Dansgaard-Oeschger events. This is the best example we have of abrupt climate change (it was the basis of that concept), but the report should mention that although the temperature shifts were accompanied by changes in methane, CO2 records in most cases don’t show them . The best example we have of abrupt climate change, not driven by orbital changes, has nothing to do with CO2.
So, the first question we should ask ourselves is how unusual is present global warming. This is a difficult question to answer, as we now measure temperatures with a resolution we cannot achieve with past temperatures. Last 2015-16 El Niño caused a temperature increase of 0.4°C over the course of two years that is now receding. We are not able to see these short-term fluctuations in past temperatures from proxies that, at best, have decadal resolution and represent local conditions. And most proxies cannot be trusted to faithfully reproduce recent changes as they usually lack enough resolution. So, we can’t compare recent temperatures with past temperatures. Biology offers us an answer. The tree-line represents the limit where climatic conditions allow the growth of new trees. Every year new tree seedlings attempt to establish themselves further up the mountain and generally fail. 52% of studies show the tree-line has been going up over the past century, and only 1% show a tree-line receding, indicating that mountain trees are generally responding to global warming and increased CO2 by raising the tree-line . However, many studies show that at most places the present tree-line is still 100-250 meters below Holocene Climatic Optimum tree-line levels . Figure 1 illustrates this in the Swiss Alps.
Figure 1. The approximate Holocene timberline and tree-line elevation (m above sea level) in the Swiss central Alps based on radiocarbon-dated macrofossil and pollen sequences .
We must take into account that present elevated CO2 levels are a huge bonus to tree growth, so if placed at similar climatic conditions present trees would have a significant, but unquantifiable, advantage over Early Holocene trees. So, the first answer to the question of how unusual is present global warming is that it is not unusual enough to have returned us to Holocene Climatic Optimum conditions. Therefore, present global warming is within Holocene variability. Reasoner and Tinner  quantify the summer temperature difference in the Alps between now and the Holocene Optimum as:
“Assuming constant lapse rates of 0.7° C / 100 m, it is possible to estimate the range of Holocene temperature oscillations in the Alps to 0.8–1.2° C between 10,500 and 4,000 cal. Y[r.] BP, when average (summer) temperatures were about 0.8–1.2° C higher than today.”
Without question we have undone most or all the cooling that took place between the Medieval Climatic Anomaly at ~1100 AD and the bottom of the Little Ice Age at ~1650 AD. Is this countertrend, multi-century, global warming we are experiencing worrisome? By objective reasons, the Little Ice Age was very worrisome. Glaciers advanced to their maximum Holocene extent, destroying farms and villages. Crops failed repeatedly causing famines like the one that killed one third of Finland’s population in 1696. Population in Iceland declined from 77,500 in 1095 to 38,000 in 1780 . Conditions have improved greatly since the Little Ice Age, coinciding with Global Warming.
It is only since 1950 that anthropogenic forcing (human GHG emissions) has really taken off. Professor Phil Jones, former director of the Climatic Research Unit at the University of East Anglia, admitted in an interview on the BBC in 2010 , that “for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different.”
Table 1. Data provided by Prof. Phil Jones to the BBC showing that different warming periods are significant but not statistically different.
So, to explain why the warming rate has not accelerated despite the huge addition of CO2, we are told that prior to 1950 global warming was mostly natural, and after 1950 is human-made. A convenient explanation for which there is no evidence, just assumptions on top of assumptions.
And it is not only temperature, but rising sea levels that show little to no acceleration , in sharp contrast to predictions. Reducing our emissions will not significantly affect sea level rate of increase, because increasing them didn’t.
Figure 2. The rise in sea level  predates IPCC calculated anthropogenic forcing  and shows no clear response to it.
The CO2 hypothesis of global warming has been consistently wrong in its predictions. In science, if your hypothesis predictions fail, there is something wrong. In 1990 the IPCC predicted a warming rate of 0.3° C/decade  for the next century, nearly double the observed rate for the past 27 years. It also predicted a 1° C warming by 2025 (0.5° C observed). In 2001 the IPCC predicted that milder winter temperatures would decrease heavy snowstorms . In 2007 the IPCC claimed that by 2020, between 75 and 250 million of people would be exposed to increased water stress due to climate change. In some countries, yields from rain-fed agriculture were to be reduced by up to 50 % . It later had to withdraw that prediction. Arctic sea ice predictions have also been consistently wrong with many polar scientists predicting the demise of summer Arctic sea ice by dates as early as 2008  to as late as 2030 . The reality is that in September 2017 there was more sea ice in the Arctic than 10 years earlier. And we could continue with many other predicted climate horrors that have failed to pass, regarding polar bears, sinking nations, food shortages, climate refugees, and extreme weather events, too long to detail , but that show a shameless promotion of alarmism based on unrealistic worst-case scenarios.
Most of these predictions arise from models that have not been properly validated and do not adequately represent the climate response to increased CO2. The current crop of models used by IPCC, CMIP5, shows a worrisome deviation from observations just a few years after being initialized in 2006 (figure 2).
Figure 3. Model CMIP5 temperature anomaly under the RCP 4.5 scenario, compared to observed HadCRUT4 temperature anomaly, both relative to 1961-1990 baseline.
Despite the recent El Niño, temperatures do not show a significant deviation from a linear increase since 1950, while models predict a much higher rate of warming.
Geologists should be aware that some emission scenarios being promoted as business as usual are completely unrealistic. RCP 8.5 contemplates a shift to a mainly coal economy with total disregard for coal reserves. How can unlimited coal growth be business as usual? Fossil fuels are finite resources and their abundance must be taken into account. Climate alarmism is being promoted as if fossil fuels were unlimited. The burning of 100 % of oil, gas, and coal proved reserves (BP Factbook of World Energy) would increase atmospheric CO2 levels to 620 ppm . By using a supply-side analysis, the value reached is equivalent, 610 ppm maximum this century . RCP 8.5 based predictions require 950 ppm by 2100. The alarmist projections clearly lack any rational basis and are agenda-driven. The reality is that we have had no problem adapting to a global warming that has been taking place since at least 1860, and there is no evidence that we will have problems adapting to future global warming until it ends.
By writing the 2010 statement and 2013 addendum, the authors are just setting the Geological Society of London in line with the politically promoted consensus on global warming. It is not different from what many other scientific societies have done recently, but it is a breach of the scientific principles that should guide the Society and an attack on the plurality of views that characterize healthy scientific debate over a hypothesis that so far is short on evidence and long on claims.
This post was lightly edited for readability by Andy May.
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