Guest essay by David Bennett Laing, Asst. Prof.of Geology, Univ. of Maine (retired)
Two different styles of volcanic eruption appear to have been the principal determinants of climate change throughout geologic time.
The very fact that opinions on climate change could have become as polarized as they have, even in scientific circles, suggests we may still have much to learn. Despite the best efforts of many of the world’s brightest minds, and the claims of some that “the science is settled,” climatic enigmas still persist.
For the past nine years, Peter Langdon Ward has been working steadily in retirement from his career as a geophysicist and volcanologist with the US Geological Survey to try to demystify some of these enigmas. Two years ago, I joined my old friend and colleague in his quest. Last month, we published a new theory of global warming that we feel accounts far better for temperature change over the past 100 years and throughout the Phanerozoic Eon than the currently favored greenhouse warming theory.
In view of the extreme difficulty in getting peer-reviewed journals to publish papers that question greenhouse theory, we decided to present our observations in a semi-popular book, “What Really Causes Global Warming? Greenhouse Gases or Ozone Depletion?”. The book is available in hardback, paperback, and ebook versions on amazon.com and on other book-seller sites. The book and the science are explained in detail at WhyClimateChanges.com, where autographed copies of the book are also available.
In brief, we find that major temperature changes throughout Phanerozoic time can be fully explained with two different styles of volcanic eruption: explosive volcanism causing global cooling and effusive volcanism causing global warming. It is well-known that aerosols from explosive volcanoes, such as the 1991 eruption of Pinatubo, reflect and scatter sunlight, causing global cooling. What we found is that all volcanoes emit chlorine and bromine, which are observed to deplete the ozone layer, allowing increased irradiance of Earth by solar UV-B radiation, causing global warming. UV-B is 48 times more energy-rich than Earth’s IR radiation absorbed by carbon dioxide. The following graphic summarizes the processes involved (Note that in Panel 2, CFCs proxy for effusive volcanism, shown in Panel 3. Their global warming effects are similar, as discussed below).
Global Warming and Global Cooling Related to Ozone Depletion
Panel 1: Under conditions normal before 1965, ultraviolet-C (UV-C) warmed the upper atmosphere, UV-B primarily warmed the ozone layer, and UV-A and visible light warmed Earth.
Panel 2: CFCs, when they rise to the level of very cold polar stratospheric clouds (PSCs), release chlorine that depletes ozone, causing more UV-B than usual to reach Earth’s surface, thus cooling the ozone layer and warming Earth.
Panel 3:Effusive volcanoes emit chlorine and bromine, which deplete ozone, leading to global warming.
Panel 4: Explosive volcanoes similarly deplete ozone, but also eject megatons of water and sulfur dioxide into the lower stratosphere, forming globe-encircling aerosols whose molecules soon grow large enough to reflect and scatter sunlight, causing net global cooling.
In the case of explosive volcanoes, the aerosol cooling effect overwhelms the warming effect from ozone depletion, but since effusive volcanoes don’t eject substantial amounts of gases into the stratosphere, warming prevails. Effusive eruptions are also much longer-lasting and can be extremely voluminous. Massive effusive eruptions in Iceland occurred precisely at the time when Earth warmed out of the last ice age (see Preboreal Warming in the following illustration).
GISP2 Volcanic Sulfate From 9 to 16 Ka
Periods of greatest warming coming out of the last ice age are contemporaneous with times of sulfate anomalies in numerous contiguous layers (note blue circles containing the number of layers). Red bars show volcanic sulfate deposited in individual layers of ice in the GISP2 borehole. The purple line shows the δ18O proxy for temperature adjusted for gas age. The Preboreal warming is contemporaneous with the largest sulfate deposit observed. The Bølling warming is contemporaneous with the largest number of contiguous layers containing volcanic sulfate. Dryas periods of increased glaciation are contemporaneous with little or no volcanism.
Less massive effusive eruptions coincided with every one of the numerous, enigmatic Dansgaard-Oeschger warming events during the ice age (see numbers 0 to 1 on the right side of the above illustration and numbers 2-12 on the right side of the next illustration).
GISP2 Volcanic Sulfate from 22 to 46 Ka
Dansgaard-Oeschger sudden warming events (numbers on the right side) all correspond to times of continuous volcanism. Red bars show the amount of sulfate in individual layers of ice in the GISP2 borehole. The purple line shows the δ18O proxy for temperature adjusted for gas age. Numbers in blue circles show the number of contiguous layers containing sulfate deposits at the time plotted. H2 to H5 are Heinrich events when large numbers of icebergs suddenly appeared in the northern Atlantic Ocean.
Much more massive effusive eruptions accompanied extreme warming events during the Paleocene-Eocene Thermal Maximum, the End-Permian Extinction, the Cretaceous-Paleocene boundary, and many other times of major rapid temperature change throughout the Phanerozoic.
We view the dramatic warming event of the late 20th century as anthropogenic, but not due to carbon dioxide. The event coincided with the release of chlorofluorocarbon (CFC) gases to the atmosphere, which are broken down by UV solar radiation in polar stratospheric clouds in late winter to release chlorine, thus mimicking the ozone depleting and global warming effects of effusive volcanism. The Montreal Protocol ended CFC production and thereby ended global warming, thus explaining the enigmatic “global warming hiatus” that prevailed from 1998 through 2013 (see following illustration). No other convincing explanation for the “hiatus” has been proposed or generally agreed upon (See ozonedepletiontheory.info/gg-warming-hiatus.html). A warming effect from the massive effusive eruption of Iceland’s Bárðarbunga volcano in late 2014 and early 2015, the largest since 1783, will likely make 2015 the warmest year on record.
Distinctly Different Trends
Trends in temperature (red bars), (NOAA), tropospheric chlorine (green line) (Solomon, 1999), and ozone depletion (black line) (Staehelin et al., 1998) (WOUDC, 2014) over the past 70 years are distinctly different from trends in concentrations of greenhouse gases such as carbon dioxide (blue dashed line) (NOAA, 2014). Ocean heat content (Levitus et al., 2012) inceased with increasing ozone depletion and continues to increase while ozone depletion remains greater than levels prior to 1970. Carbon dioxide levels appear related to ocean heat content through the solubility of CO2 as a function of water temperature.
Global temperature has plateaued rather than fallen, ice masses still continue to melt globally, and ocean heat content continues to rise, because chlorine remains in the stratosphere and continues to destroy ozone catalytically. This will continue for several decades, and due to heat storage in the oceanic thermal reservoir, it is likely that eventual lowering of global temperature will not occur unless there is a series of explosive volcanic eruptions. Until (and if) these occur, it seems equally likely that we will simply have to adapt to a world that is about one Fahrenheit degree warmer than it was in the mid-20th century, but at least we shouldn’t have to worry about “climate Armageddon” due to further warming, as long as we remain vigilant against further releases of existing CFC stockpiles and other chemicals that deplete the ozone layer.
In the book, we also discuss apparent problems with greenhouse warming in considerable detail on both theoretical and observational grounds. An exhaustive literature search revealed that only one actual experiment has ever been performed to test greenhouse warming theory empirically. It was done by Knut Ångström in 1900, and he concluded that any warming effect from increasing atmospheric CO2 concentration was negligible. Accordingly, Peter Ward has issued a $10,000 challenge to anyone who can demonstrate by experiment that greenhouse gases are more effective at warming Earth than ozone depletion. To date, he has had no takers (see WhyClimateChanges.com/Challenge/).
Meanwhile, we sought to assess the relative response of global temperature to mean monthly variations in ozone depletion and in atmospheric carbon dioxide over the same time interval in the northern hemisphere and found, in the following graph, a close correlation with temperature anomalies in the case of ozone depletion, but we also found that the carbon dioxide peak lags the temperature anomaly variation curve by two months, indicating little possibility of a significant influence of carbon dioxide variation on global temperature. A possible, but slight, influence is evident in the small upward deflection of the temperature anomaly curve in June.
The Relationship of Ozone Depletion to Temperature
Mean monthly values of northern hemisphere temperature anomalies (red) and ozone depletion anomalies (green) for the period 1975 to 1998 and of atmospheric carbon dioxide concentrations at Mauna Loa, Hawaii, (blue) since 1961, normalized as percentages. Carbon dioxide values, peaking in May, show only a minor effect on temperature anomalies, but coincidence of the peaks in ozone depletion and temperature in March suggest a possible causal relationship.
We would welcome your thoughts on the foregoing, especially if they follow a careful reading of the book or the website WhyClimateChanges.com. It is clearly rather important for all living things on Earth that we get this right.
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