The Cretaceous-Tertiary (K-T boundary) extinction ~66 million years ago is perhaps the most famous extinction event in Earth’s history. It featured a massive asteroid impact which led to the extinction of an estimated 76% of all fossilizable species, and marked the end of the ~170 million+ year reign of the dinosaurs (Pope 1998). Initially regarded as a radical proposition, this is the Alvarez hypothesis, after Luis Alvarez, the lead scientist of the team that discovered the first of multiple lines of smoking gun evidence for the impact of an asteroid ~10 km across under Chicxulub on the coast of the Yucatan Peninsula right around the time of the K-T boundary (Alvarez 1979, Smit 1981, Smit 1980, Bohor 1984, Bohor 1987, Bourgeois 1988 & Hildebrand 1991). [caption id="attachment_574" align="alignnone" width="1106"] An artist's interpretation of a hypothetical asteroid impact. Sources: Here and here.[/caption] (more…)
The Climatological effects of Volcanic Eruptions: The End Permian Extinction, the Toba Super-Volcano, and the Volcanic Explosivity Index
Volcanic eruptions can have both short-term and long term effects on Earth’s climate. In the short term, they release large quantities of ash and sulfur dioxide (SO2) into the stratosphere, which quickly gets blown all around the globe. The sulfur dioxide subsequently reacts to form droplets of sulfuric acid (H2SO4), which then condense into fine aerosols. These aerosols reflect sunlight back into space, thereby cooling the troposphere below. These effects can last for 1 – 3 years. In the long term, they can increase atmospheric concentrations of CO2 which can lead to global warming via the greenhouse effect over long periods of heightened volcanic activity For years it was thought that the volcanic ash was primarily responsible for cooling effects by blocking sunlight. However, it was later discovered that its effects are short-lived, and that the total amount of sulfur-rich gases released in an eruption was a more important determinant of an eruption’s global cooling effects. (more…)
In parts I and II, we looked at axial obliquity, axial precession, apsidal precession, orbital eccentricity and orbital inclination, and how their cycles can affect the climate. In this installment of the series, we’ll look briefly at how these cycles look when combined, and then discuss one of the most prominent unsolved problems raised by the theory: The 100,000 Year problem. [caption id="attachment_550" align="alignnone" width="1053"] Putting it all together[/caption] Notice that the peaks and valleys in temperature are roughly periodic, and that with the possible exception of apsidal precession, there are slight fluctuations in the periods and amplitudes of these orbital cycles. One reason for this has to do with fluctuations in solar output, but another likely reason has to do with the very causes of these orbital cycles themselves: namely, these cycles are driven by mutual gravitational perturbations between the Earth, Sun, Moon, and to a lesser extent, Jupiter and the other planets in the solar system (Borisenkov 1985, Spiegel 2010) . (more…)
Milankovitch Cycles and Climate: Part II – Orbital Eccentricity, Apsidal Precession and Orbital Inclination
In part I, we looked at some of the ways in which changes in axial obliquity and precession can affect the climate. In this article, we’ll look at orbital eccentricity, apsidal precession and orbital inclination, and some of their climatological consequences.
Orbital Eccentricity:This refers how elliptical earth's orbital path is. The greater the eccentricity of a planet’s orbital path, the less circle-like and more elliptical (oval-like) it is. An ellipse has an eccentricity greater than or equal to zero, but less than one. An eccentricity value of e = 0 corresponds to a perfect circle, whereas e = 1 corresponds to a parabola, and e > 1 corresponds to a hyperbola. At higher eccentricity values (albeit less than one), there is a greater discrepancy between a planet’s perihelion and aphelion: a planet’s nearest and furthest points from the Sun during its orbit. (more…)
The theory of Milankovitch cycles is named after Serbian astronomer and geophysicist, Milutin Milanković, who in the 1920s postulated three cyclical movement patterns related to Earth’s orbit and rotation and their resultant effects on the Earth’s climate. These cycles include axial tilt (obliquity), elliptical eccentricity, and axial precession. In aggregate, these cycles contribute to profound long term changes in earth's climate via orbital forcing.
Axial Obliquity:The Earth’s rotational axis is always tilted slightly; currently, its axis is about 23.4 degrees from the vertical. Alternatively, you could say that its equatorial plane is tilted about 23.4 degrees relative to its orbital plane. This tilt is responsible for Earth’s seasons. During the Northern Hemisphere (NH) summer, Earth is further away from the Sun than it is during the NH winter due to its slightly elliptical orbit, yet it receives more sunlight because it’s tilted towards the Sun. During this same time period, the Southern Hemisphere (SH) is tilted away from the Sun, which is why NH summer coincides with SH Winter and vice versa. Contrastingly, during the NH winter, the Earth is closer to the Sun, yet receives less sunlight because it’s tilted away from it. During that same period, the SH is tilted towards the Sun, and is thus experiencing summer. (more…)
How Continental Positioning affects Climate: Part II – Possible Snowball Earth Triggering Mechanisms + Regional Effects of Mountain Ranges
In Part 1 of this article, I outlined some of the variables which can affect Earth’s climate, and gave a brief overview of plate tectonics, and how changes in continental positioning can lead to climate change through albedo feedback and via the alteration of ocean circulation and heat distribution patterns. In doing so, I used the example of the Rodinia Supercontinent and the Snowball Earth hypothesis of the Neoproterozoic era in order to relate the concepts to events in Earth’s prehistory. For the sake of completeness, I want to finish up that example by briefly going over a few proposed triggering mechanisms that could have made a runaway albedo feedback loop possible in the Cryogenian period. After that, I want to go over the ways in which the presence of mountain ranges can affect local and regional climate. (more…)
IntroductionExtremely popular on Facebook and other social media is the idea that an inclusive cure for cancer has been found but is being suppressed. The reason given for the suppression is universally the same. The premise is that companies stand to make more money by treating a chronic disease than from curing it. It's a simple idea with a simple justification, but the implications are staggeringly complicated. If we consider what the world would have to look like for this conspiracy hypothesis to be true, we immediately see numerous holes and contradictions. It is the nature of human thinking to become upset with behavior we see as unfair. If we are told that the rich and powerful are allowing human suffering to continue for the sake of their wallets, the inclination is to be outraged. Unfortunately, it's also human nature to justify such feelings once we have them. This causes many to focus on the outrage and forget to think things through and, when presented with the various logical snags inherent to this trope, to rationalize with whatever justifications and compartmental logic is necessary to maintain the outrage. It's a basic phenomenon we see with virtually all forms of pseudoscience: Start with a conclusion and do whatever it takes to support it. (more…)
How Continental Positioning affects Climate: Part I – Plate Tectonics, Albedo, and the SnowBall Earth Hypothesis
About 700 – 800 MYA, during the Neoproterozoic era (in the late Precambrian), it has been proposed that the Supercontinent, Rodinia occupied an equatorial position on the Earth. Perhaps counter-intuitively, this tropical arrangement of the continents may have set the stage for a massive glaciation known as “Snowball Earth” during the Cryogenian period, despite equatorial regions receiving the most sunlight due to the orientation of the Earth with respect to the sun. Indeed, the fact that equatorial regions receive the most sunlight is part of the reason why tropical rainforest biomes exist where they do. So how could this have happened? Why would an equatorial continental arrangement render such a glaciation more likely? More on the Snowball Earth hypothesis in a moment: More generally however, what factors are capable of inducing changes in the climate? There are several of them. First of all though, what do we mean by climate, and how does it differ from weather? (more…)
July 29, 2016 Earlier today, the president signed S. 764 into law: a Federal level law that stipulates that the Secretary of Agriculture is to decide on a mandatory nation wide standard by which all foods derived from sources which have been modified by in vitro recombinant DNA techniques will be labeled. Biotechnology advocates have largely opposed any Bill which unjustifiably singles out one particular breeding method for mandatory labeling (either Federally or at the State level). Although this Bill was intended to be a compromise, the new Bill will not satisfy GE food opponents, simply because it won't be conspicuous enough for them to easily construe them as warning labels. (more…)
A popular theme among movements which oppose certain aspects of modern science and technology is the notion that people were healthier in the "good old days," back before the introduction of many modern scientific advancements. The idea is that there was once a time when there were no artificial chemicals, no fluoridated water, no genetically engineered crops, no vaccines or other modern medical science, all food was organic, and everyone led longer, happier, and healthier lives. There are many variations of this particular worldview aesthetic, and different ones have different ideas as to what the biggest alleged culprits are. Some hypothesize various conspiracies involving governments and/or corporations, whereas others may simply view new technology as "unnatural" (ergo undesirable) in their estimation. The common thread, however, is the belief that people are worse off now than in centuries past, and that one or more forms of human intervention are at fault. (more…)