Creationism in Crisis - Why Earth is Fine Tuned for Extinction

An arid and uninhabitable planet awaits us - in 250 million years.

September: Nature Geoscience extreme heat | News and features | University of Bristol

Creationists like to imagine that Earth is fine-tuned for life. This belief depends on the parochial ignorance of the creationist of course, because they will be oblivious of the fact that, cozy though their small bit of the planet might be, most of it is uninhabitable by humans without specialist equipment, and even cloths and houses are required in the temperate areas. Human life would be impossible without modern technology in the oceans, deserts, arctic waste, the tops of high mountains or just a few thousand feet above the surface of the planet (this is why modern aircraft that fly at 30-60,000 feet need to be pressurised).

But a planet that is fine-tuned for life would also have an infinite life-span, not a time-limited one where the life-time is limited by entirely natural processes, such as plate tectonics and the solar cycle. In fact, the life span of Earth is a mere blink on a cosmic time-scale that is measured by the life of suns.

Long before the sun becomes a red giant and swallows up the inner planets at the end of its life, shortly before becoming a super nova and blowing away the outer planets, Earth's continents will have coalesced into another single super-continent, reminiscent of Pangea, and the climate will have made life untenable for most species of mammal, according to researcher at Bristol University.

The resulting increase in volcanic rifting and out-gassing, combined with 'continentality' and an increase in solar energy output, will result in a 'wet-bulb' temperature of >35^oC and a 'dry bulb' temperature of >40^oC - temperatures at which mammalian thermoregulation fails, leading to death in about 6 hours.

The team's findings are published open access in Nature Geoscience and explained in a Bristol University press release:

A new study shows unprecedented heat is likely to lead to the next mass extinction since the dinosaurs died out, eliminating nearly all mammals in some 250 million years time.

The research, published today [25 September 2023] in Nature Geoscience and led by the University of Bristol, presents the first-ever supercomputer climate models of the distant future and demonstrates how climate extremes will dramatically intensify when the world’s continents eventually merge to form one hot, dry and largely uninhabitable supercontinent.

Image shows the warmest month average temperature (degrees Celsius) for Earth and the projected supercontinent (Pangea Ultima) in 250 million years, when it would be difficult for almost any mammals to survive.

Image: University of Bristol

The findings project how these high temperatures are set to further increase, as the sun becomes brighter, emitting more energy and warming the Earth. Tectonic processes, occurring in the Earth’s crust and resulting in supercontinent formation would also lead to more frequent volcanic eruptions which produce huge releases of carbon dioxide into the atmosphere, further warming the planet.

Mammals, including humans, have survived historically thanks to their ability to adjust to weather extremes, especially through adaptations such as fur and hibernating in the cold, as well as short spells of warm weather hibernation.

While mammals have evolved to lower their cold temperature survivable limit, their upper temperature tolerance has generally remained constant. This makes exposure to prolonged excessive heat much harder to overcome and the climate simulations, if realised, would ultimately prove unsurvivable.

Lead author Dr Alexander Farnsworth, Senior Research Associate at the University of Bristol, said: “The newly-emerged supercontinent would effectively create a triple whammy, comprising the continentality effect, hotter sun and more CO₂ in the atmosphere, of increasing heat for much of the planet. The result is a mostly hostile environment devoid of food and water sources for mammals.

“Widespread temperatures of between 40 to 50 degrees Celsius, and even greater daily extremes, compounded by high levels of humidity would ultimately seal our fate. Humans – along with many other species – would expire due to their inability to shed this heat through sweat, cooling their bodies.”

Although human-induced climate change and global warming is likely to be a growing cause of heat stress and mortality in some regions, research suggests the planet should largely remain habitable until this seismic landmass change in the deep future. But when the supercontinent forms, findings indicate only somewhere between 8% and 16% of land would be habitable for mammals.

Co-author Dr Eunice Lo, Research Fellow in Climate Change and Health at the University of Bristol said: “It is vitally important not to lose sight of our current Climate Crisis, which is a result of human emissions of greenhouse gases. While we are predicting an uninhabitable planet in 250 million years, today we are already experiencing extreme heat that is detrimental to human health. This is why it is crucial to reach net-zero emissions as soon as possible.”

The international team of scientists applied climate models, simulating temperature, wind, rain, and humidity trends for the next supercontinent – called Pangea Ultima – expected to form in the next 250 million years. To estimate the future level of CO₂ the team used models of tectonic plate movement, ocean chemistry and biology to map out inputs and outputs of CO₂.

The future CO₂ calculations were led by Professor Benjamin Mills at the University of Leeds, who said: “We think CO₂ could rise from around 400 parts per million (ppm) today to more than 600 ppm many millions of years in the future. Of course, this assumes that humans will stop burning fossil fuels, otherwise we will see those numbers much, much sooner.”

Dr Farnsworth, also a visiting Professor at the Tibetan Plateau Earth System, Environment and Resources (TPESER), at the Chinese Academy of Sciences Institute of Tibetan Plateau Research said: “The outlook in the distant future appears very bleak. Carbon dioxide levels could be double current levels. With the Sun also anticipated to emit about 2.5% more radiation and the supercontinent being located primarily in the hot, humid tropics, much of the planet could be facing temperatures of between 40 to 70 ^oC.

“This work also highlights that a world within the so-called ‘habitable zone’ of a solar system may not be the most hospitable for humans depending on whether the continents are dispersed, as we have today, or in one large supercontinent.”

In addition, the research illustrates the importance of tectonics and continental layouts when conducting research into planets beyond our solar system, called exoplanets. Although the Earth will still be within the habitable zone in 250 million years’ time, for mammals the formation of a supercontinent with elevated carbon dioxide will make most of the world uninhabitable. The findings suggest the landmass layout for a distant world could be a key factor when determining how liveable it is for humans.

Abstract

Mammals have dominated Earth for approximately 55 Myr thanks to their adaptations and resilience to warming and cooling during the Cenozoic. All life will eventually perish in a runaway greenhouse once absorbed solar radiation exceeds the emission of thermal radiation in several billions of years. However, conditions rendering the Earth naturally inhospitable to mammals may develop sooner because of long-term processes linked to plate tectonics (short-term perturbations are not considered here). In ~250 Myr, all continents will converge to form Earth’s next supercontinent, Pangea Ultima. A natural consequence of the creation and decay of Pangea Ultima will be extremes in P_CO2 due to changes in volcanic rifting and outgassing. Here we show that increased P_CO2, solar energy (F_☉; approximately +2.5% W m−2 greater than today) and continentality (larger range in temperatures away from the ocean) lead to increasing warming hostile to mammalian life. We assess their impact on mammalian physiological limits (dry bulb, wet bulb and Humidex heat stress indicators) as well as a planetary habitability index. Given mammals’ continued survival, predicted background P_CO2 levels of 410–816 ppm combined with increased F_☉ will probably lead to a climate tipping point and their mass extinction. The results also highlight how global landmass configuration, P_CO2 and F_☉ play a critical role in planetary habitability. The Earth may become inhospitable to land mammals in about 250 Myr owing to climate warming and drying associated with the assembly of the next supercontinent, Pangaea-Ultima, according to combined tectonic, climate and mammal habitability modelling.

Main

Anthropogenic emissions of greenhouse gasses are pushing Earth’s climate towards a warmer state not seen for millions of years¹, with repercussions for ecosystem resilience. Yet, it is unknown whether or when Earth’s dominant terrestrial animal species, mammals, will ever reach a climatic tipping point whereby their ascendancy is threatened. Sherwood and Huber² have suggested that current global warming will raise temperatures above terrestrial mammalian physiological limits, rendering some parts of the world uninhabitable. Mid-to-late century International Panel on Climate Change Sixth Assessment Report^3,4 high-emission scenarios suggest that some physiological thermal thresholds will be exceeded in small, mainly coastal, regions of Africa, Australia, Europe and South Asia^5,6. Even with the combustion of all available fossil fuels (+12 °C by 2300), most of the land surface would still be habitable². What is certain is that the Earth will leave the Sun’s habitable zone in several billion years⁷ when solar luminosity (F_☉; W m⁻²) reaches a point where radiative heating and moist processes initiate a runaway greenhouse. However, conditions that threaten mammalian predominance on Earth may naturally arise sooner.

[…]

Fig. 1: PU temperature and habitability.

a, Mammalian species diversity without the influence of humans (reproduced from ref. 41). b, Habitable regions (green area) in the pre-industrial simulation. c–h, Cold month mean temperature (CMMT; ^oC) (c,f), warm month mean temperature (WMMT; ^oC) (d,g) and habitable regions (green area) (e,h) under two end members of our sensitivity analysis: low-P_CO2 conditions (280 ppm) PU planetary configuration (+250 Ma) (c–e) and high-P_CO2 conditions (1,120 ppm) PU configuration (+250 Ma (f–h), with global land surface temperature (GLST) (grid-weighted) indicated.

Extended Data Fig. 1: Mean annual dry-bulb 1.5 m air temperature for each experiment.

Mean annual 1.5 m air temperature C) for each experiment at present day (column 1), +2.5% present day solar luminosity (column 2) and +2.5% present day solar luminosity with a doubling of the topography (column 3) at 0 pm, 70 ppm, 140 ppm, 560 ppm and 1120 ppm CO2.

Extended Data Fig. 2: Mean annual wet-bulb 1.5 m air temperature for each experiment.

Warmest month mean 1.5 m wet-bulb temperature (^oC) for each experiment at present day (column 1), +2.5% present day solar luminosity (column 2) and +2.5% present day solar luminosity with a doubling of the topography (column 3) at 0 pm, 70 ppm, 140 ppm, 560 ppm and 1120 ppm CO2.

Extended Data Fig. 3: Humidex for each experiment.

Warmest month HUMIDEX for each experiment at present day (column 1), +2.5% present day solar luminosity (column 2) and +2.5% present day solar luminosity with a doubling of the topography (column 3) at 0 pm, 70 pm, 140 pm, 560 pm and 1120 ppm CO2.

Extended Data Fig. 4: Amount of habitable land for each experiment.

Habitability for each experiment at present day (column 1), +2.5% present day solar luminosity (column 2) and +2.5% present day solar luminosity with a doubling of the topography (column 3) at 0 pm, 70 pm, 140 pm, 560 pm and 1120 pm CO2. Green = habitable area. Beige = fails heat stress metrics. Blues = fails cold stress metrics (see Methods). Red = Fails Heat stress metrics and is a (warm) desert.

Extended Data Fig. 7: Mean annual precipitation for each experiment.

Mean annual precipitation (mm/day) for each experiment at present day (column 1), +2.5% present day solar luminosity (column 2) and +2.5% present day solar luminosity with a doubling of the topography (column 3) at 0 ppm, 70 ppm, 140 ppm, 560 pm and 1120 ppm CO2.

Farnsworth, A., Lo, Y.T.E., Valdes, P.J. et al.
Climate extremes likely to drive land mammal extinction during next supercontinent assembly. Nat. Geosci. 16, 901–908 (2023). https://doi.org/10.1038/s41561-023-01259-3

Copyright: © 2023 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

Given enough time, it is possible, providing the change is slow enough, that a new class of mammals able to regulate their body temperature in a much hotter environment could evolve, but the changes will need to be profound, because mammals have evolved to live on parts of the planet where the temperature stays within limits and the heat generated by their metabolism can be dissipated or conserved as necessary. Many mammalian metabolic processes depend on a narrow range of temperatures to work optimally.

In high ambient temperatures, the problem is not so much the difficulty in dissipating excess heat as not being able to prevent absorbing more than is dissipated. What would be needed would be some sort of refrigeration system and the possibility of evolving one is probably very low.

Tell me about mammalian thermoregulation. Is there an upper limit at which this fails? Mammalian thermoregulation is the process by which mammals maintain their body temperature within a relatively narrow range to ensure optimal physiological and biochemical functioning. The average body temperature for most mammals is around 98.6 degrees Fahrenheit (37 degrees Celsius). Thermoregulation is essential because enzymes and other biochemical processes within the body are temperature-sensitive, and even slight deviations from the optimal temperature can impair these processes.

Mammals have evolved various mechanisms to regulate their body temperature in response to environmental changes. These mechanisms include:

1. Sweating: Many mammals, including humans, have sweat glands that release moisture onto the skin's surface. When this sweat evaporates, it cools the body, helping to reduce body temperature.
2. Vasoconstriction and Vasodilation: Mammals can control blood flow to the skin by constricting (narrowing) or dilating (expanding) blood vessels. Vasoconstriction reduces heat loss, while vasodilation increases it.
3. Shivering: When it's cold, mammals can generate heat through involuntary muscle contractions, such as shivering, to warm up.
4. Piloerection: In some mammals, particularly those with fur or hair, piloerection refers to the raising of hair or fur to trap a layer of insulating air close to the skin, helping to preserve heat.
5. Behavioral Responses: Mammals can also engage in various behaviors to regulate their body temperature, such as seeking shade or water to cool down or basking in the sun to warm up.
6. Metabolic Adjustments: Mammals can adjust their metabolic rate to produce more or less heat, depending on the environmental conditions. In cold environments, they may increase their metabolic rate to generate more heat.

While mammalian thermoregulation is highly effective at maintaining a stable internal temperature over a broad range of environmental conditions, there is an upper limit beyond which these mechanisms can fail. This upper limit, known as the "critical thermal maximum" or "upper lethal temperature," varies among different mammal species. Factors that influence this limit include the species' evolutionary adaptations, habitat, and physiological traits.

Extreme heat can overwhelm the body's ability to dissipate heat, leading to heat stress or even heat stroke, which can be fatal. Prolonged exposure to temperatures significantly above the body's normal range can damage cells and tissues, denature enzymes, and disrupt the body's overall function. Mammals adapted to hot environments often have specific physiological and behavioral adaptations to deal with high temperatures, such as efficient cooling mechanisms and the ability to tolerate higher body temperatures.

In summary, mammalian thermoregulation is a complex and highly effective system for maintaining body temperature within a narrow range. However, there is an upper limit at which these mechanisms can fail, and prolonged exposure to extreme heat can be life-threatening for mammals, including humans. The upper limit varies between species and is influenced by a variety of factors.

So, even if we don't succeed in killing ourselves off before then, it looks like our 'fine-tuned-for-life' planet will exterminate us before the sun does. So much for the creationist god having a plan for us and knowing all things, including the future. It could have designed a better planet orbiting a sun with a much longer life span, yet chose not to, if you believe that childish nonsense.

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