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Mars Is Coming Out Of An Ice Age (reuters.com)
Taco Cowboy quotes a report from Reuters: An analysis of radar images that peered inside the polar ice caps of Mars shows that Earth's neighbor is coming out of an ice age that is part of an ongoing cycle of climate change, scientists said on Thursday. Using images taken by satellites orbiting Mars, the researchers determined that about 20,872 cubic miles (87,000 cubic km) of ice has accumulated at its poles since the end of the ice age, mostly in the northern polar cap. Scientists are keenly interested in piecing together the climate history of Mars, which contains strong evidence that oceans and lakes once pooled on its surface, bolstering the prospects for life. From the perspective of an Earthling, every day on Mars may feel like an ice age. According to NASA, temperatures on Mars may hit a high at noon at the equator in the summer of roughly 70 degrees Fahrenheit (20 degrees Celsius), or a low of about minus-225 degrees Fahrenheit (minus-153 degrees Celsius) at the poles. The Martian ice began its retreat about 370,000 years ago, marking the end of the last ice age, according to the research published in the journal Science
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Since we've already accounted for the effect of Earth's orbit and tilt (which run on 100,000 and 20,000 year cycles), unless you have a bitchin' theory for how Mars' orbit and tilt afffect the climate of the Earth, we're still pretty damn confident that it's the humans.
Very true. Well, if you are a poikilothermic animal, that is. Or if you're an insect and would like to grow larger. Because that's pretty much not possible with petty oxygen levels of about 20%. You should also not be living near a shore, unless you're an aquatic animal (but if you are, life's going to be great... provided you're not too dependent on, you know, a shore).
So yeah, life would be a lot better if conditions were again as they used to be back then. If you're a lizard. Or a dragonfly. Or a fish.
Huh? You're a human? Boy, sucks to be you!
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
OK, apparently the answer is "yes", so I'll spell out why the notion is stupid. First, let's be clear what AC is implying: that the fact life thrived under high CO2 Jurassic conditions means that a rapid shift of climate in that direction will be good for the environment. Or at least harmless.
The Jurassic period was over 200 million years ago. Not only did the continents we're familiar not exist, neither did any of the species that currently populate the Earth. In fact major classes and orders of species had yet to emerge. Mammals. Flowering plants -- including all grasses (and that means every cereal crop) and most orders of common trees other than conifers and ginkos. Modern conifers and ginkos of course aren't the same as their ancestors; they've evolved to be adapted for modern conditions.
For that matter every single species currently living on Earth has evolved over the last two hundred million years to thrive and compete in a low CO2, lower O2 atmosphere than in the Jurassic. If you could wave a magic wand and instantly restore Jurassic atmosphere the result would be rapid, mass extinction of most of the species familiar to us. This won't largely be due to individual plants not surviving, but in a massive competitive advantage for plants on the right end of the bell curve for being able to exploit these conditions. Naturally this would be accompanied by massive animal die-offs. Many animals will die off due to direct effects (ocean acidification), others by having the plants they depend on directly or indirectly disappear. This in turn will result in more plant species extinction as animal species they depend upon disappear.
The higher oxygen levels will also hurt some species. O2 isn't just necessary to life, it's also toxic to life at high partial pressures. The level at which it is toxic to humans is slightly higher than Jurassic levels, but many other species won't tolerate it. It's just like water; all plants need water, but watering some plants too much will kill them.
So the result of a shift to a Jurassic atmosphere wouldn't look much like the Jurassic period. Jurassic ecosystems had evolved over tens and hundreds of millions of years along with the changing levels of CO2 and O2. In our rapid CO2 shift scenario plant life would grow explosively, but not all plant life. Very soon we'd be living in a planet overgrown with weeds. This in fact is just a more severe version of the scenario we're actually facing, in which we lose quite a bit of biodiversity as the atmosphere changes on faster-than-evolutionary timescales. But of course the situation *will* right itself -- in a few million years.
So to recap, you can't compare the effect of CO2 in the modern era to the Jurassic era, because the Jurassic era was 200 million years ago. The sun was different, the continents were different, the species on the planet were different, and all those species had adapted over millions of years to gradual changes in the atmosphere.
It's probably true that there's no reason to prefer living on a planet with 200 ppm CO2 to one with, say, 2000 ppm CO2;but there's every reason to prefer living on a planet where the atmosphere has been changing slow enough for evolution to track.
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Actually, it's Uranus that has that extreme axial tilt. But you are correct, being a resident of the equator on such a planet (if it were rocky, and you were OK with temperatures that varied by hundreds of degrees) would be interesting.
Gamingmuseum.com: Give your 3D accelerator a rest.
One of the drivers of climate change, on the scale of 10's to 100's of thousands of years are the regular changes in a planets orbit, eccentricity, axial tilt, whether summer in a hemisphere happens at perihelion etc. This will drive climate change on both the Earth and especially Mars as its orbit is so eccentric. They're named Milankovitch cycles, https://en.wikipedia.org/wiki/...
https://en.wikipedia.org/wiki/Inverted_totalitarianism
I considered the "living fossil" argument, but in general the "living fossil" thing is a bit misleading. When organisms are discovered living that are known from the fossil record (or vice versa), initially the public news is that a "living fossil" has been discovered, but then the systematics geeks get to work and the modern and fossil versions end up classified differently. They continue to be promoted as "living fossils" to a public that needs every encouragement to care about science and the environment, but researchers generally have a more nuanced view than the simple but romantic picture of a population that has remained totally unchanged for millions of years. That just doesn't happen.
The "living fossil" par excellence is of course the Coelecanth. However in the 80 years since the first living example was discovered, living Coelacanths have been placed in a separate genus (Latimeria) from any example in the fossil record. The anatomical resemblances between Latimeria and fossil genera are striking, amazing even. The differences perhaps may be too subtle for a layman to discern, but to a taxonomist they're there. Same goes for horseshoe crabs, ginkgos, etc.
If you think about how genetics works, the idea that a species could be a stable construct over millions of years is extremely implausible. Even if you can't see an anatomical distinction, if you had a time machine and brought back a DNA sample it's bound to put the ancient population in a different taxon just by genetic drift alone. That doesn't count selective advantage for mutations that adapt an individual for changing environmental conditions such as heat and gas composition and, for marine organisms, pH.
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I did some looking into the effects of solar changes on global and solar-system temperatures, because I wondered how much of an effect it might have, if any.
Solar output has been dropping over the last several decades. The sun does (obviously) affect the surface temperature, but to the extent that it does it has been driving temperatures DOWN: http://woodfortrees.org/plot/s...
That means something else has been not only counteracting the cooling effect of the sun but also warming the planet at a rate unprecedented in the last 10,000 or so years.
Meanwhile Mars has been coming out of an ice age for the last 370,000 years (according to TFS). There are other factors at play here than just the sun.
Scientists who have attempted to quantify the human contribution to the current temperature rise have found that anthropogenic sources account for between 80% and 150%. See Tett et al. 2000, Meehl et al. 2004, Stone et al. 2007, Lean and Rind 2008, Huber and Knutti 2011, Gillett et al. 2012, Wigley and Santer 2012 , and Jones et al. 2013. It may be unintuitive to think that humans may have cause more than 100% of the current warming, but remember that natural factors have generally been forcing planet towards another glacial period. We've just had the weakest solar cycle in over 100 years. If solar variability is a strong contributor to global mean temperature then other forces have not only caused all of the warming that we have recently observed, but also caused enough additional warming to offset the cooling caused by the sun.