Is Global Warming a Good Thing?
Could global warming be good? Well, not for us, but for the world as a whole?
The sun is getting hotter(The sun gets about 10% hotter every billion years.) but the world is getting colder.
The earth is thought to be about 4.6 billion years old so that would mean (alllie figures) the sun has gotten about 70% hotter since the earth formed. The earth was hotter when life originated. That is probably why there are heat-loving (or at least heat tolerant) bacteria (thermophiles) that can live above the boiling point of water. Maybe it was that hot when they evolved. But why, you ask, if the sun has gotten hotter, has the earth gotten colder? And the earth has gotten colder. For instance, the earth is generally free of snow and ice even at high altitudes except during ice ages so we have been in an ice age for about 40 million years. During an ice age there are cycles of advancing and retreating glaciers. Just as we see now. The realization that we are in an ice age once made scientist think that the earth was in danger of turning into a “snowball earth.”
So why has the earth gotten colder?
There are lots of theories but the main one has to do with the atmosphere. With what we call greenhouse gases.
When the early earth coalesced out of the protoplanetary disk and stabilized, it is thought to have had an atmosphere of hydrogen and helium. That got blasted away by the solar wind. This early earth was bombarded by asteroids and comets. It grew. The bombardments brought gases from space or released them from under the earth’s surface. The new atmosphere was thought to be mostly hydrogen(H2), water(H20), methane(CH4) and ammonia(NH3). The sun’s radiation (no ozone to block it out back then) broke water into oxygen(O2) and hydrogen(H2). The oxygen reacted with methane to form carbon dioxide(CO2) and water and with the ammonia to form water and free nitrogen(N2). This produced high levels of carbon dioxide in the atmosphere which would have given the ancient sky a reddish cast. Methane and carbon dioxide are greenhouse gases. As is water vapor. It is thought they kept the earth from turning into a snowball. Kept it warm. But not so warm as Venus with its almost pure carbon dioxide atmosphere holding in its heat and turning it into a hot, dark burning hell.
Life evolved. It metabolized. It reproduced. Then life developed a neater trick. Through mutation it learned to turn light energy into chemical energy using carbon dioxide and water. This was the most popular trick of all, the trick on which almost all life on earth came to depend. Photosynthesis. But photosynthesis does two things, that, in the long run, proved disastrous. One, it produces a poisonous pollutant, a pollutant that, as it grew in concentration in the atmosphere and water, killed almost all life. The poison? Oxygen. That was a big change. Almost everything died. Except for a few organisms that hid away from the poison. And a very few that evolved to tolerate it. Or use it. That path leads to us.
The second thing photosynthesis did was use up the carbon dioxide in the atmosphere, to bind it in a thousand different compounds that, when an organism died, ended up in the rocks and ocean bottoms of earth. As carbon dioxide was removed from the atmosphere, heat radiated back into space and the world began to cool. Then earth suffered its first ice age (as far as we know) and one of its most severe. It lasted 300 million years.
Then carbon dioxide slowly weathered out of the rocks, by erosion, by volcanoes dissolving calcium carbonate rock laid down in previous eons and spitting out carbon dioxide. The earth warmed. As it did the oceans were able to hold less carbon dioxide and released more of it to the atmosphere. The glaciers retreated. The ice melted. The plants grew and multiplied in the oceans (and later on the land), burying the carbon in the ground (say as coal and oil) until there was so little carbon dioxide in the atmosphere that the world again cooled and the poles froze and the glaciers marched south.
This has happened many times in earth’s history. All of the carbon in the oil and coal and most carbonate rocks was once in the atmosphere. Much of it while there was life on earth. There is no reason that higher levels of carbon dioxide would kill everything. It didn’t before. It was the ice ages that killed, sometimes killed most forms of life. As time has passed more and more of the earth’s carbon as ended up underground until now there is only about 0.04% carbon dioxide in the atmosphere.
Maybe that is why we are here!! To help the carbon get out of the ground, to forestall snowball earth!! Some carbon deposits would never weather out. They are too deeply buried. Maybe we are doing a good thing digging up the carbon compounds and burning them. Maybe we are SAVING the earth, helping in a cycle that will make life on earth possible long into the future! Maybe we are Gaia’s trick to save the world!
We have already increased carbon dioxide in the atmosphere by about a third in the last 150 years. There is more carbon dioxide in the atmosphere now than any time in the last 20 million years. But that isn’t much when you consider that there was ten times as much carbon dioxide in the atmosphere 200 million years ago and 20 times as much 400 million years ago. William Ruddiman claims we have already disrupted the cycle of glaciation as far back as 8000 years ago due to our intense farming.
But wait. The sun is getting hotter. If we put all that carbon back into the atmosphere, will the earth get hotter and hotter too? We will end up like Venus? Well, the scientists say yes. Perhaps within the next billion years. Hmmm, hard to worry about that. But if we are here to save the world, it matters.
Should we care if it gets hotter?
We evolved in a narrow range of temperature. We are adapted to the way it is NOW. We did not evolve in a hotter earth, an earth so hot that most reptiles did not need to generate their own heat. The action of the sun and the atmosphere on them was sufficient to keep them warm enough to keep their temperatures in an optimum range for the activity of their enzymes. But WE evolved during an ice age. We made our great leap forward to civilization during an ice age!! The hotter climate may not suit us. The ice will all melt. The oceans will rise. And all the coastal cities will flood. Even far inland the earth will subside under the weight of water and there will be less and less land. Many forests will become deserts. Much farm land will be lost. Millions, maybe billions will die!! And it will be… hot.
I hate hot.
So what should we do!! If we were as smart as we think we are we would figure out what temperature is best for us and keep atmospheric carbon dioxide in the range that is most likely to maintain that temperature. Instead we blindly go on our greedy way, spilling carbon dioxide into the atmosphere like that bunch of mindless cyanobacteria excreted oxygen that once destroyed the world.
Haven’t we learned anything in 3 billion years?
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I have thrown in the towel where wikipedia is concerned. I used to think it was lame and I could find better information on my own but more and more I find if I look at a hundred pages I rarely find anything as good as wikipedia. At least for science.
The new study helps explain how Earth may have avoided becoming frozen solid early in its history, when astrophysicists believe the sun was 25 percent fainter than today. http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2232
In the very long term, astrophysicists believe that the sun’s output increases by about 10% per billion (109) years. In about one billion years the additional 10% will be enough to cause a runaway greenhouse effect on Earth - rising temperatures produce more water vapour, water vapour is a greenhouse gas (much stronger than CO2), the temperature rises, more water vapour is produced, etc. http://en.wikipedia.org/wiki/Ice_ages#Major_ice_ages
On long timescales, atmospheric CO2 content is determined by the balance among geochemical processes including organic carbon burial in sediments, silicate rock weathering, and vulcanism. The net effect of slight imbalances in the carbon cycle over tens to hundreds of millions of years has been to reduce atmospheric CO2. The rates of these processes are extremely slow; hence they are of limited relevance to the atmospheric CO2 response to emissions over the next hundred years. In more recent times, atmospheric CO2 concentration continued to fall after about 60 myr BP, and there is geochemical evidence that volume concentrations were less than 300 ppm by about 20 myr BP. Low CO2 concentrations may have been the stimulus that favored the evolution of C4 plants, which increased greatly in abundance between 7 and 5 myr BP. Present carbon dioxide levels are likely higher now than at any time during the past 20 myr[17] and certainly higher than in the last few hundred thousand. http://en.wikipedia.org/wiki/Carbon_dioxide_in_the_Earth%27s_atmosphere
William Ruddiman has proposed the early anthropocene hypothesis according to which the anthropocene era, as some people call the most recent period in the Earth’s history when the activities of the human race first began to have a significant global impact on the Earth’s climate and ecosystems, did not begin in the eighteenth century with advent of the industrial era, but dates back to 8000 years ago, due to intense farming activities of our early agrarian ancestors. It was at that time that atmospheric greenhouse gas concentrations stopped following the periodic pattern of the Milankovitch cycles. In his overdue-glaciation hypothesis Ruddiman claims that an incipient ice age would probably have begun several thousand years ago, but the arrival of that scheduled ice age was forestalled by the activities of early farmers. Other important aspects which contributed to ancient climate regimes are the ocean currents, which are modified by continent position as well as other factors. They have the ability to cool (i.e. aiding the creation of Antarctica) and the ability to warm (i.e giving the British Isles a temperate as opposed to a boreal climate). http://en.wikipedia.org/wiki/Ice_ages#Changes_in_Earth.27s_atmosphere
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© Alllie 2007
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