Quote:
Originally Posted by Waxing_Gibbous
One of my wife's colleagues, a teacher for heaven's sake, believed that 90% of the Carbon in the atmosphere came from humans!!!
Not even close:
80% comes from the oceans.
10-15% from Photosynthesis (she also didn't know that plants give off CO2)
5% comes from 'other sources', People, Vulcanism, seepage from the earth etc.
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If anything, we should at least get the numbers right (Source:
http://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atmosph ere):
Quote:
Many sources of CO2 emissions are natural. For example, the natural decay of organic material in forests and grasslands, such as dead trees, results in the release of about 220 gigatonnes of carbon dioxide every year. In 1997, Indonesian peat fires were estimated to have released between 13% and 40% of the average carbon emissions caused by the burning of fossil fuels around the world in a single year. Although the initial carbon dioxide in the atmosphere of the young Earth was produced by volcanic activity, modern volcanic activity releases only 130 to 230 megatonnes of carbon dioxide each year, which is less than 1% of the amount released by human activities.
These natural sources are nearly balanced by natural sinks, physical and biological processes which remove carbon dioxide from the atmosphere. For example, some carbon dioxide dissolves in sea water, and some is directly removed from the atmosphere by land plants for photosynthesis.
...
Burning fossil fuels such as coal and petroleum is the leading cause of increased anthropogenic CO2; deforestation is the second major cause. In 2008, 8.67 gigatonnes of carbon (31.8 gigatonnes of CO2) were released from fossil fuels worldwide, compared to 6.14 gigatonnes in 1990. In addition, land use change contributed 1.20 gigatonnes in 2008, compared to 1.64 gigatonnes in 1990.
This addition, about 3% of annual natural emissions as of 1997, is sufficient to exceed the balancing effect of sinks. As a result, carbon dioxide has gradually accumulated in the atmosphere, and as of 2008, its concentration is 38% above pre-industrial levels.
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So, the amount of CO2 in the atmosphere
has increased by 38% due to human activities, which is the key point. Humans are burning off all the carbon that took millions of years to get deposited as fossil fuels - all released back into the atmosphere in just a couple hundred years. That has never happened before. And while one can argue at length over the possible consequences of that it does seem rather obvious that such a massive increase in such a short time since industrialisation is going to have a significant effect. And the most logical effect is a global warming.
Sure, there have been climate change before and, yes, it is constantly ongoing due to change in solar output, change in Earths orbit, the precession etc etc, but all happen over geologic time scales where ecosystems have time to adjust and evolve to suit the changing conditions. A rapid change, such as the one that might logically follow the current fast burning of all fossil fuels, will of course have catastrophic consequences for the global economy and for our biosphere as a whole. Yes, the Earth will keep spinning and we'll still be here, but it will make the recent financial crisis seem like a tiny blip.
Quote:
Originally Posted by Waxing_Gibbous
Nothing. Not one single doomsday scenario that has been predicted since this claptrap started making the rounds in the '70s has come to pass. The icecaps have NOT melted. Forests continue to grow. Animal species continue to breed and thrive. The Ozone layer remains intact.
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The ozone layer remains intact only because the use of ozone depleting gases were banned on a global scale very quickly when it became apparent how serious the problem was. It is only now starting to slowly recover.