Earth’s carbon dioxide levels reach highest point in 800,000 years
<a href="http:&#x2F;&#x2F;earthguide.ucsd.edu&#x2F;virtualmuseum&#x2F;climatechange2&#x2F;07_1.shtml" rel="nofollow">http:&#x2F;&#x2F;earthguide.ucsd.edu&#x2F;virtualmuseum&#x2F;climatechange2&#x2F;07_1...</a><p>On a geologic timescale, CO2 levels were many times higher than they are today.<p>&gt;In very general terms, long-term reconstructions of atmospheric CO2 levels going back in time show that 500 million years ago atmospheric CO2 was some 20 times higher than present values. It dropped, then rose again some 200 million years ago to 4-5 times present levels--a period that saw the rise of giant fern forests--and then continued a slow decline until recent pre-industrial time.<p>CO2 levels over the past ~5 million years are at the lowest point in over 200 million years. On a geological timescale, CO2 levels are <i>returning</i> to normal, not going away from it.