Measurements of that far back are general constructed through analyses of rocks. There's;s a new paper just published in PNAS that reports on findings from doing what is analogous of CT scans on the earth's surface to learn how active volcanoes were, and thereby how much CO2 was put into the atmosphere, in past eons.
http://www.pnas.org/content/111/12/4380....
The reasons that study of past periods now is important is that it helps us understand how current and future atmospheres will affect climate. For example, our understanding of the greenhouse effect was advanced by studying Venus. Likewise, our understanding of climate is advanced by learning how past atmospheres affected temperatures on earth. 250 years ago there was much more CO2 in the atmosphere and it was much warmer.
CO2 is CO2, then and now, but hundreds of millions of years ago, as through nearly the whole natural history of the earth since then, the levels of CO2 changed only slowly over tens of thousands of years. It is changing now thousands of times as fast, due to the burning of fossil fuels (sold by companies which have duped half the posters in this category with their anti-science lies).
Biological processes and physics are not much different 10s of millions of years ago as it is now. Only things that changes is species because of adaption by natural selection due to changes in the climate. In other words evolution.
Life is doing now what it has done for hundreds of millions of years. More than 95% of all the species that has ever lived since life on earth began is extinct. Why? Because climate and conditions are dynamic. Why the hell AGW cultists actually believe before humanity this was natural and then all of the sudden humanity is now causing it and can stop it is beyond belief. It is the height of vanity to elevate humanity to such a near god like powerful presence on earth over nature itself.
250 million yrs is not that long ago, life first started on Earth 3.5 billion yrs ago when CO2 was probably above 90% like Mars and Venus are now
oh!! its quite unacceptable....but it is so...it can be proved, because plants, which are today photosynthesizing, that time too did....and you know, they need particular CO^2 level in outer environment, i.e.0.3%(approx) to remain their stomata open.. , so it can be said that since 250 million years ago, plants existed, so the CO^2 level in the atmosphere at that time would be nearly same as its now existing...
you may be confused about increased fossil fuel burning and other such pollution may have increased CO^2 level in atmosphere, but you should know, that the CO^2 level in the lower atmosphere remains nearly same(as plants didn't photosynthesize at lower or higher CO^2 level than normal), but the excess of it rises above in the atmosphere and forms layer( which causes global warming; you know the rest)......hope it helped.....liked your question..keep it up...clear your doubts, being human....:)
http://news.yahoo.com/dinosaur-era-had-5...
They can't, but science tries to be the "tell all" when it comes to studying the planet's history. They can't tell us in absolute terms 'what the ideal temperature of the planet is suppose to be'. They say that 250 million years ago CO2 levels were 5 times what they are today and the planet was more arid, more vegetative, and much warmer, but that can't tell us much about how fast the climate changed in relation to CO2 levels. CO2 levels have risen 40% in 250 years (established norm is around 280ppm and current levels are 400ppm), yet temperatures have only risen 0.45C (current global average temperature stands at 14.45C) above the established normal temperature of 14C. http://data.giss.nasa.gov/gistemp/tabled...
Hey Dook - " ... It is changing now thousands of times as fast, due to the burning of fossil fuels (sold by companies which have duped half the posters in this category with their anti-science lies). ... "
We've told you a million times before to stop exaggerating!
Well it is simple, we are living now not 250 million years from now.
For the past 800,000 years, they look at ice. before then, at fossils.
see
http://en.wikipedia.org/wiki/Carbon_diox...
Wasn't the atmosphere completely different? the CO2 content from that period should not be relevant to today's threat of climate change?
