我的问题:
石炭纪为3.5 - 2.7亿年前。当时CO2的含量接近3000 ppm,但在这一时期结束时下降到200-300 ppm。这一时期的地球平均温度为20-25 $^{\circ}$C,到石炭纪末期下降到平均12 $^{\circ}$C。所以,你的问题的答案是,石炭纪因为气候变化而结束,CO2是主要原因。< / p >
A lot of CO2 was also used in the creation of calcium carbonate (limestone) there was also heavy volcanic activity during this period this do lower the temperature at least in the short time during the eruption and a few years there after.
The last part of your question is basically can the CO2 level get too low.
The level of CO2 are regulated by plants if it falls, several things will happen,plants will grow slower the temperature on the earth will go down making plants grow even slower.
But this is highly unlikely to happen as long as the supply of CO2 is continued.
edit:link http://www.geocraft.com/WVFossils/Carboniferous_climate.html
The Permian however saw severe warming near its end and a rapid rise in CO2 at the same time, but most of it was relatively stable and unchanging both in CO2 and temp. It also included one of the largest volcanic events in earth's history, and again changing tectonic position. So although the link between CO2 and temperature is really well established we can't even say for sure such slow coal formation actually reduces atmospheric CO2 concentrations.
Compare CO2 above to temp (red line) below. Note that just three variables together predict temprature amazing well.
当然,这只是CO2的一个因素。过去的火山活动也可能与此有关。< / p >