A question about the Antarctic Ice Core Data Graph...?

Question

Could someone help me to interpret this graph here
http://www.ccs.neu.edu/home/gene/peakoil/co2-400k-years.gif

It appears that quite frequently(specifically at the 325,000, 135,000, and 20,000) the CO2 line rises after the temperature rises? By this I mean, at the points mentioned above, the temperature rises and then there is space to the right between the temp line and CO2 line? Does this mean that there is no correlation between temp rising and CO2?

Also at the right end of the graph it shows the highest concentration of CO2 on the whole graph but not the highest temperature. Does this also mean there is no correlation between the two variables?

Answer 1

It's a good question and it doesn't have a simple answer but here goes...

Increasing temperatures lead to an increase in the levels of CO2 and conversely, increasing levels of CO2 lead to an increase in temperatures - this is known as the Feedback Effect or Feedback Cycle.

To give you an example - trapped in and beneath the ice are billions of tons of carbon dioxide and methane. The Siberian permafrost alone has approximately 70 billion tons of methane trapped beneath it due to biomass decomposition (methanogenesis). As the world warms up (as it has done several times of it'sown accord) it causes the ice to melt which releases the trapped greenhouse gases. These greenhouse gases escape into the atmosphere where they contribute to the greenhouse effect thus causing the world to warm even more, in turn melting more ice, releasing more gas, causing more warming and so it goes on.

Historically this is what's happened - changes in the way the world moves (Milankovitch Cycles) and changes in the sun (Solar Variation) have led to an increase in global temperatures which has triggered a release of greenhouse gases. This is why the graph shows temperatures rising before CO2 levels have risen.

In recent times we've upset the natural balance by introducing large quantities of greenhouse gases into the atmosphere. Just as it has in the past, this has led to a warming of the planet and we're now seeing melting of parts of the Polar ice caps and the Siberian permafrost I mentioned earlier (1 million square kilometres have melted in the last 5 years).

CO2 levels are currently at 385 parts per million by volume (ppmv) of the atmosphere - the highest they've been since humans occupied the planet. The temperature isn't yet the highest it's been because there's a lag between rising CO2 levels and rising temperatures. There are other factors that need to be taken into account as well and to go into all of them really would complicate things.

It's a little bit like when you heat a room in your house - you turn the heating on but it takes a few hours before the room reaches it's maximum temperature. Similarly when you turn the heating off it's a few hours before the room fully cools down. A similar thing is happening in nature, but in nature of course, things happen much more slowly.

Even if we were to immediately stop producing any more greenhouse gases the world will keep warming for a long time yet - significantly for a few decades, slowing down over the next few decades, then rising very slowly for a few thousand years (the different greenhouse gases have different atmospheric lifespans).

Hope this helps.

Answer 2

no it means that there is a correlation, increased temperatures increase the co2, because more plants grow, and thus, more plants die, yes they absorb some co2 and expel o2 during their lives but the amount of co2 let off by the decomposition of plant matter would be higher. Also increases in temperature warm the frozen methane deposits on the bottom of the ocean, this adds further warming, further waring means more areas able to grow plants, more plants alive means more plans die.

Answer 3

Many will go out on a ridiculous limb and claim there is a feedback situation with CO2. Feedbacks in nature are rare because if there is a potential for a feedback the feedback is INEVITABLE and quickly plays out.