Posted by: drgeophysics | October 10, 2009

Last Time Carbon Dioxide Levels Were This High: 15 Million Years Ago

The climatic system is like a dragon, only fools pull its tail!

The climatic system is like a dragon, only fools pull it's tail!

The concentration of CO2, a greenhouse gas, is presently increasingly rapidly because of human activity.  An obvious question is when was the last time the earth system had this concentration of atmospheric CO2?  This has recently been addressed by a young scientist at UCLA.  The answer suggests that we must complete CO2 stablization and sequestration activities with the utmost urgency.

This is of great importance to the climatic system of the earth.

This is of great importance to the climatic system of the earth.

The variation of atmospheric gas levels has been well recorded by bubbles in ice.  Surprisingly these are straight forward to sample and analyze.  In addition, a ratio of Oxygen isotopes (Oxygen 18 and Oxygen 16, sometimes written as O18/O16) represents a proxy for global average temperature.  This oxygen isotope ratio is also present in these tiny bubbles preserved at the time of ice formation.

The age dating of the ice layers is easy.  Therefore, in one record one has an accurate age, atmospheric gas composition, and global average temperature.  Wow! This ice bubble record goes back about 800,000 years and is very important to understanding climate change, especially the speed of shifts between three basic types of global earth climate.  These are 1) a climatic system similar to the one we enjoy today, 2) a much hotter system (sometimes called jungle-earth) and 3) a much colder system.  The most recent example of the colder system are the last ice ages.    The most famous of the the ice cores is the Vostok Ice Core.  Here is a site, which describes the project and from which data can be downloaded.

Here is a site summarizing all the available ice core data relevant to atmospheric composition variation.

So, back to our question, with respect to the concentration of atmospheric CO2, what about older ages in the earth’s history?  This exciting article shows that at UCLA a young scientist has been able, through isotope measurements in other systems, show that the last 800,000 years of C)2 atmospheric composition were accurately determined by another recording method in the geologic system.  She has then extended this record back much further and compared the concentration of atmospheric CO2 to it’s present level.

The earlier climates of the earth are well recorded by fossil systems, shore lines, geological deposition systems distinctive of climate, and Oxygen isotopes, which are also well preserved in fossils (you record the Oxygen isotope ratio of the present earth  in your bones).  In my own work I know that it is simple to find fossils from large tropical turtles in the deserts of Wyoming from 40 million years ago.   Fossils give a rich record of paleoclimate and can be accurately dated.

What we have shown is that in the last period when CO2 levels were sustained at levels close to where they are today, there was no icecap on Antarctica and sea levels were 25-40m higher,” said research leader Aradhna Tripati from the University of California at Los Angeles (UCLA).

Yes,  you read that correctly, sea levels 25-40 meters higher and no icecap on Antarctica.  The inertia of the climate system, feedbacks within climate-relevant biological, geological, atmospheric, meteorological, hydrological, and oceanic systems , and tipping points with respect to key parameters are all being studied.

Here is the UCLA article as reported in ScienceNow.

Here is the BBC science report of this scientific article (it is easily understandable). I would not bother to use the quotes around the word ‘scary’.  These new observations are both significant and sobering.  The stupidity of mixing politics with science is unbelievable to me; as a society we have pointlessly wasted so much time.

As earlier reported (more than two years ago!) on the BBC science page.

Billions of people face shortages of food and water and increased risk of flooding, experts at a major climate change conference have warned.

Here is the older story.

Variation of greenhouse gases, and the resulting changes in the characteristics of the earth’s atmosphere has been thoroughly studied, but one must review the physics and chemistry of carbon dioxide.  Here is the wiki link to review the chemistry and physics of carbon dioxide.

Here is the famous Mauna Loa carbon dioxide record (continually updated, with data in spreadsheet format available).

Here is a link to the monthly Mauna Loa data showing the seasonal and anthropogenic variation in atmospheric CO2. Have fun with this dataset; thank you NOAA!

The NOAA Earth System Research Laboratory is located here.

There are a variety of reports that put these observations into perspective and present plans for greenhouse gas reduction, including posts on this web site.


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