Greenhouse Gases and Temperature

Ice cores drilled from the thickest part of the eastern Antarctic ice sheet give us 800,000 years of data.  Carbon dioxide (CO2) and methane (CH4) levels in the atmosphere at the time of freezing of the ice can be measured.  Similarly the temperature at the time can be calculated.  This gives us a plot of variation of temperature, methane, and carbon dioxide over time.  Ice core data

Ice core data compiled from figures of Loulergue et al (p. 383) and Luthi et al (p. 379), Nature, 15 May 2008 are shown in the figure on the right.

Click on figure to enlarge. 

Note that the present is on the left at zero time, and the deep past is on the right at 800,000 years before present.  The estimated appearance of homo sapiens, at 200,000 to 300,000 years ago, is well within this time period.

From the figure one can see that the maximum temperature above the zero line (taken as 1950) is 4 degrees C, or about 7.4 degrees F.  These temperature maxima correspond to CO2 maxima of about 300 ppm (parts per million) and CH4 maxima of about 800 ppb (parts per billion).

Today, measured concentrations of CO2 in the atmosphere are about 400 ppm, and methane is over 1800 ppb. These values are literally off the chart of the figure on the right.  GHG relative to ice corsIn fact all greenhouse gases are at record levels.  The physics of this circumstance tells us that further warming is unavoidable.


All Greenhouse Gases Aren’t Alike

The principal greenhouse gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and the chlorofluorcarbons (CFCs).  They vary according to how much warming each can cause relative to CO2 (set at 1).  This is called their Global Warming Potential or GWP.  They also vary by how long they stay in the atmosphere.   The […]

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Why Hasn’t it Warmed More?

Why Hasn’t it Warmed More? Looking at the ice core data  over the last 800,000 years, a carbon dioxide level of 300 ppm correlates with an increased temperature of almost 4 degrees Celsius. Currently the carbon dioxide in our atmosphere is over 400 ppm, but we’re only at about 1 degree warming. So why hasn’t it warmed more? […]

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