Temperature and CO₂ Correlation

From a plot of atmospheric CO₂ and Earth surface temperature over the last 400,000 years (Figure 4) we see a strong correlation between temperature and CO₂. It is noteworthy that the concentration of CO₂ during this period did not exceed 300 ppmv, in contrast to recent measurements that show concentrations exceeding 370 ppmv and rising steadily.

Reconstructed Earth Surface Temperature, 1000-2000

A 1999 report by Mann et al (1999) shows that the surface temperature change for Planet Earth over the last 1,000 years as reconstructed from ice cores, lake sediments and tree rings (Figure 5). The yellow bars on this graph show the range of uncertainty for each proxy measurement. Overall the graph shows that the temperature of the planet has decreased gradually over the period from year 1000 to about 1900. Since then, the temperature has risen abruptly at a rate uncharacteristic of the behavior of the preceding 900 years. This graph provides strong evidence that conditions of the planet have changed dramatically in the last 100 years.

If we plot current atmospheric CO₂ levels on the historical record of Figure 4 we see that current levels far exceed levels of the last 400,000 years (Figure 6). If human-induced emissions of the CO₂ continue at current rates of increase, atmospheric CO₂ will surpass 300% of pre-industrial levels by 2100 (Figure 7). The question then is what happens to global mean temperatures on the graph in Figure 7? Is the recent rise in temperature shown in Figure 3 the early sign of the trend to be expected in Figure 7?

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