How accurate is this fit?
Considering the difficulties of gathering data from centuries past, amazingly close. We know, for example, that up until 1950, deforestation was putting about as much CO2
into the atmosphere as were burning fossils, but it's not easy to know how many trees were chopped down in, say, 1850, and how much CO2
this put into the air. In spite of imperfect data, the fact that a simple calculation predicts the extraordinary shape of actual CO2
so well is clear evidence this can not be a coincidental convergence. Human CO2
emissions must have caused the upsurge is atmospheric CO2
The link between human activity and rising CO2
levels is the first step. The next one is between CO2
and global warming. That was predicted over 100 years ago, but the evidence has become convincing only very recently. ZFacts will be adding pages about this during February, 2006.
Where did the numbers come from? CO2
Levels. These come from two sources. From 1958 forward, they are from a weather station high atop the Mona Loa volcano in Hawaii. They are so accurate, they show levels going up every autumn, when the leaves fall, and coming down every spring. Earlier data are from ice cores
in Antarctica. The two sources agree remarkably well. (All actual data points are shown in the top graph.) The next graph shows the emissions data.