[aruanan]

If humans continue to fill the atmosphere with carbon dioxide, there can be little doubt that the average temperature of the world will increase above what it would have been otherwise.

The CO2 effect with temperature is logarithmic; that is, you need increasingly larger amounts of it to make increasingly smaller upward effects on temperature. Its greatest effect per ppm is in the 0 to 100 ppm range. So if you had X effect at 100 ppm, tripling it will not have 3X effect. The earth isn't going to become a scorched wasteland from increased levels of CO2. The earth now, in terms of geological history, is at an extremely low level of atmospheric CO2. It has been decreasing for a long, LONG time, so long, in fact, that the entire range of human history is barely visible on that scale. The recent supposed increase since the late 19th century is the tiniest blip, especially considering that the 280 ppm figure often cited as the 19th century concentration was arrived at by extreme cherry picking of the data from the 19th century. The actual average for that century was somewhere above 300 ppm.

[hinckley buzzard]

The CO2 effect with temperature is logarithmic; that is, you need increasingly larger amounts of it to make increasingly smaller upward effects on temperature.

Correct. Some researchers have shown that the large majority of the "greenhouse effect" from CO2 has already occurred; that a hypothetical doubling of CO2 would lead to only miniscule changes in teperature, if at all. The whole hullabaloo is at best, scrambling to lock the door after the horses escaped.

[larryjohnson]

Data point: My 1959 General Meteorology text has CO2 at 330 ppm.