herebus, that was the point I was making, not looking at small snapshots of time, which is what the proponents of AGW are precisely doing. If charts that reconstruct the past climate are looked at carefully enough, many short term "hockey sticks" can found, but rather than each time the climate taking off in a catastrophic direction, the overall long term trend persisted.
sandlion, laboratory experiments indicate that 1200ppm CO2 appear best for optimum plant growth. Obviously warmer rather than cooler conditions also result in better growth as long as sufficient moisture is available. As an aside, plants that grow best in drier conditions have long tap roots that are able to access water available deeper down rather than rely on he moisture of the top soil.
There is an experiment being conducted at a research station in Victorias wheat growing region where a plot of wheat grown in the field under otherwise normal conditions is having its immediate atmosphere enriched with CO2 being released and wafted across the plot. As yet I haven't seen any reports but it should be interesting to see if what can be found in the laboratory can be duplicated in the field.
