PA,
Thanks for you reply. I am not sure I properly understand what you are saying with your somewhat abbreviated sentences. I also wonder if your example for a single year of US grain harvest is of much value. We also know that crops and agriculture practices adapt relatively quickly to climate changes.
I like to try to understand the outer limits, then narrow down. If there is evidence of sudden breaks in the trend between the outer limits I’d like to understand the reason for them.
So, I begin at one end, the ice-age temperatures. We know that life struggled when the temperatures were colder. Much of the planet was dry, barren land. Vegetation productivity was way down. We are very much better off now. We are much better off now than even the Little Ice Age.
At the hot end of the scale – Jurassic, Cretaceous, Tertiary – life thrived.
So the overall trend from cold to hot is established – life thrives when the planet is warmer and struggles when colder. Life does better as the planet warms.
We also know, at temperatures close to current, vegetation productivity is improving as the planet has warmed 1C over the past 200 years or so and as CO2 concentrations have increased.
It seems to me, the overall trend suggests warming planet and increasing CO2 concentrations are more good than bad.I don’t see p[ersuasive evidence suggesting it is likely we will reach a temperature where the trend reverses while we remain in the current coldhouse phase – and that won’t stop until tectonic plate movements separate N and S America.
It seems to me there is less risk from warming than there is from cooling and our GHG emissions are, to some extent, mitigating the the risk of cooling – i.e. delaying the next abrupt cooling event and reducing the magnitude and rate of change.
Unfortunately, I am no aware of much research being done to properly evaluate all the probabilities and consequences of both possibilities, warming or cooling.
