Sigh, nobody really knows what'll happen. It is true that

carbon dioxide is the limiting nutrient for most plants.



Measuring the effect of enhanced carbon is difficult, and

it appears the effect is not linear. It depends on things like soil that vary locally.



Anyhow, the globe isn't warming, so it's like a theological debate.

It is warming, but not by much and it's nothing to panic over.

Yeah, show me the global observations at surface.



All the ones I've seen exclude almost everything below 50 degrees S and above 70 degrees N, plus most of western Asia south of the Oxus-Jaxartes, plus eastern Mongolia/western Tibet, plus about a quarter of the Amazon basin.



In other words, the three coldest parts of the globe are not measured and people say the globe is warming. GIGO

Well, just because we don't know for sure that the globe is warming doesn't mean the majority of measurements haven't shown an increase compared to a hundred years ago.



But the pace of warming and the magnitude are small compared to natural changes over the last 40,000 years; the greenhouse effect due to human-added carbon dioxide can only account for a warming of about .01 degrees; in short, there is no known mechanism by which humans could be responsible for the warming.



The higher crop yields from higher CO2 concentrations have been known for decades, the lower nutritive value may be junk science.



All in all, no reason to reduce CO2 emissions.

How do you know what the global surface temperature was a hundred years ago? Nobody measured it.



Nobody has ever measured it. We don't know what it was last year.

We may not know a global mean but we have measurements at specific locations that go back ~250 years (e.g. sea surface measurements on the Atlantic) and other means of getting local temperature time series going back tens of thousands of years (e.g. isotopic abundances in the Greenland and Antarctic ice caps).



These local series are evidence
for global temperature variations.

That's not true. The Australian ice core at Law Dome in Antarctica shows that one period of warming in Greenland was preceded in Antarctica by 500 years.



We know that over the period of observation (no more than 250 years, as you say), there are opposite trends on scales of very large regions -- east and west N.

America have been going in different directions for decades, at least.



What we don't know -- and as far as I can imagine, will never be able to recover -- is just how long these divergences can last. 500 years minimum, anyhow.

Harry, it's just a question of the weight of the evidence. I agree it's possible that the earth hasn't warmed at all in the last hundred years. I also agree that some spots on the earth have cooled down. But if a majority of the measurements show an increase, isn't that evidence for warming?



In any case I don't think it's important because we shouldn't act any differently whether the earth is warming or not.

I agree the Earth is probably warming, as it

has been for the past 18K-20K years, net,

though there have been fairly lengthy periods

within that time when it was cooling.



It had better be warming, because if it isn't,

we're heading into another Ice Age. The

present interval of warmth has been the longest

in 2 million years.



NOAA, to take one example, annually publicizes

what it calls the average global temperature

to two decimal points. Fraud, fraud, fraud.



It is important to recognize frauds. Clarifies the

discussion