[Frumious Bandersnatch]

The last 25 years of the 20th century had a warming trend of 0.4 C -- more than double the "full century" rate.

But it has fluctuated even during that time frame. For instance, the decade of the 80s had a general cooling trend (not much, mind you) which was captured by U.S. satellites even after corrected for error.

Also, a lot of trends are localized, so to extrapolate them in a global sense is not fair (e.g. Al Gore indicates that a lot of glaciers are melting. This is true, but out of context, as we know from the small subset of glaciers studied that about half are melting and half are expanding).

One of the big bugaboos of global warming theorists is that it would cause the oceans to rise significantly. It is well known that all of the free floating ocean ice could melt tomorrow without measurably increasing the ocean depth. What we have to worry about is the landlocked ice - most especially the West Antartica Ice Sheet. But this is not even close to melting, so this rising oceans scare a bunch of bunk.

I've noticed that CO2 has replaced CFCs as the new scare tactic. If you recall, it was absolutely "proven" that CFCs would cause dramatic climate change. The problem with that premise was that this was being touted well after CFCs were generally banned and Mt. Pinatubo (which put more CFCs into the atmosphere than all human industry has) proved otherwise.

It seems to me that CO2 is that latest scare de jour. You might keep in mind that an honest assessment of any climate model predicting the future is to see how well it predicts the past. So far, no climate model has a very good track record in this regard.

One last set of things. So far, we don't know if climate change is caused by human activities or not. Increased sun activity (of which, coincidentally, there has been a great amount in the last century) would be far more plausible. But even given that, is global warming necessarily bad? I know the assumption is, but just a few degrees change increases the crop land available.

[cogitator]

But it has fluctuated even during that time frame. For instance, the decade of the 80s had a general cooling trend (not much, mind you) which was captured by U.S. satellites even after corrected for error.

Climate is still variable. El Nino, PDO, NAO, QBO -- it's not static and it's not linear.

What we have to worry about is the landlocked ice - most especially the West Antartica Ice Sheet. But this is not even close to melting, so this rising oceans scare a bunch of bunk.

James Hansen has stated several times that the "dangerous anthropogenic influence" would lead to ice sheet collapse. He's the one saying that it is necessary to start acting within the next decade to attempt to prevent something that could happen a century or more from now. Most people would admit that an ice sheet collapse wouldn't be a good thing.

If you recall, it was absolutely "proven" that CFCs would cause dramatic climate change.

I don't recall that the danger from CFCs and ozone depletion was expressed as a climate-change problem. My sense is that it was expressed as an environmentally-damaging problem.

You might keep in mind that an honest assessment of any climate model predicting the future is to see how well it predicts the past. So far, no climate model has a very good track record in this regard.

When this topic has been raised, I have referred to a discussion of the subject, which is below. You can evaluate it at your convenience; I can't add significantly to it.

http://mustelid.blogspot.com/2005/09/junkscience-is-junk.html

But even given that, is global warming necessarily bad? I know the assumption is, but just a few degrees change increases the crop land available.

It really depends on the rate of warming; ecosystems only adapt slowly. A perfect example is how treelines move in response to warming or cooling. Trees don't walk up or down mountains; if climate changes such that the habitable zone of a given species changes altitude, trees that fall out of the habitable zone will die, and new trees in the new habitable zone range will have to take root and grow. Some trees grow fairly fast, other's don't.