Ever heard of physics? When you pump 16 billion tons of unasorbed C02 into the atmosphere yearly, you're not talking about an occasional major volcano eruption, or a peaks after an ice age, where the earth has thousands of years to adjust, and where it has ALL its natural C02 aborbing mechanisms in place. It's a sustained deliberate increase in global warming gases HUMAN CAUSED which has snowballing effect, along with human destruction of natural C02 absorption systems.

"CO2 and methane levels are higher today than they have been in at least the past 800,000 years."

1) What meaurement methods are used? If actual measurements are used for current levels, then a comparison to ice core analysis is an apples-to-oranges argument, and not really valid.

2) I am not familiar with the details of ice core analysis. Are the analyses valid for short-term effects? Can we really tell what the levels were in individual years, or decades, or centuries?

"The strong correlations of methane and CO2 with temperature reconstructions are consistent back 800,000 years."

1) Correlation does not necessarily imply causation. Possibly a fourth variable affects all three items shown here.

2) Although the scale makes it difficult, it appears from the graphs that temperature changes predate methane level changes, which predate CO2 level changes. Not a strong argument for CO2 and/or methane driving temperature change.

"The long-term cyclic changes in temperature, methane and CO2 that follow slow changes in Earth’s orbit are consistent back 800,000 years.

1) The fourth variable mentioned above. If all three variables follow "slow changes in Earth's orbit" then it is even less likely that there is a causal relationship between them.

2) If this statement is true, it would (in my opinion) argue AGAINST any human activity being the cause of temperature change. If temperature changes have happened for 800,000 years, and follow changes in the Earth's orbit, then what makes anyone believe that anything humans can do will alter that pattern?

"Cold phases remain roughly similar throughout the 800,000 year record, but starting about 450,000 years ago, warm phases got warmer. Why?"

Why, indeed. I would say, without reservation, that the answer to that question is NOT human activity. Again, it would seem to indicate that the phenomenon is a wholly natural one, and that nothing we humans can do will alter it. What happens, happens.

"What accounts for the unusually low value for CO2 (172 ppm) about 667,000 years ago?"

Environmental regulations of the government in place at that time? A precursor to the Kyoto treaty? I suspect, once again, that human activity did not contribute to this datum, one way or the other. Again, a fairly strong argument that climate change, CO2 levels, and other natural phenomena are exactly that: natural. Human beings affect such things only by virtue of being a part of nature.

Disclaimer: My degree is in electrical engineering, and I work for an environmental engineering company. I strongly believe in our mission, and in the need for environmentally friendly solutions, in and of themselves. I am not convinced that AGW is real or controllable, or that it is a reason, by itself, to do anything.

And the ice caps at the south pole are growing. Maybe not at the north pole. And you keep treating the IPCC as gospel. Why then is there a petition of 30000+ scientists in this country alone that there is no convincing evidence that man is causing global warming, and that evidence shows that higher co2 and methane is actually beneficial??? And I was not convinced by Chameides' weak arguments.

Disclosure: I have a MS is Engineering and am not affiliated with any group benefiting from carbon sales or use, political organization, etc. Just like to get to the bottom of things.

The IPCC devotes Chapter 4 of its Fourth Assessment Report to "Snow, Ice and Frozen Ground". It's a comprehensive review of all the changes we're seeing due to global warming. Here are just a few excerpts: "Snow cover has decreased in most regions…. decline in annual mean arctic sea ice extent…. Mass loss of glaciers and ice caps…. thinning, reduction or loss of ice shelves…. The permafrost base has been thawing…. extent of seasonally frozen ground has decreased."

Bill Chameides did a great series of posts about how we know humans are responsible for recent rapid global warming.

Fortunately, the main conversation among policymakers today is not about the science or whether to implement climate legislation, but how to do it most effectively. Environmental Defense Fund believes that the answer is cap-and-trade, and that the Climate Security Act is a strong start.