[Edi]

If we intend to be serious about stopping the man-made effect that contributes to (as opposed to being the sole cause of) global warming, all of us would have to take a massive hit into our lifestyles, is what he means, I suspect.

It just so happens that the 650 skeptics are a drop in a bucket compared to the larger body of climate scientists who have achieved a consensus that humans have a significant effect on global warming, increasing it. That's comparable to some intelligent design proponents who made a lo tof hay about some Steve somebody who was a scientist and backed their crazy ideas. An Australian organization of scientists signed up 700 scientists from that same field whose first name was Steve to refute his bull**** and in the glkobal warming discussion, the 650 denier scientists are a comparable example.

The primary cause of global warming is build-up of atmospheric greenhouse gases, notably CO2. The amount of atmospheric CO2 has increased fivefold in the last 150 years and almost all of that carbon has a radiological footprint of being millions or tens or hundreds of millions of years in age. That means that nearly all of it is of fossil origin, i.e. coal. Unless that is taken out of the atmosphere by some means, there is no way to return to the same mechanisms that caused the early medieval warm bump and the mini ice age in the 1600s.

The increase of the greenhouse gases leads to less reradiation of heat into space, so the earth absorbs more from the sun than it emits back out on the night side. Increase of temperature causes the ice caps to melt, which reduces albedo, which again reduces the amount reflected and reradiated out.

If there are slight dips and and bumps in a curve that overall has an upward trend, the individual dips and bumps don't mean much. Likewise, a transitory local weather phenomenon does not mean much, because the heat distribution throughout the world is not even by a long shot and local variation can be significant without impacting the overall trends at all.

There are also some other factors that cause variation. Large volcanic eruptions cool temperatures because of the obscuring effect the ash has on the sun, causing less heat to reach the ground. Another factor on the geological timescales is continental placement. The earth has been much warmer at some points, because during those periods there was no Central American isthmus to block the warm equatorial current that would have counteracted the effect of the cold currents circling Antarctica and some other continents were likewise in other places.

The fact that things have been warmer in the past is also not at all an argument for why warming back up to those temperatures would be beneficial for humankind as a whole, because our current societies were built during a colder period and the warming is causing a LOT of damage to the environment. That is an undisputed fact and only a fool would argue nothing should be done to mitigate that damage.