Over at Spiegel Online is an energetic and extended article knocking hard at some key arguments proposed by those who insist that human activity is causing grave long-term damage to the Earth’s climate.

Here is the essence of what I think about this policy area.

Over at Watt’s Up With That? Willis Eschenbach likewise explains in simple expert terms what he thinks, breaking down the many issues (and slogans) into manageable propositions.

Extracts:

Despite millennia-long volcanic eruptions, despite being struck by monstrous asteroids, despite changes in the position of the continents, as near as we can tell the average temperature of the earth has only varied by about plus or minus three percent in the last half-billion years. Over the last ten thousand years, the temperature has only varied by plus or minus one percent.

Over the last 150 years, the average temperature has only varied by plus or minus 0.3%.  For a system as complex and ever-changing as the climate, this is nothing short of astounding.

Before asking any other questions about the climate, we must ask why the climate has been so stable…

More:

Since 1980, there has been a huge increase in computing power. Since 1980, there has also been a huge increase in the size and complexity of computer models. Since 1980, thousands of man hours and billions of dollars have been thrown at this question. Despite these advances, the modern estimate of the climate sensitivity is almost unchanged from its 1980 value.

To me, this lack of any advance in accuracy indicates that we have an incorrect understanding of the forces governing the climate.

And this (emphasis added):

Is climate science a physical science?

Well, sort of. It is a very strange science, in that to my knowledge it is the only physical science whose object of study is not a thing, not a physical object or phenomenon, but an average. This is because climate is defined as the average of weather over a suitably long period of time (usually taken to be 30 years.) The implications of this are not widely appreciated. Inter alia, it means that statistics is one of the most important parts of climate science.

Unfortunately, a number of what I might call the “leading blights” of climate science, like Michael Mann with his HockeySchtick, have only the most rudimentary understanding of statistics. This initially got him into trouble in his foray into the area of paleoclimate statistics, trouble which he has only compounded by his later statistical errors…

Finally:

Regarding climate, what action (if any) should we take at this point?

… I think that the earth actively maintains a preferred temperature. I think that man is having an effect on local climate in various places, but that globally man’s effect is swamped by the regulating action of clouds and thunderstorms. I think that the local effect is mainly through LU/LC changes and soot. I think that the climate regulating mechanism is much stronger than either of these forcings and is stronger than CO2 forcing. I think that at this point the actions we should take are “no regrets” actions.

Elegantly and convincingly done. Read the whole thing and the Spiegel piece, to see how the debate has shifted sharply since the Copenhagen debacle.