Challenge issued to environmental journalists and advocates of catastrophic AGW (Anthropogenic Global Warming):

NOTE: The IPCC TAR host sites have an unfortunate tendency to become unavailable without notice so we are posting double links to both a primary and mirror site. If this does not resolve the issue we'll establish our own mirror.

We believe climate models are programmed with excessive climate sensitivity based on a flawed understanding of past ice ages. Moreover, climate models wrongly magnify potential warming to accommodate positive feedback mechanisms while comparison with empirical measure shows negative feedback dominates, reducing warming experienced to about half theoretical values.

The challenge is for you to actually check the numbers -- see for yourselves whether we are wrong or not. Look up Stefan's Constant or just use 5.67 x 10-8 (close enough for our purpose but look it up to be sure). The textbook derivation of globally averaged greenhouse, using Stefan's Constant, evaluates to roughly 33 °C and 150 Wm-2. The IPCC Third Assessment Report alt: Third Assessment Report (Equation 6.1) states: "The climate sensitivity parameter (global mean surface temperature response ΔTs to the radiative forcing ΔF) is defined as: ΔTs / ΔF = λ." A blackbody-equivalent Earth climate sensitivity parameter (λ) would be 33 / 150 = 0.22 °C per Wm-2. Real world measures (here) indicate Earth responds with only half the efficiency of a blackbody with a lambda (λ) value of just 0.1 °C per Wm-2.

Now use it to check the assertion: "Global climate forcing was about 6 1/2 W/m2 less than in the current interglacial period. This forcing maintains a global temperature difference of 5 °C, implying a climate sensitivity of 3/4 ± 1/4 °C per W/m2." Either consult your texts for Earth's temperature in Kelvin and any other numbers you need or see the numbers we've used here. Off you go -- we'll wait. If you can show us where we're wrong we'll retract and correct.

If it's proving too hard following a moderately complex document, try this simple one where we find significant heating does not trigger self-perpetuating enhanced greenhouse from the most prolific and important greenhouse gas -- water vapor. Same deal -- show us where we're wrong and we'll retract and correct.

So far the most substantive contention has been sloppy capture from .pdf source for the quote above, which previously read Wm2 rather than either W/m2 or Wm-2 on this page but not in the analysis document.

Beyond that there must be a strawman rebuttal in the wild because there have been some near-identical assertions that we wrongly treat Earth as a blackbody rather than a graybody [no, read the document and see that we repeatedly demonstrate blackbody calculations using the Stefan-Boltzmann Constant overstates Earth's climate sensitivity by roughly double] and that we ignore feedback [again no, our findings suggest that negative feedback dominates].

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