The email was talking about how to change the existing record to reduce the warming blip of the 40s (observation which didnt fit into the models).
Even if we accept this interpretation of the e-mail in question, it's still only relevant if we accept the oft presented misrepresentation of the anthropogenic warming hypothesis.
Exaggerated warming in the '40s
does not contradict the hypothesis which, to be clear, asserts that:
1. The earth as a grey-body emits over a range of frequencies in long-wave radiation.
2. Some of the gasses in the earths atmosphere are predicted, and observed, to absorb long-wave radiation across certain bands. We call these gasses greenhouse gasses.
3. That energy is predicted, and observed, to be stored as kinetic energy - IE Heat energy.
4. The conservation of mass predicts that for every kilogram of carbon burned four kilograms of carbon dioxide are produced.
5. The conservation of mass also predicts that every kilogram of carbondioxide put in the atmosphere stays in the atmosphere until it is removed (usually by natural processes)
6. The conservation of energy predicts that energy stored by the atmosphere is retained by the atmosphere until it is released by the atmosphere in some form.
7. The beer-lambert law predicts that as the partial pressure of a gas increases, so does the amount of electromagnetic radiation that it absorbs, and that this is true across all absorption bands. This has also been observed to be true.
The corrollary of 4 is that:
8. As we burn fossil fuels, the partial pressure of carbon dioxide in the atmosphere increases at some rate that is the balance of the rate at which it is going out versus the rate at which it is going in.
The prediction of these eight points, the hypothesis of anthropogenic global warming, is that we expect to see a generalized warming trend over long time scales
super imposed on top of natural climate cycles. This is where the denier fallacy creeps in. You would only expect to see a monotonic increasing function in the temperature if there are no natural climate cycles. But we know we don't have that. The idea that periods of exaggerated warming or stasis somehow contradicts the hypothesis of anthropogenic warming is a denialist myth based on a strawman fallacy. The hypothesis of anthropogenic warming does not predict that anthropogenic warming somehow magically supplants natural climate cycles, but rather, it predicts that anthropogenic warming acts in addition to the natural climate cycles, reducing the impact of cooling phases and exaggerating the impact of warming ones.
This is why the blip in the '40s and the current slow-down are actually pretty much irrelevant to the basic prediction If I have two functions, one of which is linear and monotonicly increasing - f(a), the other of which varies as a wave and has positive and negative phases - f(b), then the total function, f(c) where f(c)=f(a)+f(b) is going to display an overal positive, linear, monotonic trend when considered over a long enough period, however, it's also going to show, over shorter periods, areas with an exaggerated slope, and areas where the slope is negative, approximately zero, or only very slightly positive, depedning on the difference between the first derivatives of the two functions.
There are other reasons as well, for example, have you ever
actually looked at the temperature record for yourself? Or does all of your research come from right-wing blogs? The reason why I ask is this - the warming blip in the '40s is not unique, neither is the current slow-down.