In article ,
flipper wrote:
And that's without even getting into their other 'tricks', like their
cute little 'secret software' that automagically creates hockey stick
trends from trendless data sets.
http://www.realclimate.org/index.php...if-the-hockey-
stick-were-wrong/
So let's try some more exciting "what ifs". In mid-20th Century,
medieval temperatures are exceeded in all the reconstructions, hence
recent (last 10-15 years, say) temperatures appear to be unprecedented
for at least a millennium (that even holds for the alternative histories
presented by the "hockey stick" critics). Now what if that were wrong -
if all proxy reconstructions as well as model simulations of the past
millennium were fundamentally in error?
Let us assume that medieval temperatures after all had been warmer than
the present. Even that would tell us nothing about anthropogenic climate
change. The famous conclusion of the IPCC, "The balance of evidence
suggests that there is a discernible human influence on global climate",
does not depend on any reconstruction for the past millennium. It
depends on a detailed analysis of 20th Century data. In fact, this
conclusion is from the 1995 IPCC report, and thus predates the existence
of quantitative proxy reconstructions like the "hockey stick".
Climate changes can have several different reasons, and the cause of any
particular climate change needs to be investigated on a case by case
basis. It cannot be found by looking at one temperature curve. Had
medieval climate been warmer than the present, this would probably have
been due to some natural cause - perhaps a peak in solar output. That
would only tell us that in principle, natural causes can cause warming
larger than what we've seen in the past decades. But we know that
already - one need only go back far enough in time (e.g., fifty million
years) to find examples of unquestionably warmer climates than today.
However, it would be naive to conclude that the observed strong 20th
Century warming therefore also must have a natural cause.
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