Although no one disputes that global temperatures have increased some over the last century, there is dispute as to whether this warming is manmade. After all, natural variability in climate is a simple fact.
British researchers now claim that their "recent work suggests a discernible human influence on climate."
"Work"? Hardly!
Research on the phenomenon of global warming depends in large part upon mathematical models. Scientists use these models in attempts to explain past and future variability in global climate.
Of course models are only THEORETICAL in nature. While they may be comprised of bits and pieces of knowldege, they heavily depend upon various assumptions. An example of one such assumption in global climate modelling is that changes in sea surface temperature and clouds due to changes in stratospheric ozone are not important to global climate change.
Assumptions can "force" the outcome of a model.
In cancer risk assessment, for example, one significant assumption is that exposure to a single molecule of a chemical carcinogen can lead to cancer. This assumption, that there is no safe level of exposure to a chemical carcinogen, results in inflated risk estimates, usually followed by unduly strict regulation.
Apparently, the assumptions used so far in global climate modeling have not permitted the models to support the notion that global warming is manmade.
Tett et al. came to their conclusion by using "less restrictive assumptions" in their modeling. As a matter of fact, they "avoided making [the more restrictive] assumptions" — assumptions that would have lead them to a different conclusion.
So perhaps their "work" does show that man has had a discernible influence on global climate. Unfortunately, their "work" actually amounted to changing key assumptions, not scientific progress.
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