For example, having but one world, it is not possible to manipulate greenhouse gases in the atmosphere while also observing the climate of an unmanipulated experimental control. Thus, there are inherent limitations on knowledge obtainable by experimentation, and computer models have been developed to help us understand the interactions of the various phenomena that determine global climate. Problems should be expected now that these models have become tools, not so much for understanding, but for making predictions. The validity of this explanation is difficult to assess because the theories of global cooling are as untestable as the theories of global warming. The antennae of healthy skeptics should shoot up when hearing untestable excuses, which tend to sound like new bogus theories invented to explain why the old bogus theory doesn't seem to work.
Nature remains unmoved by the popular theories of the day.
The findings of one scientist backed by sound experimental results are more reliable than the contrary opinions of 999 others who lack such results. Neither should scientific truth be sought by appeal to authority. Scientific understanding, to be sound, must instead be advanced by appeal to experimental and observational evidence. This, and not intelligent scientists or logical thought, is the unique characteristic that distinguishes science from other ways of knowing. Asimov 's popular guides to science recount dozens of instances where the vast majority of scientists and the leading authority figures have been wrong.