Take a very commonplace, often discussed and critical topic: Are we detecting a greenhouse effect, and related to this, is it exacerbated by "homogenic factors," i.e., human actions? Most would be inclined to give a positive answer to both of these questions. But, if pushed, what would be the evidence, and how well grounded would it be for such affirmations?
Within scientific communities and associated scientifically informed circles, the answers have to be somewhat more ambiguous, particularly when rigorous questions concerning evidence are raised. Were scientific truth to be a matter of consensus, and some argue that scientific truth often turns out to be just that, then it is clear that there is beginning to be a kind of majority consensus among many earth science practitioners that the temperature of the Earth, particularly of the oceans, is indeed rising and that this is a crucial indicator for a possible greenhouse effect.
Most of these scientists admit that the mean oceanic temperature has risen globally in the last several decades. But this generalization depends upon how accurate measurements may be, not just for samples, but also for the whole Earth. Hot spots, for example the now four year old hot spot near New Guinea which is part of the El Niño cycle, does not count by itself because it might be balanced by cold spots elsewhere. And the fact of the matter is that "whole earth measurements" are still rare and primitive in the simple sense that we simply do not have enough thermometers out. Secondly, even if we had enough thermometers, a simply synchronic whole earth measurement over three decades is but a blip in the diachronic history of ice age cycles over the last tens of thousands of years. Thirdly, even if we know that the earth is now heating up, has an ever increasing ozone hole, and from this strange weather effects can be predicted, how much of this is due to homogenic factors, such as CFCs, CO2 increases, hydrocarbon burning, and the like? Is it really the case, as Science magazine claimed in l990, "24% of greenhouse encouraging gases are of homogenic origin"?
17. In this passage the author is primarily interested in
(A) Whether scientific truths are simply a matter of consensus
(B) Determining how well established the greenhouse effect is and to what degree it is worsened by human actions
(C) Whether the hot spot El Niño is balanced elsewhere by cold spots
(D) Determining if most scientists would be inclined to give a positive answer to the question of whether there is a greenhouse effect and if it is worsened by human actions
(E) Making a simple synchronic whole earth measurement more than a blip in the diachronic history of Ice Age cycles over the last tens of thousands of years.
18. The author of the passage would be most likely to agree with which of the following statements about the greenhouse effect?
(A) 24% of greenhouse encouraging gases are of homogenic origin.
(B) There is a greenhouse effect that is exacerbated by homogenic factors.
(C) The ozone hole is increasing due to homogenic factors, such as CFCs, CO2 increases, hydrocarbon burning, and the like.
(D) One can determine if mean oceanic temperatures have risen globally in the last several decades only if measurements of ocean temperatures are precise.
(E) Hot spots, such as the El Niño cycle, should not be counted as a factor in the greenhouse effect.
19. It can be inferred from the passage that
(A) We cannot be certain that strange weather effects are a result of the earth heating up and an ever-increasing ozone hole.
(B) The greenhouse effect is the most widely discussed topic in the scientifically informed circles.
(C) If the temperature of the oceans has ceased to rise at an ever-increasing rate, then the rate of global warming has increased.
(D) Strange weather effects have been shown to be due to the diachronic effects of hydrocarbon burning and not to increases in CFC.
(E) Strange weather effects are caused by the increase use of CFCs, CO2, and similar gasses.
20. The author’s claim that, a simply synchronic whole earth measurement over three decades is but a blip in the diachronic history of ice age cycles over the last tens of thousands of years would be strengthened if the author
(A) Indicated the minimum number of thermometers necessary for a whole earth measurement.
(B) Described the factors that precipitated the start of a new ice age.
(C) Compare synchronic whole earth measurements with diachronic whole earth measurements.
(D) Proved that the mean number of years required to detect significant changes in weather patterns is greater than thirty.
(E) Specified the exact location and quantity of thermometers placed by scientists around the globe.
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