Home LSAT Prep Free LSAT Prep June 2007 LSAT Question Explanations June 2007 - Sec 2 - LR...

June 2007 - Sec 2 - LR - Q5

Video Transcript:

0:06
Question 5 - Scientists:
0:10
Earth's average annual temperature has increased by about 0.5 degrees Celsius over the last century. This warming is
0:18
primarily the result of the buildup of minor gases in the atmosphere, blocking
0:23
the outward flow of heat from the planet. Alright so argument or facts? We
0:31
have an argument. The scientist is trying to explain something to us and his
0:35
conclusion is that this warming is primarily the result of the buildup of
0:40
minor gasses in the atmosphere blocking the outward flow of heat from the planet.
0:45
So that's the scientist's conclusion or hypothesis. You notice this is a
0:50
cause-and-effect argument. There is something that this scientist is trying
0:54
to explain to us. There is an observed effect. And what is that observed effect? It
1:01
is that the Earth's average annual temperature has increased by about 0.5 degrees Celsius over the last century.
1:11
What is the scientist's proposed explanation for this observed effect of
1:16
the Earth's warming? It is the buildup of minor gases. So he's proposed cause is
1:24
this buildup of minor gases that are blocking the outward flow of heat from the
1:31
planet. So now that we have a clear understanding of this passage let's
1:35
proceed to the questions stem. Which of the following if true would count as evidence against the
1:41
scientist's explanation of the Earth's warming. You notice 'evidence against'. This is a
1:48
weakening question.
1:49
Asking us to weaken this scientist's explanation of the earth's warming. So let's take a look at (A).
1:59
Only some of the minor gasses whose presence in the atmosphere
2:03
allegedly resulted in the phenomenon described by the scientist were produced by
2:08
industrial pollution.
2:13
OK, that is completely irrelivant
2:15
This argument is not about where these minor gases are coming from.
2:23
So (A) would be eliminated. Moving to (B). Most of the warming occurred before 1940 while most of
2:36
the buildup of minor gases in the atmosphere occurred after 1940. So what (B) is telling us
2:44
on this timeline that we have
2:47
1940
2:53
Prior to 1940 had most of the warming. After nineteen forty we had most of the minor
3:01
gas buildup. So does that weaken this
3:07
arguement? And it does because it shows that our observed effect, the warming, was
3:15
present without this proposed cause of the buildup of minor gases because again
3:22
most of the warming occurred before the nineteen forties while most of the
3:25
buildup of minor gases occurred
3:27
after the nineteen forties. So (B) does weaken by showing effect without cause. And
3:37
we know that's one of the three ways to weaken a cause-and-effect argument. So (B) would be the correct
3:41
answer. But again let's make sure because (C) is a very popular answer choice among
3:48
students. (C) tells us over the last century earth received slightly more
3:54
solar radiation in certain years than it did in others. And a lot of students pick (C)
4:00
because the test makers are trying to trick you into thinking that (C) is an
4:05
alternate cause. But is it really an alternate cause? We know alternate causes are
4:12
another way to weaken it cause-and-effect argument. But if you noticed (C) doesn't
4:19
tell us that over the last century earth received slightly more solar radiation
4:24
than the previous century. It says in certain years than it did in other
4:31
years. So you notice it is not an alternate cause because (C) is not
4:36
comparing this past century to the century before it it is comparing certain
4:41
years with in this last century with other years within this last century. So it
4:47
is not an alternate cause because our observed effect was that the earth's average annual
4:55
temperature
4:57
the average
5:00
increased. So even though we had slightly more radiation in certain years than in others
5:06
still on average there was a temperature increase of 0.5 degrees Celsius. So, (C) would be eliminated.
5:13
It's a trap answer. They're trying to trick you into thinking that that is an
5:19
alternate cause. And it said over the last century earth received slightly more
5:24
solar radiation than it did in the previous century that would be an
5:30
alternate cause and it would have been the correct answer. Checking (D). Volcanic
5:35
dust and other particles in the atmosphere reflect much of the Sun's
5:39
radiation back into space before it can reach earth's surface. Ok great. So what?
5:45
That does nothing to our argument here. So (D) would be out. (E) The accumulation of minor
5:51
gases in the atmosphere has been greater over the last century than any other
5:56
time in history. And you notice (E) actually strengthens this argument by
6:02
showing that this cause has been most pronounced in this past century than at
6:06
any other time in earth's history. So clearly strengthens the argument. But again we
6:11
are trying to weaken. So (E) would be eliminated. Again remember that (C) was not
6:18
an alternate cause. Trap answer choice. (B) again the correct answer because it
6:23
shows effect without cause.