Logical Reasoning

PT7 · S4 · Q8 George: Some scientists say that

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George: Some scientists say that global warming will occur because people are releasing large amounts of carbon dioxide into the atmosphere by burning trees and fossil fuels.

Conclusion

The predicted (global) warming is already occurring.

Evidence

In George's area: a month of springlike weather last winter, and unusually mild temperatures making leaves turn color three weeks late.

Evaluate

This ends up testing one of the 10 Famous Flaws. If we don't recognize that intuitively, then we get there by pretending we're doing a Weaken question.

Us: Global warming is not occurring already George: then how come we had a month of spring weather last winter, and this fall is so mild that the leaves were late in turning color?

What could we say in response to his evidence?

Us: You definitely had a warmer year, it sounds like! But that doesn't mean that the Earth overall is warmer. It's possible that other parts of the world had colder than average years. We can't judge global temperature changes just be looking at one area.

In other words, this is a Sampling flaw. George assumes that if HIS AREA is warming, then the GLOBE overall is warming.

Goal

Look for an answer asking whether the warming in George's area is typical / representative of the Earth's climate overall.

Which one of the following would it be most relevant to investigate in evaluating the conclusion of George’s argument?

whether carbon dioxide is the
No Impact
Whether carbon dioxide is the only cause of global warming addresses what causes warming, but not whether warming is happening. We can't weaken George's argument by saying, "there are other gases that also cause global warming". If anything that might help George argue that global warming is already happening. If we say that global warming is only caused by CO2, that also doesn't weaken. We have no way to argue that "since global warming is caused only by CO2, it isn't currently happening."
7% picked this
when leaves on the trees
Weaker Impact
It doesn't matter what the specific date is when leaves usually change color. The logical force of George's evidence would be the same no matter what. Whenever they usually turn color, this year was three weeks after that. A late leaf date help him make his point of unusually mild fall temperatures no matter where in the calendar that typical leaf date lands.
6% picked this
what proportion of global emissions
No Impact
Whether CO2 emissions are 10% from trees and 90% from fossil fuels or the other way around would make no difference to George's argument. Neither ratio gives us a way to argue that global warming isn't currently happening.
5% picked this
whether air pollution is causing
No Impact
We never talked about any trees losing leaves. We can say, "NO, air pollution hasn't caused a single tree to lose a single leaf" or "YES, air pollution has caused at least one tree to lose at least one leaf". Neither one of those is going to weaken George's argument or give us a good way to argue that global warming isn't currently happening.
6% picked this
Correct
whether unusually warm weather is
Why this is right
This gets at the sampling / representation issue. If we say, "George, I hear you -- your area has had a warm year. But ... unusually warm weather isn't occurring elsewhere on the globe more frequently than before", that's a great way to argue that "global warming isn't happening yet".
Skill tested: Evaluate · how this choice captures the argument's function is the move to repeat next time.
77% picked this

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