For each of the past three years, temperatures have hit peaks not seen since the birth of meteorology, and probably not for more than 110,000 years. The amount of carbon dioxide in the air is at its highest level in 4 million years. This does not cause storms like Harvey - there have always been storms and hurricanes along the Gulf of Mexico - but it makes them wetter and more powerful. As the seas warm, they evaporate more easily and provide energy to storm fronts. As the air above them warms, it holds more water vapour. For every half a degree Celsius in warming, there is about a 3% increase in atmospheric moisture content. Scientists call this the Clausius-Clapeyron equation. This means the skies fill more quickly and have more to dump. The storm surge was greater because sea levels have risen 20 cm as a result of more than 100 years of human -related global warming which has melted glaciers and thermally expanded the volume of sea water.

  1. The storm Harvey is one of the regular, annual ones from the Gulf of Mexico; global warming and Harvey are unrelated phenomena.
  2. Global warming does not breed storms but makes them more destructive; the Clausius-Clapeyron equation, though it predicts potential increase in atmospheric moisture content, cannot predict the scale of damage storms might wreck.
  3. Global warming melts glaciers, resulting in sea water volume expansion; this enables more water vapour to fill the air above faster. Thus, modern storms contain more destructive energy.
  4. It is naive to think that rising sea levels and the force of tropical storms are unrelated; Harvey was destructive as global warming has armed it with more moisture content, but this may not be true of all storms.


The paragraph argues that global warming causes sea levels to rise and fill the skies with water vapour, thus leading to wetter and more damaging storms and hurricanes. A contradicts received wisdom by stating that global warming and rampaging storms are unrelated. B focuses on the downsides of the Clausius-Clapeyron equation, which are not mentioned in the paragraph at all. D is verbose, refer to 'but this may not be true of all storms', an uncertain statement anyway from the paragraph point of view. C faithfully captures the essence of the paragraph.

The correct option is C.

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