157-3-709
This dust-driven cooling, though, is patchy—and in some places it may not even be helpful. Dust that cools a desert can change local airflow patterns and lessen the amount of rain that falls in surrounding areas. This causes plants to die, and provides more opportunities for wildfires, increasing the atmospheric carbon-dioxide level.
To get a better sense of the net effects brought about by the ups and downs of dust, it would help to have a detailed historical record of the dustiness of the planet. And this is what Natalie Mahowald of Cornell University and 19 colleagues have achieved. They analysed cores from glaciers, lake bottoms and coral reefs and measured how the levels of some telltale chemicals changed with depth, and thus with time. They then used models of global wind circulation to deduce which dust sources have become stronger and which weaker. Their conclusion, published recently in Atmospheric Chemistry and Physics, is that in fits and starts over the past century the air became twice as dusty.
Part of the increase stems from human activities—directly, in the case of construction, or indirectly, when it results from clearing vegetation from marginal land in order to farm it. Another part of the explanation may be global warming itself, shifting the boundaries of deserts and intensifying dust production in some areas.


A. 어휘
dust-driven cooling 먼지가 일으키는 냉각현상.
patchy 누덕누덕 기운, 작은 땅을 합친. lessen 감소시키다.
surrounding areas 둘러싸고 있는 지역.
get a better sense of 보다 더 잘 이해하다. brought about 발생하다.
cores 핵심, 중심부. glaciers 氷河(빙하). coral 산호. reefs 암초, 砂州(사주).
coral reefs 珊瑚礁(산호초). measure 측정하다.
telltale 자동표시기, 고자질하는. telltale chemicals 표시 화학물질.
circulation 순환. deduce 推論(추론)하다.
in fits and starts 오락가락하며, 간혈적으로. stems from 생기다.
clearing 개간하다. vegetation 식물, 초목.
marginal land 한계 토지(수지가 맞지 않는 땅). boundaries 境界(경계).