According to the passage, the rise in global tempe

单项选择题

FLOODS. DROUGHTS. HURRICANES. TWISTERS. Are all the bizarre weather extremes we’ve been having lately normal fluctuations in the planet’s atmospheric systems Or are they a precursor of the kind of climactic upheavals that can be expected from the global warming caused by the continued buildup of CO₂ and the other so-called greenhouse gases Scientists are still not sure. But one of the effects of the unusual stretch of weather over the past 15 years has been to alert researchers to a new and perhaps even more immediate threat of the warming trend: the rapid spread of disease-bearing bugs and pests.
Climate change, whether natural or man-made, may already be spreading disease and pestilence, according to a host of new studies, including a major report being prepared by the World Health Organization and other international institutions for release this season. Malaria, for example, has been flourishing in recent years owing to unusually hot weather. Similarly, climate disruptions may be giving new life to such ancient scourges as yellow fever, meningitis and cholera, while fostering the spread of emerging diseases like hantavirus.
Underlying all these outbreaks is the same Darwinian mechanism: unusual weather such as dry spells in wet areas or torrential rains in normally dry spots tends to favor so-called opportunistic pests — rodents, insects, bacteria, protozoa, viruses — while making life more difficult for the predators that usually control them. Episodes of extreme weather are routinely followed by outbreaks of plagues, both old and new.
Of all the infectious diseases humans will have to contend with as the world gets warmer, malaria may be the worst. Malaria is already the world’s most widespread mosquito-borne illness. Rising temperatures will not only expand the range of Anopheles mosquitoes, but make them more active biters as well. Paul Epstein, an epidemiologist with the Harvard School of Public Health, notes that a temperature rise of 2℃ would more than double mosquito metabolism, forcing them to feed more often. A 2℃ rise in global temperatures could also expand malaria’s domain from 42% to 60% of the planet. When temperatures rise above 40℃, mosquitoes begin to die off — but at those temperatures, so do people and the crops on which they live.

According to the passage, the rise in global temperatures

A．results from the accumulation of CO₂ and greenhouse effect.
B．results in floods, droughts, hurricanes and twisters.
C．has alerted researchers to the effects of weather extremes.
D．has had all the effects of unusual weather for 15 years.