Carbon Dioxide and Earth's Future Pursuing the ... - Magazooms

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2.80 and 4.94. Clearly, therefore, the state of the North Atlantic AMO is tremendously
important to hurricane genesis and development; and this striking natural variability makes it
impossible to determine if there is any long-term trend in the TC data that might possibly be
due to 20th-century global warming.
One year later, Zeng et al. (2009), as they describe it, “synthesized field measurements, satellite
image analyses, and empirical models to evaluate forest and carbon cycle impacts for historical
tropical cyclones from 1851 to 2000 over the continental U.S.” In doing so, they determined
“there were more forest impacts and greater biomass loss between 1851 and 1900 than during
the 20th century.” On average, for example, they found that “147 million trees were affected
each year between 1851 and 1900,” which led to “a 79-Tg annual biomass loss.” Average
annual forest impact and biomass loss between 1900 and 2000, on the other hand, “were 72
million trees and 39 Tg, which were only half of the impacts before 1900,” which results they
say are in “accordance with historical records showing that Atlantic tropical cyclones were more
active during the period from 1870 to 1900.” In addition, they note that the amount of carbon
released from the downed and damaged trees “reached a maximum value in 1896, after which
it continuously decreased until 1978,” whereupon it leveled off for the remaining two decades
of the 20th century.
Taking a longer look at the subject, Chenoweth and Divine (2008) examined newspaper
accounts, ships’ logbooks, meteorological journals and other documents in order to reconstruct
a history of tropical cyclones passing through the 61.5°W meridian between the coast of South
America (~9.7°N) and 25.0°N over the period 1690-2007, which they describe as “the longest
and most complete record for any area of the world.” This work, however, was inconclusive for
most of the time period, as the two researchers say they could find “no evidence of statistically
significant trend in the number of tropical cyclones passing through the region on any time
scale.” But they did note that “hurricane frequency is down about 20% in the 20th century
compared to earlier centuries,” and that “this decline is consistent with the 20th century
observed record of decreasing hurricane landfall rates in the U.S. (Landsea et al., 1999; Elsner et
al., 2004) and proxy reconstruction of higher tropical cyclone frequency in Puerto Rico before
the 20th century (Nyberg et al., 2007), as well as model-simulated small changes in Atlantic
basin tropical cyclone numbers in a doubled CO2 environment (Emanuel et al., 2008; Knutson et
al., 2008).” They also report that “the period 1968-1977 was probably the most inactive period
since the islands were settled in the 1620s and 1630s,” which finding “supports the results of
Nyberg et al. (2007) of unprecedented low frequency of major hurricanes in the 1970s and
1980s.” In addition, it strongly suggests that the subsequent short-term increase in cyclone
numbers has had absolutely nothing to do with the supposedly unprecedented concurrent
warming of the globe, as it appears to be nothing more than a simple recovery from a shortterm
dip (within a century-scale lull) that reduced yearly cyclone numbers to their lowest levels
of the past three centuries.
Going still further back in time, Wallace and Anderson (2010) collected a total of 37 sediment
cores along eight transects within Laguna Madre, an elongate water body located behind the
narrow low-elevation barrier that is Texas (USA’s) South Padre Island; and based on the vertical
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