MYTH 9: GLOBAL WARMING HAS ACCELERATED IN THE PAST FIFTY YEARS
Since the beginning of the Industrial Revolution in the mid-eighteenth century,
human activities have added a considerably larger share of heat-trapping greenhouse
gases to the atmosphere than during any previous era.
For that reason, discussion of global warming has emphasized the role that these
activitiesnotably, coal combustion for electricity generation and oil
combustion for transportationmay play in climate change. It is not surprising,
then, that more than three-quarters of respondents believe that the planet warmed
more during the latter half of the twentieth century, when global energy consumption
was greater and fossil-fuel combustion was much higher.
Nevertheless, scientists generally believe that the earth warmed at least as
much, if not more, from 1900 to 1950 than during the subsequent fifty years.
Indeed, the global climate pattern saw a relatively pronounced rise in temperatures
from shortly after the turn of the century to about 1945. Then temperatures
cooled somewhat until 1976, when they began to rise again with slightly more
what degree are human-induced greenhouse gases responsible for warming the atmosphere?
The answer is unclear. Despite the certitude with which the media and politicians
treat the issue, the science remains muddled. Temperatures fluctuate: they go
up in some regions, down in others, and may be affected by naturally occurring
phenomena, such as El Niño.
There are somemost notably, former vice president Al Gorewho argue
that the climate fluctuations of the twentieth century are due to greenhouse
gas emissions, particularly carbon dioxide generated by burning fossil fuels.
But other observers are not so sure. According to the George C. Marshall Institute,
Much of the observed temperature rise of 0.5°C [approximately 1°F]
occurred before 1940, whereas most of the additional carbon dioxide (over 80
percent) entered the atmosphere after 1940.
The increase in greenhouse
gases cannot explain the rapid rise in temperature prior to 1940, and it cannot
explain the drop in temperature from 1940 to 1970.
Natural factors must
have caused most of that [early-twentieth-century] warming.
In their book Energy: The Master Resource, Robert L. Bradley, Jr. and
Richard W. Fulmer raise an interesting point about the supposed impact of carbon
dioxide as the principal agent of climate change: The most common greenhouse
gas is water vapor, which accounts for about 94 percent of the natural greenhouse
effect. Its atmospheric concentration is ten times that of CO2. Water vapors
impact on the climate is complex and not well understood. It can both warm and
cool the atmosphere.
The lack of certainty that surrounds the climate-change debate was underscored
in December 2006, when Britains Sunday Telegraph reported that
the United Nations Intergovernmental Panel on Climate Change (IPCC) was preparing
to reduce its overall estimate of mankinds impact on climate change by
as much as 25 percent. The story also noted that the IPCC had already been
forced to halve its predictions for sea-level rise by 2100, one of the key threats
from climate change.