4
The number of major ice ages the Earth has experienced, dating back 2.7 billion years ago, according to scientists. metro
Published 23:06, April the 26th, 2009
Climate change: As old as the hills
Humans cause global warming, right? Well, not always
As dire warnings attributed to man-made global warming persist that New
York City risks being washed out by rising sea levels and melting glaciers at
the poles will cause a worldwide shortage of freshwater, it’s worth noting
that events like these are nothing new in the Earth’s very long history.
For millions of years, our planet has seen a continuum of one ice age thawing
into a warming period, then refreezing into another ice age. And it might
surprise you to know that we are living through an ice age right now, known as
the Holocene period. Ice ages are made up of glacials and interglacials.
Glacials reference a time when the Earth is cooler and the buildup of ice
expands around the globe. Interglacials are periods when temperatures rise and
the planet thaws, making it more conducive for human inhabitance. Carbon
dioxide is only one explanation for the shift in cooling to warming and vice
versa. There are a host of other natural explanations.
WHEN THE PLANET COOLS
3 causes
1. A reduction in carbon dioxide
When tectonic plates are positioned in a way that alter wind and oceanic
currents, the natural weathering process does not scrub CO2 from land and emit
it into the air, keeping temperatures cool.
2. Flow of warm water
The nearly landlocked Arctic Sea retains colder water at the North Pole while
Antarctica rests directly over the South Pole, blocking out warm water. This
allows ice sheets to form, which reflects the sun’s radiation instead of
absorbing it, keeping temperatures cool.
3. Variations in Earth’s orbit
Though still under study, scientists have found a link between glacial and
interglacial periods and the tilt of the Earth’s axis. When the Earth is
positioned at a larger distance from the sun, combined with a tilt away from
the sun, the Earth experiences cooling. The reverse is true during warming.
This happens every 100,000 years. metro
WHEN THE PLANET WARMS
3 causes
11,000
Number of years the current interglacial period we are living in has
lasted. Most scientists predict that interglacials last an average of
12,000 years.
METRO
1. An increase in carbon dioxide
The Earth naturally emits thousands of tons of carbon dioxide every year.
Before humans inhabited the Earth, this natural process was one of the single
most important factors in warming. Human activity has added to already
naturally high CO2 levels through deforestation and industrial pollutants.
2. Variations in the sun’s intensity
Scientists predict the sun’s output increases by 10 percent every billion
years. In one billion years, that extra 10 percent widely increases the amount
of water vapor on Earth, which traps heat and contributes to global warming.
3. Volcanism
Scientists determined that underwater volcanoes may have produced enough
methane to help heat up the ocean and melt the ice that formed atop it. Though
it’s not enough on its own to end glacial periods, it probably helped.
Published 22:56, April the 26th, 2009
The single most important issue is whether climate change is natural or
human-caused.
In principle, both options are plausible.
But we know that climate changes naturally, on time scales of decades and
centuries.
So which is the more important cause: the human release of gases or
natural cycles? One cannot go by the majority view — science does not work
like politics.
We cannot use the fact that there is a rough correlation between
temperature increase and increase in CO2. During much of the 20th century,
from 1940 to 1975, the climate cooled while CO2 levels rose. And during the
past decade, climate has again been cooling in spite of rising CO2.
The answer is to look at the pattern of warming trends and see if it
agrees with what models predict. The models all predict the existence of a
“hot spot” — a maximum warming trend in the tropical region. The
observations from weather balloons show the opposite result, a slight
cooling trend. This disagreement between calculated and observed
fingerprints of temperature trends is the strongest argument against any
appreciable human contribution to climate.
Published 22:42, April the 26th, 2009
Temps cooling amid CO2 alert
It might make a lot more sense to draw a correlation between man-made
carbon dioxide levels and rising temperatures if the temperatures hadn’t
decreased in the last decade.
Studies show that average global temperatures have decreased as much as
0.2 degrees Celsius over the last ten years — just as human activity is
thought to be taking its biggest toll on the planet’s climate.
The decrease is small, to be sure, but, say skeptics, it disproves the
argument that rising man-made CO2 levels are the driving force behind
global warming.
It’s only natural
“The Earth’s climate has always alternated between warming and cooling phases,” said William Happer, who served the Department of Energy under former President George H.W. Bush. “In the medievel warming period, when the Norse settled Greenland, the Earth warmed as fast or faster than it has since 1800. ... What should world governments have done in the year 900 A.D., when people noticed that the climate was warming and the ice was melting in southern Greenland?”