1. Earth's Temperature : A Brief History Of Recent Changes
Approximate temperature range:
Low: 5°C... 41°F
High: 17°C... 63°F
variety : 12°C... 22°F
Atmospheric Carbine Dioxide under 300 ppmv
in the Iast 10 ,000 many years :
Hunter-gathers grew to become farmers
Plant as well as animal varieties were domesticated
Civilizations were developed
Global mean temps probably didn't vary by more than 1°C... 2°F in a 100-year period
the surface temperature of the world tends to increase rapidly after which settle down again in cycles
of approximately 100,thousand years because shown above in this UN atmosphere Programme
(UNEP) chart. The blue line traces the temperature differences (within degrees Celsius) over the last
420,000 many years compared to the existing time, understood to be the year 1950.
In 1950, according to NASA's Goddard start for room Studies, the actual mean surface temperature
of the world was 14° Celsius or even 57° Fahrenheit. Thus the earth's absolute temperature (as
opposed to its temperature alter ) during the last 420,000 many years varied from a low around 5°C
or even 41°F to a high of about 17°C or even 63°F, a variety of approximately 12°C or 22°F.
Although this particular range is no more than exactly what most of us experience in the course of the
year's period going from summer in order to winter, UNEP refers to these temperature modifications
as "very significant" and to the earth's climate throughout most of these many years as "unstable."
Towards the base of the variety the temperature was chilly enough for glaciers to improve in size and
also at the top was warm enough for glaciers to become reduced by melting. The actual colder many
years are referred to as periods of glaciation and also the warmer many years as intervals of
interglaciation.
Although estimations of the age of our varieties , homo sapiens, vary broadly , 420,thousand years
most likely covers the majority of if not all in our existence on this planet. But it was only 10 ,000 or so
years ago that we learned how you can grow our own food, the development that resulted in the
creation of set communities, the actual division of labor and all the benefits of what we phone
civilization.
This last 10 ,000 many years (see vertical red line drawn on the population chart above), known as
the Holocene Epoch, has been among interglaciation exactly where temperatures, when compared to
prior 410,000 many years , have been remarkably stable. Through the Holocene, based on UNEP,
"based on the incomplete evidence available , it is unlikely that global mean temps have diverse by a
lot more than 1°C [2°F] in a hundred years."
If we were to trace the concentration of carbon dioxide (C02) in the atmosphere over the same
420,000 many years , we would look for a very similar design to surface temperature. Atmospheric

2. co2 is the most large of the so-called greenhouse gases that soak up heat branched out from the
floor and then expand some of it back to the Earth's surface , keeping our planet warmer compared to
it otherwise would be. Without greenhouse gases and atmospheric water watery vapor (which serves
the same perform ), the imply temperature of the world would be about 0°F or even minus 18°C
instead of (within 1950) 57°F or 14°C.
The concentration of carbon dioxide in the atmosphere during the last 420,thousand was never up to
300 components per million by volume (ppmv) till about a century ago when it rose about 300 ppmv,
reaching 311 ppmv within 1950. It has been rising since.
The 100 ,000 year cycles of Earth's temperature shown in the UNEP charts was first hypothesized by
a Serbian astrophysicist as well as mathematician called Milutin Milankovitch in the 20's and ‘30s.
Building on the work of other researchers who experienced observed how the Earth's orbit around the
sun was irregular in 3 particular aspects , Milankovitch created a model to show how the amount of
sunlight (solar the radiation ) reaching our planet varied based on the interaction from the cycles of
these three irregularities , which are described below:
The eccentricity cycle affects how much more sunlight the Earth receives when it is closest to the
sun (perihelion) compared to when it is furthest from the sun (aphelion) as well as enhances or even
decreases the result on sunlight of the additional two irregularities. But it is not really strong enough to
create our months.
The obliquity cycle produces our months. The greater the actual tilt, the greater pronounced the
times of year -- hotter summers, cooler winters.
The precession cycle causes the times of year to migrate , which is why it is also called the
Precession of the Equinoxes -- as well as why the age of Pisces will ultimately pass the actual torch
to the Age of Aquarius.
1. Eccentricity: inside a cycle of roughly 100 ,000 many years , the shape from the Earth's orbit
around the sun varies from an almost perfect group to a better elliptical shape , with the sun nearer 1
end (instead of in the middle), after which back to a more circular shape.
2. Obliquity: inside a cycle around 40,thousand years, the actual tilt from the Earth's axis relative to
the actual plane of its orbit round the Sun differs from 22.1 degrees in order to 24.five degrees as well
as back.
3. Precession: In a cycle of a small over twenty ,000 many years , the point of the earth's axis
wobbles so that the northern axis factors now in order to Polaris (its northern border Star) however
will eventually point to Vega prior to returning to Polaris.
But Milankovitch wasn't simply interested in tracking changes in sunlight with his model -- he wanted
to clarify why ice ages happened , why at various times in the background of the Earth glaciers were
formed and later on melted aside.
To that end he constructed a numerical model for the 600,thousand years prior to 1800 which
calculated solar radiation as well as surface temps at particular latitudes, particularly Latitude 65°
North -- the latitude of Fairbanks, Alaska as well as Oulu, Finland -- in the month of July. Their theory
was that within cooler summers the winter snows did not totally melt however over time

3. accumulated and led to glaciation.
As might happen , say, once the Earth's orbit is maximally elliptical, obliquity is minimum (less tip ,
cooler summers ) and the north Hemisphere's summer time occurs when the planet is furthest from
the sun.
Milankovitch's theory was mostly ignored till , in 1976, a study based on deep-sea deposit cores
within Antarctica substantiated that changes in temperature going back 450,thousand years mostly
conformed in order to changes in the earth's orbit. The actual eccentricity, obliquity and precession
variations within Milankovitch's model are said to possess accounted for, respectively, 50%, 25% and
10% of temperature change. Milankovitch's theory is now accepted as the greatest explanation of
climate change "on time weighing scales of hundreds and hundreds of years." And the theory
suggests that to expect time for Earth to begin a new long-term cooling cycle.
In 1967 the Russian scientist named Mikhail Budyko made a prediction: increasing man-made co2 in
the environment would conquer any cooling effects soon and cause Earth's temperature to increase.
By coincidence, which same year a young Iowan named james Hansen joined NASA's Goddard
Institute for Space research in new york city as a study associate. He had just finished his doctoral
thesis on the atmosphere from the planet Venus where co2 was thick and the surface temperature
would be a scorching 460°C (860°F), right now he was assigned to the question elevated by Budyko -
- might climate forcings (as they are called) from human causes cancel out natural forcings of cooler
temps and cause global warming soon ?
Hansen and his colleagues built a simple environment model reflecting various assumptions of
human activity. What they found was , in Hansen's words, "which human-produced greenhouse
gases should become a dominating forcing and even exceed additional climate forcings, such as
volcanoes or the sun , at some point in the future." when ? They didn't know.
They began collecting temperature data from weather channels around the world. Finally , in 1981, in
an analysis released in Science and referenced in a front page article in the New York Times, they
verified Budyko's conjecture , showing which temperatures experienced started rising a decade
prior to.
In 1988, on a record-breaking hot summer time day within Washington, deb.C., having "weighed the
costs of being wrong versus the costs of not really talking," Hansen testified before our elected
representatives that he was 99% assured we were inside a long-term heating trend anf the husband
suspected greenhouse gases were causing it. His accounts and claims to reporters afterward were
widely reported in the media. Global warming had gone public.
In the two years since Hansen's testimony, the actual increases in both greenhouses gases and
temperature have accelerated. The chart below from a recent NASA report compares the situation
today to 1880, a century or so after the (human-made) Industrial revolution got going ahead.
Atmospheric carbine dioxide, the major culprit among greenhouse gases , reached 384 ppmv
(components per million by volume ) in 07 compared to 290 in 1880, about 280 before the
commercial Revolution started , and never a lot more than 300 during the 420,thousand years prior to
the Industrial revolution.

4. Atmospheric co2
• is 35% higher than when Industrial revolution began
• is higher than any kind of period within last 420,000 years
• is primary cause of temperature increase (not really the other way around)
If no action is take to abate greenhouse gases --
Earth's temperature
• may increase by 2-6°C... 4-11°F in the 21st Century
which will be higher than at any point
• in the last 10 ,000 many years (Holocene Epoch) when we developed the foods which support all of
us and the fruit of our civilization
• since the middle Pliocene Epoch 3 million years ago when sea level may have been 25 meters or 80
feet higher than today
The temperature increase was much less dramatic -- 0.85°C (1.53°F) -- however much of the actual
carbon dioxide added in this time period will remain in the atmosphere as well as continue to warm
the Earth for hundreds of years to come.
The NASA statement said that the actual "only viable description for heating after 1950 is an rise in
greenhouse gases."
So what happened in order to Milankovitch?
Before the Industrial revolution and the huge increase in populace that followed, temperature change
over the long term was mostly caused by alternation in sunlight described by the Milankovitch Cycles.
Temperature change influenced change in greenhouse gases, that in a so-call positive feedback
mechanism then accelerated the actual temperature alter.
Now, nevertheless , the recent surge within greenhouse gasoline emissions offers trumped the actual
Milankovitch cycles. The number one cause of the current upwards trend within Earth's temperature
is the increase within atmospheric co2 , not an rise in sunlight. And also the increase in co2 is
triggered primarily by human exercise , notably the actual burning of fossil fuel (oil, natural gas and
fossil fuel ), not through the temperature increase -- even though in an additional positive suggestions
mechanism the actual temperature increase may help to improve the amount of co2 in the
environment.
James Hansen took global warming public in the Congressional accounts in the summer of 1988,
however Congress has never taken action , and neither has the Executive department. Indeed, the
final three administrations (Bush, Clinton, Bush) have tried to snout him.
In its 2007 global warming Synthesis Report, the Intergovernmental Panel on Climate Change
(IPCC), which discussed that seasons Nobel serenity Prize along with Al Gore, projected temperature
increases in the 21st century of from 2 in order to 6°C (four to 11°F) if no action is actually taken past
what small has already been come to mitigate greenhouse gas emissions.
Should we be worried? should our grandkids ?
According in order to Hansen, "in the event that further global warming reaches two or three degrees
Celsius, we will likely see modifications that make planet a different planet than the one we know.

5. The last time it was which warm was... About three million years ago, when sea level was believed to
have been about twenty five meters (80 feet) higher than today."
In 04 2008, Hansen and 7 other researchers from as many universities as well as institutions posted
an abstract to Science entitled Target atmospheric co2 : Where should humanity goal ? their own
conclusion: "If mankind wishes in order to preserve a planet similar to the 1 on which civilization
developed and also to which life on Earth is actually adapted, paleoclimate evidence and ongoing
climate change suggest that CO2 will need to be reduced from its current 385 ppm [in 2008] in order
to at most 350 ppm."
When bill McKibben, longtime global warming activist and author of The End of Nature, study these
words , he began a new grassroots climate motion called 350.org "to make sure everybody knows the
target to ensure that our political leaders feel real pressure to act."
He admits it's a bit of the Hail Mary. The last year when carbon dioxide was down to 350 was 1987.
What if we do not make it?
"People may doubtless survive on a non-350 planet," McKibben writes, "however those who do will
be so preoccupied, dealing with the limitless unintended consequences of an overheated planet,
which civilization may not."
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