TEMPERATURE VARIATION ANCIENT AND MODERN
2 million years ago: Cycles in Earth’s relation to the sun produce alternating Ice Ages (lasting 90,000 to 100,000 years) and “intergalacials” (lasting 10,000 to 20,000 years). The onset of the glacial period is often slow but ends abruptly at the transition to the warm period. The average global temperature changes 5-7 degrees C during this transition but may rise as much as 10-15 degrees C over a time span of less than 75 years at higher latitudes.
Let us take a look at the climate of the past:
- 130,000 to 110,000 years ago: Eemian intergalacial, warm.
- 110,000 years ago: Fairly sudden shift to glacial conditions, over perhaps 400 years or less. Northern forests retreat south, ice sheets begin to take over much of the Northern hemisphere. Trees give way to grass, and then to deserts, as more water is frozen in ice sheets instead of falling as rain on vegetation.
- 60,000 to 55,000 years ago: In-between phase, partial melting of glaciers.
- 21,000 to 17,000 years ago: Last Ice Age reaches its coldest point. Deserts and semi-deserts take over much of the global land area. Sea levels are 400′ lower than today.
- 14,000 years ago: sudden warming, raising Earth temperatures to roughly present levels. Forests began to spread and the ice sheets to retreat. Sea levels begin to rise.
- 12,500 years ago: The Younger Dryas. After only 1,500 years of recovery from the Ice Age, the Earth suddenly shifts back into a new, short-lived ice age. The dramatic cooling seems to have occurred within 100 years or less. Another 1,000 years or so of ice age follow before another sudden shift back to climate warming.
- 11,500 years ago: The present intergalacial period known as the Holocene. The planet warms from ice age to nearly present world temperatures in less than 100 years. Half of the warming may have occurred in 15 years. Ice sheets melt, sea levels rise again, and forests expand. Trees replace grasslands and grass replace deserts.
- 9,000 to 5,000 years ago: Climate Optimum, warmer and wetter than the Earth’s present climate. The Saharan and Arabian deserts become wetter, supporting hunting, herding, and agriculture. The climate may have been “punctuated” by a cold, dry phase 8,200 years ago, with Africa drier than before.
- 2,600 years ago: Cooling event with relatively wet conditions in many parts of the world.
- 600 to 200 BC: Unnamed cold period preceding the Roman Warming.
- 200 BC to 600 AD: Roman Warming. Grape growing advances northward in both Italy and Britain.
- 600 to 900 AD: “Dark Ages” cold period.
- 900 to 1300 AD: Medieval Warming or Little Climate Optimum, recorded by histories in both Europe and Asia.
- 1300 to 1850 AD: Little Ice Age.
- 1850 to 1940: Warming, especially between 1920 and 1940.
- 1940 to 1975: Cooling trend.
- 1976 to 1978: Sudden warming spurt.
- 1979 to present: A moderate warming trend, very slight according to satellites and weather balloons, somewhat stronger according to surface thermometers.
Note: the figures provided for the last 1,000 years are clearly confirmed by means of Tree Rings and Ice cores in addition to human records.
Please anyone, explain to me how we know the climate changes of the present have anything at all to do with man and how our ever changing climate is any different from the continual and much more radical changes that have been going on since the beginning of time. Also, please stop calling me a "denier" - I know the climate changes radically in both directions, always has, always will. The only proper debate is the cause.
Adapted from Physical Evidence of Earth's Unstoppable 1,500 Year Climate Cycle by S. Fred Singer & Dennis T. Avery. Note: "Cliff's Notes" is a registered trademark and has absolutely no connection to this "Cliff Note"
Al Gore needs this cheat sheet!ReplyDelete
Main energy source of the planet is the sun. It's light hits the atmosphere, hits the planet, warms the planet. The warmth is emitted back from the planet. Warmth is the same as infrared light. Because of the physical attributes of CO2, CO2 deflects infrared light. This is easily proveable in a laboratory and undisputed.
So CO2 in the atmosphere prevents infrared light to emit into space, thus warming the atmosphere.
Now the biggest producer for CO2 is the planet itself. It produces around 770 Gigatonnes of CO2 a year. And it dissolves around 788 Gigatonnes of CO2 a year. Since we produce 29 Gigatonnes of manmade CO2 a year, 11 Gigatonnes a year get into the atmosphere. So since the industrial revolution, the concentration of CO2 in the Atmosphere has been rising. This is undisputed, too. And since this has been happening for 150 years now and CO2 emissions are accelerating every year, we are currently at the highest CO2 concentration in the atmosphere in 15 to 20 million years. Which is some time before man started to walk erect.
If you take the first two points together the question is not "Are we warming the planet" but "How much are we warming the planet".
So you have the surface temperature difference DeltaT, which is a product of the radiative forcing of CO2 DeltaF (the amount of infrared that doesn't get into space), measured in W/m^2 and a Climate Sensitivity Lambda, measured in Kelvin / W/m^2.
The formula is
DeltaT = Lambda * DeltaF
The big question is: How big is Lambda, the climate sensitivity.
It is undisputed that for a doubling of CO2 you get at least a 1 Degree Kelvin rise in average global temperature, due to the physical infrared-absorption characteristics of CO2, if there are no feedbacks at all (glaciers melting, clouds forming etc.).
So the question isn't "Does man change climate with CO2" but "How much?".
Of course there are natural changes in climate due to Milankovich cycles or similar. But these occur over way longer time periods, like thousands of years.
Concerning sudden changes in climate: External Factors exist. Volcanic Activity (just look at what Pinatubo did in 1991) or Meteors come to mind.ReplyDelete
Abrupt changes are not too strange when you think about the Albedo characteristics of ice and snow. Ice and snow have an albedo of about 0.5, reflecting about half of the sun's rays back. 50% of the energy is absorbed, resulting in warmth. Now when ice melts, it becomes water. Water has an albedo of 0.06, absorbing 94% of the energy as warmth.
So this effect works as a positive feedback in both directions.
It gets colder => more ice => less energy absorption, more reflection => it gets colder.
It gets warmer => more water => more energy absorption, less reflection => it gets warmer.
The amount and direction of these feedbacks is currently a big question mark in climate science.
Wikipedia lists the Climate Feedbacks nicely, stating their possible negative or positive nature.
If a lot of positive feedbacks exist, changes can be swift and a balance can be very delicate.
Explaining sudden climate shifts towards the cold: Take a look at supervolcanoes, like the one below yellowstone. If such a beast erupts, like Toba 75.000 years ago, or Taupo, around 22.600 years ago, the implications are severely for the climate.ReplyDelete
Toba alone is estimated to have resulted in global cooling of 3-5 degrees Celsius.
Shmience: I really wish it was "pretty easy"ReplyDelete
It would make my "job" a whole lot easier.
I just finished preparing a new post which details some (not all) of the reasons I don't think it is so simple: "2009 Paper: Nature Rules Climate" so please have a look and tell me what I've missed.
why ice ages could be unpredictableReplyDelete