Has the earth ever experienced a warming period throughout history, If so when?

Hello Nicole,

Ever since the Earth first formed some 4½ billion years ago the climate has always been in a state of flux. When the Earth was in its infancy it was highly radioactive and so hot that rocks were liquefied. It took 700 million years of cooling before the first solid rocks began to form, shortly thereafter the radioactive decay diminished and the temperature cooled to such a point that water vapour liquefied.

After a further 800 million years of cooling Earth entered it’s first ice age and since then we’ve had three billion years of alternate warming and cooling periods.

With the Earth stabilised, the most influential forces that affected the climate came not from the Earth itself but from the Sun; and more specifically, the relationship that Earth has with the Sun as a consequence of it’s ever changing position in space.

There are many cycles that Earth goes through as it moves in space including the shape of it’s orbit around the Sun, the way it wobbles on it’s southern axis like a wobbly spinning top, the way it bounces up and down in space as it orbits the Sun and the way it moves backward and forward on it’s axis like an inverted pendulum.

These changes happen very slowly, the different cycles being between 21,000 and 410,000 years in duration. As the Earth goes through these cycles there is a change in the relationship with the Sun which leads to an increase or decrease in the amount of heat energy we receive.

Each of these cycles has a warming and a cooling phase and because they’re of different durations it’s possible to get periods when all the cycles are simultaneously either warming or cooling. Similarly, there are times when the warming effect of some cycles is countered by the cooling effect of others.

Of all of the cycles the most profound one in terms of its climatic influence is the one we call eccentricity or circularity, namely the shape of Earth’s orbit around the Sun.

As you’ll no doubt be aware, Earth has an elliptical orbit but the shape of that ellipse isn’t constant. It’s always changing, either tending toward or away from circularity.

It’s this changing orbital shape that gives rise to the ‘ice ages’ (glacial maxima), these occur at regular intervals of 100,000 years and are characterised by 90,000 years of gradual cooling followed by 10,000 years of comparatively rapid warming. Depending on the influence of the other cycles, this particular one causes temperature swings of about 7°C.

The most recent warming period ended some 8,000 years ago and since then the general trend has been one of cooling – as we head toward the next glacial maximum.

There have been numerous such events and each one has had it’s own warming period.

There is a much more pronounced effect on our climate, one in which the average global temperature falls to just 4°C and most of the planet becomes frozen and at the other extreme the average temperature rises to 35°C and tropical plants flourish in the polar regions.

This cycle is tied to the orbit of the entire solar system around the galactic centre and lasts for approx 125 million years. Unlike the shorter ‘ice age’ cycles this one has equal periods of warming and cooling and thus there are periods of approx 60 million years when the general trend is a warming one. Within the upward trend there will be many short term cooling events but the overall trend is one of warming.

Presently Earth is in a cooling phase in respect of this cycle and has been for about 50 million years. Today the average global temperature is around 15°C meaning that, compared to Earth’s very long term average, we’re in a relatively cool phase.

Because these cycles occur over such long periods of time and because there are so many influences on our climate, the temperature change will never be a smooth one, it will always be a trend and there will be many shorter term events when the temperature moves in the opposite direction to the overall trend.

If you want to put these changes into some sort of numerical context then the galactic cycles see temperatures change by about 0.0000005°C per year, the ‘ice ages’ are typified changes of approx 0.00008°C per year during the cooling stage and of 0.0007°C per year during the warming phase. Natural warming and cooling events that are related to increased or decreased solar activity will typically cause temperature changes of about 0.00006°C per year. The present global warming has resulted in an average temperature increase of 0.0177°C per year.

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Yes.

Abrupt cooling about 15,000 years ago gives way to abrupt warming at the end of the Younger Dryas period some 11,600 years ago, with a climatic ripple effect impacting habitats around the world.

The Medieval Warm period . It went up 4 degrees and everybody was doing well.

Swamps dried up and Malaria went away. No SUVs or Factory's at that time

Many of them.

Look at this graph:

http://upload.wikimedia.org/wikipedia/commons/6/60...

And this paper, published in 2005

http://lorraine-lisiecki.com/LisieckiRaymo2005.pdf

Summer...every year

absolutely. it's when most of our coal was laid down.