Critical turning point can trigger abrupt climate change

April 21st, 2009 - 2:14 pm ICT by ANI  

Washington, April 21 (ANI): A new research by scientists from the Niels Bohr Institute indicates there can be changes in the CO2 levels in the atmosphere that suddenly reach a critical turning point and with that trigger dramatic climate changes.

The Earth’s climate is essentially contolled by three different cycles.

All three cycles are caused by the pull of the other planets in the solar system on the Earth, and one could say that they control the Earth’s climate by causing changes in the Sun’s radiation.

Solar radiation varies in the two hemispheres during the summer due to these cycles in the Earth’s tilt and the elliptical orbit and this has profound implications for whether ice caps can build up in the northern hemisphere, where the largest land areas are.

The ice ages have come and gone the last 20 million years and for the last few million years, we know with reasonable accuracy how often they come.

In the period before about 1 million years ago, the ice ages occurred around every 40.000 years, then it happened suddenly that the period changed so that it became circa 100.000 years between ice ages.

It is a mystery because nothing changed in the behaviour of the Earth’s orbit 1 million years ago. It is therefore due to a change that comes from the climate itself.

With completely new research results, geophysicist Peter Ditlevsen, Centre for Ice and Climate at the Niels Bohr Institute, has found part of the explanation for the mystery of the sudden change of the ice ages.

He has made model calculations of the climate of the past and compared it to the concrete data from seabed cores, which tell us about the climatic fluctuations of the past.

From the results, he has been able to construct a diagram over the possible climatic conditions resulting from the variation in solar radiation.

It appears that the ice ages and interglacial periods are not a gradual fluctuation between cold and warm climates.

What happened 1 million years ago was that the climate system went from a situation where it fluctuated between two states (cold and warm) with a 40.000 year cycle, corresponding to the dominant change in the Sun’s radiation.

The climate does not become gradually colder or warmer; it jumps from the one state to the other.

That which gets the climate to jump is that when the solar radiation changes and reaches a certain threshold - a ‘tipping point’, the existing climate state, e.g. an ice age, is no longer viable and so the climate jumps over into another state, e.g. a warm interglacial period. (ANI)

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