So much for the notion that today’s climate is “unusual”. It turns out that some earlier interglacials were much warmer than the current one and that the variations cannot be explained by greenhouse gases alone.
Source: Alfred Wegener Instutute
A new temperature reconstruction suggests that (NATURAL) feedback mechanisms and amplifiers had to be at play.
Der Spiegel here has the story on a team of German scientists led by Martin Melles of the University of Cologne. In 2008/2009 his team extracted a sediment core from Lake El’gygytgyn in northeast Siberia, 100 miles north of the Arctic Circle. The team extracted a 135-meter long sediment core from the lake’s bottom, analyzed it and produced a temperature reconstruction going back 2.8 million years.
What makes this core unique is the lake’s history. It was formed 3.6 million years ago by a meteorite leaving a huge crater. The crater filled with water to form the lake and year by year the bottom accumulated sediment. Because the lake was not covered by a glacier during the ice ages, it sediment core is complete and without holes. Each layer of sediment provides a record like pages in a diary.
What has the reconstruction revealed?
The scientists reconstructed the climate from this core and found some big suprises. According to Der Spiegel there were “some extreme warm periods in the Arctic that up to now had been unknown.”
Der Spiegel adds
The core from Lake El’gygytgyn shows a regular change between warm and cold periods in the Arctic – thanks to changes in the Earth’s orbit, fluctuating greenhouse gases and changing solar activity. However from the back and forth in temperatures and precipitation, some extreme events stand out: The scientists have compared two “normal” warm periods – the current one, which has been ongoing for the last 12,00 years, and another one 125,000 years ago, and compared them to the so-called super warm periods. These occurred 400,000 and one million years ago.”
How warm was it?
Der Spiegel reports on what the scientists found:
During the super warm times, the high temperatures were up to 5°C above the normal highs – that is at about 13°C. Moreover, about 600 liters of precipitation fell per square meter, about double what is normal. ‘For climatology, that’s worlds apart,’ Melles describes the differences. Around Lake El’gygytgyn, where today one finds tundra and little plant growth, green fir trees once grew. During these times, the scientists say, a large part of the Greenland ice sheet was gone.’
One sees a clear agreement between the super warm periods in the Arctic and the disappearance of the West Antarctic ice sheets,’ Melles says. Information on the retreat of this massive ice sheet was gathered from the ‘Andrill’ core in the Antarctic. It’s evaluation has shown that the West Antarctic was ice-free in warm times.
The question of course is what is the connection between the Arctic and Antarctic melting at the same time? Gee, that’s a tough one.
The Melles and his team speculate that melting water being conveyed by ocean currents, and thus coupling the two poles, could be a factor. Another theory they propose is that if sea level rises 5 meters or more, the water flow though the Bering Strait might be enough to warm the Arctic.
Amazing how what seems obvious eludes government-funded scientists. Maybe the connection is the sun?
The paper’s abstract adds:
Climate simulations show these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences. The timing of Arctic warming relative to West Antarctic Ice Sheet retreats implies strong interhemispheric climate connectivity.”
We all suspect that feedbacks and amplifiers are at play. But some scientists are doing all they can to ignore some of the mechanisms being proposed and supported by a growing body of evidence.
If there’s anything that can’t be ignored, it is that the study shows once again that scientists are more baffled than ever on how the climate really works, and so their models have to be considered accordingly.