June 17, 2013
Cold Snap 116 Million Years Ago Triggered Global Cooling
Lee Rannals for redOrbit.com - Your Universe Online
The researchers said they were able to confirm a link between global cooling and a crash in the marine ecosystem during the mid-Cretaceous greenhouse period. This study quantifies the amplitude and duration of the temperature change for the first time. The team was able to show that a global temperature drop of up to 9 degrees Fahrenheit resulted in a major shift in the global carbon cycle over a period of 2.5 million years.
The scientists' study found how the opening and widening of new ocean basins around Africa, South America and Europe created additional space where large amounts of atmospheric CO2 was fixed by photosynthetic organisms like marine algae. These organisms were then buried in the sediments on the sea bed, producing organic, carbon rich shale in these new basins.
The massive carbon fixing mechanism resulted in a drop in the levels of atmospheric CO2, reducing the greenhouse gas effect and lowering global temperature. Essentially this effect did the opposite of what we are experiencing today through global warming.
Scientists said the global cooling period came to an end after about two million years following the onset of a period of intense local volcanic activity in the Indian Ocean. Volcanic gas from this activity helped replace carbon in the Earth's atmosphere with CO2 from the planet's interior, re-instating a greenhouse effect that led to a warmer climate.
This study helps show how global climate is linked to processes taking place in the Earth's interior at million year time scales. These processes help modify ecospace for marine life, which drives the evolution.
Studies have focused on global warming and the impact a few degrees change could have on past and present ecosystems. However, this research shows that if global temperatures swing the other way the result can be just as severe.
"As always it's a question of fine balance and scale," explains Thomas Wagner, Professor of Earth Systems Science at Newcastle University, and one of the leaders of this study. "All earth system processes are operating all the time and at different temporal and spatial scales; but when something upsets the balance — be it a large scale but long term natural phenomenon or a short and massive change to global greenhouse gases due to anthropogenic activity — there are multiple, potential knock-on effects on the whole system."
He said the trick is to try to identify and quantity the initial drivers and consequences, which remains an ongoing challenge in climate research.
A few weeks ago another group of scientists was able to create a more reliable projection of global warming. They found a 63 percent chance of uncertainty in projected warming was due to a single source, while 37 percent of uncertainty came from the combination of these sources.
“Our results reconfirm the need for urgent and substantial reductions in greenhouse gas emissions if the world is to avoid exceeding the global warming target of 2 degrees needed to minimize dangerous climate change,” said Dr Roger Bodman from Victoria University.