A second study links climate change with shifts in the Earth’s orbit
By Summit Voice
SUMMIT COUNTY — The Southwest could be headed for a sudden shift in climate, with prolonged droughts becoming the norm, according to a pair of studies of rock formations found in caves of the region.
The calcite layers of the towers, called speleothems, help scientists document changes in precipitation, just like tree rings. The information from the formations help fill gaps where there are no trees or ice cores to study. The towers form during thousands of years by mineral-rich drips of water.
The recent studies focused on caves in Arizona and New Mexico, showing that rainfall patterns shifted quickly as the climate changed during the last ice age. The moisture records matched up with temperature data from ice cores taken in Greenland, where other research teams have recently documented acceleration in the rate of ice-melt.
After comparing their results, the scientists determined that the climate in the Southwest quickly shifted from wet to dry as the North Atlantic cooled and warmed between 50,000 and 10,000 years ago. the findings reinforce predictions of abrupt climate change during the coming century, as emissions of greenhouse gases, such as carbon dioxide, heat the atmosphere. The studies were published in the February 2010 issue of the journal Nature Geoscience.
Many climate-change models indicate that warming of the North Atlantic will drastically shift upper level winds like the jet stream northward, resulting in Chinese monsoons and drought in the southwestern U.S.
“They’re telling us a consistent story, absolutely,” said Kim Cobb, a climatologist at the Georgia Institute of Technology. “As global warming continues, the position of the jet stream is going to change, and it’s going to bring dire conditions to the American Southwest.” Read the full story here.
Changes in Earth’s orbit may affect global climate
Another recent climate change study may complicate the equation, as a UC Santa Barbara geologist has linked changes in climate to shifts in the Earth’s orbit. By studying sediment cores, Lorraine Lisiecki showed that the timing in shifts of the Earth’s orbit coincide with periods of major glaciation.
Lisiecki studied ocean sediment cores from 57 locations around the world. Analyzing sediments enables scientists are able to chart the Earth’s climate going back in time millions of years.
The Earth’s orbit around the sun changes shape every 100,000 years, becoming either more round or more elliptical. Glaciation of the Earth also occurs every 100,000 years.
“The clear correlation between the timing of the change in orbit and the change in the Earth’s climate is strong evidence of a link between the two,” said Lisiecki. “It is unlikely that these events would not be related to one another.”
The research showed that the largest glacial cycles occurred during the weakest changes in the eccentricity of Earth’s orbit –– and vice versa. Stronger changes in the Earth’s orbit correlated to weaker changes in climate.
“This may mean that the Earth’s climate has internal instability in addition to sensitivity to changes in the orbit,” said Lisiecki.
She concluded that the pattern of climate change over the past million years likely involves complicated interactions between different parts of the climate system, as well as three different orbital systems. The first two orbital systems are the orbit’s eccentricity, and tilt. The third is “precession,” or a change in the orientation of the rotation axis.