A NASA/university study of data on Earth's rotation, movements in Earth's molten core and global surface air temperatures has uncovered interesting correlations.
The changing face of Earth’s climate is more and more being attributed to humans and our effect on the planet and its atmosphere. The latest set of observations which back up our dominant role in changing the climate comes not from any of the normal sources – land, sea, air – but rather from deep in our planets core.

Researchers Jean Dickey and Steven Marcus of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and colleague Olivier de Viron of the Universite Paris Diderot and Institut de Physique du Globe de Paris in France set out to discover, in what is a first of its kind study, how Earth’s rotation, movements in Earth’s core, and global surface air temperature can all be related.

The scientists combined data from a model of fluid movement within our planet’s core and data on yearly averaged length-of-day observations together with two time series of observed annual globa average surface temperatures. The first one was from NASA’s Goddard Institute of Space Studies in New York that extends back to 1880, and another from the United Kingdom’s Met Office that extends back to 1860.

However, since air temperature is composed of both natural temperature changes and changes caused by humans, the researchers subtracted from the total observed temperature records the human-produced temperature changes to generate a corrected temperature record.

What they found once again confirms the massive impact that humans have had on the climate.

From the beginning of their data sets to 1930, the uncorrected temperature data strongly matched with data on movements of Earth’s core and the length of day. However, the two then diverged, with global surface air temperatures continuing to increase but without corresponding changes in the Earth’s core or length of day.

This convergence from 1930 onwards matches with a well-documented increase in global warming that has been attributed by many to human-produced greenhouse gases.

However, in removing any impact humans have had on the climate from the data, the researchers were able to witness the natural variances in the climate. They found that the corrected temperature record remained strongly linked to movement in the Earth’s core and the length of day throughout the entire dataset.

“Our research demonstrates that, for the past 160 years, decadal and longer-period changes in atmospheric temperature correspond to changes in Earth’s length of day if we remove the very significant effect of atmospheric warming attributed to the buildup of greenhouse gases due to mankind’s enterprise,” said Jean Dickey. “Our study implies that human influences on climate during the past 80 years mask the natural balance that exists among Earth’s rotation, the core angular momentum and the temperature at Earth’s surface.”

Dickey and the scientists involved in the study, which was published recently in the Journal of Climate have no explanations for the mechanism driving these linkages, though there are hypotheses.

Since scientists know air temperature can’t affect movements of Earth’s core or Earth’s length of day to the extent observed, one possibility is the movements of Earth’s core might disturb Earth’s magnetic shielding of charged-particle (i.e., cosmic ray) fluxes that have been hypothesized to affect the formation of clouds. This could affect how much of the sun’s energy is reflected back to space and how much is absorbed by our planet. Other possibilities are that some other core process could be having a more indirect effect on climate, or that an external (e.g. solar) process affects the core and climate simultaneously.

Regardless of the eventual connections to be established between the solid Earth and climate, Dickey said the solid Earth’s impacts on climate are still dwarfed by the much larger effects of human-produced greenhouse gases. “The solid Earth plays a role, but the ultimate solution to addressing climate change remains in our hands,” she concluded.

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