This follows on nicely from a Talkshop post a few days ago on some underrated effects of Earth’s eccentricity, citing recent studies and an opinion piece by two of the authors calling for the recognition of ‘eccentriseasons’. Here the study found orbital factors ‘exert a decisive influence’ on the climate variations they looked at, and known long-period cycles related to obliquity and precession were identified in the data. The usual nods to IPCC climate theories of alleged human-caused changes now and in the future are uttered, but add nothing to the science.
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A research team led by the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) has analyzed 50,000 years of mid-latitude hydroclimate of the South-East Pacific using special moisture related indicators in marine sediment cores.
They have found that natural variations in the Earth’s orbital parameters exert a decisive influence, says Phys.org.
Understanding the causes of changing humidity and precipitation in the Earth’s past is crucial for better assessments of the planet’s future hydroclimate changes through improved modeling.
One field that climate researchers around the world are focusing on is hydroclimate—i.e. the entirety of all long-term weather phenomena in a region that determine the amount of precipitation and humidity. After all, the Intergovernmental Panel on Climate Change (IPCC) states unequivocally [Talkshop comment – assumption alert]: As climate change progresses, the risk of hydroclimate extremes—both droughts and heavy rainfall events—increases.
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The study provides a glimpse into the paleoclimatic past by analyzing several sediment cores from the South-East Pacific, which were recovered from water depths between 850 and 3,300 meters on the continental slope off the northern and southern Chilean coast.
“Marine sediments, which are deposited over thousands of years in layers that can be dated quite well, are excellent archives from which we can reconstruct past environmental conditions on Earth using certain indicators—so-called environmental proxies,” explains Kaiser.
The cores used in the present study reflect a period of about 50,000 years. The research team primarily focused on the content of deuterium, a naturally occurring hydrogen isotope, in leaf waxes of land plants, which are deposited in marine sediments.
“We know that different deuterium levels say a lot about the precipitation conditions in a region—about the amount and intensity of the precipitation, and even about the origin of the humidity from which the precipitation has formed,” Kaiser explains the approach.
The results show clear patterns for the sources of humidity and the amount of precipitation in the mid-latitude hydroclimate of the southeast Pacific: While in southern Chile the rain was mainly brought by the sub-Antarctic westerly winds, the precipitation in the mid-latitudes of Chile also came from the subtropics. The amount and origin of precipitation from these sources in the two regions, however, is subject to significant fluctuations over the millennia.
“It was particularly interesting for us that the fluctuations in the amount and intensity of precipitation follow distinctive time cycles, which only became visible thanks to the long period represented by the sediment cores: In central Chile, the cycle length is 23,000 years, whereas in southern Chile it is 41,000 years,” Kaiser points out.
These temporal patterns correlate very well with temporal cycles of natural changes in the Earth’s orbit around the sun: During a phenomenon known as “precession,” which correlates with the shorter precipitation cycle in central Chile, the Earth’s axis undergoes a cone-shaped rotation and thus changes the planet’s orientation in relation to the sun.
In addition, the Earth’s axis also changes its inclination within the planet, which is known as the “Earth axis tilt phenomenon” and also affects the planet’s positioning towards the sun. It correlates with the longer time cycle of precipitation in southern Chile.
“Both orbital phenomena influence the intensity of the solar radiation in different regions by changing the tilt of the planet. And this in turn has consequences for the winds that transport moisture and rain,” says Kaiser. That the Earth’s orbital variability has climatic consequences has long been hypothesized and taken into account in regional climate models, the paleoclimate expert continues.
“However, based on the results of the deuterium measurements, our study provides concrete evidence that the hydroclimate of Chile’s mid-latitudes is substantially controlled by orbital parameters. And hydroclimatic extremes in south-central Chile, such as the very high levels of precipitation during the last ice age and the pronounced drought of the early Holocene, can also be plausibly explained by orbital changes,” says Kaiser.
Full article here.
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Image: Earth’s Axial Tilt, or Obliquity [Credit: Wikipedia]
via Tallbloke’s Talkshop
September 12, 2024 at 05:18AM
Iowa Climate Science Education 