(AGENPARL) – gio 10 novembre 2022 Having trouble viewing this press release? [Read it online](https://link.mediaoutreach.meltwater.com/ls/click?upn=uDPfAnrJXoDw8-2BCe3b2e6gTQXqoFtB58fI1KeAEfz1zz70vO1yrPEXWZw37gEy2xTKKiOplabeKfbLfagfvPDIUcm3SfEs74cHz8Ni-2F6jq666fCNJDjh-2BIzQWvcdXVoPAgz4FjOl5wTLk-2B4oEWDv7W6Z2l15M0MX-2FG9F377JfTZYVyfVvoebefsbGgInNI0Hk4kp_mLoYh0p4AWg4foFr5HgrZ1QioQ33bLwdnQ-2BsYGKFX9mv8wVBOgi5GpVq-2FNhlrfTl-2BTI61oGMQNfTGLPKQc-2F-2BKWIb2uEidh5Cy9Snrxt2Kvdg46NMTv1EBYVNMuj4LXg-2F-2FKNOBiucUSSnREnmtIhA75FBOpMnmtDV-2Bl-2FcpsqNwmQJgEAhyEt00Io1rc-2B-2Bfbjmeu9tTvGdnBXxAxS1Vv025-2FWwJ7nKG5DU-2BDdXLi-2F5sa-2BQhR-2FOCXz8HmHwLbZAWE1NDsqShn-2F9w5kw8ShcBEjgOOOsPh5rBDF3EVloW7F7KbVMoXMSDmpnrrJzi44xhgF6x4UrT0Q7Av2sQIiFiPO9fGl8tkUvky0Ao5aT2iWY9sug-2FDSpipLinYNGiI3EB2a5DM-2BRcXar7ugoshMonkjmmA-3D-3D).
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For immediate release
[Earth-sun distance dramatically alters seasons in equatorial Pacific in a 22,000-year cycle](https://link.mediaoutreach.meltwater.com/ls/click?upn=uDPfAnrJXoDw8-2BCe3b2e6gTQXqoFtB58fI1KeAEfz1zz70vO1yrPEXWZw37gEy2xTKKiOplabeKfbLfagfvPDIUcm3SfEs74cHz8Ni-2F6jq666fCNJDjh-2BIzQWvcdXVoPAgz4FjOl5wTLk-2B4oEWDv7W6Z2l15M0MX-2FG9F377JfTZYVyfVvoebefsbGgInNI0HLMkJ_mLoYh0p4AWg4foFr5HgrZ1QioQ33bLwdnQ-2BsYGKFX9mv8wVBOgi5GpVq-2FNhlrfTl-2BTI61oGMQNfTGLPKQc-2F-2BKWIb2uEidh5Cy9Snrxt2Kvdg46NMTv1EBYVNMuj4LXg-2F-2FKNOBiucUSSnREnmtIhA75FBOpMnmtDV-2Bl-2FcpsqNwmQJgEAhyEt00Io1rc-2B-2Bfbjmeu9tTvGdnBXxAxS1Vv0257DvZqPwJ9v-2B0q8ZF-2FUOmbkBj7oNlPXFtp2LJw-2FZjDi22s5NW-2FxEzP8yMlqf8XPGwftsYdHq7Ll983rZ-2FdNQ7oAe1mLtkZFk-2Fgu4YoYITykCbdPb8AlNEt9Tmvi9w-2B4blX-2FlNLOMIEprp4-2FtnZIxwyE5iO0Lz8QhYx1m4XtYM97sWbWkM-2BorgyLoxUxPfRFOkg-3D-3D)
By Robert Sanders | Media Relations
November 10, 2022
https://link.mediaoutreach.meltwater.com/ls/click?upn=uDPfAnrJXoDw8-2BCe3b2e6gTQXqoFtB58fI1KeAEfz1zz70vO1yrPEXWZw37gEy2xTKKiOplabeKfbLfagfvPDIUcm3SfEs74cHz8Ni-2F6jq666fCNJDjh-2BIzQWvcdXVoPAgz4FjOl5wTLk-2B4oEWDv7W6Z2l15M0MX-2FG9F377JfTZYVyfVvoebefsbGgInNI0HUeXT_mLoYh0p4AWg4foFr5HgrZ1QioQ33bLwdnQ-2BsYGKFX9mv8wVBOgi5GpVq-2FNhlrfTl-2BTI61oGMQNfTGLPKQc-2F-2BKWIb2uEidh5Cy9Snrxt2Kvdg46NMTv1EBYVNMuj4LXg-2F-2FKNOBiucUSSnREnmtIhA75FBOpMnmtDV-2Bl-2FcpsqNwmQJgEAhyEt00Io1rc-2B-2Bfbjmeu9tTvGdnBXxAxS1Vv0252NRvrdB01A7LD0uc-2B6jPlosseQCWNDXy8BmD5Zll2QelG8EArM0i7Qo82TcC6qyEA1namahaqstiWDOSwecJyppk4-2Fu22bOP9Lsd2tqf9DuMLVIrAsWaHZ6lr-2BrTvbkg6PuBzOR5HvwxNvB174MVDgohTyuaG4gkpDqCjruAaWPRlq4cR0aU7cBaqA9JIcf7Q-3D-3DA temperature map of the Pacific Ocean for December 1993 showing a cold (blue) tongue of surface water stretching westward along the equator from the coast of South America. The temperature and extent of the cold tongue changes with the seasons, but new climate simulations show that the annual change in Earth’s distance from the sun also affects the cold tongue seasonal cycle. This influences El Niño conditions that impact weather in North America and globally.
Berkeley — Weather and climate modelers understand pretty well how seasonal winds and ocean currents affect El Niño patterns in the eastern equatorial Pacific Ocean, impacting weather across the United States and sometimes worldwide.
But new computer simulations show that one driver of annual weather cycles in that region — in particular, a cold tongue of surface waters stretching westward along the equator from the coast of South America — has gone unrecognized: the changing distance between Earth and the sun.
The cold tongue, in turn, influences the El Niño-Southern Oscillation (ENSO), which impacts weather in California, much of North America, and often globally.
The Earth-sun distance slowly varies over the course of the year because Earth’s orbit is slightly elliptical. Currently, at its closest approach — perihelion — Earth is about 3 million miles closer to the sun than at its farthest point, or aphelion. As a result, sunlight is about 7% more intense at perihelion than at aphelion.
Research led by the University of California, Berkeley, demonstrates that the slight yearly change in our distance from the sun can have a large effect on the annual cycle of the cold tongue. This is distinct from the effect of Earth’s axial tilt on the seasons, which is currently understood to cause the annual cycle of the cold tongue.
Because the period of the annual cycle arising from the tilt and distance effects are slightly different, their combined effects vary over time, said lead researcher [John Chiang](https://link.mediaoutreach.meltwater.com/ls/click?upn=uDPfAnrJXoDw8-2BCe3b2e6kzK2xglucHo-2F2skI-2FJis-2FOr-2FamBgXpgFR6UUOKNhfKY8tAIjieTNFLH0Wvw9pV-2B8w-3D-3DNYph_mLoYh0p4AWg4foFr5HgrZ1QioQ33bLwdnQ-2BsYGKFX9mv8wVBOgi5GpVq-2FNhlrfTl-2BTI61oGMQNfTGLPKQc-2F-2BKWIb2uEidh5Cy9Snrxt2Kvdg46NMTv1EBYVNMuj4LXg-2F-2FKNOBiucUSSnREnmtIhA75FBOpMnmtDV-2Bl-2FcpsqNwmQJgEAhyEt00Io1rc-2B-2Bfbjmeu9tTvGdnBXxAxS1Vv025y7KDe5Al1norlS-2F4CS6xe2dkeEvpDWI-2FMVTlCEFrUyjZTPTR1N3RKbZjgsmMd055fN7UQEEQw3cebCTI2c60z8gttpH3t0VyI0xxWM5okpeQZJp7y7umDwj3csJ61x4jrVECQ4uu0vF5kGAlVes9Ezw0UtHYxcOMdKScVDx-2BUNN6lvXx-2BG0xOdeo-2FszikAhOA-3D-3D), UC Berkeley professor of geography.
“The curious thing is that the annual cycle from the distance effect is slightly longer than that for tilt — around 25 minutes, currently — so over a span of about 11,000 years, the two annual cycles go from being in phase to out of phase, and the net seasonality undergoes a remarkable change, as a result,” Chiang said.
Chiang noted that the distance effect is already incorporated into climate models — though its effect on the equatorial Pacific was not recognized until now — and his findings will not alter weather predictions or climate projections. But the 22,000-year phase cycle may have had long-term, historical effects. Earth’s orbital precession is known to have affected the timing of the ice ages, for example.
The distance effect — and its 22,000-year variation — also may affect other weather systems on Earth. The ENSO, which also originates in the equatorial Pacific, is likely affected because its workings are closely tied to the seasonal cycle of the cold tongue.
“Theory tells us that the seasonal cycle of the cold tongue plays a key role in the development and termination of ENSO events,” said [Alyssa Atwood](https://link.mediaoutreach.meltwater.com/ls/click?upn=uDPfAnrJXoDw8-2BCe3b2e6rNVDNZ-2Bq-2Fj2Lq2swImDleQrgd-2BfkUX8q0-2F4kZ8QV-2BR7EhtF_mLoYh0p4AWg4foFr5HgrZ1QioQ33bLwdnQ-2BsYGKFX9mv8wVBOgi5GpVq-2FNhlrfTl-2BTI61oGMQNfTGLPKQc-2F-2BKWIb2uEidh5Cy9Snrxt2Kvdg46NMTv1EBYVNMuj4LXg-2F-2FKNOBiucUSSnREnmtIhA75FBOpMnmtDV-2Bl-2FcpsqNwmQJgEAhyEt00Io1rc-2B-2Bfbjmeu9tTvGdnBXxAxS1Vv025-2BQCNHIRSVoCtbAMbnvLha7Jv9UtdD4kxNgrYX-2FqPuk4-2F91hLBo6yGu4NMbmVMN4fluuZuBtN0Qthw5eSLDMiyLjH2KlFFUV8Aw1jNhhrcod7MVvgyOy1KOt59ejsdGgJT4tsFDjMfgfyOoo0tsWDdVBZrGqdbzjs0Q-2F6TU8NlDb5Y0P1DH7eZKMSlMhSxnPDg-3D-3D), a former UC Berkeley postdoctoral fellow who is now an assistant professor at Florida State University in Tallahassee. “Because of this, many of ENSO’s key characteristics are synced to the seasonal cycle.”
For example, ENSO events tend to peak during Northern Hemisphere winters, she said, and they don’t typically persist beyond northern or boreal spring months, which scientists refer to as the “spring predictability barrier.” Because of these linkages, it is reasonable to expect that the distance effect could also have a major impact on ENSO — something that should be examined in future studies.
“Very little attention has been paid to the cold tongue seasonal cycle because most people think it’s solved. There’s nothing interesting there,” Chiang said. “What this research shows is that it’s not solved. There’s still a mystery there. Our result also begs the question whether other regions on Earth may also have a significant distance effect contribution to their seasonal cycle.”
“We learn in science classes as early as grade school that the seasons are caused by the tilt of Earth’s axis,” added [Anthony Broccoli](https://link.mediaoutreach.meltwater.com/ls/click?upn=uDPfAnrJXoDw8-2BCe3b2e6gpFuSge1tAvyRwod3D9dNFdSh55YxA1xoviMh0Ep1oNFu4f5uWeLyY-2F2pg-2B7hrE1w-3D-3DnnBj_mLoYh0p4AWg4foFr5HgrZ1QioQ33bLwdnQ-2BsYGKFX9mv8wVBOgi5GpVq-2FNhlrfTl-2BTI61oGMQNfTGLPKQc-2F-2BKWIb2uEidh5Cy9Snrxt2Kvdg46NMTv1EBYVNMuj4LXg-2F-2FKNOBiucUSSnREnmtIhA75FBOpMnmtDV-2Bl-2FcpsqNwmQJgEAhyEt00Io1rc-2B-2Bfbjmeu9tTvGdnBXxAxS1Vv0254C8DSKLFaWDjMlXifnDDrUXfTTR8DR9H2xA6WjxiezsGC8GUPFC2aggYER3L-2BBuBgYuBK8A597DnBRsmp-2FjwA5CqLj96oR4Hkf4FbhIooy4ASEXFKmcKEadwhTGDKkneRCzJ-2FzerT14zxGRm-2BaiMSR5zN-2Bczqs5C8ve4lAdk-2B0-2F7sk-2BhkBmgibGvtnYQR537g-3D-3D) of Rutgers University. “This is certainly true and has been well understood for centuries. Although the effect of the Earth-sun distance has also been recognized, our study indicates that this ‘distance effect’ may be a more important effect on climate than had been recognized previously.”
Chiang, Atwood, Broccoli and their colleagues [reported their findings](https://link.mediaoutreach.meltwater.com/ls/click?upn=uDPfAnrJXoDw8-2BCe3b2e6mamJTVsLlR7PvP29P2NUt-2BmxjM2BnCEicDMYzDHBoICOw-2BrYepMyIASDwANV5ILvQ-3D-3D5NLH_mLoYh0p4AWg4foFr5HgrZ1QioQ33bLwdnQ-2BsYGKFX9mv8wVBOgi5GpVq-2FNhlrfTl-2BTI61oGMQNfTGLPKQc-2F-2BKWIb2uEidh5Cy9Snrxt2Kvdg46NMTv1EBYVNMuj4LXg-2F-2FKNOBiucUSSnREnmtIhA75FBOpMnmtDV-2Bl-2FcpsqNwmQJgEAhyEt00Io1rc-2B-2Bfbjmeu9tTvGdnBXxAxS1Vv0255TqIygFOmRC380hrtxOZs-2B2ySsQa5gJ9QnsgnqBwbixKQU6cNq5sIwRoh1veTugmyCRTF86iEYm0hp9B48Q1xbO2inoPhGTZ7-2Fjfox-2BtOlKQaAWi9IJ8Zua7rIAlxGHF-2FM-2Bvo8l8-2FyRECAiwo3T0T6OFDHUsbDGOLYAR-2B8YAMTbIySfIasm8tQO8BIZ5YbFug-3D-3D) this week in the journal Nature.
Two distinct yearly cycles affect Pacific cold tongue
The main driver of global weather changes is seasonal change. Earth’s equator is tilted relative to its orbit around the sun, so the Northern and Southern hemispheres are illuminated differently. When the sun shines directly overhead in the north, it’s warmer in the north and colder in the south, and vice versa.
These yearly changes have major effects on the Pacific equatorial trade winds, which blow from southeast to northwest across the south and equatorial Pacific and push surface waters westward, causing upwelling of cold water along the equator that creates a tongue of cold surface water that stretches from Ecuador across the Pacific — almost one-quarter the circumference of the planet.
The yearly hemispheric changes in seasonal temperature alters the strength of the trades, and thus cause a yearly cycle in the temperature of the cold tongue. This, in turn, has a major influence on ENSO, which typically peaks during Northern Hemisphere winter.
The occurrence of El Niño — or its opposite, La Niña — helps determines whether California and the West Coast will have a wet or dry winter, but also whether the Midwest and parts of Asia will have rain or drought.
“In studying past climates, much effort has been dedicated to trying to understand if variability in the tropical Pacific Ocean — that is, the El Niño/La Niña cycle — has changed in the past,” Broccoli said. “We chose to focus instead on the yearly cycle of ocean temperatures in the eastern Pacific cold tongue. Our study found that the timing of perihelion — that is, the point at which the earth is closest to the sun — has an important influence on climate in the tropical Pacific.”
In 2015, Broccoli, co-director of the Rutgers Climate Institute, along with his then-graduate student Michael Erb, employed a computer climate model to show that the distance changes caused by Earth’s elliptical orbit dramatically altered the cold tongue yearly cycle. But climate modelers mostly ignored the result, Chiang said.
“Our field is focused on El Niño, and we thought that the seasonal cycle was solved. But then we realized that the result by Erb and Broccoli challenged this assumption,” he said.
Chiang and his colleagues, including Broccoli and Atwood, examined similar simulations using four different climate models and confirmed the result. But the team went further to show how the distance effect works.
Earth’s ‘marine’ and ‘continental’ hemispheres