Evidence shaky for Sun's major role in past climate changes

Sep 30, 2004
The Sun

Computer models of Earth's climate have consistently linked long-term, high-magnitude variations in solar output to past climate changes. Now a closer look at earlier studies of the Sun casts doubt on evidence of such cycles of brightness, their intensity and their possible influence on Earth's climate. The findings, by a solar physicist and two climate scientists funded by the National Science Foundation, appear in the October 1 issue of the journal Science.

"The relationship between the Sun's variability and its influence on climate remain open questions," according to Cliff Jacobs, program director in NSF's division of atmospheric sciences, which funded the research. "This study adds another piece to the puzzle and will spur efforts to unravel this complex relationship."

Scientists have attributed observed climate changes to a combination of natural variations and human activities. Computer models of global climate reproduced an observed global warming during the first half of the 20th century when two solar influences were combined: a well-documented 11-year sunspot cycle and decades-long solar cycles now in dispute.

A more pronounced warming observed during the century's last decades is attributed to greenhouse gases accumulating in Earth's atmosphere and is not part of the study.

"Removing long-term solar cycles from the input to climate models takes away about a tenth of a degree [Celsius] of early 20th century warming," says Tom Wigley, a climate scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colo. "This suggests that other influences on past climate changes may play a greater role than the solar one."

Peter Foukal of Heliophysics Inc., Gerald North of Texas A&M University, and Wigley co-authored the paper.

The 11-year sunspot cycle is not questioned in the Science paper, but its effect alone is "probably too little for a practical influence on climate," the authors write. They also briefly consider possible influences of ultraviolet and cosmic ray fluxes in Earth's climate.

The scientists think that long-term brightness variations of the Sun may exist, but more convincing evidence is needed, they say. New technologies now available can provide better data for understanding Sun-climate relations, they conclude. NASA co- funded the research.

Source: National Center for Atmospheric Research

Explore further: Hubble sees 'ghost light' from dead galaxies

add to favorites email to friend print save as pdf

Related Stories

A global natural gas boom alone won't slow climate change

Oct 15, 2014

A new analysis of global energy use, economics and the climate shows that without new climate policies, expanding the current bounty of inexpensive natural gas alone would not slow the growth of global greenhouse ...

Mangroves protecting corals from climate change

Oct 08, 2014

Certain types of corals, invertebrates of the sea that have been on Earth for millions of years, appear to have found a way to survive some of their most destructive threats by attaching to and growing under ...

Recommended for you

Possible bright supernova lights up spiral galaxy M61

1 hour ago

I sat straight up in my seat when I learned of the discovery of a possible new supernova in the bright Virgo galaxy M61. Since bright usually means close, this newly exploding star may soon become visible ...

Fifteen years of NASA's Chandra X-ray observatory

2 hours ago

This Chandra X-ray Observatory image of the Hydra A galaxy cluster was taken on Oct. 30, 1999, with the Advanced CCD Imaging Spectrometer (ACIS) in an observation that lasted about six hours.

Confirming a 3-D structural view of a quasar outflow

2 hours ago

A team of astronomers have observed a distant gravitationally-lensed quasar (i.e., an active galactic nucleus) with the Subaru Telescope and concluded that the data indeed present a 3-D view of the structure ...

Hubble sees 'ghost light' from dead galaxies

17 hours ago

(Phys.org) —NASA's Hubble Space Telescope has picked up the faint, ghostly glow of stars ejected from ancient galaxies that were gravitationally ripped apart several billion years ago. The mayhem happened ...

Cassini sees sunny seas on Titan

18 hours ago

(Phys.org) —As it soared past Saturn's large moon Titan recently, NASA's Cassini spacecraft caught a glimpse of bright sunlight reflecting off hydrocarbon seas.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.