Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sun’s direct role in global warming may be underestimated

04.10.2005


Study does not discount the suspected contributions of ’greenhouse gases’ in elevating surface temperatures

At least 10 to 30 percent of global warming measured during the past two decades may be due to increased solar output rather than factors such as increased heat-absorbing carbon dioxide gas released by various human activities, two Duke University physicists report.

The physicists said that their findings indicate that climate models of global warming need to be corrected for the effects of changes in solar activity. However, they emphasized that their findings do not argue against the basic theory that significant global warming is occurring because of carbon dioxide and other "greenhouse" gases.



Nicola Scafetta, an associate research scientist working at Duke’s physics department, and Bruce West, a Duke adjunct physics professor, published their findings online Sept. 28, 2005, in the research journal Geophysical Research Letters.

West is also chief scientist in the mathematical and information sciences directorate of the Army Research Office in Research Triangle Park.

Scafetta’s and West’s study follows a Columbia University researcher’s report of previous errors in the interpretation of data on solar brightness collected by sun-observing satellites.

The Duke physicists also introduce new statistical methods that they assert more accurately describe the atmosphere’s delayed response to solar heating. In addition, these new methods filter out temperature-changing effects not tied to global warming, they write in their paper.

According to Scafetta, records of sunspot activity suggest that solar output has been rising slightly for about 100 years. However, only measurements of what is known as total solar irradiance gathered by satellites orbiting since 1978 are considered scientifically reliable, he said.

But observations over those years were flawed by the space shuttle Challenger disaster, which prevented the launching of a new solar output detecting satellite called ACRIM 2 to replace a previous one called ACRIM 1.

That resulted in a two-year data gap that scientists had to rely on other satellites to try to bridge. "But those data were not as precise as those from ACRIM 1 and ACRIM 2," Scafetta said in an interview.

Nevertheless, several research groups used the combined satellite data to conclude that that there was no increased heating from the Sun to contribute to the global surface warming observed between 1980 and 2002, the authors wrote in their paper.

Lacking a standardized, uninterrupted data stream measuring any rising solar influence, those groups thus surmised that all global temperature increases measured during those years had to be caused by solar heat-trapping "greenhouse" gases such as carbon dioxide, introduced into Earth’s atmosphere by human activities, their paper added.

But a 2003 study by a group headed by Columbia’s Richard Willson, principal investigator of the ACRIM experiments, challenged the previous satellite interpretations of solar output. Willson and his colleagues concluded, rather that their analysis revealed a significant upward trend in average solar luminosity during the period.

Using the Columbia findings as the starting point for their study, Scafetta and West then statistically analyzed how Earth’s atmosphere would respond to slightly stronger solar heating. Importantly, they used an analytical method that could detect the subtle, complex relationships between solar output and terrestrial temperature patterns.

The Duke analyses examined solar changes over a period twice as long -- 22 versus 11 years -- as was previously covered by another group employing a different statistical approach.

"The problem is that Earth’s atmosphere is not in thermodynamic equilibrium with the sun," Scafetta said. "The longer the time period the stronger the effect will be on the atmosphere, because it takes time to adapt."

Using a longer 22 year interval also allowed the Duke physicists to filter out shorter range effects that can influence surface temperatures but are not related to global warming, their paper said. Examples include volcanic eruptions, which can temporarily cool the climate, and ocean current changes such as el Nino that affect global weather patterns.

Applying their analytical method to the solar output estimates by the Columbia group, Scafetta’s and West’s paper concludes that "the sun may have minimally contributed about 10 to 30 percent of the 1980-2002 global surface warming."

This study does not discount that human-linked greenhouse gases contribute to global warming, they stressed. "Those gases would still give a contribution, but not so strong as was thought," Scafetta said.

"We don’t know what the Sun will do in the future," Scafetta added. "For now, if our analysis is correct, I think it is important to correct the climate models so that they include reliable sensitivity to solar activity.

"Once that is done, then it will be possible to better understand what has happened during the past hundred years."

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>