Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

RAS Gold Medal winner: greenhouse gases not Sun driving climate change

18.04.2007
Professor Nigel Weiss, 2007 winner of the Royal Astronomical Society (RAS) Gold medal, will rebut claims that a fall in solar activity could cancel out the effects of man-made global warming.

In a lecture on Wednesday 18 April at the RAS-sponsored National Astronomy Meeting in Preston, Professor Weiss, who is Emeritus Professor in Mathematical Astrophysics at the University of Cambridge, will describe how solar activity was an important factor in past climate change but that current global warming is very much driven by human activity – specifically the emission of greenhouse gases.

Solar magnetic activity manifests itself in sunspots, flares and coronal mass ejections, which give rise to magnetic storms on earth. The incidence of sunspots, which are the sites of strong magnetic fields, varies cyclically with a period of about 11 years. This cyclic pattern is occasionally interrupted by grand minima, like the Maunder Minimum in the 17th century, when scarcely any spots appeared. From variations in Carbon-14 (which is preserved in trees) and Beryllium-10 (which can be measured in polar ice cores) we know that grand minima have recurred irregularly for at least the last 50,000 years.

For the past 50 years, solar activity has in fact been abnormally high, but such grand maxima do not last forever. The current boom will inevitably be followed by a slump, though it is impossible to forecast quite when this will happen, or how deep the ensuing grand minimum will be.

Although sunspots are themselves dark, they are accompanied by bright faculae. Satellite observations show that the solar output of radiation (irradiance) is actually greater at sunspot maximum than at sunspot minimum, though the change of only 0.1% is slight, corresponding to a variation of 0.1 degrees Celsius in average global temperature. A grand minimum might lead to a similar reduction in irradiance.

Of course, the effects of solar variability on the earth's climate, which is a very complex system, could be amplified by other processes. For instance, the Sun's ultra-violet emission doubles from sunspot minimum to maximum, and ultra-violet radiation affects the ozone content of the stratosphere, which is coupled to the troposphere below it and so influences the overall climate. Again, it has been suggested that solar modulation of the flux of galactic cosmic rays affects cloud formation, altering the amount of radiation the Earth reflects back into space and affecting climate (though this hypothesis is very shaky). There might also be a coupling between variations in solar activity and natural oscillations in the atmosphere or ocean.

The extent of any such climatic modulation can be estimated from the long-term record of global temperatures. Until the beginning of the last century, variations in solar activity, along with aerosol emission from volcanoes, dominated climatic variability. There is persuasive evidence that grand minima were indeed associated with colder periods and grand maxima with warm periods. During the past millennium, there were several such maxima and minima, with associated fluctuations of around 0.3 degrees Celsius in global temperature. But these changes are significantly smaller than the increase of almost one degree over the last hundred years so it follows that solar activity is not a major contributor to current global warming.

A minority of commentators have suggested that solar activity is a more important cause than human, and that a fall in solar activity would lead to cooling that could cancel out the effects of greenhouse gases.

While there have been reports that Professor Weiss backs this view, he stressed that this was untrue and that the man-made causes of global warming were of grave and far greater concern.

“Although solar activity has an effect on the climate, these changes are small compared to those associated with global warming,” he said. “Any global cooling associated with a fall in solar activity would not significantly affect the global warming caused by greenhouse gases.”

“This is of course a controversial issue and there is a vocal lobby arguing against the link between anthropogenic gas emissions and climatic change. However I share the view of the majority of the scientific community that the evidence for such a link and thus the occurrence of man-made global warming is significant and a matter of grave concern.”

Robert Massey | alfa
Further information:
http://www.ras.org.uk

More articles from Physics and Astronomy:

nachricht Hope to discover sure signs of life on Mars? New research says look for the element vanadium
22.09.2017 | University of Kansas

nachricht Calculating quietness
22.09.2017 | Forschungszentrum MATHEON ECMath

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>