Increased energy from the Sun could be contributing to climate change on Earth. Some researchers claim this is helping to raise average temperatures and is the real cause of global warming.
A leading US scientist urges caution however, saying that the jury remains out on whether the Sun is to blame for the world's rising temperatures. Dr Judith Lean, of the Naval Research Laboratory in Washington DC, will discuss the issue this morning at Britain's annual National Astronomy Meeting, now under way in Dublin.
This is the first time the meeting has been held outside the United Kingdom. Organised with the support of the Royal Astronomical Society and the UK's Particle Physics Astronomy Research Council, it brings together many of the experts in astronomy and solar science. The conference runs all week at Dublin Castle, coming at the invitation of the Astronomical Science Group of Ireland.
Dr Lean described the findings of a study highlighting the solar influence on global warming as "very controversial". The new study proposes that the Sun has brightened steadily over the past 20 years, which, if true, could account for at least half of the 0.3 degrees of global warming noted since 1980.
The study was done using data from satellites, Dr Lean said, but they were not using a common scale. This made it difficult to get agreement between the sources and to eliminate effects caused by the recording instruments.
She mentioned another study that did take instrument effects and differences between recording sources into account. This study also looked at the number of sunspots on the solar surface, something that strongly affects solar output. This study showed sunspot activity had not increased, nor was there any sign that long-term solar brightness had changed.
"Other claims in recent years have also exaggerated the role of the Sun in climate change," Dr Lean says. One published in 1991 suggested that the Sun caused the entire 0.8 degree rise in global temperatures seen since 1885, with none of it linked to human activity. New longer-term studies have countered this position however.
"Temperature changes in concert with solar activity are indeed apparent during the past millennium, but are typically of the order of 0.2 to 0.5 degrees on time scales of hundreds of years," Dr Lean says. "Since 1885, global warming in response to changes in the Sun's brightness is now thought to have been less than 0.25 degrees," she adds.
Today's first full day of scientific sessions during the week-long meeting will also include one involving research by experts at University College Dublin looking at "gamma-ray bursts". These astoundingly large cosmic explosions are the most powerful known in the universe and while they occur the "burster" emits more visible light that the light from an entire galaxy of stars.
This afternoon Dr Sheila McBreen will tell a conference session that spinning black holes could be responsible for at least some of the gamma-ray bursts (GRBs) now being detected by astronomers.
The mechanism behind GRBs remains uncertain, but several theories have been proposed. "The detail in the structure of the gamma-ray signals holds key information about what is happening to the 'central engine' during a burst event," Dr McBreen says.