It is looking more and more likely that the global warming phenomenon is the fault of human beings, and not some natural cosmic event, according to scientists at the Bermuda Biological Station for Research (BBSR).

Last summer, a controversial report was published in the journal GSA Today claiming that cosmic ray activity, recorded in meteorites, were the primary contributor to the recent global warming ? not human emissions.

Scientists speculate that cosmic rays, energetic particles from space, may affect weather patterns by increasing cloud cover, which helps cool the earth.

The theory, put forward by scientists Nir Shaviv and Jan Veizer, suggested fewer cosmic rays are reaching earth because of a blocking effect created by increasing solar activity, reducing the amount of cooling.

The theory sparked renewed international debate on the cause of global warming.

However: ?Even if the link could be proved in the future, the relationship between cosmic ray output and the earth?s climate may only act over many millions of years,?said senior BBSR research scientist Dr. Nicholas Bates.

?Global warming over the past century or so has very different mechanisms responsible, which act over very short timescales compared to geological time.?

In the January 27 issue of the journal Eos, eleven other scientists also challenged the findings of Shaviv and Veizer, saying their analysis was seriously flawed and relationships between cosmic ray activity and climate change were not convincingly demonstrated.

Global warming over the last century is primarily the result of the build-up of carbon dioxide and other greenhouse gases in the atmosphere, they said.

Dr. Bates, who has been studying global climate change at the BBSR since 1986, agreed, saying the advent of industrial emissions and their sharp escalation over the last half-century is dominant. ?Climate changes since the pre-industrial age have large human footprints all over them.?

Other short-term factors include volcanic eruptions, and changes in solar activity and weather patterns.

The three hottest years on record have occurred within the past decade, according to the BBSR. The United Nations World Meteorological Organisation reports the year 2003 was the third warmest on record.

The year 1998 was the warmest since instrumental recordings began in 1861.