Scientists say that newly discovered evidence suggests that the universe may have gone through a warming trend early in its history.
Astronomers measured the temperature of the gas that lies in between galaxies, and found a clear indication that it had increased steadily over the period from when the universe was one-tenth-to-one quarter of its current age.
This cosmic climate change is most likely caused by the huge amount of energy output from young, active galaxies during this epoch.
"Early in the history of the universe, the vast majority of matter was not in stars or galaxies", said George Becker of the University of Cambridge.
"Instead, it was spread out in a very thin gas that filled up all of space."
"The gas, which lies between us and the quasar, adds a series of imprints to the light from these extremely bright objects and by analyzing how those imprints partly block the background light from the quasars, we can infer many of the properties of the absorbing gas, such as where it is, what it's made of, and what its temperature is.
"Just as Earth's climate can be studied from ice cores and tree rings, the quasar light contains a record of the climate history of the cosmos
"One billion years after the Big Bang, the gas we measured was a 'cool' 8,000 degrees Celsius. By three and a half billion years the temperature had climbed to at least 12,000 degrees Celsius," he said.
The warming trend is believed to run counter to normal cosmic climate patterns.
"The likely culprits in this intergalactic warming are the quasars themselves", explained fellow team member Martin Haehnelt.
"Over the period of cosmic history studied by the team, quasars were becoming much more common. These objects, which are thought to be ant black holes swallowing up material in the centres of galaxies, emit huge amounts of energetic ultraviolet light. These UV rays would have interacted with the intergalactic gas, creating the rise in temperature we observed," he said.
The findings were published in the journal Monthly Notices of the Royal Astronomical Society.