Everyday English –Mystery drove global warming
- Source: Global Times
- [13:46 July 15 2009]
- Comments
A runaway spurt of global warming 55 million years ago turned Earth into a hothouse, but how this happened remains worryingly unclear, scientists said Monday.
Previous research into this period, called the Palaeocene- Eocene Thermal Maximum, or PETM, estimates that the planet’s surface temperature soared by between 5 and 9 degrees Celsius in just a few thousand years.
The Arctic Ocean warmed to 23 C (73 F), or about the temperature of a lukewarm bath that we take on a regular basis.
How PETM happened is unclear, but climatologists are eager to find out, as this could shed light on aspects of suspected global warming today.
What seems clear is that a huge amount of heat-trapping greenhouse gases – natural, as opposed to man-made – were released in a very short time.
The theorized sources include volcanic activity and the sudden release of methane hydrates in the ocean.
A trio of Earth scientists, led by Richard Zeebe of the University of Hawaii, is trying to account for the carbon that was spewed out during PETM.
They believe that levels of atmospheric carbon dioxide (CO2) rose by 70 percent during PETM’s main phase to reach 1,700 parts per million, attaining a concentration of between four and five times that of today.
But all this CO2 can only account for between 1 and 3.5 C of PETM’s warming if the models for climate sensitivity are right.
Scientists believe there must have been other factors that stoked temperatures higher.
Even though there are big differences between Earth’s geology and ice cover then and now, the findings are relevant as they highlight the risk of hidden mechanisms that add dramatically to warming. Some of these so-called positive feedbacks are already known.
For instance, when a patch of Arctic Sea ice melts, this exposes the uncovered sea to sunlight, depriving it of a bright, reflective layer.
That causes the sea to warm, which leads to the loss of more ice, which in turn helps the sea to warm, and so on.
But these “feedbacks” are poorly understood, and some scientists believe there could be others still to be identified.
After the big warm-up, the planet eventually cooled around 100,000 years later, but not before there had been a mass extinction, paving the way for the biodiversity that is familiar to us today.
Man-made global warming, driven mainly by the burning of oil, gas and coal, has resulted in a temperature rise of around 0.8 C over the past century.
AFP
Notes:
Spurt – (verb) To suddenly expel in a gushing flow, increased activity, especially just before the end of a race.
Boys have a growth spurt in their late teenage years and almost become much taller overnight.
Trailing behind the leader towards the end of the race, the runner had a last spurt of energy and managed to cross the finish line first.
Lukewarm – (adjective) Barely or moderately warm. It can also be used to describe a response being not very warm or enthusiastic.
The public's response to the mayor's announcement of raising taxes was lukewarm because while people wanted better social services, they were not keen to pay for them.
Spewed – (verb) To throw up something from the stomach (vomit), or to gush or flow out plentifully.
When the baby was fed some food he didn’t like, he spewed it out onto the floor, leaving a mess for his mother to clean up.
Every year factories spew a lot of pollutants into the air; more legislation is needed to prevent so much pollution from entering our atmosphere.
Depriving – (verb) To take something away forcefully, to keep from having, using or enjoying.
When people go on a diet, they deprive themselves of their favorite foods like ice cream and chocolate; however, it is a balanced diet with lots of fruits and vegetables as well as regular exercise that will help reduce weight.