The Telegraph
Since 1st March, 1999
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Sky falling and fast, warn scientists
- Pollution warms surface of Earth, but cools and shrinks upper atmosphere

New Delhi, Nov. 24: Forget the fable of Chicken Little — the sky is indeed falling. The upper zone of Earth’s atmosphere is cooling and shrinking, an international team of scientists said today.

The researchers, including an atmospheric physicist from India, said that while carbon dioxide and other greenhouse gases are warming the surface of Earth, they are simultaneously cooling its upper atmosphere.

“The evidence is very clear. It’s based on direct observations of temperatures in the atmosphere,” said Gufran Beig, a team member and deputy director at the Indian Institute of Tropical Meteorology (IITM) in Pune. “The upper atmosphere is cooling fast, much faster than the surface of the Earth is warming,” he said.

In a report in the US journal Science today, Beig and his colleagues said temperatures have dropped by 2 to 3 degrees Celsius per decade in the region of the atmosphere 50 km to 100 km above Earth’s surface.

The cooling of the upper atmosphere may change the life spans of satellites with orbits within 500 km and even disrupt long distance short wave radio communication, Beig said.

Geostationary satellites, which are used in communication and relaying television signals and parked much higher — about 36,000 km — will remain unaffected.

“When you cool something, it shrinks. The upper region of the atmosphere is contracting. The upper level of the atmosphere has fallen by 8 to 10 kilometres over the past three decades,” Beig said.

Earlier studies have shown that temperatures in the upper atmosphere over India have dropped by about 10 degrees over the past 30 years.

The temperatures in the region higher than 100 km are falling even faster.

Carbon dioxide and other so-called greenhouse gases such as methane and an oxide of nitrogen are responsible for global warming. These gases are released during the burning of fossil fuels and other human activity.

While carbon dioxide near Earth’s surface absorbs solar radiation and traps heat from the sun, higher up it behaves differently. It interacts with solar radiation and emits heat, leading to cooling.

“Our findings show human activities on Earth’s surface can have significant changes on even the uppermost regions of the atmosphere,” Jan Lastovicka, a scientist at the Institute of Atmospheric Physics in Prague, Czech Republic, told The Telegraph.

Over the past three decades, the temperature on Earth’s surface has increased by about 0.2 to 0.4 degrees Celsius, but the decrease in the upper atmosphere has ranged from 5 to 10 degrees Celsius, the scientists said.

The cooling region of the atmosphere is called the ionosphere and is used in long-distance radio communication.

“The changes we’re seeing might lead to deterioration of short wave radio reception,” Beig said.

“This is also causing concern because civilisation today is increasingly dependent on space-based technologies,” Lastovicka said.

He said the exact impact on satellites is unclear, but there are concerns that a lower density of the ionosphere will lead to an increase in the penetration of high energy particles from space which could lead to degradation of solar panels which power onboard systems.

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