The Sky

[Pootle]

How high do you have to go before it starts getting cold?

[Kerplunk]

What do you mean by cold? On a winters day it is cold at ground level.

[JudgeJ]

The lowest level of the earth�s atmosphere is known as the troposphere. This extends to about 7 or 8 miles (about 12 km). It is within this layer that all of the world�s weather variations take place. As you ascend through this layer generally temperature drops by about one degree Centigrade for each 1,000 feet (300m) until a minimum of around minus 60 degrees Centigrade is encountered. (These are general figures and will vary according to individual local conditions). Some commercial flights provide in-flight data for their passengers and it is not unusual to see outside temperatures of -50 degrees at 35,000 feet.

The reason for this is that atmospheric pressure drops rapidly in these first few miles (85% of the earth�s atmosphere is contained in the troposphere) so there is less air to retain the Sun�s heat.

Above the troposphere is the stratosphere. Here the temperature stabilises and then begins to rise with altitude as the effect of the Sun's radiation takes a hold. Above the stratosphere (c. 50 km) is the mesosphere where the temperature again declines.Above about 85 km comes the thermosphere, where temperature begins to rise again.

[Pootle]

Thank you Judge for your comprehensive answer

[The Cowboy]

Judge,

You give easy to understand explanations. Thank you as well.

Cowboy

[heathfield]

In school, we were taught that the mean fall in temperature with height was one degree Fahrenheit for every 300 feet of altitude. Never forgotten it. These days they'll no doubt say one degree Centigrade for every 165 metres. Who can remember a figure like that in later life?