Planet Earth's atmosphere
'We are upsetting the atmosphere upon which all life depends. In the late 80s when I began to take climate change seriously, we referred to global warming as a ‘slow-motion catastrophe’ one we expected to kick in perhaps generations later. Instead, the signs of change have accelerated alarmingly.'
David Takayoshi Suzuki, Scientist and broadcaster
The atmosphere is the thin envelope of gas that protects the Earth from ultraviolet radiation from the sun and regulates global temperature. Without the protection of the atmosphere life on Planet Earth would cease to exist. Understanding the atmosphere, its chemistry and physics, is central to understanding climate change.
Planet Earth’s atmosphere is much thinner than most people imagine. The densest, innermost part of the atmosphere, the troposphere, is just 17 km thick at the equator and 7 km thick at the poles. 75% of atmospheric gases are found in the troposphere. The Kármán line, 100 km up in the stratosphere, is usually used as the point where the atmosphere ends.
The Earth is 12,700 km in diameter - comparatively the atmosphere is a very thin layer. The cosmologist Carl Sagan noted that the atmosphere would be equivalent to a single layer of varnish on an ordinary classroom globe.
'…we face an enormous problem, which is global warming… because the atmosphere is so small and we’re putting so much crap into it… Burn a ton of coal you get 3.7 tons of carbon dioxide… How many people are there in the planet? 6.6 billion… Our planet is lit up like a bloody Christmas tree at night now with so many cities around the world, most of them dependant on fossil fuels, putting all of that pollution up into the atmosphere.'
Tim Flannery, author of ‘We Are the Weathermakers’, talking to secondary school students in Melbourne, Australia
The concentrations of greenhouse gases in the Earth's atmosphere have changed since the industrial revolution, c1750, increasing as a result of human activity.
The global mean concentration of carbon dioxide (CO2) in parts per million (ppm)
| Pre-1750 | 2005 | |
|---|---|---|
| Carbon dioxide | 280 | 379 |
The global mean concentration of Nitrous oxide (N2O) and Methane (CH4) in parts per billion (ppb)
| Pre-1750 | 2005 | |
|---|---|---|
| Nitrous oxide | 275-280 | 319 |
| Methane | 750 | 1774 |
Source: IPCC WG1 AR4 Report
Since 1957 Mauna Loa Observatory, an atmospheric research facility on Mauna Loa volcano, Hawaii, has continuously monitored levels of carbon dioxide in the atmosphere. Mauna Loa is special as it is high and well away from any nearby sources of CO2. The air it samples effectively represents the average CO2 concentration for the entire northern hemisphere. Over the decades the observatory has measured rising carbon dioxide concentrations in the atmosphere.
The data is presented in a graph that is sometimes known as the ‘Mauna Loa Curve’ or the ‘Keeling Curve’. Dr Charles David Keeling of the Scripps Institution of Oceanography was the first person to regularly take readings of atmospheric carbon dioxide concentrations at Mauna Loa, alerting the world to the role of human activity in global warming. When Dr Keeling died in 2005 it was said that ‘His pioneering work on atmospheric carbon dioxide fundamentally changed the way we view the planet and our role on it’.
'[Levels of] Greenhouse gases in the Earth's atmosphere are currently higher than has been seen in over 150,000 years.'
Greenpeace International