Global warming is likely anthropogenic

In its simplest form, the argument for anthropogenic climate change goes as follows. 1. The Earth's atmosphere keeps the planet much warmer than it would be without an atmosphere.1 2. The main gases which contribute to this are carbon dioxide, methane and water vapor. Collectively these are called greenhouse gases.2 3. The ability of these gases to act as greenhouse gases can be shown in a laboratory.3 4. The quantity of these greenhouse gases in the atmosphere has increased sharply since the Industrial Revolution, and their concentration continues to do so.4 5. The concentration of these gases has increased as a consequence of human activity.5 6. The temperature of Earth's atmosphere has been increasing and continues to increase.6 7. The increase in global temperature correlates with the increases of greenhouse gases.7, 8 8. The increase in temperature has been caused by the increase in greenhouse gases.9, 10, 11 Many different observations find a distinct human fingerprint on climate change: 1. Humans are currently emitting around 30 billion tonnes of CO2 into the atmosphere every year. Of course, it could be coincidence that CO2 levels are rising so sharply at the same time so let's look at more evidence that we're responsible for the rise in CO2 levels.12 2. When we measure the type of carbon accumulating in the atmosphere, we observe more of the type of carbon that comes from fossil fuels.13 3. This is corroborated by measurements of oxygen in the atmosphere. Oxygen levels are falling in line with the amount of carbon dioxide rising, just as you'd expect from fossil fuel burning which takes oxygen out of the air to create carbon dioxide.13 4. Further independent evidence that humans are raising CO2 levels comes from measurements of carbon found in coral records going back several centuries. These find a recent sharp rise in the type of carbon that comes from fossil fuels.14 5. So we know humans are raising CO2 levels. What's the effect? Satellites measure less heat escaping out to space, at the particular wavelengths that CO2 absorbs heat, thus finding "direct experimental evidence for a significant increase in the Earth's greenhouse effect"15, 16, 17 6. If less heat is escaping to space, where is it going? Back to the Earth's surface. Surface measurements confirm this, observing more downward infrared radiation A closer look at the downward radiation finds more heat returning at CO2 wavelengths, leading to the conclusion that "this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming.18, 19, 20 7. If an increased greenhouse effect is causing global warming, we should see certain patterns in the warming. For example, the planet should warm faster at night than during the day. This is indeed being observed.21, 22 8. Another distinctive pattern of greenhouse warming is cooling in the upper atmosphere, otherwise known as the stratosphere. This is exactly what's happening.23 9. With the lower atmosphere (the troposphere) warming and the upper atmosphere (the stratosphere) cooling, another consequence is the boundary between the troposphere and stratosphere, otherwise known as the tropopause, should rise as a consequence of greenhouse warming. This has been observed.24 10. An even higher layer of the atmosphere, the ionosphere, is expected to cool and contract in response to greenhouse warming. This has been observed by satellites.25, 26 Overall, there is reason to believe that humans are the main cause of our recent global warming. 1 http://earthguide.ucsd.edu... 2 http://lwf.ncdc.noaa.gov... 3 http://www.enviroliteracy.org... 4 http://www.eia.doe.gov... 5 http://www.eoearth.org... 6 http://web.archive.org... 7 http://www.desmogblog.com... 8 http://www.realclimate.org... 9 http://magma.nationalgeographic.com... 10 http://www.environmentaldefense.org... 11 http://rationalwiki.org... 12 http://cdiac.ornl.gov... 13 http://www.esrl.noaa.gov... 14 http://www.sciencemag.org... 15 http://www.nature.com... 16 http://spiedl.aip.org... 17 http://www.eumetsat.eu... 18 http://www.agu.org... 19 http://www.agu.org... 20 http://ams.confex.com... 21 http://www.met.sjsu.edu... 22 http://www.knmi.nl... 23 http://www.agu.org... 24 http://www.math.nyu.edu... 25 http://www.ufa.cas.cz... 26 http://www.skepticalscience.com...