YouTube video on the empirical evidence for man-made global warming
Posted on 28 February 2010 by John Cook
A common skeptic argument is that there is no empirical evidence for man-made global warming. People who make this claim can't have looked very hard. As most don't have the time to scour through the peer-reviewed scientific literature, the multiple lines of independent evidence for global warming are given here. To make the science even more accessible in this time of multimedia and short attention spans, there is now a YouTube video outlining the empirical evidence for man-made global warming.
The video is by greenman3610, producer of the Climate Crock of the Week series. Also be sure to check out the (more info) link in the right margin where links to all the peer-reviewed papers are provided. This is a powerfully visual way of communicating the science of climate change - I strongly recommend you all view the video, pass it onto your friends (and if you're feeling really energetic, follow the paper links to learn more about the science).
There are a number of papers showing that greenhouse gases trap heat which causes radiative forcing which drives climate.
Harries 2001, Griggs 2004, Chen 2007 all find less radiation escaping out to space at the wavelengths that greenhouse gases absorb energy. Eg - greenhouse gases trapping heat.
Wang 2009, Philipona 2004, Evans 2006 provide additional independent confirmation of this result, using surface measurements to find more longwave energy returning back to the Earth's surface. Evans 2006 is particularly interesting because it looks at the longwave spectrum to quantify the individual contribution of each greenhouse gas.
"...telling folks to wade through peer-reviewed wallpaper is just a cop-out. Present your data. One sentence or graphic per paper linked"
This is good advice. In fact, so good that I have already attempted to do this on multiple occasions to the point where I'm waiting for people to start complaining I'm being repetitive. I first attempted to document the independent lines of evidence that humans are causing global warming last October with Empirical evidence that humans are causing global warming. I wrote a similar article last December, this time with bullet point lists and one sentence per paper linked, in What happened to the evidence for man-made global warming? Then last week, and I thought maybe I was pushing the repetitiveness at this point, I summarised all the science in Senator Inhofe's attempt to distract us from the scientific realities of global warming.
However, your comment has demonstrated that people are still failing to recognise the many independent lines of empirical evidence for man-made global warming so I will probably need to resummarize all the scientific evidence every month or so.
Nevertheless, the question of whether such a tiny amount of CO2 could have such a dramatic effect on climate doesn't need to be addressed by metaphors. The effect has been directly measured by Evans 2006 which looks at the spectrum of downward infrared radiation (eg - infrared energy that is trapped by greenhouse gases and sent back down to the Earth's surface) and quantifies the individual contribution of each greenhouse gas.
Evans 2006 and a number of other papers provide a number of independent lines of evidence that CO2 is trapping heat. Following on from this, a number of papers examining different periods of Earth's history and all find consistent results that our climate is highly sensitive to changes to the planet's energy balance. In other words, when we add heat to the climate, positive feedbacks amplify the warming. Lastly, many, many papers look at the impact of warming temperatures and the result is the net negative impacts of global warming on humanity far outweight the positive benefits.
All the peer-reviewed research conclusively shows that increasing CO2 has strong negative impacts on humanity. It's a complex subject and it's the kind of thing that you can't prove on the back of a napkin - it required a lot of research and data to get to where we are now. But if you take in the full picture of what the peer-review science is telling us, to me the most persuasive element that humans are causing global warming which has negative impacts on humanity is the fact that independent measurements all paint the same picture.