2011-09-21 11:48:18BLOG EXPERIMENT CONDITION 2: warmist post, skeptic comments
John Cook


As the second part of our experiment on science blogging, we'll be showing 4 conditions to lab participants at the Uni of W.A. The condition for this thread is Warmist Blog Post, Skeptic Comments. So would be great if a handful of SkSers could post scathing, very skeptic comments to our "How we know..." blog post - posted here in this forum thread. We need exactly 10 skeptic comments. 

How we know we're causing global warming in a single graphic

Posted on 27 July 2011 by John Cook

In 1859, physicist John Tyndall ran an experiment demonstrating the greenhouse effect. Visible sunlight easily passes through our atmosphere to warm the Earth. However, invisible heat rays rising from the Earth’s surface, otherwise known as infrared radiation, don’t easily escape back to space. What Tyndall showed by shining heat rays through tubes filled with different gases is that certain gases like water vapour and carbon dioxide block the heat rays. These became known as greenhouse gases.

Tyndall also made several predictions of what we should expect to see if greenhouse gases were causing warming (Tyndall 1861). In fact, we expect to see a number of distinctive greenhouse patterns in global warming. Observing these patterns strengthens the evidence that humans are causing global warming, as well as eliminates other possible natural causes. Let's have a look at the many human fingerprints on climate change:

How we know we're causing global warming

Humans are raising CO2 levels

The first point to establish is that humans are the cause of the rise in atmospheric CO2 levels. This fact is common sense. The amount of CO2 in the atmosphere is going up by around 15 billion tonnes per year. Humans are emitting around twice that much! On top of this, there are a number of lines of evidence to confirm that we're the cause of rising CO2 levels.

When we measure the type of carbon accumulating in the atmosphere, we observe more of the type of carbon that comes from fossil fuels (Manning 2006). As you burn fossil fuels, you take oxygen out of the atmosphere. Measured oxygen levels are falling in line with the amount of carbon dioxide rising (Manning 2006). There's been a sharp rise in "fossil fuel carbon" in corals (Pelejero 2005) and sea sponges (Swart 2010). Anthropogenic CO2 is penetrating even to the ocean depths (Murata 2010). Measurements of radiocarbon in tree-rings confirms human activity is the cause of rising CO2 (Levin 2000). Even the pages of ancient books trace the rising effects of fossil fuel pollution going back to beginnings of the industrial revolution (Yakir 2011).

So many independent lines of evidence (and common sense) confirm that yes, we are responsible for the recent rise in atmospheric CO2.

The extra CO2 is trapping heat

Our understanding of the greenhouse effect provides a number of verifiable predictions. If carbon dioxide is trapping more heat, we should see less heat escaping to space. Satellites measuring infrared radiation coming from Earth find less heat escaping to space over the last few decades, at those exact wavelengths that carbon dioxide absorbs energy (Harries 2001Griggs 2004Chen 2007). The researchers who analysed this data described this as:

"...direct experimental evidence for a significant increase in the Earth's greenhouse effect".
Harries 2001

If less heat is escaping to space, there's only one place it can go - back to the Earth's surface. Scientists check this by measuring infrared heat coming down from the atmosphere. These measurements confirmed the satellite data - more heat is returning to the Earth's surface (Philipona 2004Evans 2006Wang 2009). This extra piece of evidence upon the existing body of evidence led scientists to conclude 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."
Evans 2006

Unfortunately the scientists underestimated the human capacity to ignore  evidence staring us in the face.

Global warming has a distinct greenhouse signature

As far back as the mid 1800s, Tyndall predicted that greenhouse warming should cause nights to warm faster than days. This is because at night, the Earth's surface cools by radiating heat out to space. Greenhouse gases trap some of this heat, slowing the night-time cooling. It took over 130 years before Tyndall's prediction was confirmed. Over the last few decades, surface measurements have observed nights warming faster than days (Braganza 2004Alexander 2006,Zhou 2009).

Tyndall made another prediction of what greenhouse warming should look like. Just as greenhouse gases slow down nighttime cooling, they also slow down winter cooling. So Tyndall anticipatedwinters warming faster than summers. Again, recent analysis of temperature trends over the last few decades bear this out (Braganza et al 2003Braganza et al 2004). Both thermometers and satellites find winters warming faster than summers.

And the evidence continues to build. Another distinctive greenhouse pattern can be found in the atmosphere. With heat being trapped, we expect to see the lower atmosphere to warm. But with less heat escaping to space and more carbon dioxide in the stratosphere, we also expect to see the upper atmosphere cool. Satellites and weather balloons both observe this curious contrast between upper cooling and lower warming (Jones 2003).

With the lower atmosphere (the troposphere) warming and the upper atmosphere (the stratosphere) cooling, the boundary between the troposphere and stratosphere, otherwise known as the tropopause, should rise as a consequence of greenhouse warming. This has been observed (Santer 2003). An even higher layer of the atmosphere, the ionosphere, is expected to cool and contract in response to greenhouse warming. Satellites measure this effect (Laštovika 2006). We are changing the very structure of our atmosphere.

What's fascinating about all these greenhouse signatures is they also rule out a number of other potential causes of global warming. If the sun was causing global warming, it would cause summers to warm faster than winter, days to warm faster than nights and the upper atmosphere to warm. Observations rule out the sun.

Similarly, the pattern of ocean warming rules out ocean cycles as the driver of global warming. The world’s oceans have been building up heat over the past half century. This isn't a case of heat shifting around due to ocean cycles but the entire global ocean system building up heat. The specific pattern of ocean warming, with heat penetrating from the surface, can only be explained by greenhouse warming (Barnett 2005).

If it walks like a duck and quacks like a duck...

Current global warming shows all the distinctive signatures of greenhouse warming. To be skeptical that humans are causing global warming, you must believe two things. Something unknown is causing warming that happens to mirror the greenhouse effect. And something unknown is somehow suppressing the well understood (and well observed) greenhouse effect. So we can accept what we know to be true (greenhouse warming) or we accept two unknowns.

The saying goes if it walks like a duck and quacks like a duck, then it must be a duck. But climate skeptics are trying to convince us it's some other, undefined animal impersonating a duck that's also mysteriously hiding the real duck.

2011-09-22 00:51:50


According to the National Parks Conservation Association, most of our coral reefs are from 5000 to 10000 years old.

Cave drawings were often made with carbon.  We find carbon when we dig in the floors of old caves.  That's coal.  Obviously, coral will contain carbon from coal burned over the last 10000 years or so.  If you assume that all that carbon in the coral came from fossil fuels only in recent years then you can draw a very pretty hockey stick.  But if you average the data over 10000 years you get a flat line.


Every year since the little ice age there have been hypothermia deaths reported in the worlds newspapers.  Every year.  No exceptions.  The hypothermia deaths statistics are out there on the web for anybody to find.  I thought global warming was supposed to put an end to these deaths.  Or maybe there is no global warming.



2011-09-22 05:21:46
Steve Brown


We all know water vapour is the most powerful greenhouse gas and it blocks all the spectral lines of CO2 so CO2 can't add additional heat.  For CO2 to do that it would have to break the law of thermodynamics.  Anyway, since John Cook edited those comments that Bishop Hill discovered through some brilliant work, this site can't be trusted - just like Piltdown Mann who tried to make the MWP disappear!

2011-09-23 13:01:35only 3%
Glenn Tamblyn


Warmists love diagrams like this. Lots of stuff happening but not much detail on why, just their speculations. Oh, and lots of not too subtle 'guilt trips' as well. But what haven't they told us? That human emissions are only 3% - 3/100ths - of what the natural world emits every year. And the oceans hold 60 times as much dissolved CO2 as all the atmosphere. All it takes is a burp in the oceans and up goes CO2. And they think we are causing something! Do the math guys then go find another 'cause'.

2011-09-24 17:40:07Cherry picking

What this post fails to mention is other factors also affect climate. Urban heat island also causes nights to warm faster than days. Ozone depletion causes the stratosphere to cool. This supposed evidence is just cherry picking supporting evidence and hiding the rest.
2011-09-24 21:49:48


What the heck? How can the author think that a colorful - dare I say cute? - picture refutes what real scientists have shredded to pieces easily? The post is just dropping names like they are reliable sources, even though Climategate tied at least some of them to fraud and misbehaving. Mark my words: you'll see some of these people being prosecuted in the not so distant future for perpetuating lies and making big bucks from that!

2011-09-25 12:21:24
Dana Nuccitelli

What this article fails to mention is that the planet hasn't warmed in 15 years - just ask Climategate Phil Jones.  Was that graphic created in 1995?  Plus sea level actually dropped since 2010, so I guess that means we know we're not causing global warming!

2011-09-25 20:11:54

The article also cites ocean warming as evidence, and yet ocean warming has stalled since 2003. As more than 90% of global warming is going into the oceans, which means ocean heat is the best measure for global warming, the conclusion is obvious - humans can't be causing global warming because global warming isn't happening!
2011-09-26 14:13:26
Glenn Tamblyn


And what else is missing from this cartoon? 


Haven't these guys even heard about the recent research at CERN (Just about the most important physics research centre in the world!) Research confirming that Cosnic Rays from outer space make these thing called CCN's that control clouds. Change the clouds and you change the Climate!  And what controls how many Cosmic Rays reach the Earth? Not CO2! The Sun. So the Sun really does control climate.

Its over you loosers, Your scam is busted. Time to see if you can handle doing Real Science!

2011-09-26 14:23:05


Good point re cosmic rays. The simplistic argument that the sun can't cause global warming only looks at one possible link between sun and climate - total solar irradiance. But the relationship between the sun and our climate is much more complicated than that, as the solar magnetic field modulates the amount of cosmic radiation hitting the earth. This affects cloud formation which also interacts with our climate in complicated ways, with lower clouds causing cooling and higher clouds causing warming. A prettily coloured graphic created for young children doesn't even begin to capture the complexities of our climate system.

2011-09-26 14:41:21
Daniel Bailey
Daniel Bailey

The sun rises and the sun sets, and hurries back to where it rises. The wind blows to the south and turns to the north; round and round it goes, ever returning on its course. All streams flow into the sea, yet the sea is never full. To the place the streams come from, there they return again. What has been will be again, what has been done will be done again; there is nothing new under the sun. Is there anything of which one can say, "Look! This is something new"? It was here already, long ago; it was here before our time.

The climate's changed before, yet we're still here. Everything will be just fine in the fullness of time.

2011-09-26 14:43:22
John Cook


This thread is finished, many thanks to all for helping!