10 indicators of a human fingerprint on climate change

10 Indicators of a Human Fingerprint on Climate Change

This post by physicist John Cook was first published in Skeptical Science.

The NOAA State of the Climate 2009 report is an excellent summary of the many lines of evidence that global warming is happening. Acknowledging the fact that the planet is warming leads to the all important question:  What’s causing global warming? To answer this, here is a summary of the empirical evidence that answer this question. Many different observations find a distinct human fingerprint on climate change:

To get a closer look, click on the pic above to get a high-rez 1024×768 version (you’re all welcome to use this graphic in your Powerpoint presentations). Or to dig even deeper, here’s more info on each indicator (including links to the original data or peer-reviewed research):

  1. Humans are currently emitting around 30 billion tonnes of CO2 into the atmosphere (CDIAC). 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.
  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 (Manning 2006).
  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 (Manning 2006).
  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 (Pelejero 2005).
  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”. (Harries 2001, Griggs 2004, Chen 2007).
  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 (Philipona 2004, Wang 2009). 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.” (Evans 2006).
  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 (Braganza 2004, Alexander 2006).
  8. Another distinctive pattern of greenhouse warming is cooling in the upper atmosphere, otherwise known as the stratosphere. This is exactly what’s happening (Jones 2003).
  9. With the lower atmosphere (the troposphere) warming and the upper atmosphere (the stratophere) cooling, another consequence is the boundary between the troposphere and stratophere, otherwise known as the tropopause, should rise as a consequence of greenhouse warming. This has been observed (Santer 2003).
  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 (Laštovi?ka 2006).

Science isn’t a house of cards, ready to topple if you remove one line of evidence. Instead, it’s like a jigsaw puzzle. As the body of evidence builds, we get a clearer picture of what’s driving our climate. We now have many lines of evidence all pointing to a single, consistent answer – the main driver of global warming is rising carbon dioxide levels from our fossil fuel burning.

John Cook, Skeptical Science.

JR:  I would add that, as science adviser John Holdren often points out, in order to refute the theory of human-caused global warming, you would not merely have to come up with an alternate explanation for all of the above observed changes.  You would have to figure out what unknown factor was blocking or negating greenhouse gases from causing them.

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37 Responses to 10 indicators of a human fingerprint on climate change

  1. EDpeak says:

    Great information..seen it before but not with so many relevant links, many thanks. But info isn’t enough, we also need media activism…I just sent the following to BBC which is usually pretty good (by mainstream media standards and sometimes even by absolute standards) on the bias and not just that but factual inaccuracy of its reporting (I filed my formal complaint under inaccuracy rather than bias, for this reason) My email:

    “Your story asserts in part that

    ‘Many climate experts say human activity is contributing to an increasingly warm planet.’

    “Next, I imagine that BBC will say that ‘many’ scientist say that the theory of evolution and gravitation are true? Many? Even ‘most’ is not right – ‘the overwhelming majority’ starts to be correct. Even Bush’s own EPA admitted it, [for] heaven’s sake.”


    I encourage other readers of this blog to be vigilant and contact BBC (use the link ) if/when they screw up again…(Can you believe it? Again saying “most” would have been bad, “many” is an even worse distortion..! Maybe b/c it was not their environment desk but filed under North America or something)

  2. MapleLeaf says:

    I could be wrong, but it looks like the NASA GISS global SAT data for July 2010 could be the warmest on record, with an anomaly of +0.71 C.

  3. climate undergrad says:

    Add to #7 (or #11) that more warming at the poles and less at the equator is also consistent with the human-caused greenhouse effect.

    I like your note Joe but I think it could be phrased clearer. Something like:

    “If humans aren’t causing global warming then there must be an alternate explanation for BOTH why the greenhouse-effect isn’t happening and why temperatures are rising.”

    Not that any non-trolls here need this clarified but it puts the whole “uncertainty” thing in perspective. One side not only performs incredible research but also quantifies the uncertainties surrounding it. The other performs no research to come up with their unsupported theories and then point to the uncertainty of the research on the other side to support them.

    And yet we all still wait for ONE major news outlet to enlighten America on the real conspiracy.

  4. Jody says:

    I think this post would be great for first time visitors of the site. It’s easy to read yet full of hard scientific fact with the relevant sources. If I may make a suggestion, highlight this post on the home page under “newcomers”.

  5. catman306 says:

    climateundergrad, the Internet is a major news outlet with a knack for breaking stories. The MSM sill catch up soon. Five years ago it was unpatriotic to bring up global warming on the internet or in mixed company. That’s progress… Whether it will happen soon enough to make any difference remains to be seen..

  6. This is superb and I will be adding to my GWMM site now. Thanks to John Cook and Joe Romm. Seriously, do either of you ever sleep? :)

  7. Jim Eager says:

    MP, where are you finding the GISS July SAT data?
    I don’t see it posted yet.

  8. Omega Centauri says:

    I want to (partially) dispute fact six. To the extent that the atmosphere/ocean were in equilibrium the heat escaping to space is the same as the sunlight absorbed. The surface/atmosphere warm up until this equilibrium is reached. But that is not entirely correct in a warming planet, as some heat is being stored in the system (roughly a third of the anthropogenic forcing), which is heating seawater (primarily). Also as the surface albedo drops, due to loss of snow/ice more sunlight is absorbed by the system and the total infrared (which we normally call heat) will be emitted by the (warmer still) system. Sounds like fine points I know, but the denialists are just waiting to pounce. Discrediting one point can be used to cast aspersions on all the rest.

  9. caerbannog says:

    Let’s see… Tinfoil-hatter extraordinaire Ken Cuccinelli will be facing off with the University of Virginia in a week or two. Should be entertaining.

    Let’s review some (but certainly not all of) the events that have transpired since the last Cuccinelli/UVA face-off in court.

    EPA brutally smacks down the tinfoil hatters (one of whom is Cuccinelli himself) regarding the the EPA’s CO2 endangerment finding.

    Record-breaking heat across much of the USA.

    Near-apocalyptic heat-wave in Russia.

    Near-apocalyptic flooding in Pakistan (with very plausible links to AGW).

    NOAA releases its latest “State of the Climate” report.

    UVA’s attorneys must be in hog-heaven right now. How many times in an attorney’s career has so much dynamite material been handed to him/her on such a magnificent silver platter???

    I’m looking forward to the biggest judicial smackdown since Kitzmiller v. Dover!

  10. paulm says:

    Things of biblical proportions now happening. More indication that ~1C GW is going to be critical….

    Fairhaven, MA: Dead Fish Wash Ashore In Thousands, Lack Of Oxygen In Warm Waters To Blame (VIDEO)

  11. Sarah Smith says:

    Record cold in the southern hemisphere takes this crackpot religion back a few notches.

  12. paulm says:

    The crack in the roof of the world: ‘Yes, global warming is real – and deeply worrying’–deeply-worrying.html

    Warming up: Daily Mail Science Editor Michael Hanlon investigates climate change in Greenland

    Read more:–deeply-worrying.html#ixzz0wGbXFL3B

  13. Chris ODell says:

    I also think fact 6 is wrong, at least for thermal radiation. Outgoing longwave radiation (OLR) is not predicted to increase under global warming. Virtually all of the AR4 climate models show it as flat in their 100-year runs for basically any scenario you choose (I’ve looked at the A1B and 1-percent-per-year-to-doubling runs myself). There is a relatively simple argument that the temperature of the atmosphere increases, but the effectively radiating level to space also increases, and they basically cancel out, meaning that the amount to space in the infrared stays the same. This is not so for downwelling longwave radiation (DLR). In that case, you have the effective radiating level moving closer to the surface, and this goes in the same direction for DLR as increasing lower trop temperature – a “double whammy” both leading to increased DLR. So yes, DLR should be increasing, and the cited papers show that it is, but OLR is expected to be flat. Satellite measurements thus far have not seen a statistically significant change in OLR (e.g. figure 2 in

    Solar radiation being reflected by the earth system, on the other hand, *may* change over time due to changes in cloud properties and surface features. In particular, melting sea ice would lead to a lower albedo in the polar regions, and a general decrease in the amount of shortwave radiation escaping to space. Though there is some indication of this in the ERBE/ERBS observations, I think it’s not clear and the jury is still out).

    Sorry to be pedantic about this, but I think the bottom line is that fact six as stated is incorrect. It could be modified to state that “Thermal infrared radiation incident upon the earth’s surface is increasing over time.” Or something like that.

  14. MapleLeaf says:

    Hi Jim @7,

    You are right, I could not find the actual data on the GISTEMP site either. However, if the you look at the second image from the top on the RHS of the GISTEMP cover page it seems that they have an image for July 2010. Here is the URL for the image in question:

    Weird eh? Perhaps the official data will be out on Wednesday….

  15. paulm says:

    #10 Sarah, No it doesn’t

  16. adelady says:

    Sarah, if there were no records being made for cold temperatures at all, we would be in even worse case than we are now.

    As of now, hot and cold record temperatures are running at about 5 to 1. Far too high. 1 to 1 is ideal, but even the 2 to 1 of recent titmes would be a vast improvement.

  17. MarkB says:


    The image seems to be the data without the ocean analysis. Maybe that’s why the official numbers aren’t posted. If that’s the case, it’s a bit of a drop from last month. There’s a good-sized la Nina developing at the moment, so cooling in the 2nd half of the year would be expected.

  18. Colorado Bob says:

    Unusually Warm Nights this Summer at Tulsa and Fort Smith

    While afternoon temperatures and heat index values have been hot lately, it is actually the overnight low temperatures that have been exceptionally warm this entire summer across the area.

    New Record Warm Minimum Temperature Set August 3, 2010 at Tulsa

    The temperature dipped to only 85° at 4:57 am CDT August 3, 2010 at the Tulsa International Airport . This sets a new record warm low temperature for August 3rd. The previous record was 81° set in 1987. This was also one of the warmest overnight lows of all-time. Record warm daily minimum temperatures were also set in June: 79° set on June 12, 2010 (previous record 78° in 2008) and 80° set on June 22, 2010 (previous record 79° in 2009).

  19. Colorado Bob says:

    Sarah Smith –

    ” Get ready little lady hell is coming to breakfast ”

    Lone Watie

  20. Colorado Bob says:

    Current temp at Tulsa 85F @ 4:00 AM.

    This can’t be good for all those Inhfoe Igloos around Tulsa .

  21. Raul M. says:

    Clear evidence of weather change from
    ICM engines. If someone leaves the common
    gas car running in the garage with the
    door closed, when reentering the garage,
    they should be able to clearly know that
    the garage climate has changed.

  22. Colorado Bob says:

    The google page this morning for :

    Floods, fires, landslides called evidence of warming

  23. Raul M. says:

    That is an old but still true one at #14.
    I think that something new would be putting
    radiant barrier paint on the college football
    players helmets so they may stay cool headed.
    Not so many years ago one died of heat stroke
    at practice, probably steam comeoff when they
    took his helmet off to have a better look at
    him. Sad but true, they could have done some
    radient barrier painting years ago.

  24. Raul M. says:

    The basic concept being more or less heat
    having an effect or is it affect.
    My personal point of view is that it
    makes a difference on where the point
    of view is. An observer might say the
    heat isn’t so bad, but the player might
    say that a few degrees of heat increase
    is noticeable or unbearable.

  25. Wit'sEnd says:

    Scientists warn Congress that Greenland Ice Sheet Faces Tipping Point in Ten Years…23′ sea level rise…how’s that for an indicator?

  26. Keith says:

    Sister Sarah,
    this is simply science, nothing more. I recall that we Americans deplored the Soviet Union and its propagandistic control of public info. via TASS, Pravda, etc. Now, I marvel that a large % of our population accepts its info. from sources spewing similar propaganda.

  27. Jim Eager says:

    When denialists use the “crackpot religion” card it means that’s all they have left.

  28. Colorado Bob says:

    Well there ain’t no beatin’ around the berg with this quote :

    ” “What is going on in the Arctic now is the biggest and fastest thing that nature has ever done,” he said.

    Speaking by phone, Alley was addressing a briefing held by the House of Representatives committee on energy independence and global warming.

    Greenland is losing ice mass at an increasing rate, dumping more icebergs into the ocean because of warming temperatures, he said.”

  29. Raul M. says:

    Hi Wit’sEnd
    If you like guitar music, you might like
    the music with the heading of Ottmar Liebert.
    I like it.

  30. Mike says:

    On #1 in Cook’s list: Is that 30 billion tonnes per year? Also the reference given does not contain this estimate.

    More generally, it would be good to quantity the percent of observed warming that is due to GHG.

    I would add the drop in ocean Ph and the 40% decline in open ocean phytoplankton to the list.

  31. Bob Doublin says:

    Sara,Sara,you simply must learn that a thirty year average is not the same at all as a GUARANTEE. Here in Seattle we have an interesting little example. The average low for February 4 is 37F. The record low is 7F. Guess what? It occurred during the thirty years used to calculate the average.My, isn’t that interesting? A record low 30 deg below the average yet in the remaining 29 years enough lows occurred above the average to offset this deficit. Will wonders never cease?

  32. Raul M. says:

    Ottmar’s site has a listening lounge where one
    may listen to very nice music compliment of the

  33. SecularAnimist says:

    Sarah Smith wrote: “Record cold in the southern hemisphere takes this crackpot religion back a few notches.”

    “Sarah Smith” (not his real name) is a Ditto-Head troll posting idiotic bumper-sticker bromides for no other reason than to impress himself with his ability to waste other people’s time with BS.

    Respond accordingly.

  34. Bob Doublin says:

    The average high for the month of July here in Seattle is 75.3F.Is there a range on either side say .5F or 1.0F or? where meteorologists would say that a July of a given year was normal even though it might be slightly below 75.3? Would this vary from month to month so that the range would be different in Dec. or April? Does this range differ for other cities so that Miami would have it’s own set of ranges just like New Orleans or Fargo? Should I really be saying standard deviation instead of range? Over the last few years I’ve become really fascinated with weather averages and how they’re playing out.

  35. John Cook says:

    Mike #30,

    Yes, that’s 30 billion tonnes of CO2 per year. If you follow my CDIAC link, you’ll see a Global link at the top of the page. Click that and then click the Digital Data to bring up the numbers of CO2 emissions per year. In 2007, global emissions were 8365 million tonnes of carbon per year. This equates to 30 billion tonnes of CO2 per year.

    So sorry, the data isn’t immediately obvious but it is in there :-) I have a page on converting carbon units to carbon dioxide units at:

  36. Byron Smith says:

    I’m a huge fan of John Cook, but he has denied being a physicist in the past, so not sure the byline is correct. From what I understand he has a physics degree (astrophysics major) but is not working as a scientist.

    Is that right John?