Is it hot in here, or is it just global warming?

By Phil Plait | August 8, 2012 9:57 am

Let me be clear right off the top: global warming is real. There is vastly overwhelming evidence for it and scientific consensus about it, and the only people still sowing doubt about it appear to be motivated more by ideology and corporate interests than scientific evidence.

Having said that, one thing I’m careful about when I talk about it is linking specific weather events to the worsening climate. We humans like to connect events if they occur at the same time, whether they are actually connected or not. So when huge storms spawning tornadoes ravaged the midwest last year, I was careful not to say it was caused by global warming. When a huge glacier calved off Greenland a few weeks ago, I was careful not to say it was caused by global warming. When Greenland got a tremendous burst of warm air that caused unprecedented ice melting, I was careful not to say it was caused by global warming. When wildfires erupted over the US and Russia this summer, I was careful not to say it was caused by global warming. I said these events are all consistent with global warming, but not necessarily caused by it.

Now, however, things have changed. New evidence has arisen that indicates the extreme heat waves that are cooking the US are in fact and in deed caused by global warming.

[UPDATE: Talk about timing: the NOAA just released their State of the Climate report, showing that July 2012 is the hottest month ever recorded in the history of the contiguous United States.]

Climate scientist James Hansen – who, in the 1980s, was the first to talk about the idea that the planet is heating up – has published research linking global warming and these extreme events. It’s explained in an article on the NASA site: Hansen and his team looked at northern hemisphere surface temperatures going back to the early 1950s. At any given time, some places are hotter than average, some cooler. So they plotted these temperature deviations from average and got a bell curve, just like the bell curve some teachers use to grade students. Most temperatures are near the average value, while very hot or very cold places are less common; the graph peaks in the middle and falls away to either side.

All well and good. But when they plotted these temperatures over time – looking at the average temperature for a given year as well as the extreme events – they saw three things, none of them good. One was that, over time, the average temperature moved to the right – that is, the the overall temperature got hotter. Second, there were fewer cooler temperatures – the graph on the left got weaker. Third, there were more extreme heating events – the graph got stronger on the right.

The green line shows the smoothed average curve for the time period of 1951 – 1980. The filled in part shows the curve for the decade of 2001 – 2011. Note that it’s skewed right, and there are more hot events as well.

It hasn’t been your imagination. We’re getting hotter, and we’re seeing more extremely hot summers. You can confirm this for yourself: walk outside.

Personal anecdotes aside, the data back that conclusion up. Statistically speaking, the temperature "anomalies" are highly significant, meaning they are almost certainly real. In the 1950s, extreme heat waves like we’re seeing now were rare to nonexistent. Today, 10% of the northern hemisphere experiences these heat waves. Dr. Hansen says that without global warming, these anomalies wouldn’t be happening. In other words, our warming planet is the culprit behind these extreme events.

This doesn’t mean every summer will be hotter than the last, or have worse heat waves. But as Dr. Hansen points out, it does mean that in general that’s what we’ll see. Climate Scientist Michael Mann describes it this way:

It is not simply a set of random events occurring in isolation, but part of a broader emerging pattern. We are seeing, in much of the extreme weather we are experiencing, the “loading of the weather dice.” Over the past decade, records for daily maximum high temperatures in the U.S. have been broken at twice the rate we would expect from chance alone. Think of this as rolling double sixes twice as often as you’d expect – something you would readily notice in a high stakes game of dice. Thus far this year, that ratio is close to 10 to 1. That’s double sixes coming up ten times as often as you expect.

What Dr. Hansen’s research shows is that again, while any specific event is hard to blame in its entirety on global warming, the overall trend we’re seeing – including these disastrous heat waves causing deaths, massive crop failures, drought, and wildfires – is linked to global warming. As he put it:

This summer people are seeing extreme heat and agricultural impacts. We’re asserting that this is causally connected to global warming, and in this paper we present the scientific evidence for that.

That’s a pretty firm commitment. And one that will, no doubt, make heads explode amongst climate change denialists. They will obfuscate, they will nitpick, they will distract, they will deny. But they are wrong. The media, and more importantly, politicians, need to understand that.

Again, as Dr. Mann says (emphasis mine):

The time for debate about the reality of human-caused climate change has now passed. We can have a good faith debate about how to deal with the problem – how to reduce future climate change and adapt to what is already upon us to reduce the risks that climate change poses to society. But we can no longer simply bury our heads in the sand.

As I’ve said before: when does weather become climate? It’s starting to feel like now.


Image credit: NASA/Goddard Space Flight Center Scientific Visualization Studio


Related Posts:

- New study clinches it: the Earth is warming up
- Climate change: the evidence
- New independent climate study confirms global warming is real
- 2011: The 9th hottest year on record

Comments (92)

  1. Brett

    Solid article, but alas, when it comes to pieces like this, you can’t allow for chinks in the armor. In this case, it’s this paragraph:

    “It hasn’t been your imagination. We’re getting hotter, and we’re seeing more extremely hot summers. You can confirm this for yourself: walk outside.”

    If an AGW “skeptic” can’t go outside on a cool day and say “hey look, global warming is a fraud!”, then you can’t encourage people do “walk outside” to confirm that AGW is real.

    Honestly, the article would’ve been as strong or stronger without that bit in there.

  2. Daniel J. Andrews

    When your head is buried in the sand that leaves another part of your anatomy precariously exposed–not to mention making you look slightly ridiculous.

    I liked the analogy of the baseball player on steroids. If he hits a home run you can’t say whether or not that was due to the steroids, but over time you can certainly identify the changes in frequency of home runs. There’s a YouTube clip on that somewhere which shouldn’t be too hard to google.

    Edit to add: agree with Brett.

  3. Cyberspice

    That doesn’t show cause and effect. There’s global warming. I.e. the Earth is warming up. And there’s “Global Warming”. I.e. humans are making it warm up. That graph shows the former but does confirm that latter. Basically its saying its hot because its got hotter.

    I’m not a nay-sayer about “Global Warming”. I feel that we should be doing what we can to reduce emissions and oil usage. But that’s just sensible anyway. I feel we need a *lot* *lot* more data to show that the current gradual increase of 1.5 (C? – there’s no units) between 1965 and 2005 (mid points of the ranges). Do we have evidence of how temperatures changed similar over the previous 100 years and so on.

    When it gets hot in the UK people buy ice-cream. Someone seeing people with ice-cream may consider it a coincidence. So they look at temperatures vs ice-cream sales over many years. And yes there’s a correlation. But does the ice-cream cause the temperature or vica versa or is it just a weird coincidence. We need more work to determine what’s going on with our climate.

    So the work says. Hey guys its warmer than it used to be. And because of the bell curve that means there’s more likely to be hot days hence more hot days. But that’s all it says.

  4. Leah

    Brett, you’re mistaking a rhetorical phrase for an argumentative one. The article is chock full of data backing Phil’s argument. This is not a white paper. Is Phil not allowed to make snarky asides in a blog post?

  5. Nathan

    @Brett – The reason for that statement is that, based on this research, the current heat wave being experienced is causally connected to global climate change.

    Of course, location and time frame reference should be given since the article will persist longer than the current heat-wave.

  6. Theron

    Seriously — we’ve gotten to “sun-rises-in-the-east, sets-in-the-west” levels of evidence, but as sure as evolution is real, the deniers will fill this comment thread with an abundance of their protestations.

  7. Brett

    @Nathan – Yes, I’m sure you can find a justification for that statement, but it’s still invalid based on the very arguments we’ve tried to use to convince doubters. Trotting it out when it conveniently fits our beliefs is nothing more than confirmation bias.

  8. We will have to help each other out in this via a network of profit and non-profit organizations (aka grassroots level). This is because so many are scared to death that somehow money and freedom will be taken from them if government attempts to help. If we can ever get the evangelicals on board that would be a great thing.

  9. Bill

    Sadly, as soon as the denialists see “James Hansen” and “Michael Mann”, they’ll shrug this piece off as yet another part of the Big Climate conspiracy. Those two have been so demonized by the right that they’ll never be seen as credible.

  10. Memo to climate contrarians wanting to argue here against the scientific consensus reached by 98% of the experts on climate :

    Before posting here please check the following sites :

    http://www.skepticalscience.com/argument.php

    Plus :

    http://greenfyre.wordpress.com/climate-denial-crock-of-the-week/#sense

    In addition to :

    http://www.realclimate.org/index.php/archives/2007/05/start-here/

    As well as the link to Potholer54′s excellent series onthe topic the first youtube video of which is linked to my name here.

    Because otherwise you’re very likely to be posting some stale climate canard that has long since been repeatedly debunked and making a fool of yourself. Seriously.

    Yes, we’ve pretty much heard it all before many times at length.

  11. Martin Bonner

    I am member of the UK Green Party. I have been worried about global warning since the late 70′s. I am sure it is a real problem. But…

    I think you are raising a straw man here. Most climate change deniers have stopped arguing that the climate is changing – they are now arguing that the change is *isn’t human caused*. This study is a neat demonstration that the climate is changing, but
    a) it doesn’t show it will go on changing (yes, yes, I know it will – see above);
    b) it doesn’t show the change is anthropogenic rather than random bad luck.

  12. thetentman

    I did notice that Phil did also say “Personal anecdotes aside”. So just relax and grab a cold one cause whatever the cause it’s hot today.

  13. Also see :

    http://co2now.org/

    &

    http://www.youtube.com/watch?v=fwpPd_bBMpg&feature=related

    &

    http://theconversation.edu.au/pages/clearing-up-the-climate-debate

    Plus the very good concise link in my name to naturalist David Attenborough’s clear The Truth About Climate Change youtube clip.

  14. I thought Phil said that tongue-in-cheek as he’s been very consistent saying that you can’t say anything about global warming based on the weather outside. But that bit did make me wince when I read it too.

    Sometimes I think the deniers who come here and try to sound intelligent and just end up looking really foolish might not be deniers at all. Maybe they actually fully accept the facts of global warming and are just doing their part to make denial seem really ridiculous. Maybe not, but they have a consistent pattern of using a lot of words with lots of syllables to make simple comments that could have been made in one-fourth the length.

  15. Lucas D. Luengo

    I have no doubt that we’re facing a global warming. That’s clear.
    What I’d like is to get some pointers to studies showing that the global warming is human-caused. I’ve seen almost no studies linking deforestation or industrial revolution to global warming (I bet it’s because I haven’t look hard enough).

  16. Ibeechu

    Actually, Phil, the data is skewed-left. Nitpicking, but it’s not often that I get to correct you :P

  17. afeman

    “James Hansen – who, in the 1980s, was the first to talk about the idea that the planet is heating up…”

    Hansen may have been instrumental in recent congressional dis/interest in the matter, but as an environmental concern it dates back at least to the 50′s:

    http://www.aip.org/history/climate/Govt.htm#S3

    Not to mention the first estimates of CO2 sensitivity by Arrhenius in the 1890′s.

  18. @6. Bill :

    Sadly, as soon as the denialists see “James Hansen” and “Michael Mann”, they’ll shrug this piece off as yet another part of the Big Climate conspiracy. Those two have been so demonized by the right that they’ll never be seen as credible.

    Whistfully wonders if they’ll take the likes of Christian evangelical, Newt Gingrich co-author and climate scientist Dr Katherine Hayhoe :

    http://www.youtube.com/watch?v=OHYhovvLQyc&list=PL029130BFDC78FA33&index=10&feature=plpp_video

    Or Koch brothers funded physicist Richard Muller :

    http://www.youtube.com/watch?v=tciQts-8Cxo&list=PL029130BFDC78FA33&index=17&feature=plpp_video

    Or even renowned physicist Stephen Hawking :

    http://www.youtube.com/watch?v=mu1PicT0TMU

    more seriously?

    Or if they do their research and look back in time they’ll realise that HIRGO (Human Induced Rapid Global Overheating) was a phenomena known and scientifically established decades before Al Gore came out with is movie. (As, guess what, a link in my name here back to 1956 illustrates and elaborates.)

  19. Weirdest summer ever here on Menorca. Normally it´s during july/august something like 35 degrees (Celcius ofcourse) and up (like 48 on a bad day). At night it might get just under 30 degrees. With still standing humid sea air.
    But this year it´s 30-34 daytime and it drops to a comfotable 22 at night.
    Still it´s dry as hell here. No rain last winter to be mentionable. Let alone right now.
    As I said, a weird summer.
    But nice at night. :)

    BTW we had in the last ten years more snow then ever.
    Snow was a once in a lifetime experience. But now it´s almost every snowing. Don´t think snow as in SNOWING, it´s flaking. And might give a slight white cover on a cold day. For say an hour. But we had three years in the last ten that we had a few days (!!) that it kept it´s white cover. Unheard of.
    So get rid of that “global warming” thing and start call it “climate change”.
    And with change, comes ehm… changes.
    But hey, they even have full blown tornadoes in Poland nowadays.

  20. I am shocked that you would put your name behind the nut that Dr. Hansen is! His data is flawed and it is amazing he still has a job. Associating yourself with the Hansen doesn’t reflect well on you or this website.

  21. Randy A.

    The ostrich-emulators in our society will never stop denying anthropogenic global warming. If they could be persuaded by reason, or even by their own senses (“We’re getting hotter… You can confirm this for yourself: walk outside.”) the debate would have concluded years ago.

    So let’s change the focus.

    We need to limit burning fossil fuels because they cause air pollution.

    We need to switch to renewable energy for energy independence, so we aren’t beholden to foreign governments for needed resources.

    We need to conserve energy, because that will conserve the money in our wallets!

    It’s just a coincidence that these things will alleviate global climate change…

  22. striker

    Come on people. This paper by Dr. Hansen is very poor science. It omits data from prior to 1950. Weather extremes and max temperature readings were much greater during the 20s and 30s than it is now. If you’re going to make the point that extremes are more common now than in the past and that the cause is linked to CO2 and not natural variations then you’ve got to do better than an obviously flawed, non-peer reviewed press release (as this doesn’t really qualify as a scientific paper).

  23. Dave

    @Ibeechu — the data don’t look terribly skewed at all to me, but what skewness there is seems to be positive. Why do you say otherwise?

  24. Good article linked to my name here :

    Global Warming’s Terrifying New Math by Bill McKibben in Rolling Stone magazine.

    Albeit by “good” I mean dang-nabbed, flippin’ disturbing. :-(

  25. Ibeechu

    @Dave, because the left-tail is longer than the right and most of the data is on the right-side; negative skew

  26. Keith Bowden

    Even before I caught your post here, my news feed popped up a rather rabid conspiratorial denial of this latest HIRGO evidence on The Guardian. :(

  27. Satan Claws

    My prediction about the future generations is that people will be too busy trying to etch out a living to be concerned about looking back at these decades to point fingers at who’s to blame; by then, we’ll all be either dead (and thusly unaccountable) or too old (and thusly too weak to defend ourselves).

    I suppose that’s what Rex Tillerson describes as “We’ll adapt to that” (for reference, look up the ClimateCrocks blog for the entries of July 30, 2012).

  28. Tony

    @SkyGazer et al, correct me if I’m wrong, but “Global warming” IS the predominant aspect of climate change that we’re concerned about, even if we expect (though we aren’t surprised by) localized climate changes. Use of the term “climate change” has less urgency (and drama, if you like) attached to it than Global Warming, which is precisely why deniers use it.

    I feel like we’re traveling on the uphill slope of a big roller coaster that’s still being built. It really is just a question of time before we can’t get off the ride anymore, except to crash at the bottom. This is already NOT a fun ride for the world, and IMO it isn’t appropriate to use watered-down terms to describe our current situation. It’s like watching your house burn down and telling your neighbors that your house isn’t really on fire; it’s just experiencing a “warming trend”.

  29. Chris

    One was that, over time, the average temperature moved to the right…the graph on the left got weaker.
    I knew it was a conspiracy, temperatures moving to the right, that’s why Republicans like global warming and Democrats are all up in arms. They want temperatures to move to the left!

  30. My original comment was marked as…
    HUH?
    Spam?
    My comment wasn´t spam.
    It was about solar power (with a link)
    o darn

    And I´ll be damned to retype that whole story again. What´s out of the pen is written and gone from the mind.

    Take this link then:
    cracked.com/quick-fixes/what-everyone-was-thinking-when-mars-rover-landed/

  31. Tim

    @Striker.

    Declaring something as “poor science” does not make it poor science.

    If you think there are real problems with the paper, e.g. it omits data prior to 1950, then you need to come up with a cogent argument as to why it’s a problem. That particular issue you raised is actually discussed in the paper under “Materials and Methods,” and further elaborated on in various sections including the section titled, “Reference Period.”

    Also: the paper is not intended to show a causal link between anthropogenic CO2 emissions and warmer temperatures. That is established in other credible research which you can find in a 30 second Google search, but I’ll link to the Skeptical Science website since it is a good consolidated reference portal for published research on the topic: http://www.skepticalscience.com/empirical-evidence-for-global-warming.htm See the section titled, “CO2 traps heat” for links to the actual research on the greenhouse effects of CO2.

    Tim

  32. Bob Koss

    I looked in anticipation for Hansen’s explanation of the excessive and prolonged heat during the decade of the 1930s. Alas, my search was in vain. He has ignored inconvenient data that may prove detrimental his presentation. Scientists don’t do that, political activists do that.

    Here is a graph of US heat waves 1895-2008.
    http://epa.gov/climatechange/science/indicators/weather-climate/heat-waves.html

    If anyone thinks the 1930s heat waves were caused by a stationary dense bubble of co2 over the US, I have a bridge you might be interested in purchasing on the cheap.

  33. jon

    Just a heads up………. You are a brilliant scientist but that doesn’t mean are correct re: man caused global warming. Lets assume you are correct which I believe you are not. What are you going to do about it? Also your data is produced by those who RELY on government grants for their very existence and those with political agendas. OH but that wouldn’t be a factor RIGHT? How about the data fraud that has been exposed? Why would they fake data? Anyway you are a brilliant IDIOT.

  34. Jack

    As much as I hate supporting the opposition, I have to say that the denialists always seemed rather rare (but vocal) to me. A lot of the political opposition I saw to the global warming legislation was about what the opposers saw as questionable evidence of human causation. It seems like the global warming supporters are spending an awful lot of time arguing against the denialists, when in my own anecdotal experience they seem few and far between compared to the camp that says, “Sure, it’s happening, but you can’t prove we’re causing it. Until you can, keep your laws off me.” That’s actually a much harder camp to argue against, because they acknowledge that global warming is happening. They even acknowledge that it may be anthropogenic. But they will refuse legislation that they perceive as big government until the evidence is “better”. In my own personal experience, these people make up the vast majority of the so-called denialists, which is a bit unfair, because they’re not really denying anything.

  35. Doug Little

    striker @22,

    You don’t even know what the point of the study is. From the NASA website

    the researchers analyzed surface temperature data to establish the growing frequency of extreme heat events in the past 30 years, a period in which the temperature data show an overall warming trend.

    They used the temperature data from 1951 to present because over this time warming on average is present. The point of the study is to try and causally link an increase in extreme heating events with the overall warming trend over this period, This is not evidence of global warming rather evidence of a link between extreme heating events and global warming. Like other people have bought up it says nothing about the causes of global warming whether man made or other, but why bring that up? this paper is not addressing that.

  36. Doug Little

    Jack,

    There is little question that the main culprit in warming is an increase in CO2.

    From the IPCC Forth Assessment Report.

    “Carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values.”

    The amount of carbon dioxide in the atmosphere in 2005 (379 ppm) exceeds by far the natural range of the last 650,000 years (180 to 300 ppm).

    The amount of methane in the atmosphere in 2005 (1774 ppb) exceeds by far the natural range of the last 650,000 years (320 to 790 ppb).

    The primary source of the increase in carbon dioxide is fossil fuel use, but land-use changes also make a contribution.

    The primary source of the increase in methane is very likely to be a combination of human agricultural activities and fossil fuel use. How much each contributes is not well determined.

    Nitrous oxide concentrations have risen from a pre-industrial value of 270 ppb to a 2005 value of 319 ppb. More than a third of this rise is due to human activity, primarily agriculture.

    So the major increase in greenhouse gasses are due to human activities. Greenhouse gasses cause the earth to warm.

  37. Raph

    I’m a little confused. What does it even mean to say something is “caused by” global warming?
    There is evidence that the Earth has been heating up over the last ~50 years. And now this article shows evidence that….the Earth has been heating up over the last ~50 years. Exactly what “cause” or even “link” is being presented? I’m sorry, but isn’t this like saying that an increase in average height is linked to more tall people? So what?

    I’d like to make it clear that I’m NOT denying that global warming exists, I’m just saying…what’s so surprising/important about this graph?

  38. Steve Metzler

    Shorter concern troll Jack (#31):

    Let’s just wait until the evidence for AGW is “better” before we do anything about the awful mess that we are in, even though the evidence which we already have is, according to the scientists who actually study this stuff, pretty much a slam dunk.

  39. Lee

    So when [A, B, C and D], I was careful not to say it was caused by global warming.

    I don’t see how you can claim that, given that all four of those posts linked to have the tag ‘climate change’, all four of them discuss the possibility of a causal connection to climate change, and the Petermann Glacier post in particular devotes the majority of its length not to the Petermann Glacier, but to climate change. While none of them explicitly state that they were caused by AGW, merely bringing up that topic in connection with the discussion introduces that idea without needing to spell out the link.

    While there is nothing wrong with introducing and discussing a particular topic, particularly on your own blog, it is generally considered a cheap rhetorical trick: introducing a topic by saying “I’m not claiming X” still introduces exactly that claim to the conversation.

    No doubt this is where I get called a concern or tone troll, but I simply have no respect for that or other sneakiness, especially when there is an abundance of actual data to make the case.

  40. Turboblocke

    Re “global warming” versus “climate change”… note that the IPCC was set up in 1988. I’ll leave it as an exercise for the reader to work out what the CC in IPCC stands for.

    You can use it the next time a denier sneers about changing the name from (A)GW to CC

  41. Julia
  42. Valeriy

    It is interesting to see, how all these plots in pro-green articles look suuuper-fancy and not strict. Also I doubt that the green line on this plot is averaged deviations, it is obviously, just fitted normal pdf.

    Oh and I began to read you blog not so long ago, and enjoyed it. It is really pity to see, that sometimes you are trying to speculate on such matters here.

  43. Unsettled Scientist

    > You can use it the next time a denier sneers about changing the name from (A)GW to CC

    You can also point out that denier’s ignorance of Frank Luntz and the Bush Administration’s decision to use the phrase “climate change” in the public discussion instead of “global warming” specifically because it seems to downplay the severity.

    http://www.guardian.co.uk/environment/2003/mar/04/usnews.climatechange

    The phrase “global warming” appeared frequently in President Bush’s speeches in 2001, but decreased to almost nothing during 2002, when the memo was produced.

  44. Robert Murphy

    Striker said:
    http://blogs.discovermagazine.com/badastronomy/2012/08/08/is-it-hot-in-here-or-is-it-just-global-warming-2/#comment-546753
    “an obviously flawed, non-peer reviewed press release (as this doesn’t really qualify as a scientific paper).”

    It was published (after peer-review) in PNAS (Proceedings of the National Academy of Science)
    http://www.pnas.org/content/early/2012/07/30/1205276109.full.pdf+html
    Try to do at least some minimal research before making disparaging claims. You’ll look less foolish.

  45. Dean

    This is an interesting paper.

    However, it does have one weakness that most of these types of papers lack: A realistic solution to cutting carbon emissions.

    Usually it’s very hand wavy “we need to use more green energy”, but never quantifies it. When you _do_ quantify it, the problem really rears it’s ugly head, as shown by Roger Pielke, Jr. in the Climate Fix.

    The problem is that no government is going to skewer it’s own economy to solve global warming. If one does, and employment takes a hit, that government gets voted out in favour of one that will sacrifice global warming for jobs.

    The magnitude of the problem is also immense. In order for the world to achieve a 50 % reduction in emissions below 1990 baseline by 2050, it would require elminating all coal and natural gas consumption, replacing it with nuclear power, replacing 40% of 2006 petroleum consumption, which would require about 3500 nuclear power plants. To meet 1.5% energy demand growth, that would require more than 12,000 nuclear power stations by 2050.

    That is one nuclear power station EVERY DAY until 2050.

    !!!!

    If you want to turn all that into solar power or wind power, go ahead, but the magnitiude is the same. It’s immense, and with population growth and the lack of political and economic will to eviscerate the enconomy, it’s just NOT going to happen.

    So we need other solutions.

    This isn’t to say we shouldn’t do anything. It’s just that we keep whistling past the graveyard, and even if we all agreed that global warming is a problem (and for the record, I 100% agree), how to solve it is an even bigger problem that just isn’t getting acknowledged.

  46. kirk

    Maybe the science is air tight and maybe not but let’s talk ENGINEERING. In Texas, we cannot continue to pave our roads with asphalt over thin layers of crushed stone based entirely on the graph above. The ENGINEERING judgement that was used until now used exactly the kind of statistical reasonableness that scientist must refer to as correlation or risk death by Fox News. When a road bed flows into a bar ditch summer after summer — the statistical underpinning of the old normal has been replaced by the new normal.

  47. Wzrd1

    @11, Martin Bonner, in the UK that is true.
    Here in the US, there are many who totally deny global warming, hence any human contribution to it cannot be discussed. They buy the special interest shills entire propaganda campaign verbatim.
    Indeed, were our forests to wither and die off, becoming a desert, they’d claim that the area was ALWAYS a desert!

  48. Doug Little

    The problem is that no government is going to skewer it’s own economy to solve global warming.

    I keep hearing this claim but as of yet have not been presented any evidence that this is the case. Generally when a big project is tackled (Manhattan Project and Apollo) the results have been nothing but positive for the economy. I don’t see how an economy can’t be similarly built around mitigating global warming, if anything the economy that gets the jump on the tech is going to be leaps and bounds ahead of everybody else in the near future. Also another good example of mitigation helping the economy was the cash for clunkers program, it was good for the economy and good for the environment.

  49. Austin Reader

    I believe that global climate change is well documented, and that science’s best supported model shows that human actions are the dominant cause, but every time Phil writes something like “the debate is closed” I wish edit his posts to be a little more about science exposition and a little less about policy advocacy.

    No theory should ever be closed for debate in science.

  50. Infinite123Lifer

    From the State of the Climate Report:

    Climate Highlights — Year-to-Date (January-July)

    The January-July 2012 period was the warmest first seven months of any year on record for the contiguous United States. The national temperature of 56.4°F was 4.3°F above the long-term average. Most of the contiguous U.S. was record and near-record warm for the seven-month period, except the Pacific Northwest which was near average.

    The first seven months of 2012 were drier than average, ranking as the 15th driest January-July on record. Below-average precipitation totals were observed for a large portion of the country, with 12 states having January-July precipitation totals among their ten driest. Above-average precipitation was observed for the Upper Midwest and the Pacific Northwest.

    Climate Highlights — 12-months (August 2011-July 2012)
    The August 2011-July 2012 period was the warmest 12-month period of any 12-months on record for the contiguous U.S., narrowly surpassing the record broken last month for the July 2011-June 2012 period by 0.07°F. The nationally-averaged temperature of 56.1°F was 3.3°F above the long term average. Every state across the contiguous U.S. had warmer than average temperatures for the period, except Washington, which was near average.

    Step outside? I know concerns from the trolls were given but this concerned troll lives in the Pacific Northwest Phil, which seems to be part of a few exceptions. Even though Seatac hit a record 93 degrees this past weekend preceeded by warm weather, and the study linked to the bottom of this comment links above average rainfall here in WA with GW I am really not going to just step outside into 70 degrees and cloudy on an August day to confirm “we’re getting hotter and we’re seeing more extremely hot summers.” You taught me better. You taught me that I cannot confirm that myself by walking outside. What gives? Heat exhaustion coupled with ever increasing denial, disgust and defamation? Eh, personal anecdotes are understandable, I mean . . . it is your blog and all ;)

    _____

    http://www.environmentwashingtoncenter.org/reports/wae/when-it-rains-it-pours

    This article was a bit . . .

    http://www.bellinghamherald.com/2012/08/01/2625556/study-links-whatcom-rains-to-global.html

  51. anon

    A couple decades of climate change is just a drop in the bucket. We have no idea if this is normal or not. We don’t have comprehensive proof that over the millennia the Earth should be some magical constant temperature. The same period referenced here (1951 – 1980) was marred with headlines of “Global Cooling.” I don’t think that made it very far.

    Also re: Greenland Ice Sheet melting: “Our results suggest that abrupt climate change initiated by GIS melting is not a realistic scenario for the 21st century.”

    http://www.agu.org/pubs/crossref/2006/2006GL026815.shtml

  52. Bobby

    @cyberspice #3 Not sure if you are a troll or not, but the units at the bottom of the graph are in standard deviations. These are not absolute temperature readings.

    So if the mean temperature is X, meaning that 50% of the temperature readings are higher, and 50% are lower, a temperature that is one standard deviation to the right of temperature X is hotter than 68% of the readings. A temperature 2 standard deviations to the right is hotter than 97% of the readings collected. A temperature 3 standard deviations to the right is hotter than 99.7% of the readings collected, etc, etc.

  53. John F

    “I am member of the UK Green Party. I have been worried about global warning since the late 70′s. I am sure it is a real problem. But…
    I think you are raising a straw man here. Most climate change deniers have stopped arguing that the climate is changing ”

    Oh no, here in the US there are still many very vocal people denying that the climate is changing.

  54. Dean

    Well, here’s an excerpt on the Iron Law of climate policy:

    http://opinion.financialpost.com/2010/10/04/book-excerpt-the-iron-law-of-climate-policy/

    The poll discussed in that excerpt is here.

    http://media.economist.com/media/pdf/Toplines20090701.pdf

    In particular look at question 15.

    People are only willing to sacrifice income for the environment if it is relatively painless.

  55. JMurphy

    anon@41, how long do you think we should wait before we make decisions about what we should do if we are actually right about the Global Warming we are experiencing ? When do you think we will know enough to make that decision ?

    And we do actually know a fair bit about global temperatures going back 65 million years (http://commons.wikimedia.org/wiki/File:65_Myr_Climate_Change.png), 5 million years (http://commons.wikimedia.org/wiki/File:Five_Myr_Climate_Change.png), 450,000 years (http://commons.wikimedia.org/wiki/File:Ice_Age_Temperature.png), 12,000 years (http://commons.wikimedia.org/wiki/File:Holocene_Temperature_Variations.png), 2,000 years (http://en.wikipedia.org/wiki/File:2000_Year_Temperature_Comparison.png), etc.

    Also, those “Global Cooling” headlines were just that – headlines, in a few papers and media outlets, during the early 70s (http://en.wikipedia.org/wiki/Global_cooling). Since then…well, I’m sure you know what most scientists accept now.

    Finally, I don’t believe the 6 year old paper you cite (on a decrease of the Atlantic Meridional Overturning Circulation (AMOC) being accelerated substantially by meltwater input from the Greenland Ice Sheet (GIS)) has any relevance to the melting and calving mentioned in the piece above – they give evidence of global warming but are not being used to suggest that the AMOC will be shut down or weakened in any way in the near future.

  56. Steve Metzler

    This. What Doug Little says @#40!

  57. Das Boese

    This paper is going to be dismissed by the denialists just like everything else, but I don’t really care, it’s still important.

    Even among the people who accept that global warming is real and man-made, like most of my fellow Europeans, there’s often still a sense of “this is a future problem”.

    It’s very important to show them that no, it isn’t, it’s happening now and it has a direct influcence on our lives ranging from rising food prices to damaging extreme weather events, storms, floods, droughts.
    Convincing people of that is essential to gaining the political power to fight it, which isn’t as lost a cause as it may seem to Americans thanks to the pluralistic systems in most of our countries. Since the political parties most likely to do something about it are the social-democratic and green ones, who knows, it might even be a chance to break the conservative stranglehold on our financial system.

  58. Jane

    Is this trend true also for the Southern Hemisphere? I know that in Australia last year we broke our ten year long drought, and experienced a cool summer and now what feels like a fairly cold winter…

    So in summer time should we be expecting hotter summers and more bushfires than in the past, and heading towards another drought?

  59. Monkey

    “However, it does have one weakness that most of these types of papers lack: A realistic solution to cutting carbon emissions’.

    You are entirely correct. It also lacks a good recipe for oatmeal banana cookies. And fried pickle soup. And nowhere in this paper that endeavours to quantify recent warming trends does the author suggest options for salt-replacing sports drinks that should be considered as a health benefit if in fact the planet is heating up.

    Sarcasm aside, this paper does what it needs to do. It presents data on a physical presence on our planet. Too often do discussions about AGW turn to political or engineering ones in response to the scientific data.

    That there is AGW is a fact. Many people, despite your assertions, still decline to accept this fact. We need to cross this boundary first, and the science is continually presenting us with more data and more evidence. Nothing – absolutely nothing – political can detract from this. That you hate Al Gore, think Cap and Trade is pointless, cannot envision spending money to mitigate further damages….none of that takes away from the fact that it is reality. That there are no solid and dependable solutions to the energy needs of the extant and growing human society DOES NOT detract from the reality of AGW. We need to stop lumping these together, and using political ideologies to denounce the reality of the natural world.

    (By “you” I mean the general denialist, not anybody specific…)

  60. Dork Vader

    Is that the french flag overimposed on the graph? ;)

  61. Daniel J. Andrews

    “However, it does have one weakness that most of these types of papers lack: A realistic solution to cutting carbon emissions’.”

    A realistic solution for the U.S. can come when the Republican Party stops denying warming is happening. Only when both parties work together and come up with ideas together will a realistic solution come along.

  62. ad

    NOAA scientist Dr. Martin Hoerling is panning it. This from The NYT:

    Dr. Hoerling contended that Dr. Hansen’s new paper confuses drought, caused primarily by a lack of rainfall, with heat waves.

    “This isn’t a serious science paper,” Dr. Hoerling said. “It’s mainly about perception, as indicated by the paper’s title. Perception is not a science.”

  63. Thameron

    “But we can no longer simply bury our heads in the sand.”

    Oh how wrong he is about that. Considering that global warming will likely create more deserts there will be more sand to bury heads in.

  64. Michael Goble

    It is obvious that climate change is occurring. It is obvious that global warming is happening. It is becoming more and more obvious that humans are contributing to the problem. What is not obvious, to me at least, is the motivation behind the deniers. Why do so many people refuse to believe the evidence. Could somebody please explain that to me.

  65. kat wagner

    So tonite on PBS news, there was a piece on drilling for natural gas. You know, fracking. Proponents (you know, gas companies) said how natural gas has much less sulfur and mercury and they’re finding more and more of the stuff all the time. But the infrastructure isn’t in place to process all this gas, so the coal companies are pushing back saying they got everything in place. Coal is so easy to dig – in Colorado, and the news piece showed this, you peel back the little layer of soil and dig out the fat seam of coal. Easy. And so many US power companies use the stuff.

    But some bigwig did say using natural gas would buy us some time to get renewable energy sources going.

    When I was in college, and that feels like a century ago (but not really), I thought we woulda got solar going pronto. I mean, it’s so damn HOT in San Clemente, and now it’s hot just about everywhere. Why don’t all these friggin’ rich people have solar panels on their roofs, for crying out loud. I’m talking about Sun Valley ID where the governator has a house. Why can’t we legislate some sense into this BS? If we don’t do something – quit burning coal, for one – will be here in 50 years talking about the same stuff? Will we have to move underground to get away from the sun?

    It’s hot out and it’s really making me grumpy.

  66. Teshi

    The ‘step outside’ remark was a bit glib, although I know it was a rhetorical device. The UK’s weather this summer has been remarkably cold and wet, on the whole so if I was entirely ignorant about how climate change works, I would not be able to ‘step outside’ and draw this conclusion.

    That said, I realise that our unusually cold, wet summer is probably related, in terms of climate, to your hot, dry one. And I still get that nervous feeling that suggests that in fact I am mostly powerless to act.

  67. KimS

    Here in the UK, it certainly doesn’t seem to have been getting hotter.

    The climate has definitely been changing, but our last five (I think) summers have been colder than average, and much much wetter. Flooding is a lot more common than it has been. We’ve also had two or three exceptionally cold winters (this last one was warm, but the two before were ridiculous – my mother in Scotland had a whole month where the temperature did not reach above 0 degrees celcius, and there were record snowfalls across the UK).

    Having said that, we’ve also had bizarre heatwaves in March for the last few years – temperatures at 25 degrees celcius, when the average maximum for March is 9 degrees celcius.

  68. Lawrence

    For those that try to pull the “economic catastrophe” argument – the USACOE estimated it would cost $10 Billion dollars to build a Levee system in New Orleans to withstand a major hurricane – this was deemed far to expensive & not built.

    After Katrina, it cost over $125 Billion dollars in reconstruction expenses to fix the damage – and we still haven’t committed to building a Levee System that would withstand another Katrina.

    We’ve seen a lot of claims of how much money it would cost to move in the direction of reducing our overall emissions, but we seem to spend 10x as much money down the line fixing the results of the latest “natural disaster” that results…..and speaking of an economic model, the first country that can discover a way to move from a petroleum-based economy to one using renewable energy sources, is going to have a huge leg-up on the rest of the world when it comes to productivity and economic power.

    It is an investment, a timely one, for the future of our country and our economy – sure, the Earth has been hotter in the past, but back then, it was the dinosaurs that had to deal with it (over millions of years), but 7 Billion people living in a sophisticated society, predicated on the easy access to gasoline and electrical power.

    Making a change makes good business sense.

  69. Andreas H

    I wonder, is it time to take a serious look at technical solutions to this problem?

    More and more studies find that even if we reduce emission levels to pre-1990 levels we will most likely only slow down the heating, but neither stop it or actually cool our planet down. If we reached the point where historically fertile land is exposed to regular droughts, we are in serious trouble.

    I have heard about numerous technical approaches to this problems, but they usually seem to be ignored as unrealistic or too expansive. Well if it starts to affect our livelihood, cost can no longer be a limiting factor.

    Proposals that I have seen include things like a space sunshade, that would directly limit the amount of light that reaches our planet. There are even combinations proposed that would allow such a sunshade to produce enormous amounts of energy. Maybe such a project if backed strongly enough could actually stop global warming as well as provide us with a huge boost of energy, maybe even start an age of energy abundance.

    There are of course also less ambitious ideas, but it seems like we are not really pushing those very hard. Let’s face it as unlikely as a technical solution might sound, it seems like changing current political mindsets seems nigh impossible.

    It might also be the sci-fi fanboy speaking, but this could be a huge opportunity to overcome the age of national states in a peaceful manner. Such a project of global scale to safe our planet seems like the kind of catalyst event that could finally end our misguided attempts to artificially slice our one planet up into hundreds of separate pieces.

  70. Nigel Depledge

    Cyberspice (3) said:

    That doesn’t show cause and effect. There’s global warming. I.e. the Earth is warming up. And there’s “Global Warming”. I.e. humans are making it warm up. That graph shows the former but does confirm that latter. Basically its saying its hot because its got hotter.

    Er, no. There’s so many tons of evidence already published that the current warming trend is human-caused. What Hansen is now saying is that we have the data to attribute some of the extreme weather we are now experiencing to the warming trend.

    Or did you not bother to read the article?

    I’m not a nay-sayer about “Global Warming”.

    This is weird, ‘cos your first paragraph sure makes it sound that way.

    I feel that we should be doing what we can to reduce emissions and oil usage. But that’s just sensible anyway. I feel we need a *lot* *lot* more data to show that the current gradual increase of 1.5 (C? – there’s no units) between 1965 and 2005 (mid points of the ranges).

    Eh?

    Do you consider the vast mountains of data that we already have to be insufficient?

    On what do you base this supposition?

    If you have genuine cause to doubt the validity of the conclusion, then you should be preparing a paper for the climatology literature right now. Are you?

    Do we have evidence of how temperatures changed similar over the previous 100 years and so on.

    Yes. Did you bother looking?

    When it gets hot in the UK people buy ice-cream. Someone seeing people with ice-cream may consider it a coincidence. So they look at temperatures vs ice-cream sales over many years. And yes there’s a correlation. But does the ice-cream cause the temperature or vica versa or is it just a weird coincidence. We need more work to determine what’s going on with our climate.

    Not really. Most of the mechanisms involved are sufficiently understood. The fundamentals are actually pretty simple. Where it gets hard is in making accurate predictions in a chaotic system (i.e. a system that is highly sensitive to small variations).

    So the work says. Hey guys its warmer than it used to be. And because of the bell curve that means there’s more likely to be hot days hence more hot days. But that’s all it says.

    No, it says more unprecedentedly hot periods. Do you see the difference?

  71. Nigel Depledge

    Brett (7) said:

    @Nathan – Yes, I’m sure you can find a justification for that statement, but it’s still invalid based on the very arguments we’ve tried to use to convince doubters. Trotting it out when it conveniently fits our beliefs is nothing more than confirmation bias.

    If the statement in question were a substantive portion of the argument, then I would agree with you.

    However, it is not.

    The statement you question is used flippantly, as a humorous reference to the heatwave currently experienced in the US. It does not seem to me that the statement in question is intended to support or bolster the central argument.

  72. Nigel Depledge

    Martin Bonner (11) said:

    I think you are raising a straw man here. Most climate change deniers have stopped arguing that the climate is changing – they are now arguing that the change is *isn’t human caused*. This study is a neat demonstration that the climate is changing, but
    a) it doesn’t show it will go on changing (yes, yes, I know it will – see above);
    b) it doesn’t show the change is anthropogenic rather than random bad luck.

    A couple of points here. First, the paper Phil discusses isn’t really about whether climate change is real or not. Neither is it about whether humans are the cause or not. Those arguments – scientifically at least – are long settled.

    The paper is about linking the weather patterns we are seeing now with climate change. IOW, the paper is stating that the weather being experienced in the US is caused by GW. It is not just random variation at the extremes within the established norm – it is different.

    Second, yes, there are still some denialists who deny that the climate is changing at all.

  73. HarryW

    Lucas@15, the best source of data is SkepticalScience.com: it will take some time studying, but *ALL* the data you need to connect the dots to humans and our current warming is there.

  74. Franco

    So, if this keeps up, how long until the mankind will die out? Is it 20 year? 200 years? 2000 years? 2000000 years?

  75. FroMax

    @Andreas H 72: I wonder, is it time to take a serious look at technical solutions to this problem?

    Basically, we have to start terraforming our own planet!

  76. Mark
  77. Mark

    follow-up: has Hansen provided his methodology? where did his data come from? reason why I ask is it clearly isn’t from the USCRN as a simple crunching of the numbers there indicates Hansen is completely off the mark. Why would Hansen not used this shiny new system that NOAA spent many $$$ to get his data? Hansen has been debunked already by his own colleagues. For Mr Plait to continue to use Hansen as his ‘go to’ man in this area shows a total disregard for the good science being conducted elsewhere. It (AGW) may be real for Mr Plait, but it has yet to be proven. And to a poster above (apologize I’m not sure which), PNAS isn’t as respected as you might think it is. Their peer review policy is something to be desired.

  78. Infinite123Lifer

    on second thought . . . with some reflection . . . after stepping outside, I think . . . yes, ‘Step Outside’ and see for yourself is brilliant, in the overall.

    SO . . .

    That’s what I thought. Look at the Universe. Look at our planet Earth. Considering the Universe as a moving entity it appears to me that the word doomed, as in “we are doomed”, is ridiculously vague. Write a book.

    SO . . .

    into extreme weather eventage.

  79. TheBlackCat

    @ Mark: “follow-up: has Hansen provided his methodology? where did his data come from? ”

    Yeah, how could we possibly find this out? If only he published details of the study in some sort of document you could read. And if only Phil had linked to that document.

    Hint: Try reading the OP again. See those bits of text that are colored differently? Those are links. Try clicking the one that says “has published research”.

    Now comes the tricky part. You want to know what methods were used, and what materials those methods were used on. Where would the nefarious Hansen hid such dangerous information?

    I’ll give you another hint: try reading the first sentence of the “Materials and Methods” section, which is near the top of the second column of the first page. I think you will find your answer there.

    reason why I ask is it clearly isn’t from the USCRN as a simple crunching of the numbers there indicates Hansen is completely off the mark. Why would Hansen not used this shiny new system that NOAA spent many $$$ to get his data?

    I don’t know, maybe because

    1. USCRN only covers the continental U.S., while the study is worldwide.

    2. USCRN only has 114 stations, while the set Hansen used has about 4000 temperature stations.

    3. USCRN is intended to provide 50-year temperature records starting in 2008. It isn’t a historical temperature record, so is entirely useless for this purpose.

  80. James

    I may just be uninitiated, and am certainly too lazy to read the entire study, but I have to wonder why the graph compares a period of 10 years (2001-2011) to a period of 29 years (1951-1980), and the ommission of the data in between (1980-2001). Is it not more useful to compare the same lengths of time, say, each 10 years?

    I have no qualms about the certainty of the conclusion, just wondering about the method.

  81. Mikey C

    James @84

    If you click through to the paper cited by Phil you’ll find your answer;

    “Reference Period. Although we had multiple reasons for choosing 1951–1980 as a base period to define temperature anomalies, as discussed under Materials and Methods, we must ask: Do our conclusions depend on the chosen base period? Could we just redefine climatology based on the most recent decades, perhaps leading to a conclusion that the only climate change has been a small shift of mean temperature that may be insignificant?
    The effect of alternative base periods on the temperature anomaly distribution is shown in Fig. 9. Use of a recent base period alters the appearance of the distribution. Climate variability increased in recent decades, and thus the standard deviation increased. Therefore, if we use the most recent decades as base period, we “divide out” the increased variability. Thus the distribution function using 1981–2010 as the base period (Fig. 9, Right) does not expose the change that has occurred toward increased climate variability.”

  82. James,
    At a guess, I’d say that it doesn’t matter how many years you use to compare since they’re averaging. The longer baseline is better for getting a smoother average, but with a time-variable phenomenon, you don’t want to use such a long average that you mix the two time intervals. Skipping the middle period was probably done simply because it would make the trend harder to see. (They could have, as you suggested, taken just the first ten years and the last ten years, I’m sure. But then the early period would be a lot noisier.)

    In the paper, they give reasons for taking the period they do. They’re somewhat arbitrary, but not entirely. They also show the average curves by decade and you can see the curves marching to the right with each decade. I think that those are probably just less effective as summaries.

  83. Steve Metzler

    @James (#84):

    Ah, the old Anthony Watts ‘trick’ to ‘hide the incline’: use the most recent baseline that you possibly can get away with, so the warming anomalies are minimised. In fact, if you can use just the current year as the baseline period, all the temperature anomalies are *negative*; therefore, it’s cooling!!!1!!! :-)

    ETA: that’s why Watts particularly likes the satellite records. Since they only started much more recently than the land records, they have a more recent baseline period (~1980 – 2010 rather than 1951 – 1980 or 1961 – 1990).

  84. Steve Metzler

    Hmm, strange. This is an AGW related thread that’s only on the second page of the BA’s site, and the deniers aren’t out in full force. Wishful thinking, but perhaps the predicament we find ourselves in is finally beginning to sink in? Nah. They must all be busy watching the Olympics… or something.

  85. Skeptical Science discusses the NOAA/Hoerling criticisms of Hansen’s paper here. Suffice to say that it appears such criticism is off-base.

  86. Nigel Depledge

    Mark (81) said:

    Hansen has been debunked already by his own colleagues.

    Citation needed.

  87. Nigel Depledge

    James (84) said:

    I may just be uninitiated, and am certainly too lazy to read the entire study, but I have to wonder why the graph compares a period of 10 years (2001-2011) to a period of 29 years (1951-1980), and the ommission of the data in between (1980-2001). Is it not more useful to compare the same lengths of time, say, each 10 years?

    It seems to me that the graph is comparing “now” (the average of the last 10 years) to a preceding baseline (data up to 1980).

    What happened between was, of course, a transition from “then” to “now”, so the intervening data would, in this format, only obfuscate the actual conclusion.

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