Climate

The Climate Science Project, Part 2: How we know global warming is happening

Skeptical Science explains: It’s the oceans!

Memo to climate scientists, environmentalists, and others:  If you’re going to give an interview or speak in public, you need to know the FULL scientific literature.  If you just stick to reading up on your area of expertise, you won’t have the sharpest answers for reporters or for a tough questioner in the audience.

Reading the BBC’s interview of Dr. Phil Jones, the climate scientist at the center of the hacked e-mail scandal, makes clear that even an experienced and widely published researcher like Jones doesn’t appear to know the full climate literature or the clearest answers to basic questions.  The interviewer, the BBC’s environment analyst Roger Harrabin, also doesn’t, or he probably wouldn’t have asked “Do you agree that from January 2002 to the present there has been statistically significant global cooling?”

Now the snappiest answer to such a question comes from Ken Caldeira to the AP in October:  “To talk about global cooling at the end of the hottest decade the planet has experienced in many thousands of years is ridiculous.” You could also quote NOAA climate monitoring chief Deke Arndt from that same story, “The last 10 years are the warmest 10-year period of the modern record.  Even if you analyze the trend during that 10 years, the trend is actually positive, which means warming.”

I’d also recommend mentioning two major scientific studies from last year, which demonstrate that when you look at where 90% of the human-caused warming was expected to go “” the oceans “” you find steady warming in recent years.  I’d keep this figure handy [I use it in my talks]:

Time series of global mean heat storage (from 0 to 1.24 miles).

One reason I am launching the Climate Science Project is to connect people to the best scientific explanations and the best answers to commonly asked questions.  Obviously, one of the first places you should start is SkepticalScience.com.  That’s where I saw this figure — and an excellent explanation of what it means.

Skeptical Science is run by physicist John Cook.  It aims to “explain what peer reviewed science has to say about global warming” and answer the most common questions and objections raised both by the well-meaning doubters and the not-well-meaning disinformers.  There’s now a must-have iPhone that is so useful I’ll make it the subject of a different post.

Right now I’m going to repost and update my October piece on

The empirical data has spoken. Cancel the global cooling party. Global warming is still happening.

The planet is heating up, thanks to human-generated emissions of greenhouse gases. But as a new NOAA-led study, “An observationally based energy balance for the Earth since 1950” (subs. req’d) concluded:

[S]ince 1950, the planet released about 20 percent of the warming influence of heat-trapping greenhouse gases to outer space as infrared energy. Volcanic emissions lingering in the stratosphere offset about 20 percent of the heating by bouncing solar radiation back to space before it reached the surface. Cooling from the lower-atmosphere aerosols produced by humans balanced 50 percent of the heating. Only the remaining 10 percent of greenhouse-gas warming actually went into heating the Earth, and almost all of it went into the ocean.

Note that this Journal of Geophysical Research-Atmospheres study was done “without using global climate models.”

Figure: “Total Earth Heat Content [anomaly] from 1950 (Murphy et al. 2009). Ocean data taken from Domingues et al 2008.”

That figure comes from the first of two posts by the terrific website Skeptical Science, which I repost below. Skeptical Science is an excellent, well-organized site to send convincible people for a shredding of the standard, long-debunked denier talking points.

Now I’m sure the anti-science disinformers out there are shrieking, “There are peer reviewed analyses that document that upper ocean warming has halted since 2003!” — a claim I dealt with in this July post.

Subsequently, however, another JGR article, “Global hydrographic variability patterns during 2003-2008” (subs. req’d, draft here [big PDF]) details an analysis of “monthly gridded global temperature and salinity fields from the near-surface layer down to 2000 m depth based on Argo measurements.” Background on Argo here. Their findings are summed up in the figure on global mean heat storage at the top of this post.

We are still warming, after all these years! And just where you’d expect it. The study makes clear that upper ocean heat content, perhaps not surprisingly, is simply far more variable than deeper ocean heat content, and thus an imperfect indicator of the long-term warming trend.

Yes, I am aware of some recent upper-ocean heat content data on the web. Please note that plots of very recent, highly variable upper-ocean content heat data down to 700 meters from unpeer-reviewed sources do not trump peer-reviewed analysis of much longer-term data down to 2000 m.

What follows is a repost of two articles from Skeptical Science discussing these figures and the recent studies in more detail:

[I have renamed the figures for the sake of clarity.]

How we know global warming is still happening, Part 1

Skeptics proclaim that global warming stopped in 1998. That we’re now experiencing global cooling. However, these arguments overlook one simple physical reality — the land and atmosphere are only one small fraction of the Earth’s climate (albeit the part we inhabit). Global warming is by definition global. The entire planet is accumulating heat due to an energy imbalance. The atmosphere is warming. Oceans are accumulating energy. Land absorbs energy and ice absorbs heat to melt. To get the full picture on global warming, you need to view the Earth’s entire heat content.

This analysis is performed in An observationally based energy balance for the Earth since 1950 (Murphy 2009) which adds up heat content from the ocean, atmosphere, land and ice. To calculate the Earth’s total heat content, the authors used data of ocean heat content from the upper 700 metres. They included heat content from deeper waters down to 3000 metres depth. They computed atmospheric heat content using the surface temperature record and the heat capacity of the troposphere. Land and ice heat content (eg – the energy required to melt ice) were also included.

[See Figure on “Total Earth Heat Contentabove.]

A look at the Earth’s total heat content clearly shows global warming has continued past 1998. So why do surface temperature records show 1998 as the hottest year on record? Figure 1 shows the heat capacity of the land and atmosphere are small compared to the ocean (the tiny brown sliver of “land + atmosphere” also includes the heat absorbed to melt ice). Hence, relatively small exchanges of heat between the atmosphere and ocean can cause significant changes in surface temperature.

In 1998, an abnormally strong El Nino caused heat transfer from the Pacific Ocean to the atmosphere. Consequently, we experienced above average surface temperatures. Conversely, the last few years have seen moderate La Nina conditions which had a cooling effect on global temperatures. And the last few months have swung back to warmer El Nino conditions. This has coincided with the warmest June-August sea surface temperatures on record. This internal variation where heat is shuffled around our climate is the reason why surface temperature is such a noisy signal.

Figure 1 also underscores just how much global warming the planet is experiencing. Since 1970, the Earth’s heat content has been rising at a rate of 6 x 1021 Joules per year. In more meaningful terms, the planet has been accumulating energy at a rate of 190,260 GigaWatts. Considering a typical nuclear power plant has an output of 1 GigaWatt, imagine 190,000 nuclear power plants pouring their energy output directly into our oceans.

Figure 1 only goes as far as 2003 as the ocean heat data used (Domingues 2008) only goes that far. What has global warming been doing since then? Since 2003, ocean heat data has been measured by the newly deployed Argo network. However, there have been teething problems with the Argo buoys experiencing pressure sensor issues that impose a cooling bias on the data. Consequently there have been several data analyses on ocean heat since 2003. One reconstruction of ocean heat show cooling since 2003 (Willis 2008). Other analyses of the Argo data show ocean warming (Levitus 2009, Leuliette 2009, Cazenave 2009).

How do we determine which analyses are more accurate? Ocean heat data can also be independently determined through other empirical means. Cazenave 2009 uses satellite gravity measurements to create two independent estimates of ocean heat – both find warming. Sea level has been inexorably rising since 2003. As a large portion of sea level rise is due to thermal expansion from ocean warming, this is an indirect confirmation of warming.

Lastly, the planet’s energy imbalance is confirmed by satellite measurements of incoming and outgoing radiation. Earth’s Global Energy Budget (Trenberth 2009) examines satellite measurements for the Mar 2000 to May 2004 period and finds the planet is accumulating energy at a rate of 0.9 ± 0.15 W mˆ’2. This is consistent with the amount of heat accumulating in the ocean. Preliminary analysis on the latest CERES satellite data shows an increasing energy imbalance from 2004 to the end of 2008 (although this data is yet to be published, more on this later).

So the point to remember when considering short term cooling trends in surface temperature records is that the atmosphere is only one small part of a planet which is in energy imbalance. Empirical measurements show the planet continues to accumulate heat. More energy is coming in than is radiating back out to space. Global warming continued past 1998 and is still happening.

How we know global warming is happening, Part 2

In our last post, we determined whether global warming was still happening by adding up all the heat content of the climate system. Murphy 2009 performed this analysis and found that that planet has been accumulating heat up to 2003. Unfortunately their data ends there as the ocean data they used from Domingues 2008 stops at the end of 2003. So how do we find out what’s happened from 2003 until now? Unfortunately, there is no time series (that I know of) of the planet’s total heat content up to present time. However, we do have the next best thing.

Global hydrographic variability patterns during 2003-2008 (Schuckmann 2009) analyses ocean temperature measurements by the Argo network, constructing a map of ocean heat content down to 2000 metres (H/T to Chris for bringing it to my attention). This is significantly deeper than other recent papers that focus on upper ocean heat, only going down to 700 metres. They constructed the following time series of global ocean heat:

Time series of global mean heat storage (0-2000 m), measured in 108 Jm-2.

Globally, the oceans have still been steadily accumulating heat right to the end of 2008. Combined with the results of Murphy 2009 who finds the planet accumulating heat right to 2003, we now see a picture of unbroken global warming. Over the last 5 years, the oceans have been absorbing heat at a rate of 0.77 ± 0.11 Wmˆ’2.

So what is our planet’s total energy imbalance? Indulge me as I perform some rough back-of-a-napkin calculations. Murphy 2009 found that about 5.6% of the planet’s energy imbalance went into the land and atmosphere. In other words, 94.4% of global warming goes into the oceans. So if the ocean is absorbing 0.77 ± 0.11 Wmˆ’2, this puts the total energy imbalance at around 0.82 ± 0.12 Wmˆ’2. This is a slight underestimate as Murphy 2009 included ocean heat down to 3000m (remember this is back-of-a-napkin stuff).

How does this value compare to other estimates of energy imbalance? Hansen 2005, using ocean heat data, calculated the planet’s energy imbalance around 2003 to be 0.85 Wmˆ’2. Trenberth 2009 examined satellite measurements of incoming and outgoing radiation for the March 2000 to May 2004 period and found the planet accumulating energy at a rate of 0.9 ± 0.15 Wmˆ’2.

All these estimates are consistent with each other. Most importantly, all find a statistically significant positive energy imbalance. The empirical data has spoken. Cancel the global cooling party. Global warming is still happening.

Precisely.

The warming of the planet is unequivocal, which means there is an overabundance of evidence.  And that means this is not the last post I will do on this subject.

Bottom Line:  If you’re going to give interviews or talks on this subject, please read the key literature, something that I aim to highlight in the Climate Science Project

I’ll have more to say about Jones’ BBC interview shortly.  I already blogged about how the Daily Mail misrepresented it.  Real Climate has more on that here.

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22 Responses to The Climate Science Project, Part 2: How we know global warming is happening

  1. mike roddy says:

    Good information, thanks to you and Skeptical Science, especially since most laymen don’t know about ocean heat absorption. It’s a great learning tool, since it’s consistent and irrefutable.

    This should be a key part of any public presentation. Maybe Gore does not quite have the right personality, nor do scientists, for different reasons. It’s time that a team of really good communicators delivered this critical information, with plenty of visual aids.

  2. Leif says:

    It would be nice to calculate the total energy imballance accumulated each day so folks could get a handle on just how much energy we are talking about we you say 0.77 Wm2 A couple of months age on this site a couple of us made an attempt to do just that. ~Comments 50 thru the end.

    http://climateprogress.org/2009/12/31/science-the-hottest-decade-ends-maunder-mininum-solar-cycle-24-global-warming/

    We melted aircraft carriers, JFK Class, ~11 per second! We also tried using the current US W87 warhead with a yield of 1.3 PJ. Answer? One every 1.3 seconds. 66,000 W87s every day.

    It would be nice to tighten up these numbers so we could use them with more confidence and clarity. Perhaps evaporate Olympic swimming pools of water to fall again as rain, floods, or even snow in the winter.

    However you look it is clearly a lot of energy. Clearly enough to make storms more vigerious or tweek a jet stream or two.

  3. Jeff Huggins says:

    Multiple Lines of Evidence

    I agree. Anyone who is going to give an interview regarding climate change should be familiar with all the key multiple lines of evidence. Being expert with respect to one or some of them is fine and naturally and necessary, of course. People can be expert with respect to every topic under the sun. But, any responsible scientist should at least “get”, and be able to clearly explain, the various (more than one) lines of evidence and reasoning that inform us that climate change is real and problematic.

    Atmospheric chemistry. Temperature measurements. Ocean chemistry, temperatures, etc. Measurements of the mass of ice, from space. And etc.

    Indeed, scientists should spend more time together, but not just with other scientists focusing on the same line of evidence as their own, but also (and very importantly) with scientists who understand the other lines of evidence.

    Cheers,

    Jeff

  4. Jeff Huggins says:

    Sorry for typos in my earlier post, “Multiple Lines of Evidence”.

    I meant to say that “Being expert with respect to one or some of them is fine and natural and necessary, of course.” And, that “People can’t [rather than can] be expert with respect to every topic under the sun.”

    Cheers,

    Jeff

  5. Zach says:

    The first two quotes are great. The ocean heat content business is far too complex to work. Finding it convincing requires a knowledge of statistics, scientific units, conventions in scientific publishing, what “back of the napkin” means, what H/T means, how deep the oceans are, what energy flux is, etc, etc. I’d bet that a vast majority of the audience who would find this argument compelling are already convinced on warming. Don’t get me wrong – I think it’s valuable. But I don’t see how Jones could’ve dropped those references in any interview format in a way that would help make the public case for curbing emissions.

    I prefer the fear-of-uncertainty approach (because it’s a fear I share): Our temperature is at its highest point since man discovered fire. We have more greenhouse gas in the atmosphere today than we did when the Americas became continents, and, unless we change what we’re doing soon, there will soon be more than there were when the dinosaurs went extinct. All of this happened in the last 150 years as we’ve burnt more and more oil and the temperature has risen faster than it has in millions of years. If we don’t change this soon, we won’t be able to change it for a thousand years. We don’t know exactly how high the temperature will go if we do nothing. Do we want to find out?

    Skeptics would attack a few points in there, saying they aren’t known with total certainty. I’d ignore them. Their attacks will be publicized to the same extent regardless of accuracy, so don’t back away from the most compelling argument when talking about this stuff.

    It’s a little ironic that Jones’ remarks about uncertainty in short time series are being abused when the Washington Post finds it factually correct to declare that a “series of mistakes” have been found in the IPCC report based on a sample size of one.

  6. Ivan Carter says:

    Joe,

    The oceans is an often overlooked part of this equation. It may be really helpful and informative for a lot of people, even some so called partial “skeptics” (though it’s hard to see how thinking we can exact a major climate forcing and not ultimately affect a geologically fragile climate system is being “skeptical”) to focus on this a little more. Particularly with the media.

    There is a great deal of emphasis, particularly in news articles, on this implicit presumption of climate linearity. Thus we tend to want to draw strong conclusions from whether say, 2008 was warmer than 1998, when of course scientifically speaking, it’s fairly meaningless.

    That (innate climate variability, which is likely only heightened by climate change, not ironed out) is also a separate issue that could use a lot more clarification; but it also ties into this idea that is being overlooked by most media sources that there is a likely lag of perhaps several decades or more between cause and effect here. Not only is climate extremely variable (and perhaps, as we increase an external system stressor upon it, even more unpredictable) from year to year, it also would not tend to reflect its original precipitating cause until decades later.

    There seems to be some general sense in the media that it does so fairly instantaneously, and therefore that climate change is defined by what we observe today and have observed so far, when those observations are largely defined by the combination of those increased changes well in the past, with decades more (already behind us) slow warming accumulation not yet reflected, more in the pipeline starting fro present day, and likely accelerating affects as normally relatively stable stases begin to change. (E.g, ice aps, for instance, which can then in turn act as tremendous driver in various compounding ways.)

    Thus many media sources tend to treat this as if what we are seeing today is the result of what we have done up to this point, when that is not the way it works.

    It also might be helpful to consider that the climate has shifted rather radically in the past, indicating a reasonable sensitivity to any type of change (whether it be through certain climate patterns coming up a certain way by change, solar pulses, extra volcanic ash, etc….) Thus we know it can and does, and that it is is not some huge linear system where one plugs in X amount of forcing input and get Y amount of return, and plug in 2x amount forcing input (solar flares or ghg increases for instance) and get 2Y amount of return. Climate pretty clearly, just looking at its history, over time does not seem to work like that.

    So combining the idea of a large cause and effect lag with the idea that the climate does not shift linearly in response to a potentially large external stressor, we see that past performance is not necessarily indicative of the rigor of future trends, which may dwarf it in comparison.

    The oceans play a key role as to why. An external forcing which leads to increased trapped heat would ultimately change the climate through oceans, which, currents aside potentially, are relatively stable — whereas the atmosphere, temperature wise, is the opposite. Oceans take an extremely long time to heat up, and oceans ultimately are the driver of climate. As they heat up, we will likely see increasingly larger changes.

    This idea is abstract to a lot of people, but when they start to see why, it is more comprehensible. Increased concentrations of gases decades ago (which have only risen greatly since and continue to rise) went into slowly warming oceans, which. little by little, as they get warmer, beget more changing atmospheric climatic conditions — which then in turn can reinforce ocean warming, and/or some other effect re getting warmer). Thus we have increased trapped heat in the atmosphere in general, which is more of a variable, combined with an increasingly powerful warming driver of climate (the oceans).

    It seems as if this is only being looked at in the first instance — increased trapping of heat in the atmosphere, thus what do we see.

    Throw back in the key, and media overlooked point, about innate climate variability and how stressors (at least until a new stasis is reached) would only tend to increase that, if anything, and this covers a big part of the picture.

    Roddy,

    Yeah, agree, it’s an important point to make. A lot of people — with science perhaps not being as natural to many as other disciplines — are really more confused about this issue (only compounded by all of the misinformation out there). And focusing on ocean trends helps explain it a great deal.

  7. Craig says:

    If ocean warming is really the more meaningful and relevant measure, then why have environmentalists and the IPCC been so busy for so many years beating the public over the head with the mean surface temperature trend?

  8. Zach says:

    @Craig – Surface temperatures are more important so far as most everything we experience is concerned. Ocean warming is more severe and less noisy, so it’s better evidence of global warming. Also, are there reliable prehistoric proxies for ocean temperature? If not, that’s a good reason to stick to atmospheric temperatures.

  9. From Peru says:

    There are new preliminary CERES radiative imbalance data?

    Where could I found them?

  10. Donald says:

    Several of the questions Harrabin asked were submitted by “sceptics”- which explains why they have a built-in misunderstanding. (ie, that short periods can say anything meaningful about the long-term trend.)

  11. From Peru says:

    I want to say, the 2004-2008 CERES data.

    Has the radiative imbalance (0,9 W/m^2 for 2000-2004)increased, reduced or stayed almost equal?

  12. fj2 says:

    This might be good material for the lecture circuit: The Columbia School of Journalism in Collaboration with the Earth Institute, Physics and Geophysics Colloquia, etc.

  13. David says:

    It is beyond comprehension how the denialists get away with absolute falsehoods like the rewriting of Dr. Jones’ meanings in the recent interview: http://www.gather.com/viewArticle.action?articleId=281474978048543

    I fully support all your work. Keep it up.

  14. fj2 says:

    It might be worth considering a highly publicized New York City media blitz to not only include Columbia Journalism, Earth Institute, and Physics colloquia but, Cooper Union’s Great Hall, NYU, CUNY, New York Academy of Sciences, Mayor Bloomberg coinciding with the publishing of the New York Academy of Sciences’ Annals “New York Panel on Climate Change, the usual media outlets, etc.

    Ref:
    Climate Change Adaptation in New York City: Building a Risk Management Response
    http://www.nyas.org/Publications/Annals/Detail.aspx?cid=ab9d0f9f-1cb1-4f21-b0c8-7607daa5dfcc

  15. fj2 says:

    Also, Columbia University professor Brian Greene is really media savy and could help even though this is not his specialty.

    http://en.wikipedia.org/wiki/Brian_Greene

  16. Leif says:

    It is helpful to think of the increase in the ocean heat index as charging a battery. ~90% of those melted aircraft carriers, 9 out of every 10 per second, have gone into raising the top 2,000 feet of ocean water the ~1C observed. (Potential energy!) And most of that has been concentrated in the polar regions. Notice the reduction of Arctic ice for example. For those that consider one degree Celsius no big deal I would remind you to look at the effects that a relatively small, but well known ~1C+or-, variation can have on the earths weather patterns. El Nino. With that in mind, now transpose that energy imbalance in spades to the Arctic Ocean, related Arctic out flows, and effects on the northern hemispheres Jet Streams. A tad more vigorous weather response would be expected, don’t you think? Even in the winter!

  17. I should probably point out that since 2006 Al Gore working with the leading scientists of the IPCC report has trained 3000 people around the world to give updated talks on the material that in a very different form appeared in An Inconvenient Truth. The training has gone on constantly and new slides linked to the newest science are constantly distributed to the presenters. Those presenters have spoken to millions of people in thousands of groups. Anyone on this list is free to go to the website of theclimateproject.com and request a free presentation for your group.

  18. Lou Grinzo says:

    Steven (#17): The problem is that such presentations have largely self-selected audiences–they’re a “pull” technology–which greatly reduces how much they actually move the needle.

    We need a “push” technology, like all those lovely ads we see on TV from the fossil fuel companies, plus the seemingly endless list of clueless (or worse) things we see in the traditional media.

    The bottom line is that the level of awareness of and the sense of urgency about the climate mess we’re in is nowhere near what’s appropriate, given the BAU human impacts. Until someone finds a way to change that it will be far too easy for politicians to lie and cater to the worst instincts of voters, which means we won’t get the public policy we need to address this.

  19. Kevin says:

    In Joe’s more recent post on the Phil Jones interview, he stresses the point that, “The period since 1995 is really too short for statistical significance, but has seen continued warming.” As a newbie, I have some questions of ignorance: Is the trend of ocean temperature since 2003 (the first graphic in this post) also over a period that is too short for statistical significance? What are the data like before 2003? How far back do the data have to go for statistical significance for the ocean temperatures? What do the data show going back that far?

  20. Barry says:

    If the point of this re-aggregation of posts is to to aid the not-yet-convinced in understanding climate change, using the word “stupid” in the title is not a good idea.

    There’s a log of good stuff on this blog, but your inability to suppress an arrogant, smug attitude guarantees that you’ll continue to preach to the choir.

  21. Michael T. says:

    Barry (#20)
    I believe Joe was referencing the “it’s the economy, stupid” phrase used by Bill Clinton. I don’t think he meant to call the skeptics or deniers stupid.

  22. Fish says:

    On the graph of Global Ocean Heat Storage, how many data collection points does this represent and where are they dispersed? Also, the units are in Joules per meter squared, if you are measuring the oceans, wouldn’t it be a volume and therefore joules per meter cubed? I see that J/m3 is energy density, but I can’t find a derieved SI unit for ‘Heat Storage’. How does this unit correlate to a temperature change?

    [JR: Check the links.]