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It's the sun
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Is global warming still happening?

The skeptic argument...

"Global warming has stopped and a cooling is beginning. No climate model has predicted a cooling of the Earth – quite the contrary. And this means that the projections of future climate are unreliable." (source: Henrik Svensmark)

What the science says...

Empirical measurements of the Earth's heat content show the planet is still accumulating heat and global warming is still happening. Surface temperatures can show short term cooling when heat is exchanged between the atmosphere and the ocean, which has a much greater heat capacity than the air.

To say we're currently experiencing global cooling overlooks 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.


Figure 1: Total Earth Heat Content from 1950 (Murphy 2009). Ocean data taken from Domingues et al 2008.

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.

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. 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:


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

Globally, the oceans continued to accumulate heat right to the end of 2008. Over the last 5 years, the oceans have been absorbing heat at a rate of 0.77 ± 0.11 Wm−2. Combined with the results of Murphy 2009, we now see a picture of continued global warming.

How does this value compare to other estimates of energy imbalance? Willis 2004 combines satellite altimetry with ocean heat measurements to find an ocean warming rate of 0.85 ± 0.12 Wm−2 from 1993 to 2003. Hansen 2005, using ocean heat data, calculated the planet's energy imbalance in 2003 to be 0.85 ± 0.15 Wm−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 Wm−2.

These results all find broad agreement and all find a statistically significant positive energy imbalance. Our climate is still accumulating heat. Global warming is still happening.

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Comments 1 to 35:

  1. Not only does this site have depth and clarity, you're a model of how to present facts without demonizing those with contrary views. Thanks!
  2. Thank you for a website that provides information without a political agenda. I would like to understand the global warming debate without feeling like I am being manipulated by someone with a political agenda and most web-sites seem to promote an agenda for one side or the other. Thanks.
  3. It is worth looking at fig 6 in Trenberth's paper...it shows ocean heat content derived from 4 sources; GODAS, JMA, ECCo-GECCO & ECCO-GODAE.
    Two data sets show an increasing trend in OHT and two show the beginning of a steep decline.
    You can download the ECCO report from
    http://www.ecco-group.org/pdfs/reports/report44.pdf
    and compare it with the graphs from GODAS ( Google
    Meridional Overturning Circulation Simulated by NCEP GODAS...quick view).
    GODAS seems to show warming is essentially confined to the North Atlantic..the tropics and N. pacific show no trend, whilst the S pacific, S. Indian and S. Atlantic show steep declines since around 2006.
    So which do we believe??
  4. i'm new to this and i'm a skeptic.
    however, i'll admit that the planet is still warming.

    using satellite data from UAH and RSS, if you look at the past decade or so including 1998, it shows a cooling trend. however, if you remove the 1998 el nino freak year, the planet is still warming at a similar rate to pre-1998.
  5. Great work, just a slight niggle:

    "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."

    A decent sized nuclear power plant is 1 GWe, which at a 33% thermal efficiency, is close to 3 GWt. 190 TWt of energy going into the ocean each year is closer to the heat output of 65,000 1 GWe nuclear power plants.
  6. If the ocean has warmed to this extent, it must surely have expelled many millions of extra tonnes of CO2 into the atmosphere.

    Has this new stream been detected at Mauna Loa? And does it advance the expected date for reaching the fateful 450ppm?
  7. I'm a first time visitor to this site and I'm impressed. (Understanding any of the science of global warming from the general press is futile!)

    I'll offer an answer and a question here:

    Australis: Just because the ocean has absorbed so much heat does not not mean that its temperature has increased a lot. That is because water has a high specific heat capacity. A few degrees of warming does imply that water could hold (at maximum) less CO2; however its CO2 content is largely a function of the equilibrium with the atmosphere. As atmospheric CO2 concentrations rise, the oceans will continue to absorb more CO2 despite their increasing temperatures. (Once they get close to carbonated water as we find in soft drinks, then a few degrees of temperature change could make a big difference! :-P )

    And now my question: Figure 1 could also be used to advance the idea that the oceans have a tremendous ability to buffer us (on land) from global warming, and that while things may change, the consequences may be overstated. I know there are potential holes in that reasoning, but I'd appreciate links to science addressing the extension of this topic to the potential impacts.

    Thanks!!
  8. Hello, this is my first comment on this page.

    My question: Wouldn't it be possible that the heat contet of oceans rise even after radiative forcing has stopped changing? I would assume that the "response time" of oceans to global warming is much longer than that of the atmosphere because of the drastic differences in their heat capacities.
  9. tulkki, regarding lag:

    Appetizer 1: It’s the sun, but skip down to the section "Ocean Thermal Inertia." Note that there is a ten-year lag from solar increase. Not 50 years.

    Appetizer 2: It’s the ocean.

    Main Course: How we know global warming is still happening
  10. ''The atmosphere is warming''

    My understanding is that is not warming enough to be able to confirm that an increased greenhouse effect is causing global warming. Also it's not warming enough in the right area which is supposed to be in the Troposphere at around 10km. Has this suddenly changed?

    Also regarding ''Oceans are accumulating energy''
    Some 3,000 scientific robots that are plying the ocean have sent home a puzzling message. These diving instruments suggest that the oceans have not warmed up at all over the past four or five years. That could mean global warming has taken a breather. Or it could mean scientists aren't quite understanding what their robots are telling them

    But Josh Willis at NASA's Jet Propulsion Laboratory says the oceans are what really matter when it comes to global warming.

    In fact, 80 percent to 90 percent of global warming involves heating up ocean waters. They hold much more heat than the atmosphere can. So Willis has been studying the ocean with a fleet of robotic instruments called the Argo system. The buoys can dive 3,000 feet down and measure ocean temperature. Since the system was fully deployed in 2003, it has recorded no warming of the global oceans
    Response: Josh Willis is right. Over 90% of global warming goes into the oceans. Some studies of upper ocean heat (using the "3000 robots" that comprise the Argo network) have shown cooling over the last few years during a time when the Pacific has transitioned from El Nino to La Nina conditions. However, when the Argo data is examined to greater depths, down to 2000 metres, it's seen that the ocean is still accumulating heat (von Schuckmann 2009):

  11. John Cook:
    Comparing the OHC results from the:

    1)Upper 700 meters : 0.089 Wm^−2
    (data source:http://climexp.knmi.nl/daily2longer.cgi, and the trend obtained in EXCEL)
    2)Upper 2000 meters: 0.77 ± 0.11 Wm^−2

    It is clear that the heat was sequestered in the Deep Oceans by the Termohaline Circulation, and that explain why the SST warming trend was near zero between 2003 and 2008.

    From this numbers is clear that if the Termohaline Circulation Shut Down then a BLAST OF HEAT will occur in the Upper Ocean and Atmosphere.

    Is there any current Climate Model of how much the warming will accelerate if the Termohaline Circulation Shut Down?
  12. IPCC projections disproved.

    As a result, CO2 has nothing to do with global warming.
  13. selti, you are wrong about the IPCC projections being disproved.

    See Comparing IPCC projections to observations. If that's not detailed enough for you, click on the link that's in that post, to Tamino's related post.
  14. #13 Tom Dayton

    How could I be wrong as I used the data without any spin. Here are the data for the mean global temperature anomaly for the Hadley center.

    Year=>anomaly (deg C)
    2005=>0.47
    2006=>0.42
    2007=>0.40
    2008=>0.33

    And the chart itself is from IPCC 2007 WG1-AR4.

    I am not wrong.

    The IPCC projections are deadly wrong.
  15. There is no global warming that is taking place at the moment.

    Here is a chart for the mean global temperature anomaly from the Hadley center.

    The above graph shows a linear warming of 0.44 deg C/ Century, and superimposed on this linear warming there is an oscillating component that moves up and down about the linear trend line.

    The linear warming of 0.44 deg C/ Century is only 0.004 deg C/ year. As a result, this linear warming is insignificant when looking at mean global temperature trends at the moment.

    To look at mean global temperature trends, this linear warming of 0.004 deg C/ year can be removed by de-trending the anomaly, which gives the oscillating global temperature anomaly pattern.

    This pattern shows global cooling and warming phases of about 30 year duration, and the current trend is global cooling until 2030.

    There is no global warming that is taking place at the moment.
  16. selti,
    the only thing your graph shows is that a linear trend from 1880 is not adequate to describe the actual temperature trend, let alone prove the existence of a periodic oscillation. Indeed, there's no cycle.

    Although in some (rare) cases it is possible to do a statistical-only analysis of physical phenomena, it needs to be done appropiately.
  17. #16 Riccardo

    There is a cycle!

    The cycle is approximate 30 years of warming followed by 30 years of cooling.

    Cooling phase from 1880s to 1910s.

    Warming phase from 1910s to 1940s.

    Cooling phase from 1940s to 1970s.

    Warming phase from 1970s to 2000s.

    And the current cooling phase from 2000s to 2030s.

    No more spin please. The data is cyclic.
  18. selti, your link "The IPCC projections are deadly wrong" is to an IPCC chart whose ranges of model runs (the shaded areas) and the observed data (the black dots and line) go up only to 2005. The black line for HADCRUT3 observed temperatures smoothed has been extended beyond that not by the IPCC, but by someone who modified (doctored, faked, falsified, as in Elvis with Bigfoot) the graph but adding an unsmoothed line! Perhaps the added black dots after 2005 really are the observed anomalies, but the line's extension is not smoothed across the dots! The resulting and false impression is that the smoothed line dove after 2005. The actual smoothed line makes a much shallower dip after 2005, especially if you add 2009 data. If you want to look at smoothed data then you must smooth it all the way from 1990 through 2008.

    If you want to look at unsmoothed data then you must look at unsmoothed data across all years, by ignoring the black line and just looking at all the black dots starting in 1990 and going up through 2008. If you want to draw a line from dot to dot you must do so for all the dots starting in 1990, not just starting in 2006.

    You must also look at either the line or the dots within the range of projections (the shaded areas) beyond 2005. That is shown on RealClimate in the post Updates to Model-Data Comparisons. Guess what? Observations are within the bounds of the projections!
  19. #18 Tom Dayton

    What I am comparing is the data after 2005.

    For all the data points after 2005, the actual anomaly measured observations are BELOW the anomaly projections with CO2 restricted at the 2000 level:

    Year Measured (deg C) Projections (deg C)
    2005 0.47 0.45
    2006 0.42 0.47
    2007 0.40 0.48
    2008 0.33 0.52

    As a result, the IPCC projections are utterly wrong.
  20. #18 Tom Dayton

    What I am comparing is the data after 2005.

    For all the data points after 2005, the actual anomaly measured observations are BELOW the anomaly projections with CO2 restricted at the 2000 level:








    Year Measured (deg C) Projections (deg C)
    2005 0.47 0.45 2006 0.42 0.47 2007 0.40 0.48 2008 0.33 0.52

    As a result, the IPCC projections are utterly wrong.

    Are you asking you me to believe you and deny my own lying eyes?
  21. selti: Look at the forest, not the individual trees.
  22. #21 Tom Dayton.

    Sooner than later, it will be established that CO2 driven global warming is the greatest scientific stuff up of all times.

    The stuff up is caused by assuming the temperature rise from 1970 to 2000 was unprecedented. Actually, as shown in this oscillating anomaly, this rise in temperature is similar to those at the end of 1880s and 1940s. Once the oscillating anomaly reaches its maximum it reverses and the cooling phase starts.
  23. selti,
    i'm afraid you didn't even bother to look at how a cycle is define and identified from the links i gave you. Indeed, statistics is no joke, just looking at a couple of up and downs does not define a cycle. It looks like you are following a pre-defined idea and do not care of contrast it with science.
    Do you have any physical _and_ statistical reason to claim that there is a cycle, other than looking at a couple of up and downs?
  24. "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."
    Information from Sydney Levitus, Geophysical Research Letters, 2009 shows that for past few years the heat content of the oceans has not been rising (rising sea level in that period can be accounted for by runoff; not temperature.)
    This is what Trenberth and Latif have been referring to.
    Basically the books don't balance.
    I appreciate that not everyone places a high faith in satellite measurements, but they all say that the earth has been absorbing more energy during that time. If so, it has to show up somewhere and the mystery is that it hasn't.
    Latif seems to think it's in the oceans. Probably more sensible than any other alternative. But he acknowledges that we don't understand enough about the natural forcing elements.
    To me this also raises serious doubts that we really can get a true average measurement of ocean heat content. To those of us who believe that scientific skepticism is healthy, it would seem to be a mistake to conclude that we know the earths total heat content is still rising without looking for alternative answers to the mystery.
    Response: Levitus' data covers only the upper ocean heat which shows more variability than the total ocean heat. Measurements of ocean heat down to 2000 metres deep show that the oceans are still accumulating heat.
  25. Doug Cannon,
    in your comment i found two different concepts mixed arbitrarly, short versus long term variability. If, with Tremberth, we can't say where the heat has gone on a sesonal or yearly basis, the same does not apply to longer periods. You are not allowed to do this extrapolation. Even worst, you cannot conclude that "we don't understand enough about the natural forcing elements." unless by "enough" you mean, for example, the timing of next El Nino and its strength or the like.
    Skepticism is definitely healthy and is at the very core of the progresses of science; misinterprenting or disregarding what is known is not.
  26. Riccardo
    Perhaps my reference to Latif implied I was focusing on a relationship between short term and long term variability. There may be one but that wasn't my intention. But trying to say too much in too few words may have caused confusion.

    I referred to the "past few years". Being more specific, the GRL data at issue is from 2005 up to 2009.
    When Trenberth said "...we can't account for the lack of warming at the moment and it is a travesty that we can't" he was referring to a similar period. He wasn't talking about a seasonal or yearly basis. He has subsequently made it clear that, his intent was to say that with todays technology we should be able to find the effect of the increased trapped heat, but we haven't yet been able to. (My reading of his meaning is that we will be able to, given all the effort being put on it.)

    I've not concluded that "we don't understand enough about the natural forcing elements" as you suggest. The point I was making is that Latif has made that conclusion; specifically about "internal decadal variability". He was talking about the North Atlantic in that particular case. In fact he is "lobbying" for a research program to be able to predict that variability.
    He wasn't referring to El Nino and neither was I.
    (I don't think you mean to say that we know enough about all the natural forcing elements except for short term phenomena like El Nino. But your comment seems to imply that.)

    So, to belabor the "arbitary mixing" a bit further: (a)the lack of warming that Latif suspects is due to natural forcing that we need to understand better and.. (b)Trenberth's frustration with our inability to find the warming that has to be there based on the absorbed/reflected radiation imbalance... are connected in a way. They relate to the same earth during the same period of time.
    It doesn't seem to arbitrary to wonder if the long term cycle in (a) is in a phase of it's cycle that affects the warming in (b).
    I shouldn't be so presumptious to think that I know the answer. I don't. But I reserve the right to wonder if understanding the decadal oscillations of the oceans and an improved ability to measure the heat content of the oceans would lead us to an answer.
  27. Doug Cannon,
    the fact that we still cannot identify the details of how heat goes around in the climate system in the short term (four years is not that much) should not rise any alarm.
    Altough some phenomena show a (sort of) cyclic behaviour they all average out in the long run. For example, look here for the PDO. In the end, they could at best justify some "noise" in the trend; no overall energy balance has been altered and these "oscillation" can just move around the heat through the climate system.
    Indeed, this is what Trenberth refers to in the stolen email, look at the other things he said.
  28. Riccardo,
    "no overall energy balance has been altered"
    I totally agree. That's the point.
    Actually, one of my sources for Trenberth's position is last week's "Economist". Unless they have totally misinterpreted his comments he believes the data show an energy imbalance. Since we all know that can't be true, something is wrong with the data.
    I think a fair paraphrasing of all Trenberth's comments would be: We don't have the right data. Yet. But we'll find it. Then the data will demonstrate there is no imbalance.
  29. Doug Cannon,
    we get always back to the same point, short and long term. There's nothing wrong in the data, just not accurate enough to details the short term variability which we all would like to account for. The long term global warming is put aside and not questioned at all by Trenberth.

    Rememebr also that there's not just black or white, we know everything or we know nothing. Indeed, it's well known that part, the largest probably, of the short term variability can be explained by ENSO alone. This part is know, but it's not all; the remainder comes from other, smaller, contributions.
  30. Doug,
    just after having hit the submit button, i ended up in Trenberth's own words:

    "It relates to our ability to track energy flow through the climate system. We can do this very well from 1992 to 2003, when large warming occurred, but not from 2004 to 2008. The quote refers to our observation system which is inadequate to observe Earth's energy flows at the accuracy needed to understand small fluctuations in climate;"

    Take his words, much better than mine.
  31. Does this data only go back to 1950?
  32. Note that NODC has updated the ocean heat content figures through 2009. You may want to update your graph.
  33. If your kid grows an inch and a half each year between fifth grade and eighth grade and then doesn't grow any more through high school, is he still growing?

    No.

    And if someone says "but but but his average height during high school is taller than his average height during middle school!" does that change your mind?

    It's not still warming. It's still warm. Perhaps it shouldn't be - the known natural forcings over the last decade should perhaps have caused cooling but haven't yet.

    Is 1998 "cherry picking one year?" No. It's one year of natural variability - but 11, going on 12, years of CO2 emissions. And 1998 is warmer than - or if you use GISS, within 0.01 deg C as warm as, each year since then. If 11 becomes 15 or 20, that's the skeptics' point - - if the climate is as CO2-sensitive as is thought, then no single year of natural variability should offset two decades of cumulative CO2 buildup.

    11 hasn't become 15 or 20, so I don't think that "it's still warm though it's neither warming nor cooling" disproves your thesis. So one has to ask, why continue to belabor the point? I understand that "it's still warm even though perhaps it shouldn't be" is complex and you might lose people at the lowest common denominator, but when you oversimplify to the point that you've reduced the thesis to a statement that isn't really accurate, you lose some critical thinkers - as with the "anthropogenic cause of tree ring divergence," this practice probably fuels more skepticism than it quells.
    Response: I understand the use of metaphors but eventually metaphors get so tortured, the usefulness fades. In the case of the 'growing kid' metaphor, an appropriate comparison would be if you had a child that would grow 2 inches in one year, shrink 1 inch the next year, grow 1.5 inches the year after that, shrink .5 inches the next year. His height is shooting up and down but gradually in the long term rising. But really, that's just a weird metaphor!

    Don't be beguiled by the year 1998. Be aware that the HadCRUT record which finds 1998 as the hottest year on record doesn't include the whole globe - it excludes regions where the warming trend is greatest. A fully global temperature record finds 2005 as the hottest year on record, 2009 as the 2nd hottest year on record and a statistically significant warming trend throughout this period.
  34. .....and GISS is Northern Hemisphere-biased. Either way, even the measures that put 2005 as the warmest put it at 0.01 deg C above 1998. I.e., about even. 1 year of natural variability offsetting 11 years of CO2 isn't "cherry picking one year." If it's "still warming" then the temperature should still be rising - rather than simply still warm relative to the recent past.

    The height analogy is a good one because the temperature has remained within a few tenths of a degree C below to, by some measures one hundredth of a degree above the 1998 mean. It's been flat.

    Perhaps it's been flat DESPITE natural forcings that ought to have pushed it down. So say that.
  35. Pat T,
    simplification is a quite risky game. Thinking of a monotonic warming when a monotonic forcing is applied is such a game.
    Look at the instrumental record and you'll see many periods of no warming and yet overall the temperature has increased. From 2002 to 2009 all the yearly averaged temperatures are within about 0.14 °C, i.e. +/- 0.07 °C. This is what the numbers say, undisputable.
    But this is only the begining of the story, not the end. Next step is understand what those numbers mean. To do this you have to look at how temperature behaves. You'll soon discover that there's an interannual varibility of about +/- 0.1 °C and that, in turn, in ten years you can not (statistically) assess a trend lower than about 0.2 °C/decade. Look at this graph (thanks to Tamino); temperature fluctuates between the lower and the upper bounds. You can (statistacally) say that temperature is still following the trend line until it goes out of the bounds. We are not there, not even close.
    This is as far as the numbers are concerned. Then comes the physics, explained by John in this post. Not the numbers nor the physics make us think it's cooling.

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