The Weekend Wonk: Trenberth on Ocean Heat and Surface Temps

June 1, 2013

I’ll be doing a longer video piece on the whole issue of climate sensitivity that has been current over the last few months.  One of the first people I wanted to talk to was Dr. Kevin Trenberth – and you can see part of the longer skype interview above.  Trenberth contributed to a recent paper showing that the deeper ocean has been collecting more heat over recent years, a factor that has to be considered in any discussion of global surface temps in the past decade or two.

Below, you can read Dr. Trenberth’s very valuable discussion of the issue, recently posted on the  “Conversation” blog series out of Australia.

The Conversation:

Has global warming stalled? This question is increasingly being asked because the local weather seems cool and wet, or because the global mean temperature is not increasing at its earlier rate or the long-term rate expected from climate model projections.

The answer depends a lot on what one means by “global warming”. For some it is equated to the “global mean temperature”. That keeps going up but also has ups and downs from year to year. More on that shortly.

Why should it go up? Well, because the planet is warming as a result of human activities. With increasing carbon dioxide and other heat-trapping greenhouse gases in the atmosphere, there is an imbalance in energy flows in and out of the top of the atmosphere: the greenhouse gases increasingly trap more radiation and hence create warming. “Warming” really means heating, and this can exhibit itself in many ways.

trenberthleftRising surface temperatures are just one manifestation. Melting Arctic sea ice is another. So is melting of glaciers and other land ice that contribute to rising sea levels. Increasing the water cycle and invigorating storms is yet another. But most (more than 90%) of the energy imbalance goes into the ocean, and several analyses have now shown this. But even there, how much warms the upper layers of the ocean, as opposed to how much penetrates deeper into the ocean where it may not have much immediate influence, is a key issue.

The ups and downs of global temperature

My colleagues and I have just published a new analysis showing that in the past decade about 30% of the heat has been dumped at levels below 700m, where most previous analyses stop.

The first point is that this is fairly new; it is not there throughout the record. The cause of the shift is a particular change in winds, especially in the Pacific Ocean where the subtropical trade winds have become noticeably stronger, changing ocean currents and providing a mechanism for heat to be carried down into the ocean. This is associated with weather patterns in the Pacific, which are in turn related to the La Niña phase of the El Niño phenomenon.

Ocean Heat Content from 0 to 300 meters (grey), 700 m (blue), and total depth (violet) from ORAS4, as represented by its 5 ensemble members. The time series show monthly anomalies smoothed with a 12-month running mean, with respect to the 1958–1965 base period. Hatching extends over the range of the ensemble members and hence the spread gives a measure of the uncertainty as represented by ORAS4 (which does not cover all sources of uncertainty). The vertical colored bars indicate a two year interval following the volcanic eruptions with a 6 month lead (owing to the 12-month running mean), and the 1997–98 El Niño event again with 6 months on either side. On lower right, the linear slope for a set of global heating rates (W/m2) is given. Skepticalscience.com

The second point is that we have found distinctive variations in global warming with El Niño. A mini global warming, in the sense of a global temperature increase, occurs in the latter stages of an El Niño event, as heat comes out of the ocean and warms the atmosphere. The ocean’s temperature is also affected by volcanic eruptions, which also affect the perceptions of global warming.

Normal weather also interferes by generating clouds that reflect the sunshine, and there are fluctuations in the global energy imbalance from month to month. But these average out over a year or so.

Another prominent source of natural variability in the Earth’s energy imbalance is changes in the sun itself, seen most clearly as the sunspot cycle. From 2005 to 2010 the sun went into a quiet phase and the warming energy imbalance is estimated to have dropped by about 10 to 15%.

Some of the penetration of heat into the depths of the ocean is reversible, as it comes back in the next El Niño. But a lot is not; instead it contributes to the overall warming of the deep ocean. This means less short-term warming at the surface, but at the expense of greater long-term warming, and faster sea level rise. So this has consequences.

Global warming is here to stay

Coming back to the global temperature record, one thing is clear. The past decade is by far the warmest on record. Human induced global warming really kicked in during the 1970s, and warming has been pretty steady since then.

While the overall warming is about 0.16°C per decade, there are three ten-year periods where there was a hiatus in warming, as the graph above shows, from 1977 to 1986, from 1987 to 1996, and from 2001 to 2012. But at each end of these periods there were big jumps. We find exactly the same sort of flat periods in climate model projections, lasting easily up to 15 years in length.

Focusing on the wiggles and ignoring the bigger picture of unabated warming is foolhardy, but an approach promoted by climate change deniers. Global sea level keeps marching up at a rate of more than 30cm per century since 1992 (when global measurements via altimetry on satellites were made possible), and that is perhaps a better indicator that global warming continues unabated. Sea level rise comes from both the melting of land ice, thus adding more water to the ocean, plus the warming and thus expanding ocean itself.

Global warming is manifested in a number of ways, and there is a continuing radiative imbalance at the top of atmosphere. The current hiatus in surface warming is temporary, and global warming has not gone away.

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17 Responses to “The Weekend Wonk: Trenberth on Ocean Heat and Surface Temps”

  1. junkdrawer88 Says:

    Thanks Peter.

    All manner of creepy crawlies are coming out of the woodwork trying to show that CO2 caused global warming is “bad science”.

    One example:

    Global warming caused by chlorofluorocarbons, not carbon dioxide, new study says

    http://phys.org/news/2013-05-global-chlorofluorocarbons-carbon-dioxide.html

    Anyone who reads comments here knows my favorite explanation of the “decoupling” (Hint: Faustian Bargain.)

    Always good to know there are a range of REASONABLE explanations.

    • skeptictmac57 Says:

      It’s like a murder crime scene where there is a smoking revolver (literally) laying on the floor next to a gun shot victim,and the scene is being scoured by a bunch of people who wandered in,scratching their perplexed heads,while searching in vain for a rope,candlestick,lead pipe,or knife.

      Regarding a “Faustian bargain”,I worry that because it is believed that the net effect of particulate pollution from burning carbon is negative,then as we mitigate fossil fuel emissions,there will likely be a point that temps may actually rise in response to cleaner air for a while,thus making it appear that the CO2 theory was all wrong,or worse,acceptance that it is correct,but that all we can do now is to burn more,so that we can get our ‘protective pollution shade back’.

      • junkdrawer88 Says:

        Two points:

        1.) The ‘protective pollution shade’ will block only so much sunshine and no more. The CO2 associated with putting up said shade accumulates. I remember the day that ‘Carbon is Forever’ finally sunk in. It was not a good day.

        2.) The ‘protective pollution shade’ will probably not be uniformly distributed over the globe, possibly leading to a further Arctic amplification. a more screwed up jetstream, and even worse weather weirding.

        Not saying you are advocating these things, just offering possible counter arguments.

        • skeptictmac57 Says:

          Yes,definitely not advocating such notions,but I do suspect that just the idea that negative aerosol feedback may be protecting us now somewhat (and I think that this is well accepted) that this could be extrapolated and misused by the FUD crowd to add another monkey wrench in the works.

          ‘Our precious aerosol parasol’

    • greenman3610 Says:

      yes, the “chlorofluorocarbons” story you mention is making the rounds. It’s bullshit, of course – old news that has been roundly debunked over the years.
      here’s some of the older takedowns, will post more when I can

      http://www.realclimate.org/index.php/archives/2008/12/ozone-holes-and-cosmic-rays/

      http://bbickmore.wordpress.com/2010/06/11/cfcs-and-waterloo/

      http://www.realclimate.org/index.php/archives/2011/07/lu-from-interesting-but-incorrect-to-just-wrong/

      http://www.skepticalscience.com/CFCs-global-warming.htm


    • I am a skeptic, but for me it is obvious – clear, that global warming will proceed.

      “Faustian bargain”, “REASONABLE explanations” …

      … contra: changes in the concentration of ozone in the stratosphere …
      I think professor S. Solomon, “boss” – the scientific part of the IPCC – is “REASONABLE” science – an eminent scientist dealing with stratospheric ozone (for many years) – including its effect on water vapor in the stratosphere – that it is obvious not: “Faustian bargain”.
      Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming (2010,

      http://www.sciencemag.org/content/327/5970/1219.abstract):

      “Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000–2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% [!!!] as compared to estimates neglecting this change.”

      Let us add to this …
      Let’s look at this figure of volcanic activity:

      For NH both strong warming 192? -3? and current (197? – 200?) preceded by a very high stratospheric volcanic activity – destroying – for many years (sulfur aerosols), ozone in the stratosphere.
      Look at this figure: http://www.eea.europa.eu/data-and-maps/figures/rate-of-change-of-global-average-temperature-1850-2007-in-oc-per-decade-2/image_preview – period of rapid cooling (the Europe) 194? – 195?, was preceded by period of exceptional peace of tectonic (an increase of ozone in the stratosphere, exceeded the hypothetical “the border” for initiating the rapid the cooling process?).

      The decrease of ozone in the stratosphere is also the reduction in Arctic phytoplankton (CLAW hypothesis), resulting in a decrease in the concentration of sulfur aerosols in the troposphere, the decrease cloudiness (unfortunately we do not have completely reliable data on changes in cloud cover over the past decades).

  2. junkdrawer88 Says:

    Re: Latent Heat (of Fusion)

    So much ice melted in the Arctic last year that it had to provide additional space in the system for the re-absorption of new heat.

    I’ve heard this often as an explanation for the mini-Arctic-rebound after 2007.

    When it’s gone….


    • Another possible contributor to a ice “rebound” is that after a lot of melting, the ocean is lower salinity, and so it freezes at a higher temperature the next time around. Remember too, that the volume of the ice has dropped a lot, and that fresh water has diluted the salty water.

      Neil

  3. prokaryotes Says:

    What are the pathway’s of removing energy form earth energy budget?

    Energy balance of Earth http://www.eoearth.org/article/Energy_balance_of_Earth#gen5


  4. […] it’s not pound-on-the-table-we’re-done science yet. I also talked to Dr. Kevin Trenberth,  who is not quite ready to go along with Francis’ model.  I’ll be posting his remarks, […]


  5. I am a skeptic, but for me it is obvious – clear, that global warming will proceed.

    “Faustian bargain”, “REASONABLE explanations” …

    … contra: changes in the concentration of ozone in the stratosphere …

    I think professor S. Solomon, “boss” – the scientific part of the IPCC – is “REASONABLE” science – an eminent scientist dealing with stratospheric ozone (for many years) – including its effect on water vapor in the stratosphere – that it is obvious not: “Faustian bargain”.
    Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming (2010,

    http://www.sciencemag.org/content/327/5970/1219.abstract):

    “Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000–2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% [!!!] as compared to estimates neglecting this change.”

    Let us add to this …:
    Let’s look at this figure of volcanic activity:

    For NH both strong warming 192? -3? and current (197? – 200?) preceded by a very high stratospheric volcanic activity – destroying – for many years (sulfur aerosols), ozone in the stratosphere.
    Look at this figure: http://www.eea.europa.eu/data-and-maps/figures/rate-of-change-of-global-average-temperature-1850-2007-in-oc-per-decade-2/image_preview – period of rapid cooling (the Europe) 194? – 195?, was preceded by period of exceptional peace of tectonic (an increase of ozone in the stratosphere, exceeded the hypothetical “the border” for initiating the rapid the cooling process?).

    The decrease of ozone in the stratosphere is also the reduction in Arctic phytoplankton (CLAW hypothesis), resulting in a decrease in the concentration of sulfur aerosols in the troposphere, the decrease cloudiness (unfortunately we do not have completely reliable data on changes in cloud cover over the past decades).

    As proof of this as above (but also below) I’m not here to present citations, but that they could be here for at least a few dozen.

    Note that the current warming agrees with Hallstatt cycle (positive phase, maximum 20150 – please look here – http://geoinfo.amu.edu.pl/sgp/LA/LA07/LA7_19.pdf, the figures are signed in English – Fig. 3. “Correlation of transgression phases of the southern Baltic and warmphases of the Holocene in the framework of the c. 2300 yrs cycle.” – let’s add a very strong “this day”; 2300 yrs cycle – the clouds, but not only, also ITCZ, westerlies, etc. …), and now the sun is, not so long ago was, the most active for more than six thousand. years (6000 years cycle – Xapsos & Burke, 2009)

    Yes, now the sun is already very low active but we should remember that: (Raspopov ( 2008, coauthors – prominent scientists: Esper, Frank, http://www.wsl.ch/info/mitarbeitende//frank/publications_EN/Raspopov_etal_PPP_2008.pdf):
    “An appreciable delay in the climate response to the solar signal can occur (up to 150 years). In addition, the sign of the climate response can DIFFER FROM THE SOLAR SIGNAL SIGN. The climate response to long-term solar activity variations (from 10s to 1000s years) manifests itself in different climatic parameters, such as temperature, precipitation and atmospheric and oceanic circulation.”
    (Helama, 2010, http://bulletin.geoscienceworld.org/cgi/content/abstract/122/11-12/1981):
    “THE NEAR-CENTENNIAL DELAY in climate in responding to sunspots indicates that the Sun’s influence on climate arising from the current episode of high sunspot numbers may not yet have manifested itself fully in climate trends.”

    There is no incompatibility between the number of natural (especially magnetic variation) process and the current warming.
    The well-known geologist Dr. M. W. Mandeville in http://www.michaelmandeville.com/vortectonics/vortex_correlations2.htm, wrote about a very strong correlation of: “…most major tectonic activity, including earthquakes, volcanism, El Nino, and global warming phenomenon …”

    This is a “Faustian bargain”? – might, but …
    “… our understanding of the indirect effects of changes in solar output and feedbacks in the climate system is minimal.” (NOAA, http://www.ncdc.noaa.gov/oa/climate/globalwarming.html)

    The factors described above are valued presently (direct RF) very, very low (eg, by M. Lockwood’s – in comparison with RF aGHGs) but … once again …,
    … remember that: “… our understanding of the indirect effects of changes in solar output and feedbacks in the climate system is minimal […].”


  6. I am a skeptic, but for me it is obvious – clear, that global warming will proceed.

    “Faustian bargain”, “REASONABLE explanations” …

    … contra: changes in the concentration of ozone in the stratosphere …
    I think professor S. Solomon, “boss” – the scientific part of the IPCC – is “REASONABLE” science – an eminent scientist dealing with stratospheric ozone (for many years) – including its effect on water vapor in the stratosphere – that it is obvious not: “Faustian bargain”.
    Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming (2010,

    http://www.sciencemag.org/content/327/5970/1219.abstract):

    “Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000–2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% [!!!] as compared to estimates neglecting this change.”

    Let us add to this …
    Let’s look at this figure of volcanic activity:

    For NH both strong warming 192? -3? and current (197? – 200?) preceded by a very high stratospheric volcanic activity – destroying – for many years (sulfur aerosols), ozone in the stratosphere.
    Look at this figure: http://www.eea.europa.eu/data-and-maps/figures/rate-of-change-of-global-average-temperature-1850-2007-in-oc-per-decade-2/image_preview – period of rapid cooling (the Europe) 194? – 195?, was preceded by period of exceptional peace of tectonic (an increase of ozone in the stratosphere, exceeded the hypothetical “the border” for initiating the rapid the cooling process?).

    The decrease of ozone in the stratosphere is also the reduction in Arctic phytoplankton (CLAW hypothesis), resulting in a decrease in the concentration of sulfur aerosols in the troposphere, the decrease cloudiness (unfortunately we do not have completely reliable data on changes in cloud cover over the past decades).

    As proof of this as above (but below) I’m not here to present citations, but that they could be here for at least a few dozen.

    Note that the current warming agrees with Hallstatt cycle (positive phase, maximum 20150 – please look here – http://geoinfo.amu.edu.pl/sgp/LA/LA07/LA7_19.pdf, the figures are signed in English – Fig. 3. “Correlation of transgression phases of the southern Baltic and warmphases of the Holocene in the framework of the c. 2300 yrs cycle.” 2300 yrs cycle – the clouds, but not only, also ITCZ, westerlies, etc. …), and now Sun is, not so long ago was the most active for more than six thousand. years (6000 years cycle – Xapsos & Burke, 2009)

    Yes, now the sun is already less active but we should remember that: (Raspopov ( 2008, coauthors – prominent scientists: Esper, Frank, http://www.wsl.ch/info/mitarbeitende//frank/publications_EN/Raspopov_etal_PPP_2008.pdf):
    “An appreciable delay in the climate response to the solar signal can occur (up to 150 years). In addition, the sign of the climate response can DIFFER FROM THE SOLAR SIGNAL SIGN. The climate response to long-term solar activity variations (from 10s to 1000s years) manifests itself in different climatic parameters, such as temperature, precipitation and atmospheric and oceanic circulation.”
    (Helama, 2010, http://bulletin.geoscienceworld.org/cgi/content/abstract/122/11-12/1981):
    “THE NEAR-CENTENNIAL DELAY in climate in responding to sunspots indicates that the Sun’s influence on climate arising from the current episode of high sunspot numbers may not yet have manifested itself fully in climate trends.”

    There is no incompatibility between the number of natural (especially magnetic variation) process and the current warming.
    The well-known geologist Dr. M. W. Mandeville in http://www.michaelmandeville.com/vortectonics/vortex_correlations2.htm, wrote about a very strong correlation of: „…most major tectonic activity, including earthquakes, volcanism, El Nino, and global warming phenomenon …”

    This is a “Faustian bargain”? – might, but …
    “… our understanding of the indirect effects of changes in solar output and feedbacks in the climate system is minimal.” (NOAA, http://www.ncdc.noaa.gov/oa/climate/globalwarming.html)

    The factors described above are valued presently (direct RF) very, very low (eg, by M. Lockwood’s – in comparison with RF aGHGs) but …
    … remember that: “… our understanding of the indirect effects of changes in solar output and feedbacks in the climate system is minimal […].”


  7. […] bomb detonations per second due to accelerated global warming. Peter Sinclair of Climate Crocks interviewed climate scientist Kevin Trenberth about the significance of the recent acceleration in ocean and global […]


  8. […] bomb detonations per second due to accelerated global warming. Peter Sinclair of Climate Crocks interviewed climate scientist Kevin Trenberth about the significance of the recent acceleration in ocean and global […]


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