Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Bluesky Facebook LinkedIn Mastodon MeWe

Twitter YouTube RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

New? Register here
Forgot your password?

Latest Posts


In 2017, the oceans were by far the hottest ever recorded

Posted on 26 January 2018 by John Abraham

Among scientists who work on climate change, perhaps the most anticipated information each year is how much the Earth has warmed. That information can only come from the oceans, because almost all heat is stored there. If you want to understand global warming, you need to first understand ocean warming.

This isn’t to say other measurements are not also important. For instance, measurements of the air temperature just above the Earth are really important. We live in this air; it affects us directly. A great commentary on 2017 air temperatures is provided by my colleague Dana Nuccitelli. Another measurement that is important is sea level rise; so too is ocean acidification. We could go on and on identifying the markers of climate change. But in terms of understanding how fast the Earth is warming, the key is the oceans. 

This important ocean information was just released today by a world-class team of researchers from China. The researchers (Lijing Cheng and Jiang Zhu) found that the upper 2000 meters (more than 6000 feet) of ocean waters were far warmer in 2017 than the previous hottest year. We measure heat energy in Joules. It turns out that 2017 was a record-breaking year, 1.51 × 1022 Joules hotter than any other year. For comparison, the annual electrical generation in China is 600 times smaller than the heat increase in the ocean.

The authors provide a long history of ocean heat, going back to the late 1950s. By then there were enough ocean temperature sensors to get an accurate assessment of the oceans’ warmth. Their results are shown in the figure below. This graph shows ocean heat as an “anomaly,” which means a change from their baseline of 1981–2010. Columns in blue are cooler than the 1981-2010 period, while columns in red are warmer than that period. The best way to interpret this graph is to notice the steady rise in ocean heat over this long time period.


Ocean heat content change since 1958. Illustration: Cheng and Zhu (2018), Advances in Atmospheric Sciences

What is interesting is that from year to year (or over the span of a few years), the heat in the oceans may increase or decrease. This is because there are natural fluctuations that can transfer extra energy to or from the waters. One such natural event is the well-known El Niño/La Niña cycle in the Pacific Ocean. During an El Niño, the Pacific Ocean tends to have very warm waters at the surface, which causes heat loss to the atmosphere (so the ocean cools and the atmosphere warms). Conversely, during a La Niña, the reverse process occurs. 

There are other fluctuations and natural occurrences like volcanic eruptions and other changes in ocean currents. But it just means we don’t want to take any one year as proof of global warming. The fact that 2017 was the oceans’ hottest year doesn’t prove humans are warming the planet. But, the long term upward trend that extends back many decades does prove global warming. The graph above is the most important image to show someone who denies the reality of a changing climate.

It’s interesting to look at the top five years on record in terms of ocean heat; they are listed below.

    1. 2017: 19.19 × 1022 J
    2. 2015: 17.68 × 1022 J
    3. 2016: 17.18 × 1022 J
    4. 2014: 16.74 × 1022J
    5. 2013: 16.08 × 1022 J


Note that these are the five hottest years ever recorded. Truly astonishing.

Click here to read the rest

0 0

Printable Version  |  Link to this page


Comments 1 to 12:

  1. "The fact that 2017 was the oceans’ hottest year doesn’t prove humans are warming the planet. But, the long term upward trend that extends back many decades does prove global warming."

    Clever little wiggle there. Implying that... hey, earth is warming but we can't be sure that humans are responsable.

    Passive agressive denialism or just misinformation?

    0 0
    Moderator Response:

    [DB] From the article's concluding paragraph:

    "Fortunately, we know why the oceans are warming (because of human greenhouse gases), and we can do something about it. We can take action to reduce the heating of our planet by using energy more wisely and increasing the use of clean and renewable energy (like wind and solar power)."

    Emphasis added.

  2. NODC is showing the same. Drop in 2016 then recovery in 2017. They had to lift the verticl scale from a max of 20 to 25 a few years back. Looks like they will have to do it again next year.

    0 0
  3. Jef

    John Abraham was just being conservative. But actually, these numbers alone do go a loing way to show it is humns becasue they rule out lots of other posibilities.

    This article from 2014 is using older data but the case is the same - the new numbers just make it clearer.

    0 0
  4. Thanks Glen - I do get it. I just hate reading "The fact that 2017 was the oceans’ hottest year doesn’t prove humans are warming the planet."

    Maybe it should have read "The fact that 2017 was the oceans’ hottest year BY ITSELF doesn’t prove humans are warming the planet." or something.

    0 0
  5. New Zealand currently has a heatwave, due to a combination of warm oceans, la nina conditions, and a stalled jet stream that is keeping colder southern air away, while northerly  tropical air flows down. We have set a record for the hottest January in history.

    I bought one of those Dyson fans (actually a fan heater, so I can use it in winter as well). I recommend this device. It's expensive, but has a very powerful fan with a focused stream of air, and a quiet fan.

    0 0
  6. Over at realclimate, there was a question posed: Over 90% of radiative imbalance is supposed to go in the oceans. But OHC increase is considerably smaller. So where is the heat going ?

    Anyone care to comment ?


    0 0
  7. I may have misunderstood the question, but there seems to be some confusion in the maths over change in forcing versus change in ERB. As earth has got hotter, much of that 500TW is going irradiated again. The non-zero ERB is because oceans are burying heat.

    0 0
  8. Sidd @6 , I haven't checked the calculation figures offered by RealClimate poster "Incognitoto" — but I am not sure where you see a problem.

    Effective radiative forcing has increased from 1 watt/sq.m. at approximate date 1975, up to 2 watts/sq.m. by 30 years later.

    Was poster "Incognitoto" referring to Ocean Heat Content in the surface 700m of the ocean, or in the surface 2000m [as mentioned in this particular SkS article, or in the total ocean?

    And was he allowing for the temporary reductions (in radiative forcings) caused by major volcanic eruptions?

    All in all, there seems no reason to doubt that "over 90% of radiative imbalance" is going into the oceans.

    0 0
  9. I havent done the calculation, but I believe the diagnotic from OHC is that ERB is 0.8w/m. Incognitoto seems to believe it should same as change in delta-F.

    0 0
  10. Thegraph slows a slight reduction in heat in year 2016.  Just below that we see the "top five" listed by joules.  At first glance it looks like a steady upward trend until one notices the years 2015 & 2016 are "flipped".

    My choice would have been to list the top five in year to year sequence so "first glance" would not have given the impression that its up, up, up, up up

    Some of you are probably thinking "swampfox doesn't have anything to do today"  and I probably don't.


    0 0
  11. swampfoxh@10,

    A Top 5 (or Top 10, or Top anything) list should never be presented in 1,3,2,4,5 order.

    0 0
  12. sidd @6,

    The missing energy is as described by scaddenp @7&9. And the basic numbers set out by Incognitoto @RealClimate are fine although some of the subsidiary numbers are well off the mark.

    Incognitoto is suggesting the net climate Forcing back 10-15 years ago was +1.6Wm^-2 (which is possible) which he equates to an energy imbalance of 800TW (actually 816TW) and that would be 25Zj/yr. He also speculates about today's net Forcing being +2.0Wm^-2 but goes nowhere with it.

    Incognitoto then suggests ΔOHC would have been 8Zj/yr, so accounting for a 250TW energy imbalance. The 0-2000m ΔOHC for 10-15 years ago (from NODC/NOAA although they don't list back to 2003 for 0-2000m any more. The earliest 5 years comes to 43.7Zj ΔOHC between 2005 & 2010) gives 39.3Zj ΔOHC between 2003 & 2008. That yields 7.86Zj/yr or a 249TW energy imbalance.

    Incognitoto adds on "less than" 10TW for melted ice and 40TW for added atmospheric H2O. The Ice estimate is probably about right for 10-15 years ago. 10TW would equate to 950Gt/yr of melt. GRACE data for Greenland & Antarctica (graphed here) suggests about 400Gt/yr. And according to PIOMAS Arctic Sea Ice would add about 300Gt/yr and a similar amount from other glaciers. The H2O is badly wrong. It would be about 2.4TW with an additional 3.0TW heating up the air. A final component is the heat required to warm the land which would be roughly similar in size to Ice & Atmosphere. (Note the SkS graphic here dates back to 2007 would predate GRACE results.)

    So the energy flux back 2003-08 exiting planet Earth to space due to the AGW temperature rise (if the 1.6Wm^-2 is accepted as a net Forcing) would be something like 525TW.

    0 0

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

The Consensus Project Website


(free to republish)

© Copyright 2024 John Cook
Home | Translations | About Us | Privacy | Contact Us