DEEP-C project

The Diagnosing Earth's Energy Pathways in the Climate system (DEEP-C) consortium is a 4-year project that is tackling the questions:

(1) What mechanisms explain the reduced global surface warming rate since around 2000

(2) Where is the excess energy due to rising greenhouse gas concentrations currently accumulating in the climate system?

We are using satellite observations, measurements below the sea surface (including the deep ocean) and detailed simulations of the atmosphere and ocean, combining expertise from the University of Reading, the National Oceanography Centre (NOC) ­ Southampton and the Met Office.

The project is funded by the Natural Environment Research Council (NERC) and runs from March 2013 - February 2017, involving partnerships with the NASA Langley Research Center and the UK Department for Energy and Climate Change (DECC) and collaboration with the National Centre for Earth Observation, the National Centre for Atmospheric Sciences-Climate and the Walker Institute for Climate Systems Research.

A more detailed outline of the rationale and work plan for DEEP-C is provided in the Project Proposal. Here are some further project links:



10th October 2016 - 8th DEEP-C meeting, Reading (Harry Pitt Seminar Room 10:30am-4pm)

18th March 2016 - 7th DEEP-C meeting, Met Office

6th November 2015 - 6th DEEP-C meeting, NOC-Southampton

9th June 2015 - 5th DEEP-C meeting, University of Reading

20th October 2014 - 4th DEEP-C meeting, Met Office

26th March 2014 - NOC-Southampton

27th September 2013 - Met Office

Monday 22nd April 2013 - Kick-Off meeting with project partners, Department of Meteorology, University of Reading (ESSC seminar room, 10:30am-4:30pm)


Team members

  • Richard P. Allan (PI, WP1 leader)
  • Elaine McDonagh (Co-PI, WP2 leader)
  • Matt Palmer (Co-PI, WP3 leader)
  • Till Kuhlbrodt, Jonathan Gregory, Brian A. King (Co-Is)
  • Chunlei Liu, Chris Roberts (researchers)
  • Tim Andrews, Doug McNeall, Mark Ringer, Doug Smith, Kathy Maskell, Norman Loeb, Chris Sear (affiliates)

    Partner Publications

    Abraham et al. (inc. M.D. Palmer), A review of global ocean temperature observations: Implications for ocean heat content estimates and climate change, Rev. Geophys, 51, 450-483, doi:10.1002/rog.20022.

    Allan, R. P., C. Liu, N. G. Loeb, M. D. Palmer, M. Roberts, D. Smith and P.-L. Vidale (2014) Changes in global net radiative imbalance 1985-2012, Geophysical Research Letters, 41, 10.1002/2014GL060962.

    Allan, R. P., C. Liu, M. Zahn, D. A. Lavers, E. Koukouvagias and A. Bodas-Salcedo (2014) Physically consistent responses of the global atmospheric hydrological cycle in models and observations, Surv. Geophys., 35, 533-552, doi:10.1007/s10712-012-9213-z

    Allan, R.P. (2011), Combining satellite data and models to estimate cloud radiative effect at the surface and in the atmosphere, Meteorological Applications, 18, p.324-333, doi:10.1002/met.285.

    Cheng, L., K. E. Trenberth, M. D. Palmer, J. Zhu and J. P. Abraham (2016) Observed and simulated full-depth ocean heat-content changes for 1970-2005, Ocean Science, 12, p.925-935, doi:10.5194/os-12-925-2016

    Desbruyères, D. G., S. Purkey, G. J. Johnson, E. L. McDonagh and B. A. King (2016), Deep and Abyssal Ocean Warming from 35 years of Repeat Hydrography, GRL, in press, DOI: doi: 10.1002/2016GL070413

    Desbruyères, D. G., E. L. McDonagh, B. A. King, F. K. Garry, A. T. Blaker, B. Moat and H. Mercier (2014) Full-depth temperature trends in the Northeastern Atlantic through the early 21st century, GRL, in press, DOI: 10.1002/2014GL061844

    Kuhlbrodt, T., R.S. Smith, Z. Wang and J.M. Gregory (2012): The influence of eddy parameterizations on the transport of the Antarctic Circumpolar Current in coupled climate models. Ocean Modelling, 52-53, 1-8, doi:10.1016/j.ocemod.2012.04.006

    McCarthy, G.D., B. A. King, P. Cipollini, E. L. McDonagh, J. R. Blundell, and A. Biastoch, On the sub-decadal variability of South Atlantic Antarctic Intermediate Water (2012) Geophys. Res. Lett., 39, L10605.

    Otto, A. et al. inc. Gregory, J.M. (2013) Energy budget constraints on climate response, Nature Geosciences, doi:10.1038/ngeo1836

    Palmer, M.D. (2012), Climate and Earth's Energy Flows, Surv in Geophysics, doi: 10.1007/s10712-011-9165-8.

    Palmer, M.D. (2017) Reconciling Estimates of Ocean Heating and Earths Radiation Budget, Current Climate Change Reports, doi: 10.1007/s40641-016-0053-7

    Palmer, M.D. and D.J. McNeall (2014) Internal variability of Earth's energy budget simulated by CMIP5 climate models, Environ. Res. Lett. 9, 034016, doi:10.1088/1748-9326/9/3/034016

    Palmer, M.D., D.J. McNeall and N.J. Dunstone (2011) Importance of the deep ocean for estimating decadal changes in Earth's radiation balance, Geophys. Res. Lett.. 38, L13707.

    Palmer, M.D., C. D. Roberts, et al. (2015) Ocean heat content variability and change in an ensemble of ocean reanalyses, Climate Dynamics, doi: 10.1007/s00382-015-2801-0


    Roberts, C.D., M.D. Palmer, D. McNeall and M. Collins (2014) Quantifying the likelihood of a continued hiatus in global warming, Nature Climate Change doi:10.1038/nclimate2531

    Roberts, M. J. and co-authors inc. Pat Hyder (2016) Impact of ocean resolution on coupled air-sea fluxes and large-scale climate, GRL, doi:10.1002/2016GL070559

    Roberts, C., M. Palmer, R. P. Allan, D. Desbruyeres, P. Hyder, C. Liu, D. Smith (2017), Surface flux and ocean heat transport convergence contributions to seasonal and interannual variations of ocean heat content, J Geophys. Res.- Oceans, doi: 10.1002/2016JC012278. draft PDF

    Liu, C. Allan, R. P., P. Berrisford , M. Mayer , P. Hyder, N. Loeb , D. Smith , P.-L. Vidale, J. Edwards (2015) Combining satellite observations and reanalysis energy transports to estimate global net surface energy fluxes 1985-2012, J. Geophysical Research, doi: 10.1002/2015JD023264

    Loeb, N. G., J. M. Lyman, G. C. Johnson, R. P. Allan, D. R. Doelling, T. Wong, B. J. Soden and G. L. Stephens (2012), Observed changes in top-of-the-atmosphere radiation and upper-ocean heating consistent within uncertainty, Nature Geoscience, 5, 110-113, doi:10.1038/ngeo1375.

    Loeb, N. G., H. Wang, A. Cheng, S. Kato, J. T. Fasullo, K.-M. Xu and R. P. Allan (2015) Observational Constraints on Atmospheric and Oceanic Cross-Equatorial Heat Transports: Revisiting the Precipitation Asymmetry Problem in Climate Models, Climate Dynamics, 10.1007/s00382-015-2766-z

    Lyman, J.M. et al. inc. M.D. Palmer (2010) Robust Warming of the Global Upper Ocean, Nature, 465, 334-337.

    Smith, D. (2013) Has global warming stalled? Nature Climate Change 3, 618-619 doi: 10.1038/nclimate1938

    Smith, D., R. P. Allan, A. C. Coward, R. Eade, P. Hyder, C. Liu, N. G. Loeb, M. D. Palmer, M. Roberts, and A. A. Scaif (2015) Earth's energy imbalance since 1960 in observations and CMIP5 models, Geophysical Research Letters, 10.1002/2014GL062669,


    von Schuckmann, K. et al. inc. M. D. Palmer (2016) An imperative to monitor Earth's energy imbalance, Nature Climate Change doi: 10.1038/nclimate2876



    March 2016 - Met Office DEEP-C partners publish perspectives in Nature Climate Change and the World Meterorological Organisation State of the Climate (p.22-23) on the imperative to monitor Earth's energy imbalance (see also Climate Lab Book blog).

    September 2015 - Members of the DEEP-C team contributed to a CLIVAR meeting Energy Flow Through the Climate System at the UK Met Office.

    August 2015 - New advances in estimating energy flows in the climate system and their links to biases in rainfall published by the DEEP-C project. A new method for estimating surface fluxes has been published in the Journal of Geophysical Research while an important new study lead by Norman Loeb published in Climate Dynamics demonstrates a link between biases in energy flows and biases in rainfall in climate models.

    July 10th 2015 - Richard Allan commented on recent Science paper by Nieves et al on the BBC Radio 4 Today program

    July 2015 - Project PIs attended the Our Common Future under Climate Change meeting (see Met Office blog and also poster detailing additional DEEP-C work

    June 2015 - DEEP-C work presented at Imperial College Seminar and NCAS group meeting

    March 2015 - An update on the hiatus in global warming at the Earth's surface- Current Weather and Climate Discussions, Department of Meteorology: PDF

    February 2015 - Work by DEEP-C Met Office partners exploited thousands of years of climate model simulations to quantify there is a 1 in 6 chance of the current hiatus continuing for another 5 years but notes that surge in surface warming (particularly over the Pacific, Arctic, southern Africa and South America) is more probable. See Roberts et al. (2015) Nature Climate Change.

    January 2015 - DEEP-C work suggests small drop in Earth's heating rate from 1999-2005 and indicates that peak in ocean heating rate in the early 2000s in some ocean datasets is likely to be spurious. See Smith et al. (2015) GRL.

    October 2014 - Improved observations of ocean heating and sea level rise

    September 2014 - Is global warming on holiday?

    August 2014 - Article and comment on recent paper indicating the role of the Atlantic in determining the hiatus

    August 2014 - Changes in global net radiative imbalance 1985-2012 published in Geophysical Research Letters. See also NCAS, and Nature Climate Change highlights and blogs from Carbon Brief and Climate Lab-book

    July 2014 - Research on changes in Earth's energy budget was presented at AMS Atmospheric Radiation conference in Boston (as part of the Tony Slingo symposium) and at the GEWEX International Science conference in The Hague.

    April 2014 - DEEP-C results were presented at the EGU meeting in Vienna.

    April 2014 - DEEP-C results were presented and discussed at the Royal Society International Scientific Seminar on Causes of Recent Temperature Trends and Implications for Projections at the Kavli Royal Society International Centre, Chicheley Hall, UK, 2-3rd April 2014.

    March 2014 - New DEEP-C publication in Environmental Research Letters demonstrating important role of internal ocean variability in decadal changes in Earthy's energy imbalance and global surface temperature trends (Palmer and McNeall, 2014; see also Guardian article).

    February 2014 - "Where has the warming gone?" talk to the Royal Meteorological Sociaty South East Group by Richard Allan.

    February 2014 - Comment on recent Nature Climate Change paper by England et al. which implicates strengthening Pacific trade winds in causing the global warming hiatus (see also Guardian article).

    August 2013 - Comment on recent Nature paper by Kosaka and Xie demonstrating the role of natural variability in the Pacific ocean in explaining the recent slowdown in global surface warming (see also BBC and Independent articles).

    July 2013 - Press briefing at the Science Media Centre on the recent slowdown in global surface warming (see briefing note). Read More...

    May 2013 - First DEEP-C publication (Prof. Gregory) Energy budget constraints on climate response, Nature Geosceinces (see also Science Media Centre | Guardian)

    May 2013: Article on DEEP-C and how scientists measure Earth's temperature by Roz Pidcock from Carbon Brief

    April 2013 - Meeting with DECC partners in London to discuss project

    April 2013 - Science Media Centre briefing

    April 2013 - DEEP-C Kick-Off Meeting at the University of Reading

    March 2013 - Comments on misleading article in Daily Mail



    Top of atmosphere and surface energy fluxes produced as part of DEEP-C are available as text and NetCDF files at the following website.

    Useful Links

    Here is a growing list of links to journal papers, blogs and web links that are of relevance to the DEEP-C project which hopes to investigate in detail the flows of energy in the climate system and mechanisms influencing the recent hiatus in global mean surface warming.
    [See Project Description above]

    Web links

    ARGO free-drifting ocean profiling floats

    Clivar Carbon and Hydrographic Data Office (CCHDO)

    Clouds and the Earth's Radiant Energy System (CERES)

    European Centre for Medium-range Weather Forecasts (ECMWF) Interim Reanalysis (ERA Interim)

    Yale Media Forum


    Met Office reports on the recent pause in global warming

    IPCC 2013 Working Group I assessment of Climate Change

    Discussion in Media/Blogs

    Is the global warming "hiatus" over? by Kevin Trenberth @ConversationUK [August 2015]

    Conversation article discussing role of Atlantic vs Pacific as drivers of hiatus [August 2014]

    Highlight of energy balance paper [August 2014]

    Dynamical retardation of tropical warming Blog by Isaac Held [April 2014]

    Hiatus in context - Nature Geosciences Editorial [February 2014]

    Pause for Thought - about communicating the surface warming slowdown by Hawkins et al [Nature Climate Change, 2014]

    Attempt to explain the warming slow-down with Arctic data gaps is only a small step towards reconciling observed and expected warming (Judith Curry) [Nature Geosciences N&V 30 January 2014].

    Case of the missing heat perspective by Jeff Tellefson [Nature 15 Jan 2014].

    ClimateLabBook and here | | | Bad Astronomy | | Myles Allen | RealClimate

    JOURNAL PAPERS : Energy imbalance/ocean heating | Modelling | Unforced Variability | Radiative Forcing | Ocean heating | Other relevant papers including Hemispheric Heat Flux Asymmetry | Feedbacks |

    Energy imbalance

    Palmer, M.D. (2017) Current Climate Change Reports: Improvements in satellite sensor calibration, estimates of total solar irradiance and more comprehensive sampling of the global oceans (e.g. Deep Argo) are key aspects to reducing uncertainties in future observations of Earth's energy imbalance.

    Johnson et al. (2016) Nature Climate Change: improved estimate of Earth's energy imbalance of +0.6 to +0.8 Wm-2 due to better ocean sampling

    Trenberth et al. (2016) J. Clim: Earth's energy imbalance from multiple sources

    Richardson et al. (2016) Nature Climate: reconciling observation-based/simulated transient climate sensitivity (TCR) through consistent sampling of surface temperature (TCR~1.7oC at 2xCO2)

    von Schuckmann et al. (2016) Nature Climate Change: An imperative to monitor Earth's energy imbalance perspective

    Cuesta-Valero et al. (2016): many CMIP5 models underestimate observed continental heat accumulation of 0.01 Wm-2 (for global area, 1950-2000) by nearly factor of 10.

    Xie et al. (2015) Nature Geoscience: top-of-the-atmosphere radiation and global mean surface temperature less tightly coupled for natural decadal variability than for greenhouse-gas-induced response.

    Loeb et al. (2015) Clim. Dyn.: Observed imbalance of 0.6 Wm-2 determined by southern hemisphere. Climate model biases in cross equatorial energy transports linked with precipitation biases.

    Liu et al. (2015) JGR: New satellite-based estimates of global net surface energy fluxes 1985-2012

    Johansson et al. (2015) Nature Clim.: the hiatus is primarily attributable to ENSO-related variability and reduced solar forcing. Including observations over the hiatus reduces most likely climate sensitivity only slightly and the lower bound of the 90% range remains around 2 °C.

    Marotzke and Forster (2015) Nature: observed/simulated 15 year surface temperature trends since 1900 dominated by internal variability so claims that climate models systematically overestimate the response to radiative forcing are unfounded. [see also critique by Nic Lewis and response from Marotske and Forster]

    Smith et al. (2015) GRL: Peak ocean heating rate in the early 2000s is likely spurious based on analysis of satellite data and CMIP5 simulations since 1960.

    Allan et al. (2014) GRL:, increase in Earth's heating rate from 0.34 Wm-2 for earlier 1985-1999 period up to 0.62 Wm-2 for 2000-2012 despite slowing in rate of surface warming.

    Trenberth et al. (2014) J. Climate: Energy imbalance of 0.5-1.0 Wm-2 in last decade from reanalyses/simulations/satellite data; discrepancies remain bertween satellite data and ocean opbservations (e.g. 2008-09).

    Trenberth and Fasullo (2013) Earth Futures: importance in Pacific Decadal "Oscillation" in explaining slowing in surface warming trend since 2000

    Otto et al. (2013) Nature Geosci.: Latest estimates of radiative forcing and ocean heating consistent with climate model equilibrium climate sensitivity; recent decade suggest minority of models may underestimate rapidity of climate response up to point of CO2 doubling.

    Loeb et al. (2012) Nature Geosci.: Observations show Earth contunued heating (at 0.5 Wm-2) since 2000

    Levitus et al. (2012) GRL: ocean heat content and thermosteric sea level change since 1955

    Hansen et al. (2011) ACP: Observed heating of 0.6 Wm-2 2005-2010; discusses contribution of changes in rate of radiative forcing increase and errors in ocean heat uptake.

    Church et al. (2011) GRL: increasing sea level and ocean heating consistent; aerosol forcing (as a residual term) may have increased in the late 1990s

    Allan, R.P. (2011) Met. Apps.: Observed variations in 60S-60N mean net radiative fluxes since 1985; influence of volcanoes + ENSO but no evidence of decerease over the period

    Lyman et al. (2010) Nature: observed ocean heating rate down to 700m 1993-2008

    Trenberth (2009) COES: a nice discussion of the many factors linking Earth's energy imbalance, heating and sea level rise ["...melting ice is a factor of 40-70 times more effective than thermal expansion in raising sea level when heat is deposited in upper 700 m..."]

    See also: Energy imbalance/ocean heating | Modelling | Unforced Variability | Radiative Forcing | Ocean heating | Other relevant papers


    Medhaug and Drange (2016) Clim. Dyn.: Decadal-scale upper 700m ocean heat anomalies, of ~7.5 1021 J comparable to the ocean heat uptake needed to maintain 10 global warming.

    Kosaka and Xie (2016) Nature Geosci.: model simulations of global warming "staircase" used to remove internal variability from observational record

    Sevellec et al. (2016) GRL: hiatus of the early 21st Century was extremely unlikely

    Mann et al. (2016) GRL: internal variability of N. Pacific played critical role in the slowdown but was not predictable; minor contribution from N. Atlantic exhibits some predictability

    Outten et al. (2015) JGR and Thorne et al. (2015) JGR: 30 member ESM ensemble shows radiative forcing unable to explain temporary slowdown in surface warming

    Medhaug & Drange (2015) Clim. Dyn: non-warming periods may last 10, 15 and 30 years for RCP8.5, RCP6.0 and RCP4.5, respectively and are possible through increased heat uptake and storage in particular in the tropical E. Pacific

    Lovejoy (2015) Geophys. Res. Lett.: Simplistic model claims to have better skill at decadal forecasting of temperature changes than CMIP3 simulations but model appears to be calibrated on observations fitted to CO2 only forcing and may be useless.

    Thorne et al. (2015) JGR: large ensemble of NorESM simulations not inconsistent with recent slowdown in surface warming with unforced variability appearing to play a leading role.

    Roberts et al. (2015) Nature Climate Change: exploited unforced variability from CMIP5 simulations to quantify there is a 1 in 6 chance of the current surface warming hiatus continuing for another 5 years but find that a surge in surface warming (particularly over the Pacific, Arctic, southern Africa and South America) is more probable.

    England et al. (2015) Nature Clim. Ch.: no difference in long term projections between models ensemble members displaying hiatus in recent period and others.

    Douville et al. (2015) GRL: over-ride model surface wind stress to show possible influence of trade winds and extratropical Pacific SST in contributing to Pacific-wide multi-decadal SST variability although model climate sensitivity may be too high.

    Watanabe et al. (2014) Nature Climate Change: prescribe observed tropical wind stress to isolate influence of internal variability on temperature trends (estimated contribution of about +0.1oC in 1980s-1990s and -0.1oC in 2000s)

    Meehl et al. (2014) Nature Climate Change: 21 of 262 CMIP5 simulations generates hiatus (1 lasting 18yrs) with associated IPO pattern. Decadal forecast of early 2000s IPO and hiatus could have been skillfull.

    Maher et al. (2014) GRL: hiatuses linked to volcanic eruptions, anthropogenic aerosol and internal variability but expected to become rare after mid 21st century

    Risbey et al. (2014) Nature Climate Change: past 15-year trends in surface temperature are captured by simulations when ensemble members displaying realistic phases of ENSO during each period compared to observations are selected

    Brown et al. (2014) GRL: top of atmosphere radiation amplifies decadal unforced variability through changes in albedo

    Palmer and McNeall (2014) ERL: CMIP5 pre-industrial control simulations demonstrate important role of internal variability in decadal trends in global surface temperature and Earth's energy imbalance

    Meehl and Teng (2014) GRL: CMIP5 decadal prediction experiments give closer agreement with observed surface temperature trends around mid-1970s and 2000s

    Kosaka and Xie (2013) Nature: Recent hiatus explained by natural variability in the Pacific ocean. Read More...

    Fyfe et al. (2013) Nature Climate Change: Commentary on why models "overestimate" global warming over the past 20 years.

    Meehl et al. (2013) J Climate: Role of Interdecadal Pacific Oscillation (IPO) in determining accelerated warming and hiatus decades (extension of Meehl et al. 2011). No surface warming for 15 years is common in grerenhouse gas forced simulations.

    Watanabe et al. (2013) GRL: increased observed ocean heat uptake explains slower surface temperature rise compared to CMIP5 simulations

    Meehl et al. (2011) Nature Climate Change: Hiatus decades identified in simulations with increasing greenhouse gas forcing and are characterized by increased ocean heating below 300m.

    Katsman and van Oldenborgh (2011) GRL: simulations suggest a mix of natural variability and increased ocean heating at depth contribute to hiatus periods in the surface temperature record

    Palmer et al. (2011) GRL: full depth of ocean required to reconcile top of atmosphere radiative imbalance with heating of the climate system

    Easterling and Wehner (2009) GRL: models simulate hiatus periods under increasing greenhouse gas forcing.

    See also: Energy imbalance/ocean heating | Modelling | Unforced Variability | Radiative Forcing | Ocean heating | Other relevant papers

    Unforced Variability

    Zhou et al. (2016) Nature Geoscience: clouds amplify cooling of E Pacific contributing to slower global warming rates

    Bellamo et al. (2016) GRL: cloud feedback amplifyies Atlantic Multidecadal Oscillation by 10-31%

    He and Soden (2016) J. Clim: lack of air-sea coupling in AMIP simulations affects realism of internal variability but is less problematic for longer term climate change

    Brown et al. (2016) GRL: basin-scale Atlantic Multidecadal Oscillation linked to cloud feedback

    Kucharski et al. (2016) Clim. Dyn.: Atlantic forcing of Pacific decadal variability especially between 1930s/40s vs 1910s/20s; 1970s/80s vs 1930s/40s; 1994-2013 vs 1970s/80s.

    Li et al. (2015) Nature Climate Change:Atlantic control on Pacific ocean responses through wind-evaporation-sea surface temperature feedbacks but role of radiative forcing or Atlantic internally generated variability in driving this seems unclear

    Brown et al. (2016) J. Clim.Reconcile contrasting local and global surface temperature/energy budget relationships through remote influence of anomalously warm conditions in causing low surface albedo near sea ice margins/high latitudes, low cloud albedo over mid/low-latitudes and a super clear-sky greenhouse effect over the deep Indo-Pacific

    Radel et al. (2016) Nature Geosci. Cloud longwave effect amplifies El Nino through influence on atmospheric circulation

    Guan et al. (2015) Sci. Rep.: combination of modes of internal variability (NAO, PDO, AMO) caused the warming-trend slowdown

    Schurer et al. (2015) GRL: Probability of hiatus or rapid warming in observations consistent with previous model studies (e.g. Roberts et al. 2015) with similar spatial pattern relating to Interdecadal Pacific and Atlantic Variability. Combination of unforced variability and timing of volcanic eruptions also important.

    Chikamoto et al. (2015) Nature Comms.: synchronization of ocean anomalies in Pacific, Atlantic and Indian oceans all basins, via global reorganizations of the atmospheric Walker Circulation, allow prediction of ENSO characteristics up to 3 years ahead.

    Dai et al. (2015) Nature Clim. Ch.: Pacific Decadal Oscillation (PDO)-like variability combined with another internal mode of climate variability with a strong signal in the Northern Hemisphere with strong links to Atlantic Multidecadal Oscillation (AMO) and West Pacific Oscillation, account for about one quarter of de-trended annual mean surface temperature variance but essentially all of the decadal variations.

    Kamae et al. (2015) GRL: Slower upper tropospheric warming 1997-2011 relate to tropical Pacific cooling which is probably unforced

    Steinman et al. (2015) Science: statistical analysis finds Pacific Multidecadal Oscillation is dominating recent slow surface warming with little influence from Atlantic Multidecadal Oscillation

    Brown et al. (2015) JGR: strong link between east Pacific and sub-decadal global mean temperature (GMT) variability. Two clusters display link with inter-decadal variability: E. Pacific and S. Ocean; models underestimate interdecadal variability and this is especially pronounced where the E. Pacific link dominates. There is some evidence of positive heat flux feedbacks to inter-decadal variability in the E. Pacific and also for high latitudes involving sea ice.

    Yao et al. (2015) Theoret. Appl. Clim.: Hiatus caused by compensation between decadal variability (quasi-60-year oscillation) and secular warming trends which may persist for several more years

    Thompson et al. (2014) Nature Geoscience: Pacific westerly wind reconstruction shows weaker trade winds coincide with a global warming effect.

    Chen and Tung (2014) Science: 30 year oscillation involving AMOC key in explaining hiatus

    McGregor et al. (2014) Nature Climate Change: recent strengthening of Walker circulation and pacific heat uptake linked to warming in Atlantic since early 1990s.

    Lovejoy (2014) GRL: recent "pause" in global surface warming has a return period of 20-50 years so it is not unusual in the context of century scale climate change

    Boisséson et al. (2014) GRL: strengthening of Pacific trades in last 20 years reproduced by simulations with prescribed sea surface temperatures

    Ding et al. (2014) Nature: Unusual ocean conditions in Pacific explain 50% of recent rapid Arctic warming

    Lu et al. (2014) GRL: On the possible interaction between internal climate variability and forced climate change

    England et al. (2014) Nature Climate: Unprecedented strengthing of Pacific trades has enhanced subsurface ocean heat uptake by shallow overturning cells.

    Chylek et al. (2014) GRL: multi-linear regression implies importance of Atlantic Multi-decadal Oscillation on decadal temperature trends (1/3 of post 1975 warming relates to positive AMO phase).

    L'Heureux et al. (2013) Nature Climate Change - trends towards a stronger, La Nina-like Walker circulation?

    Balmaseda et al. (2013) GRL: increased ocean heating below 700m due to surface wind forcing may have contributed to surface warming hiatus since 2004.

    Guemas et al. (2013) Nature Climate Change: initialisation of models helps to explain hiatus due to changes in upper ocean heating linked to natural variability (see also comment by DEEP-C Met Office partner, Doug Smith)

    Sohn et al. (2013) Climate Dynamics: recent observed variations in the Walker circulation inconsistent with climate models

    Luo et al. (2012) PNAS: strengthening Pacific trade winds in last 2 decades linked with Indian ocean warming

    Chikamoto et al. (2012) GRL: rather than cycles, step-wise shifts are an important manifestation of natural unforced climate variability

    Foster and Rahmstorf (2011) ERL: warming trend evident in recent period when ENSO is accounted for

    Merrifield (2011) J Climate: an observed shift in Pacific ocean circulation during the 1990s

    Knight et al. (2009) BAMS state of the climate: Do global temperature trends over the last Decade falsify climate prediction?

    See also: Energy imbalance/ocean heating | Modelling | Unforced Variability | Radiative Forcing | Ocean heating | Other relevant papers

    Radiative Forcing

    Dewitte & Nevens (2016) ERL: new total solar irradiance estimate, 1363 Wm-2 at solar minimum

    Checa-Garcia et al. (2016) ERL: CFC decline + less growth in methane & low-level ozone pollution contributed to slower surface warming

    Takahashi and Watanabe (2016) Nature Climate: Aerosol forcing, mainly volcanic, contributed one third of unprecedented strengthening of Pacific trade winds during 1991-2010

    Smith et al. (2016) Nature Climate: Aerosol forcing may indirectly explain slowdown in surface warming through influence on ocean circulation

    Gettelman et al. (2015) Clim. Dyn.: Aerosol-cloud interactions forcings may have contributed to the spatial patterns of recent temperature change, but not to the global mean slowing of surface warming for the period 2000-2010.

    Santer et al. (2015) GRL: multi-variable volcanic signal detection indicates volcanic forcing contributes in addition to unforced variability in explaining hiatus. Volcanic signals may have aliased onto the observed tropical SST.

    Ridley et al. (2014) GRL: satellite measurements underestimate contribution of volcanic aerosol between tropospause and 15km at mid to high latitudes and therefore radiative forcing effect. Since 2000 an estimated cooling effect from volcanic aerosol is estimated to be -0.19 Wm-2 approximating to a cooling of 0.05 to 0.12o.

    Hegglin et al. (2014) Nature Geosci.: model nudging technique improves record of stratospheric water vapour, suggesting previous estimates of surface cooling due to stratospheric water vapour decreases in 2001 (e.g. Solomon et al. 2010) are overestimated.

    Huber and Knutti (2014) Nature Geosci.: ENSO variability and natural radiative forcings account for hiatus and apparent observation/CMIP5 model discrepancy

    Kühn et al. (2014) GRL: Asian aerosol emissions cannot explain the 16 year hiatus in global warming

    Haywood et al. (2013) Atmos. Sci. Lett.: global mean cooling of around −0.02 to −0.03 K over the period 2008-2012 due to small volcanos which are therefore not primary cause of the recent slow-down in global mean surface warming.

    Fu (2013) Nature Climate Change reports on study by Garfinkel et al. indicating that disproportionate warming of Indian Ocean and West Pacific may be cooling climate slightly by reducing amount of water vapour entering the stratosphere.

    Forster et al. (2013) JGR total anthropogenic and natural adjusted radiative forcing of 1.9±0.9 Wm-2 from CMIP5 models for 2010

    Neely et al. (2013) GRL: simulations indicate that moderate volcanic eruptions, not increased Asian SO2 emissions, explain recent observed increase in stratospheric aerosol

    Fyfe et al. (2013) GRL: simulations show observed increases in stratospheric aerosol concentration since the late 1990s has decrease the rate of global warming.

    Murphy (2013) Nature Geosciences: no evidence for increased direct aerosol cooling effect 2000-2012

    Huber and Knutti (2012) Nature Geoscience

    Solomon et al. (2011) Science: small but significant cooling effect from volcanic eruptions since 2000

    Kaufmann et al. (2011) PNAS: the solar cycle, changes in sulfate aerosol and natural variability mask greenhouse gas warming in 1998-2008 period

    Solomon et al. (2010) Science: changes in stratospheric water vapour may influence decadal temperature trends

    Murphy et al. (2009) JGR: infer aerosol radiative forcings as a residual between measured terms (greenhouse gas and natural forcings, ocean heat content, outgoing radiation to space)

    See also: Energy imbalance/ocean heating | Modelling | Unforced Variability | Radiative Forcing | Ocean heating | Other relevant papers

    Ocean Heating

    ROberts et al. (2017) JGR-Oceans: Non-Ekman ocean heat transport processes dominate mixed layer ocean heat content in equatorial oceans & regions of strong ocean currents/eddy activity & force atmospheric response.

    Llovel & Terray: ocean heat uptake strongest around 40oS; rapid upper ocean warming is linked to a poleward shift of mean wind stress curl enhancing Ekman pumping for the 45oS-60oS band.

    Robson et al. (2016) Nature Geosci: upper N Atlantic cooling since 2005 linked to reduced ocean circulation/heat transport, linked to record low densities in the deep Labrador Sea, deep ocean warming since 1995 and long-term freshening

    McKinnon & Huybers (2016) GRL: use seasonal energy budget as a constraint on inferred planetary heat content

    Desbruyères et al. (2016) GRL: deep ocean below 2000m contributes 0.065+-0.04 Wm-2 to global heating rate 1991-2010 (2/3s of which from 2000-4000m layer)

    Cheng et al. (2016) Ocean Science: full-depth ocean heating increased from 0.46 Wm-2 to 0.75 Wm-2 (global average) from 1970-2005 to 1992-2005, similar to CMIP5 median.

    Liu et al. (2016) Nature Comms.: heat redistribution in upper 350m between Pacific/Indian Oceans closely tied to surface warming hiatus and linked to Indonesian throughflow response to intensified Pacific trade-winds (see also response to comment by Chen and Tung)

    Somavilla et al. (2016) GRL: mid-2000s heat transfer from upper to deeper N Atlantic ocean following strong winter mixing in early 2005 rather than increased AMOC

    Wijffels et al. (2016) Nature Climate Change: steady accumulation of heat by the oceans up to the large El Nino of 2015/16; an intensifying hemispheric asymmetry, with 7599% of the heat accumulating south of the Equator, merits consideration.

    Glecker et al. (2016) Nature Climate Change: Model estimates verified with long term ocean heating observations show nearly half of the industrial-era increases in global ocean heat content have occurred since about 1997 with over a third of this below 700m depth.

    Palmer et al. (2015) Climate Dynamics: Ocean heat content variability and change in an ensemble of ocean reanalyses

    Johnson et al. (2015) J. Atmos. Ocean. Tech.: Informing Deep Argo Array Design for monitoring decadal-scale deep ocean temperature trends

    Nieves et al. (2015) Science: observations show that heating below the upper 100m ocean have more than compensated slight cooling in the upper 100m over the 2003-2013 period, confirming that redistribution of the heat in the vertical, and in particular in the 100-300m layer in the Indian and Pacific oceans, explain the suppressed rates of surface warming.

    Zika et al. (2015) GRL: deep ocean heating due to collapse of "thermally direct" circulation (reduced upward heat flux at higher latitudes e.g. Antarctic bottom water circulation) but continued thermally indirect circulation (upwelling/downwelling at same density) at lower latitudes. The large-scale circulation rather than small-scale mixing determine the heat uptake changes.

    Czaja and Marshall (2015) Clim. Dyn.: Why is there net surface heating over the Antarctic Circumpolar Current?

    Feng et al. (2015) GRL: Increased rainfall led to freshening of Indonesian throughflow in 2010/11 La Nina event (1999-2001 event also led to freshening)

    Lee et al. (2015) Nature Geoscience: analysis of 0-700m ocean heat content data and simulations suggests that strengthened Pacific trade winds and heat flow through the Indonesian archipelago led to heat build up in the Indian ocean, helping to explain the slower surface warming rate since 2000 (although inadequacies in the observations and the unsampled 700-2000m layer mean that the analysis may be incomplete as discussed in Nature N&V by Julia Rosen).

    Liang et al. (2015) J. Climate: mechanisms for vertical redistribution of ocean heat content; upward heat transport in deep ocean, implying cooling; advection plays a more important role in setting the spatial patterns of vertical heat exchange

    Roemmich et al. (2015) Nature Climate: Steady heating of 0.4-0.6 Wm-2 in upper 2000m ocean from 2006-2013, mostly from mid-latitude Southern oceans. SST follows 0-100m ocean heat content which varies with ENSO but is opposed by 100-500m heat content (apart from in 2013 when almost all of upper 2000m was anomalously warm).

    Desbruyères et al. (2014) GRL: full depth temperature changes in northeastern Atlantic since 2003 imply donward heat flux of 0.53 Wm-2 highlighting potential role of this ocean basin in the recent hiatus.

    Drijfhout et al. (2014) GRL: Surface warming hiatus caused by increased heat uptake across multiple ocean basins. Heat uptake was estimated to have increased by 0.7 Wm-2 from 1990s to 2000s (about 0.5 Wm-2 global mean).

    Cheng and Zhu (2014) GRL: Introduction of Argo introduces artifical jump in ocean heating record; accounting for this suggests a continuous upper ocean (0-700m) warming (0.36+-0.08Wm-2) since 1966.

    Llovel et al. (2014) Nature Climate Change: Combine ocean mass data from satellite with satellite altimeter data to infer ocean heating of 0.64 Wm-2 for 2005-2013. Removing upper 2000m heating rate from Argo suggests minimal contribution to ocean heating and sea level rise from deep ocean below 2000m.

    Durack et al. (2014) Nature Climate Change: based on simulations and satellite altimeter data, argue that upper ocean heating (0-700m) has been underestimated in Southern Ocean due to assumptions involving infilling sparse data. New estimates of 0-700m heating 1970-2004 of 0.12-0.35 Wm-2.

    Wunsch & Heimbach (2014) J. Phys. Oceanography: combine modelling and observations to examing deep ocean heating, finding cooling of the deep ocean but small heating overall

    von Schuckmann et al. (2014) Ocean Sci.: closing ocean energy and sea level budget to within uncertainty in the Argo era.

    Mayer et al. (2014) J. Clim: interannual variability in ocean heat content in tropical basins dominated by surface fluxes rather than inter-basin transport, although Indonesian Throughflow heat transport is significant.

    Kostov et al. (2014) GRL: Atlantic Meridional Overturning Circulation plays an important role in setting the effective heat capacity of the World Ocean

    Robson et al. (2014) Nature Geosciences: Observed slowing of Atlantic Meridional Overturning Circulation part of a decadal trend not a short-term fluctuation.

    Cazenave et al. (2014) Nature Climate Change: reduced rate of sea level rise since 2006 (relative to 1994-2005 period) due to internal variability and associated movement of water over land redistribution of heat in the ocean during La Nina. Note: extending sea level records past 2012, the slowdown in sea level rise is not apparent

    Lyman and Johnson (2013): sampling strategies and layer estimates of ocean heat content since 1950. 2004-2011 heating of 0-1800m layer 0.56 Wm-2; 0.46 Wm-2 for 0-700m 1983-2011.

    Hobbs and Willis (2013) GRL: 135 year warming of oceans attributed to anthropogenic factors and energy imbalance of 0.1 Wm 1873-1955.

    Rosenthal et al. (2013) : pacific ocean heat content (OHC) higher than recent decade for much of last 10,000 years but recent rates of increase in ocean heating are unprecedented

    Purkey and Johnson (2013) : freshening of deep Antarctic bottom waters since 1980s (see also perspective by Bindoff and Hobbs)

    Masuda et al. (2010) : computer simulations reveal fast teleconnection between changes in air-sea heat flux off the Adélie Coast of Antarctica and the bottom-water warming in the North Pacific.

    Purkey & Johnson (2010) Observed ocean heating from 1990s-2000s below 4000m and 1000-4000m in southern ocean equivalent to nearly 0.1 Wm-2 globally

    Kouketsu et al. (2010): Observationally-derived estimates of heating below 3000m from 1990s-2000s of about 0.05 Wm-2

    Gregory et al. (2013): Climate models without preindustrial volcanic forcing underestimate historical ocean thermal expansion

    See also: Energy imbalance/ocean heating | Modelling | Unforced Variability | Radiative Forcing | Deep ocean heating | Other relevant papers

    Other relevant papers


    Delworth et al. (2015) J. Clim.: North American drought linked to unusual Pacific conditions, likely internal variability. Using coupled models forced with wind stress, continued anomalous wind stress would extend drought conditions but eventually this effect diminishes due to reemergence of warmer water that was initially subducted into the ocean interior.

    Trenberth et al. (2014) Nature Climate Change: Seasonal aspects of the recent pause in surface warming


    Song et al. (2016) SREP: hiatus in greenhouse effect increase - this seems to be mixing cause and effect since more frequent, cooler La Nina events will reduce the water vapour greenhouse effect although the cahanges in cloud could be interetsing

    Peyser et al. (2016) GRL: dynamically-related sea level rise pattern as a predictor for global surface warming suppression or surge

    Turner et al. (2016) Nature: hiatus in Antarctic Peninsula warming linked to natural climate fluctuations

    Li et al. (2015) GRL: observed Eurasian winter cooling trend 1998-2012 contributed to suppressing of global warming trend and arises from internal variability

    Ying et al. (2015) GRL: using breakpoint analysis only DJF shows interuption of land warming trend.

    Trenberth et al. (2015) Science: a variety of evidence shows that there has been a "hiatus" and signs are it is now over but we need to understand the processes that generate decadal fluctuations in climate further.

    Saffioti et al. (2015) GRL: Northern Hemisphere winter cooling 1998-2012 mostly explained by missing observations (particularly for recent years) and internal variability in the atmospheric circulation of the NH extratropics.

    Gleisner et al. (2015) GRL: Recent global warming hiatus dominated by low latitude surface temperature trends and not explained by missing data in high latitude regions

    Cohen et al. (2012) GRL: hiatus influenced strongly by northern hemisphere land (away from the tropics) in winter.

    Observing systems

    Cowtan et al. (2015) GRL: using model SST and land air temperature makes a more consistent comparison with observations and reduces the differences between CMIP5 and observed recent warming trends

    Karl et al. (2015) Science: update to account for changing coverage of ship and buoy measurements increases surface warming trend since 1998 up to magnitude of 1950-1999 trend (although does not show that recent period contains slower warming than 1980s/90s and coupled model simulations)

    Cowtan and Way (2013) Q. J. Roy. Meteorol. Soc.: improved infilling of data gaps in HadCRUT4 increases surface warming trend in 2000s slightly

    Kennedy (2013) Rev. Geophys.: A review of uncertainty in in situ measurements and data sets of sea-surface temperature.

    Abraham et al. in press Rev. Geophys.: A review of global ocean temperature observations: Implications for ocean heat content estimates and climate change.

    Kennedy et al. (2012) Remote Sensing of Environment: uncertainty in sea surface temperature record

    Nuccitelli et al. (2012) Physical Letters A: errors in methodology for estimating ocean heating rate.

    Lyman and Johnson (2008) J. Clim.: sampling of ocean heat content and uncertainty estimates

    Inter-hemispheric heating asymmetries

    Boos & Korty (2016) Nature Geosci.: zonal+meridional energy fluxes determine regional ITCZ shifts; feedbacks also required to explain green Sahara in mid-holocene

    Byrne and Schneider (2016) GRL: physical mechanisms causing narrowing of ITCZ in warmer climate

    Adam et al. (2016) GRL: hemispherically antisymmetric precipitation biases related to the cross-equatorial atmospheric energy transport; symmetric biases related to atmospheric net energy input near equator

    Hawcroft et al. (2016) Clim. Dyn.: correction of southern ocean cloud reflectivity bias doesn't fix cross equatorial energy transport bias due to ocean transport adjustment in HadGEM2-ES (see similar results for CESM-CAM5 by Kay et al. (2016) J. Clim..

    Haywood et al. (2015) GRL: removing asymmetry in hemispheric albedo in HadGEM2-ES climate model improves rainfall distribution and tropical cyclones

    Ruzmaikin et al. (2015) JAS: link between AMOC and inter-hemispheric heating variation on multi-decadal timescales

    Pausata et al. (2015) PNAS: long lasting effects of high latitude volcanic eruptions on ENSO and AMOC through hemispheric heating asymmeries

    Allen et al. (2015) J./ Clim.: interhemispheric aerosol radiative forcing and cloud interaction effects explain tropical precipitation shifts in late 20th century

    Dong and Sutton (2015) Nature Climate Change: greenhouse gas focing explains much of increase in Sahel rainfall since 1980s through enhanced meridional temperature gradient with a secondary role for aerosol

    Brönnimann et al. (2015) Nature Geosci.: Southward shift of northern tropical belt 1945-1980 linked to inter-hemispheric cooling/heating of sea surface, particularly in Atlantic

    Stephens et al. (2015) Rev. Geophys.: The albedo of Earth - hemispheric symmetry in albedo due to brighter northern hemisphere surface but more clouds in southern hemisphere; interhemispheric radiative imbalance of 0.6 Wm-2 explained by outgoing longwave (higher in north). Models do not consistently simulate the interhemispheric differences and represent unrealistic seasonal cycles in albedo and overestimate its interannual variability.

    Feng et al. (2015) Adv. Atmos. Sci. Simulation of the equatorially asymmetric mode of the Hadley circulation in CMIP5 models

    Loeb et al. (2015) Clim. Dyn.: Observed imbalance of 0.6 Wm-2 determined by southern hemisphere. Climate model biases in cross equatorial energy transports linked with precipitation biases.

    Haywood et al. (2013) Nature Clim.: high latitude volcanic eruptions induce Sahel rainfall changes linked to asymmetric hemispheric cooling effect

    Frierson et al. (2013) Nature Geoscience: northward transport of energy in Atlantic explains present day position of ITCZ in northern hemisphere

    Broecker & Putnam (2013) PNAS: Hydrologic impacts of past shifts of Earth's thermal equator offer insight into those to be produced by fossil fuel CO2

    Chiang et al. (2012) JGRENSO and Atlantic ITCZ position

    Riehl & Simpson (1979) Contrib. to Atmos. Phys. - Heat balance of the equatorial trough zone, revisited


    Terai et al. (2016) JGR: mid/high latitude cloud feedback too negative in climate models

    Brient and Schneider 92016) J. Clim.: Satellite data show low clouds amplify climate variability and imply models with higher climate sensitivity are more realistic

    Rugenstein et al. (2016) GRL: Dependence of global radiative feedbacks on evolving patterns of surface heat fluxes


    Fyfe et al. (2016) Nature Climate Change: there was a significant slowing in surface warming from the 1990s to the 2000s

    Lewandowsky et al. (2015) Sci. Rep.: hiatus or pause are unsuitable definitions for the temporary slowing in surface warming

    Josey et al. (2015) Clim. Dyn.: Strong evaporation & heat loss from N. Atlantic linked to wet UK winter 2013/14 & cold sub-polar water late 2014

    Lewandowsky et al. (2015) BAMS: argue that the the notion of a "pause" in global warming was adopted by the scientific community in its problem-solving and answer-seeking role and has led to undue focus on, and mislabeling of, a recent climatic fluctuations

    Rajaratnam et al. (2015) Climatic change: statistical analysis shows there is no hiatus in the increase in the global mean temperature, no statistically significant difference in trends, no stalling of the global mean temperature, and no change in year-to-year temperature increases.

    Wild et al. (2015) Clim. Dyn.: The energy balance over land and oceans: an assessment based on direct observations and CMIP5 climate models

    Lewandowsky et al. (2015) Glob. Env. Ch.: "Seepage paper" - uses global warming "hiatus" as an example of where scientific process may be altered by vested interests.

    Trenberth et al. (2015) JGR: large changes in net imbalance from month to month fluctuations in cloud while year to year changes dominated by ENSO when ASR and OLR act in unison. Strong local relationship between tropospheric T and OLR; land and ocean regressions contrast (cloud changes drive land T change while SST change drives local cloud change). Regression between net imbalance and surface T of 2.18 Wm-2K-1 cannot reliably infer climate sensitivity. Changes in SSM/I January 1992, SST data in mid 2001 and loss of F13 SSM/I in 2009 cause spurious decrease in ERA-Interim water vapour, SST and net flux repectively while an increase in CERES clear-sky net flux after January 2008 may be affected by the change in clear-sky screening data.

    Pretis et al. (2015) Climate Change: testing whether particular mechanisms improve simulation of hiatus in a statistically significant sense no evidence is found that the slowdown in global mean surface temperature increases are uniquely tied to episodes of La Niña-like cooling.

    Estrada et al. (2013) Nature Geosci.: Statistical analysis of radiative forcings suggests role of ozone, methane and CFCs in the slowdown of global warming sinc ethe 1990s.

    Heaviside and Czaja (2012) QJRMS: Deconstructing the Hadley Cell Heat Transport.

    Simmons et al. (2009) JGR: declining trends in relative humidity over land in recent decade

    Harries and Futyan (2006): time-scales of water vapour, clud and radiation associated with growth and decay of Mt. Pinatubo perturbation to net imbalance: temperature and humidity responses are delayed by 2-3 years although the 6.7 micron brightness temperature changes share some characteristics with the rapidly responding radiative SW fluxes, presumably due to an aerosol signal affecting this water vapour absorption channel.

    See also: Energy imbalance/ocean heating | Modelling | Unforced Variability | Radiative Forcing | Deep ocean heating | Other relevant papers


    Work in progress (Chunlei Liu)... See also: surface | uncertainty | LH | CLiVAR | asym

    Richard P. Allan
    Location: Department of Meteorology (2U15)

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