AGW Observer

Observations of anthropogenic global warming

Archive for September, 2010

Papers on volcanoes and climate

Posted by Ari Jokimäki on September 29, 2010

This is a list of papers on the climate effects of volcanoes. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Volcanoes and climate – Cole-Dai (2010) A review article “Of the natural forcings causing short-term climatic variations, volcanism, along with its climatic impact, is perhaps the best understood. The primary net result of the impact is the reduced receipt of solar energy at Earth’s surface due to the scattering of incoming solar radiation by secondary sulfate aerosols formed from volcanic sulfur. The quantitative effects can be measured in energy-balance-based climate models, which require validation using high-quality paleoclimatic and paleovolcanic data. An important advancement in the effort to understand the role of volcanism in climate change in the recent decade is the significant improvement in paleovolcanic records from polar ice cores, represented by long records with unprecedented temporal accuracy and precision, and by the potential to identify climate-impacting stratospheric eruptions in the records. Other improvements include (1) the investigation of long-term relationship between eruptions (including super-eruptions) and climate variations, beyond an eruption’s radiative impact of up to a few years; (2) a better understanding of the response to volcanic perturbation of feedback mechanisms in the climate system; and (3) the limited role of volcanic eruptions in the era of human-induced greenhouse warming. Urgent research/investigation is needed to evaluate the geoengineering proposition to counteract greenhouse warming by injecting sulfur dioxide into the stratosphere, which is based on the significant cooling effects of stratospheric volcanic eruptions, and its serious unintended consequences.” Jihong Cole-Dai, Wiley Interdisciplinary Reviews: Climate Change, 2010, DOI: 10.1002/wcc.76. [Full text]

Climate response to large, high-latitude and low-latitude volcanic eruptions in the Community Climate System Model – Schneider et al. (2009) “Explosive volcanism is known to be a leading natural cause of climate change. The second half of the 13th century was likely the most volcanically perturbed half-century of the last 2000 years, although none of the major 13th century eruptions have been clearly attributed to specific volcanoes. This period was in general a time of transition from the relatively warm Medieval period to the colder Little Ice Age, but available proxy records are insufficient on their own to clearly assess whether this transition is associated with volcanism. This context motivates our investigation of the climate system sensitivity to high- and low-latitude volcanism using the fully coupled NCAR Community Climate System Model (CCSM3). We evaluate two sets of ensemble simulations, each containing four volcanic pulses, with the first set representing them as a sequence of tropical eruptions and the second representing eruptions occurring in the mid-high latitudes of both the Northern and Southern hemispheres. The short-term, direct radiative impacts of tropical and high-latitude eruptions include significant cooling over the continents in summer and cooling over regions of increased sea-ice concentration in Northern Hemisphere (NH) winter. A main dynamical impact of moderate tropical eruptions is a winter warming pattern across northern Eurasia. Furthermore, both ensembles show significant reductions in global precipitation, especially in the summer monsoon regions. The most important long-term impact is the cooling of the high-latitude NH produced by multiple tropical eruptions, suggesting that positive feedbacks associated with ice and snow cover could lead to long-term climate cooling in the Arctic.” Schneider, D. P., C. M. Ammann, B. L. Otto-Bliesner, and D. S. Kaufman (2009), J. Geophys. Res., 114, D15101, doi:10.1029/2008JD011222.

Bipolar correlation of volcanism with millennial climate change – Bay et al. (2004) “Analyzing data from our optical dust logger, we find that volcanic ash layers from the Siple Dome (Antarctica) borehole are simultaneous (with >99% rejection of the null hypothesis) with the onset of millennium-timescale cooling recorded at Greenland Ice Sheet Project 2 (GISP2; Greenland). These data are the best evidence yet for a causal connection between volcanism and millennial climate change and lead to possibilities of a direct causal relationship. Evidence has been accumulating for decades that volcanic eruptions can perturb climate and possibly affect it on long timescales and that volcanism may respond to climate change. If rapid climate change can induce volcanism, this result could be further evidence of a southern-lead North–South climate asynchrony. Alternatively, a volcanic-forcing viewpoint is of particular interest because of the high correlation and relative timing of the events, and it may involve a scenario in which volcanic ash and sulfate abruptly increase the soluble iron in large surface areas of the nutrient-limited Southern Ocean, stimulate growth of phytoplankton, which enhance volcanic effects on planetary albedo and the global carbon cycle, and trigger northern millennial cooling. Large global temperature swings could be limited by feedback within the volcano–climate system.” Ryan C. Bay, Nathan Bramall, and P. Buford Price, PNAS April 27, 2004 vol. 101 no. 17 6341-6345, doi: 10.1073/pnas.0400323101. [Full text]

Volcanic eruption frequency over the last 45 ky as recorded in Epica-Dome C ice core (East Antarctica) and its relationship with climatic changes – Castellano et al. (2004) “The sulphate glacio-chemical profiles constitute a reliable proxy marker for reconstruction of past volcanic history, assuming a reliable method to distinguish sulphate spikes and to evaluate the flux of individual events is set up. The resulting volcanic event profile is used to reconstruct past event frequencies, and to investigate possible links between volcanism and climatic changes. Volcanic event signatures are useful also in comparing time scales from ice cores drilled at different locations. In this paper, a new method to pick out volcanic signals is proposed. It improves on methods based on the calculation of a threshold using a general mean value plus a multiple of the standard deviation by adding: (1) quantification of nonvolcanic sulphate contributions; (2) sulphate fluxes, instead of concentrations, accounting for accumulation rate changes; (3) data treatment using a log-normal statistic, instead of a Gaussian-type distribution, to take into account the real sulphate distribution; (4) a smoothed curve (weighted fitting) to better understand the residual variability of the sulphate background. This method is used to detect volcanic events throughout the 45 ky time span of the EDC96 ice core, drilled at Dome C on the East Antarctic plateau. A total of 283 volcanic signatures are recovered, with a mean of 6.3 events per millennium. The temporal event frequencies indicate that the last 2000 years were probably characterized by the highest volcanic activity in the period covered by the core and that there is no clear link between number of events recorded and climatic changes.” E. Castellano, S. Becagli, J. Jouzel, A. Migliori, M. Severi, J. P. Steffensen, R. Traversi and R. Udisti, Global and Planetary Change, Volume 42, Issues 1-4, July 2004, Pages 195-205, doi:10.1016/j.gloplacha.2003.11.007.

Volcanic and Solar Forcing of Climate Change during the Preindustrial Era – Shindell et al. (2003) “The climate response to variability in volcanic aerosols and solar irradiance, the primary forcings during the preindustrial era, is examined in a stratosphere-resolving general circulation model. The best agreement with historical and proxy data is obtained using both forcings, each of which has a significant effect on global mean temperatures. However, their regional climate impacts in the Northern Hemisphere are quite different. While the short-term continental winter warming response to volcanism is well known, it is shown that due to opposing dynamical and radiative effects, the long-term (decadal mean) regional response is not significant compared to unforced variability for either the winter or the annual average. In contrast, the long-term regional response to solar forcing greatly exceeds unforced variability for both time averages, as the dynamical and radiative effects reinforce one another, and produces climate anomalies similar to those seen during the Little Ice Age. Thus, long-term regional changes during the preindustrial appear to have been dominated by solar forcing.” Shindell, Drew T., Gavin A. Schmidt, Ron L. Miller, Michael E. Mann, 2003, J. Climate, 16, 4094–4107. [Full text]

Volcanic eruptions and climate – Robock (2000) A review article. “Volcanic eruptions are an important natural cause of climate change on many timescales. A new capability to predict the climatic response to a large tropical eruption for the succeeding 2 years will prove valuable to society. In addition, to detect and attribute anthropogenic influences on climate, including effects of greenhouse gases, aerosols, and ozone-depleting chemicals, it is crucial to quantify the natural fluctuations so as to separate them from anthropogenic fluctuations in the climate record. Studying the responses of climate to volcanic eruptions also helps us to better understand important radiative and dynamical processes that respond in the climate system to both natural and anthropogenic forcings. Furthermore, modeling the effects of volcanic eruptions helps us to improve climate models that are needed to study anthropogenic effects. Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e-folding residence time of about 1 year. Large ash particles fall out much quicker. The radiative and chemical effects of this aerosol cloud produce responses in the climate system. By scattering some solar radiation back to space, the aerosols cool the surface, but by absorbing both solar and terrestrial radiation, the aerosol layer heats the stratosphere. For a tropical eruption this heating is larger in the tropics than in the high latitudes, producing an enhanced pole-to-equator temperature gradient, especially in winter. In the Northern Hemisphere winter this enhanced gradient produces a stronger polar vortex, and this stronger jet stream produces a characteristic stationary wave pattern of tropospheric circulation, resulting in winter warming of Northern Hemisphere continents. This indirect advective effect on temperature is stronger than the radiative cooling effect that dominates at lower latitudes and in the summer. The volcanic aerosols also serve as surfaces for heterogeneous chemical reactions that destroy stratospheric ozone, which lowers ultraviolet absorption and reduces the radiative heating in the lower stratosphere, but the net effect is still heating. Because this chemical effect depends on the presence of anthropogenic chlorine, it has only become important in recent decades. For a few days after an eruption the amplitude of the diurnal cycle of surface air temperature is reduced under the cloud. On a much longer timescale, volcanic effects played a large role in interdecadal climate change of the Little Ice Age. There is no perfect index of past volcanism, but more ice cores from Greenland and Antarctica will improve the record. There is no evidence that volcanic eruptions produce El Niño events, but the climatic effects of El Niño and volcanic eruptions must be separated to understand the climatic response to each.” Robock, A. (2000), Rev. Geophys., 38(2), 191–219, doi:10.1029/1998RG000054. [Full text]

Radiative forcing from the 1991 Mount Pinatubo volcanic eruption – Stenchikov et al. (1998) “Volcanic sulfate aerosols in the stratosphere produce significant long-term solar and infrared radiative perturbations in the Earth’s atmosphere and at the surface, which cause a response of the climate system. Here we study the fundamental process of the development of this volcanic radiative forcing, focusing on the eruption of Mount Pinatubo in the Philippines on June 15, 1991. We develop a spectral-, space-, and time-dependent set of aerosol parameters for 2 years after the Pinatubo eruption using a combination of SAGE II aerosol extinctions and UARS-retrieved effective radii, supported by SAM II, AVHRR, lidar and balloon observations. Using these data, we calculate the aerosol radiative forcing with the ECHAM4 general circulation model (GCM) for cases with climatological and observed sea surface temperature (SST), as well as with and without climate response. We find that the aerosol radiative forcing is not sensitive to the climate variations caused by SST or the atmospheric response to the aerosols, except in regions with varying dense cloudiness. The solar forcing in the near infrared contributes substantially to the total stratospheric heating. A complete formulation of radiative forcing should include not only changes of net fluxes at the tropopause but also the vertical distribution of atmospheric heating rates and the change of downward thermal and net solar radiative fluxes at the surface. These forcing and aerosol data are available for GCM experiments with any spatial and spectral resolution.” Stenchikov, G. L., I. Kirchner, A. Robock, H.-F. Graf, J. C. Antuña, R. G. Grainger, A. Lambert, and L. Thomason (1998), J. Geophys. Res., 103(D12), 13,837–13,857, doi:10.1029/98JD00693.

Modelling the distal impacts of past volcanic gas emissions. Evidence of Europe-wide environmental impacts from gases emitted during the eruption of Italian and Icelandic volcanoes in 1783 – Grattan et al. (1998) “This paper investigates the impact of volcanogenic aerial pollution upon the European environnement. Focusing on the year 1783 it is reavealed that a Europe-wide toxic fog, composed of volcagenic gases and aerosols caused respiratory illness, crop damage, panic and extreme weather. It is proposed that similar events may have occured in the past and should be considered as an agent of change by archaeologists and historians.” J Grattan, M Brayshay, J Sadler, Quaternaire, 1998, vol. 9, no 1 (75 p.) (1 p.1/4), pp. 25-35. [Full text available in abstract page]

A 110,000-Yr Record of Explosive Volcanism from the GISP2 (Greenland) Ice Core – Zielinski et al. (1996) “The time series of volcanically produced sulfate from the GISP2 ice core is used to develop a continuous record of explosive volcanism over the past 110,000 yr. We identified 850 volcanic signals (700 of these from 110,000 to 9000 yr ago) with sulfate concentrations greater than that associated with historical eruptions from either equatorial or mid-latitude regions that are known to have perturbed global or Northern Hemisphere climate, respectively. This number is a minimum because decreasing sampling resolution with depth, source volcano location, variable circulation patterns at the time of the eruption, and post-depositional modification of the signal can result in an incomplete record. The largest and most abundant volcanic signals over the past 110,000 yr, even after accounting for lower sampling resolution in the earlier part of the record, occur between 17,000 and 6000 yr ago, during and following the last deglaciation. A second period of enhanced volcanism occurs 35,000–22,000 yr ago, leading up to and during the last glacial maximum. These findings further support a possible climate-forcing component in volcanism. Increased volcanism often occurs during stadial/interstadial transitions within the last glaciation, but this is not consistent over the entire cycle. Ages for some of the largest known eruptions 100,000–9000 yr ago closely correspond to individual sulfate peaks or groups of peaks in our record.” Gregory A. Zielinski, Paul A. Mayewski, L. David Meeker, S. Whitlow and Mark S. Twickler, Quaternary Research, Volume 45, Issue 2, March 1996, Pages 109-118, doi:10.1006/qres.1996.0013.

Potential climate impact of Mount Pinatubo eruption – Hansen et al. (1992) “We use the GISS global climate model to make a preliminary estimate of Mount Pinatubo’s climate impact. Assuming the aerosol optical depth is nearly twice as great as for the 1982 El Chichon eruption, the model forecasts a dramatic but temporary break in recent global warming trends. The simulations indicate that Pinatubo occurred too late in the year to prevent 1991 from becoming one of the warmest years in instrumental records, but intense aerosol cooling is predicted to begin late in 1991 and to maximize late in 1992. The predicted cooling is sufficiently large that by mid 1992 it should even overwhelm global warming associated with an El Nino that appears to be developing, but the El Nino could shift the time of minimum global temperature into 1993. The model predicts a return to record warm levels in the later 1990s. We estimate the effect of the predicted global cooling on such practical matters as the severity of the coming Soviet winter and the dates of cherry blossoming next spring, and discuss caveats which must accompany these preliminary simulations.” Hansen, J., A. Lacis, R. Ruedy, and M. Sato (1992), Geophys. Res. Lett., 19(2), 215–218, doi:10.1029/91GL02788. [Full text]

Volcanic winter and accelerated glaciation following the Toba super-eruption – Rampino & Self (1992) “THE eruption of Toba in Sumatra 73,500 years ago was the largest known explosive volcanic event in the late Quaternary1. It could have lofted about 1015 g each of fine ash and sulphur gases to heights of 27–37 km, creating dense stratospheric dust and aerosol clouds. Here we present model calculations that investigate the possible climatic effects of the volcanic cloud. The increase in atmospheric opacity might have produced a ‘volcanic winter’2—a brief, pronounced regional and perhaps hemispheric cooling caused by the volcanic dust—followed by a few years with maximum estimated annual hemispheric surface-temperature decreases of 3–5 °C. The eruption occurred during the stage 5a-4 transition of the oxygen isotope record, a time of rapid ice growth and falling sea level3. We suggest that the Toba eruption may have greatly accelerated the shift to glacial conditions that was already underway, by inducing perennial snow cover and increased sea-ice extent at sensitive northern latitudes. As the onset of climate change may have helped to trigger the eruption itself4, we propose that the Toba event may exemplify a more general climate–volcano feedback mechanism.” Michael R. Rampino & Stephen Self, Nature 359, 50 – 52 (03 September 1992); doi:10.1038/359050a0.

The Great Tambora Eruption in 1815 and Its Aftermath – Stothers (1984) “Quantitative analytical methods are used to reconstruct the course of events during and after the cataclysmic eruption of Mount Tambora, Indonesia, on 10 and 11 April 1815. This was the world’s greatest ash eruption (so far as is definitely known) since the end of the last Ice Age. This synthesis is based on data and methods from the fields of volcanology, oceanography, glaciology, meteorology, climatology, astronomy, and history.” Richard B. Stothers, Science 15 June 1984: Vol. 224. no. 4654, pp. 1191 – 1198, DOI: 10.1126/science.224.4654.1191.

The Mount St. Helens Volcanic Eruption of 18 May 1980: Minimal Climatic Effect – Robock (1981) “An energy-balance numerical climate model was used to simulate the effects of the Mount St. Helens volcanic eruption of 18 May 1980. The resulting surface temperature depression is a maximum of 0.1°C in the winter in the polar region, but is an order of magnitude smaller than the observed natural variability from other effects and will therefore be undetectable.” Alan Robock, Science 19 June 1981: Vol. 212. no. 4501, pp. 1383 – 1384, DOI: 10.1126/science.212.4501.1383.

Perturbation of the zonal radiation balance by a stratospheric aerosol layer – Harshvardhan (1979) “The effect of stratospheric aerosols on the earth’s monthly zonal radiation balance is investigated using a model layer consisting of 75% H2SO4, the primary constituent of the background aerosol layer. The reduction in solar energy absorbed by the earth-atmosphere system is determined through the albedo sensitivity, and the optically thin approximation is used in conjunction with the Henyey-Greenstein phase function for scattering. An infrared radiative transfer model is used to estimate the increased greenhouse effect from the aerosol layer, and the infrared heating compensates for the albedo effect in altering the radiation balance. The results indicate that the dominant influence of the thin model stratospheric aerosol layer is an increased reflection of solar energy all over the globe except for the polar-winter region, but the change in the radiation balance is uniform and small equatorward of 50 deg.” Harshvardhan, M. R., Journal of the Atmospheric Sciences. Vol. 36, pp. 1274-1285. July 1979.

Volcanic Explosions and Climatic Change: A Theoretical Assessment – Pollack et al. (1976) “Volcanic explosions introduce silicate dust particles and sulfur gases into the stratosphere. The sulfur gases are slowly converted to sulfuric acid particles. We have performed radiative transfer calculations at visible and infrared wavelengths to determine the effect of these aerosols on the global energy budget. A numerical method that allows for the vertical inhomogeneity of the atmosphere and that permits an accurate solution of the multiple scattering problem is used to determine the variation of the global albedo with stratospheric aerosol burden. These results are employed together with a calculation of the thermal radiation at the top of the atmosphere to determine the net change in mean surface temperature. Both calculations use measured optical constants for the aerosol species of interest. We find that increases in both silicate and sulfuric acid aerosols lead to an increase in the global albedo. However, this cooling is offset by the enhanced greenhouse warming due to the aerosol opacity at infrared wavelengths. During the first few months following a volcanic explosion, when the aerosols are mostly dust grains of fairly large diameter, the two effects either cancel out or a small net warming of the surface occurs, accompanied by an increase in stratospheric temperatures. Our calculations indicate that the observed heating of the stratosphere following the eruption of Mt. Agung was due chiefly to the absorption of upwelling terrestrial radiation by the added particles. However, at later times, and during most of the posteruption period, smaller sized dust and sulfuric acid aerosol particles caused a net cooling. The integrated effect over all stages following a volcanic eruption is a net cooling of the surface. Our calculations yield an estimate of the globally averaged temperature change caused by a given level of volcanic activity. A study of observed levels of volcanic activity suggests that observed climatic changes may be caused directly by single and especially by multiple volcanic explosions.” Pollack, J. B., O. B. Toon, C. Sagan, A. Summers, B. Baldwin, and W. Van Camp (1976), J. Geophys. Res., 81(6), 1071–1083, doi:10.1029/JC081i006p01071.

Volcanic Dust in the Atmosphere; with a Chronology and Assessment of Its Meteorological Significance – Lamb (1970) “After defining the terms commonly used in reporting volcanic eruptions and noting previous approaches to assessment of their magnitudes, this study proceeds to examine aspects of importance, or possible importance, to meteorology-principally the dust veils created in the atmosphere, particle sizes and distribution, heights, fall speeds and atmospheric residence times. Later sections deal with spread of the dust by the atmospheric circulation and the direct effects apparent upon radiation, surface temperature and extent of ice in the polar regions. These effects, as well as various crude measures of the total quantity of solid matter thrown up, are used to arrive at numerical assessments of volcanic eruptions in terms of a dust veil index (d.v.i.). The latitude of origin of the dust (latitude of the volcano) receives some attention, and apparently affects the course of development of the atmospheric circulation over the three or four years following, at least in the case of great eruptions (d.v.i. > 100 over one hemisphere). Effects upon the extent of ice on the polar seas may be of somewhat longer duration, and thereby influence the atmospheric circulation over a longer period of years, since there seems to be some association with the cumulative d.v.i. values when successive great eruptions occur with only few years between. The time distribution of volcanic dust since the last Ice Age, and since A.D. 1500, are indicated in as much detail as the evidence permits. Some associations with changes of climate are suggested, but it is clear that volcanic dust is not the only, and probably not the main, influence in this. The appendices give a chronology of eruptions (including those which it seems possible to dismiss as regards any effect on world weather or climate) and a chronology of d.v.i. values. A third appendix displays by means of graphs the variation of some circulation parameters in January and July in the region of northwest Europe over the years immediately following forty of the greatest eruptions since 1680.” H. H. Lamb, Phil. Trans. R. Soc. Lond. A 2 July 1970 vol. 266 no. 1178 425-533, doi: 10.1098/rsta.1970.0010.

Recent secular changes of the global temperature – Mitchell (1961) As described by Robock (2000): “Mitchell [1961] was the first to conduct a superposed epoch analysis, averaging the effects of several eruptions to isolate the volcanic effect from other presumably random fluctuations. He only looked at 5-year average periods, however, and did not have a very long temperature record.” Mitchell, J. M., Jr., Ann. N. Y. Acad. Sci., 95, 235–250, 1961.

Volcanic dust and other factors in the production of climatic changes, and their possible relation to ice gases – Humphreys (1913) As described by Robock (2000): “Humphreys [1913, 1940] associated cooling events after large volcanic eruptions with the radiative effects of the stratospheric aerosols but did not have a sufficiently long or horizontally extensive temperature database to quantify the effects.” Humphreys, W. J., J. Franklin Inst., Aug., 131–172, 1913.


Posted in Climate science | Leave a Comment »

Papers on rescuing old weather observations

Posted by Ari Jokimäki on September 25, 2010

This is a list of papers on the rescuing of old weather observations (from ship logbooks for example). The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

The weather of the First Fleet voyage to Botany Bay, 1787–1788 – Gergis et al. (2010) “Researchers from the University of Melbourne recently stumbled upon a culturally priceless ship’s logbook containing the weather conditions experienced during the British First Fleet’s voyage to Botany Bay in 1787-1788 (Figure 1). … Aboard the First Fleet’s flagship HMS Sirius was a young marine, William Bradley, who kept a daily logbook of weather observations including temperature, barometric pressure and winds (Figure 2).” Joëlle Gergis, Philip Brohan, Rob Allan, Weather, 2010, DOI: 10.1002/wea.608.

Rescuing old meteorological data – Le Blancq (2010) “This short paper describes the recent rescue and digitisation of Jersey surface pressure data and some potential uses.” Frank Le Blancq, Weather, Volume 65, Issue 10, pages 277–280, October 2010, DOI: 10.1002/wea.510.

The importance of ship log data: reconstructing North Atlantic, European and Mediterranean sea level pressure fields back to 1750 – Küttel et al. (2010) “Local to regional climate anomalies are to a large extent determined by the state of the atmospheric circulation. The knowledge of large-scale sea level pressure (SLP) variations in former times is therefore crucial when addressing past climate changes across Europe and the Mediterranean. However, currently available SLP reconstructions lack data from the ocean, particularly in the pre-1850 period. Here we present a new statistically-derived 5° × 5° resolved gridded seasonal SLP dataset covering the eastern North Atlantic, Europe and the Mediterranean area (40°W–50°E; 20°N–70°N) back to 1750 using terrestrial instrumental pressure series and marine wind information from ship logbooks. For the period 1750–1850, the new SLP reconstruction provides a more accurate representation of the strength of the winter westerlies as well as the location and variability of the Azores High than currently available multiproxy pressure field reconstructions. These findings strongly support the potential of ship logbooks as an important source to determine past circulation variations especially for the pre-1850 period. This new dataset can be further used for dynamical studies relating large-scale atmospheric circulation to temperature and precipitation variability over the Mediterranean and Eurasia, for the comparison with outputs from GCMs as well as for detection and attribution studies.” M. Küttel, E. Xoplaki, D. Gallego, J. Luterbacher, R. García-Herrera, R. Allan, M. Barriendos, P. D. Jones, D. Wheeler and H. Wanner, Climate Dynamics, Volume 34, Numbers 7-8, 1115-1128, DOI: 10.1007/s00382-009-0577-9. [Full text]

Arctic marine climate of the early nineteenth century – Brohan et al. (2010) “The climate of the early nineteenth century is likely to have been significantly cooler than that of today, as it was a period of low solar activity (the Dalton minimum) and followed a series of large volcanic eruptions. Proxy reconstructions of the temperature of the period do not agree well on the size of the temperature change, so other observational records from the period are particularly valuable. Weather observations have been extracted from the reports of the noted whaling captain William Scoresby Jr., and from the records of a series of Royal Navy expeditions to the Arctic, preserved in the UK National Archives. They demonstrate that marine climate in 1810–1825 was marked by consistently cold summers, with abundant sea-ice. But although the period was significantly colder than the modern average, there was considerable variability: in the Greenland Sea the summers following the Tambora eruption (1816 and 1817) were noticeably warmer, and had less sea-ice coverage, than the years immediately preceding them; and the sea-ice coverage in Lancaster Sound in 1819 and 1820 was low even by modern standards.” Brohan, P., Ward, C., Willetts, G., Wilkinson, C., Allan, R., and Wheeler, D., Clim. Past, 6, 315-324, doi:10.5194/cp-6-315-2010, 2010. [Full text]

Marine Observations of Old Weather – Brohan et al. (2009) “Weather observations are vital for climate change monitoring and prediction. For the world’s oceans, there are many meteorological and oceanographic observations available back to the mid-twentieth century, but coverage is limited in earlier periods, and particularly also during the two world wars. Before 1850 there are currently very few instrumental observations available. Consequently, detailed observational estimates of surface climate change can be made only back to the mid-nineteenth century. To improve and extend this early coverage, scientists need more observations from these periods. Fortunately, many such observations exist in logbooks, reports, and other paper records, but their inclusion in the climatic datasets requires that these paper records be abstracted from the world’s archives, digitized into an electronic form, and blended into existing climate databases. As a first step in this direction, selected Royal Navy logbooks from the period of 1938–47, kept in the U.K. National Archives, have been photographed and digitized. These have provided more than 1,500,000 new observations for this period, and a preliminary analysis has shown significant improvements to the record of climate change in the mid-twentieth century.” Brohan, Philip, Rob Allan, J. Eric Freeman, Anne M. Waple, Dennis Wheeler, Clive Wilkinson, Scott Woodruff, 2009, Bull. Amer. Meteor. Soc., 90, 219–230. [Full text]

Ships’ Logbooks in Climatological Research – Wheeler & Garcia-Herrera (2008) “This paper traces the history of the use of ships’ logbooks in climatological studies from the earliest days of the 17th century to the present day. Although early theories concerning global air circulations by Halley and Hadley were based on information gathered by mariners and recorded in their logbooks, it has only been in the last two decades that interest has returned to this important, but long-overlooked, source of climatic information. Attention is drawn to the many advantages offered by logbooks, in particular the long period of time that they collectively cover, their near-global geographic range, the large number of such documents that have survived, and the degree of detailed and reliable record that they provide. Before the mid-19th century, much of the recorded information is noninstrumental in character but its scientific potential is reflected in the variety of approaches and methods that have been used in its analysis and in the equally wide range of outcomes, from databases to synoptic charts and long-time series indices that have emerged from the most recent research. Attention is also drawn to the benefits to be derived from old and more recent instrumental logbook data. As only a small percentage of the tens of thousands of logbooks that have been preserved have thus far been examined, the potential for yet further development is enormous.” Dennis Wheeler, Ricardo García-Herrera, Annals of the New York Academy of Sciences, Volume 1146, Trends and Directions in Climate Research pages 1–15, December 2008.

Advances in the Use of Historical Marine Climate Data – Kent et al. (2007) A review article discussing also old measurements. Kent, Elizabeth, and Coauthors, 2007, Bull. Amer. Meteor. Soc., 88, 559–564. [Full text]

Ship Logbooks Help Analyze Pre-instrumental Climate – Garcia-Herrera et al. (2006) “The Climatological Database for the World’s Oceans: 1750–1854 (CLIWOC) project, which concluded in 2004, abstracted more than 280,000 daily weather observations from ships’ logbooks from British, Dutch, French, and Spanish naval vessels engaged in imperial business in the eighteenth and nineteenth centuries. These data, now compiled into a database, provide valuable information for the reconstruction of oceanic wind field patterns for this key period that precedes the time in which anthropogenic influences on climate became evident. These reconstructions, in turn, provide evidence for such phenomena as the El Niño–Southern Oscillation and the North Atlantic Oscillation. Of equal importance is the finding that the CLIWOC database—the first coordinated attempt to harness the scientific potential of this resource [García-Herrera et al., 2005]—represents less than 10 percent of the volume of data currently known to reside in this important but hitherto neglected source.” García-Herrera, R., G. P. Können, D. A. Wheeler, M. R. Prieto, P. D. Jones, and F. B. Koek (2006), Eos Trans. AGU, 87(18), doi:10.1029/2006EO180002. [Full text]

Description of the Cliwoc Database – Können & Koek (2005) “We developed a user-friendly database with the 1750–1854 CLIWOC data, which is suitable to be integrated with the ICOADS database. The meteorological content focuses on wind direction and wind speed. The data, stored in the IMMA format, are accessible in numerical and in their original descriptive forms. Apart from alphanumerical meteorological information, the database contains nautical information relevant to historians, and provides access to a considerable number of images of logbook pages. The construction of the database involved a number of difficulties, including language, unit conversion, terminology and zero meridian problems. We believe that this publicly accessible database can give an important contribution to the understanding of low-frequency climate variability, as it extends the current climatological ocean databases by more than a century and probes deep into the pre-industrial era.” G. P. Können and F. B. Koek, Climatic Change, Volume 73, Numbers 1-2, 117-130, DOI: 10.1007/s10584-005-6946-4. [Full text]

CLIWOC: A Climatological Database for the World’s Oceans 1750–1854 – Garcia-Herrera et al. (2005) “We have compiled a meteorological database over the world’s oceans by digitizing data from European ship logbooks of voyages in the period 1750–1854. The observations are carefully reviewed and transformed into quantitative data. The chief contents of the database are wind direction and wind force information, from a period without standardized scales. It is found that the information content of these so-called non-instrumental data is much higher than previously believed. The 105-year CLIWOC database extends existing meteorological world ocean databases like ICOADS back in time by a full century.” R. García-Herrera, G. P. Können, D. A. Wheeler, M. R. Prieto, P. D. Jones and F. B. Koek, 2005, Climatic Change, Volume 73, Numbers 1-2, 1-12, DOI: 10.1007/s10584-005-6952-6. [Full text]

An Examination of the Accuracy and Consistency of Ships’ Logbook Weather Observations and Records – Wheeler (2005) “Logbooks have survived in large numbers and contain notable quantities of climatological information. This paper examines the degree to which these data are reliable and consistently recorded. This is done by comparing the daily observations entered in the logbooks of vessels sailing in convoy, at which times the respective ships’ officers would independently estimate and record the prevailing wind force and wind direction. The results are described using a variety of descriptive summary statistics. In general, wind force records are highly correlated and wind direction differences are relatively small compared with the natural variability of this phenomenon. Wind directions were studied and found to have a bias towards 4-, 8- and 16-point compass readings at the expense of 32-point readings. Corrections were needed to convert the recorded directions, which were made by reference to magnetic north, to their true north equivalents.” Dennis Wheeler, Climatic Change, Volume 73, Numbers 1-2, 97-116, DOI: 10.1007/s10584-005-6950-8. [Full text]

Understanding seventeenth-century ships’ logbooks: An exercise in historical climatology – Wheeler (2004) “The present writer can also confirm the usefulness of logbooks in climatic research, having used them to reconstruct the weather at the time of naval battles in the late eighteenth and early nineteenth centuries; studies have also been carried out to examine the reliability with which shipboard observations can be made and to investigate the vocabulary of ships’ officers of the Georgian Navy. The results have consistently supported the view that eighteenth-century logbooks are a reliable source of information. This paper develops these themes, but in the particular context of the oldest English logbooks, those from the late seventeenth century.” Dennis Wheeler, Journal of Maritime Research, March 2004, ISSN: 1469-1957. [Full text available in the abstract page]

The Weather of the European Atlantic Seaboard During October 1805: An Exercise in Historical Climatology – Wheeler (2001) “Several thousand ships’ logbooks have survived from the eighteenth and nineteenth centuries.They provide a valuable source of climatic information. This paper takes the Battle of Trafalgar as an example of how this source can be used to provide a better knowledge and understanding of weather and climate from those distant times. The reliability of the non-instrumental climatic records of the logbooks is confirmed and a simple statistical measure is used to quantify their degree of consistency. Reconstructions of daily weather patterns are made and a zonal index is calculated to represent the circulation patterns of the region. The movements of pressure systems are plotted and indicate that the zonal index was negative (air pressure increasing from south to north) for most of the month. The storm that followed the battle is identified as one of notable severity. This extreme behaviour is interpreted within the context of longer-term aspects of the contemporary climate.” Dennis Wheeler, Climatic Change, Volume 48, Numbers 2-3, 361-385, DOI: 10.1023/A:1010789509980.

Summer sea ice severity in Hudson Strait, 1751–1870 – Catchpole & Faurer (1983) “Annual indices of sea ice severity in Hudson Strait, for the period 1751 to 1870, are derived from written historical evidence contained in ships’ log-books. These logs were all kept on Hudson’s Bay Company ships sailing from London to the Company’s trading posts. The log-books are homogeneous in nature and this property facilitates their numerical interpretation. The annual indices are subjected to face validity testing which indicates that they may plausibly be accepted as measures of sea ice severity. The results are examined in relation to the presentday behaviour of sea ice in Hudson Strait and they provide evidence that the summer severity of ice conditions is mainly determined by atmospheric circulation conditions.” A. J. W. Catchpole and Marcia-Anne Faurer, Climatic Change, Volume 5, Number 2, 115-139, DOI: 10.1007/BF00141266. [See also Catchpole & Halpin (1987) and Catchpole & Hanuta (1989)]

Past Climates from Unexploited Written Sources – Landsberg (1980) Helmut E. Landsberg, Journal of Interdisciplinary History, Vol. 10, No. 4, History and Climate: Interdisciplinary Explorations (Spring, 1980), pp. 631-642.

Closely related

CLIWOC – Climatological Database for the World’s Oceans 1750-1850

Posted in Climate science | Leave a Comment »

A day in climate science

Posted by Ari Jokimäki on September 23, 2010

I have set up quite a few climate related journals to my RSS feed reader. This morning there were about 40 papers waiting for me. And I did clear the reader yestarday evening. That’s not unpredently large amount, by the way. It is actually quite common to have few tens of new papers over night. So, what kind of papers they published while I was sleeping? Let us see what we have there in order to get a glimpse of a regular day in climate (and related) science:

Atmospheric molecular hydrogen (H2): Observations at the high-altitude site Jungfraujoch, Switzerland – Reimann (Tellus A)
Measurements of H2 from 2005 to 2009. Generally most H2 in May, lowest H2 in November. Seasonal amplitude lower than usually in similar stations, which probably is related to soil H2 sink.

An evaluation study of the DRP-4DVar approach with the Lorenz-96 model – Liu et al. (Tellus A)
I freely admit that I have no good idea what this is about (just read the abstract yourself), but apparently the DRP-4DVar works well. Good for it! 🙂

A comparison of nine monthly air-sea flux products – Smith et al. (International Journal of Climatology)
Studies the air-sea heat flux with several different observational techniques. There seems to be similar latent heat flux patterns in in different techniques but also large differences between them in variability and magnitudes. Regional analysis reveals some possible sources for differences. Important conclusion here is: “This analysis provides an example of how the choice of a flux product, and understanding the strengths and weaknesses of that product, can alter research findings.”

Temperature interpolation based on local information: the example of France – Joly et al. (International Journal of Climatology)
Adresses the problems of interpolation in a heterogenous area be developing local interpolation methods. The abstract is quite technical but I’ll just quote a few sentences at the end: “These results are compared with results from three global interpolation methods: (1) regression, (2) ordinary kriging, and (3) regression with kriging of residuals. We then develop the original results from local interpolation such as mapping of the coefficients of determination and of the parameter estimate related to altitude and to distance to the sea. These developments highlight the processes that dictate the spatial variation of climate.”

Attribution of the river flow growth in the Plata Basin – Doyle & Barros (International Journal of Climatology)
The flow in Plata Basin rivers has grown. This study tries to determine why. The flow in the most rivers had grown due to increased precipitation and/or decreased evaporation due to land use (deforestation for example). The more frequent and intense El Niño events were contributing strongly only in the Middle Paraguay Basin through increased precipitation.

Moisture and heat budgets associated with the South American monsoon system and the Atlantic ITCZ – Garcia & Kayano (International Journal of Climatology)
What the title says. “ITCZ” is “inter-tropical convergence zone”. “Analyses are based on the correlation maps between these terms and the expansion coefficient of the SAMS mode, previously identified.” And the result: “The results here provide observational support to the relationship between the SAMS and the Atlantic ITCZ.”

Biogeochemical weathering under ice: Size matters – Wadham et al. (Global Biogeochemical Cycles)
The basal regions of continental ice sheets are studied from biosphere point of view using chemical datasets. “We show that size of the ice mass is a critical control on the balance of chemical weathering processes and that microbial activity is ubiquitous in driving dissolution.” And: “Our model of chemical weathering dynamics provides important information on subglacial biodiversity and global biogeochemical cycles and may be used to design strategies for the first sampling of Antarctic Subglacial Lakes and other sub-ice sheet environments for the next decade.”

Correction to “Spatial distribution of soil organic carbon in northwest Greenland and underestimates of high Arctic carbon stores” – Burnham & Sletten (Global Biogeochemical Cycles)
Sometimes a research article contains a mistake (which can be big or small) and has to be corrected.

Introduction to special section on the Eruption of Soufrière Hills Volcano, Montserrat, the CALIPSO Project, and the SEA-CALIPSO Arc-Crust Imaging Experiment – Voight & Sparks (Geophysical Research Letters)
For this we only have the title.

Ion outflows and artificial ducts in the topside ionosphere at HAARP – Milikh et al. (Geophysical Research Letters)
Not necessarily very much climate related. Short abstract, though, let’s quote it in full: “New results of the DMSP satellite and HAARP digisonde observations during HF heating at the High-Frequency Active Auroral Program (HAARP) facility are described. For the first time, the DMSP satellites detected significant ion outflows associated with 10–30% density enhancements in the topside ionosphere above the heated region near the magnetic zenith. In addition, coincident high-cadence skymaps from the HAARP digisonde reveal field-aligned upward plasma flows inside the F-peak region. The SAMI2 2 model calculations are in fair agreement with the observations.”

Water ice clouds over the Martian tropics during northern summer – Heavens et al. (Geophysical Research Letters)
Other planets have climates too. Lead author has quite suitable name for this study. 🙂 The conclusion could very well be from Earth: “By underestimating the altitude at which water ice clouds form, models also may underestimate the intensity of the meridional circulation at higher altitudes in the tropics during northern summer.”

Simulations of underwater plumes of dissolved oil in the Gulf of Mexico – Adcroft et al. (Geophysical Research Letters)
Studies relating to the Deepwater Horizon start to emerge. “A simple model of the temperature-dependent biological decay of dissolved oil is embedded in an ocean-climate model and used to simulate underwater plumes of dissolved and suspended oil originating from a point source in the northern Gulf of Mexico, with an upper-bound supply rate estimated from the contemporary analysis of the Deepwater Horizon blowout.” One of their results: “For all plume scenarios, toxic levels of dissolved oil remain confined to the northern Gulf of Mexico, and abate within weeks after the spill stops.”

Semidirect radiative forcing of internal mixed black carbon cloud droplet and its regional climatic effect over China – Zhuang et al. (Journal of Geophysical Research)
A local study on Black Carbon cloud droplet radiative forcing. “…cloud droplets with BC can absorb more solar radiation and reduce their single-scattering albedo (SSA), leading to a positive cloud radiative forcing (SSA forcing) at TOA.” Result: “It is obvious that SSA forcing and its climate responses are weaker compared to BC direct, indirect, and semidirect effects. However, it does have nonnegligible influence on regional climate changes over China.”

Explicit validation of a surface shortwave radiation balance model over snow-covered complex terrain – Helbig et al. (Journal of Geophysical Research)
“A model that computes the surface radiation balance for all sky conditions in complex terrain is presented.” This results in a good agreement with measurements and models.

Regional downscaling for stable water isotopes: A case study of an atmospheric river event – Yoshimura et al. (Journal of Geophysical Research)
Abstract says it best: “In this paper an isotope-incorporated regional model is developed and utilized for simulations of an atmospheric river event that occurred in March 2005. A set of sensitivity experiments and comparisons with observations confirm that the kinetic isotopic exchange between falling droplets and ambient water vapor below the cloud base was mostly responsible for the initial enrichment and subsequent rapid drop of the deuterium abundance in precipitation observed during the event even under humid conditions. According to the budget analysis the increase in isotopic composition during the latter half of the event was primarily due to horizontal advection. The contribution of condensation from different atmospheric heights to the ground precipitation was not reflected in the precipitation isotopes.”

EGATEC: A new high-resolution engineering model of the global atmospheric electric circuit—Currents in the lower atmosphere – Odzimek et al. (Journal of Geophysical Research)
Global atmospheric electric conditions are studied by a model. “The model confirms that the global atmospheric electric activity peaks daily at ∼21 UT. The diurnal variation of the ionospheric potential and the global current have a maximum at 12 and 21–24 UT in July and at 9 and 21 UT in December, and a global minimum at 3–6 UT independent of season. About 80% of the current is generated by thunderstorm convective clouds and 20% by mid-level rain clouds.”

Insights into an Asian dust event sweeping Beijing during April 2006: Particle chemical composition, boundary layer structure, and radiative forcing – Wang et al. (Journal of Geophysical Research)
Dust effect to local climate is studied. ” The enhancement of dust loadings in the atmosphere of Beijing during the dust event resulted in a cooling effect by –62.0 W m−2 radiative forcing at the top of atmosphere.”

Temporal variations of atomic oxygen in the upper mesosphere from SABER – Smith et al. (Journal of Geophysical Research)
Measurements of oxygen in the high atmosphere. It varies a lot during the day and there’s also a seasonal variation.

Correction to “An aircraft-based upper troposphere lower stratosphere O3, CO, and H2O climatology for the Northern Hemisphere” – Tilmes et al. (Journal of Geophysical Research)
Another correction? Well, it really is not that rare to find some mistakes in published research articles. Researchers are human and these things happen.

A comparison of early Paleogene export productivity and organic carbon burial flux for Maud Rise, Weddell Sea, and Kerguelen Plateau, south Indian Ocean – Faul & Delaney (Paleoceanography)
Biological productivity in oceans in the past is being studied here. “In both regions, export productivity, organic C burial flux, and the fraction of organic C buried relative to export productivity decreased from the Paleocene/early Eocene to the middle Eocene. A shift is indicated from an early Paleogene two-gyre circulation in which nutrients were not efficiently recycled to the surface via upwelling in these regions, to a circulation more like the present day with efficient recycling of nutrients to the surface ocean. Export productivity was enhanced for Kerguelen Plateau relative to Maud Rise throughout the early Paleogene, possibly due to internal waves generated by the plateau regardless of gyre circulation.”

Short term variations of tracer transit speed on alpine glaciers – Werder et al. (The cryosphere)
The daily dynamics of a glacier in Schwitzerland is being measured and modelled.

Observations and modelling of the wave mode evolution of an impulse-driven 3 mHz ULF wave – Borderick et al. (Annales Geophysicae)
Ultra Low Frequency wave event is being studied. If I interpret correctly, the wave started from solar wind changes and then advanced in our atmosphere in 1998.

Empirically modelled Pc3 activity based on solar wind parameters – Heilig et al. (Annales Geophysicae)
This study is also about solar wind and some pulsations it causes.

Neogene stratigraphy of Taylor Valley, Transantarctic Mountains, Antarctica: Evidence for climate dynamism and a vegetated Early Pliocene coastline of McMurdo Sound – Fielding et al. (Global and Planetary Change)
A valley floor in Antarctica is being studied for finding resolution to some past climate problems. Studied time period reaches millions of years into the past.

3-D Reconstruction of Active Regions with STEREO – Aschwanden & Wülser (Journal of Atmospheric and Solar-Terrestrial Physics)
A study of active regions in solar corona.

(As I’m writing this, another 18 papers popped up from AMS. I’m not going through them here…)

The brazilian decimetric array and space weather – Sawant et al. (Journal of Atmospheric and Solar-Terrestrial Physics)
Another Sun related study.

Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the Geomagnetic Polarity and Astronomical Time Scale – Wade et al. (Earth-Science Reviews)
Review articles are always interesting, if one manages to find their full text. This one has rather well-constrained subject area, as you can see from the title.

The carbon balance of tropical forest regions, 1990–2005 – Malhi (Current Opinion in Environmental Sustainability)
The carbon sink/source situations of different forest regions is being estimated here. (By the way, I find the title of the journal rather poor for a scientific journal.)

The potential of New Zealand kauri (Agathis australis) for testing the synchronicity of abrupt climate change during the Last Glacial Interval (60,000–11,700 years ago) – Turney et al. (Quaternary Science Reviews)
Timings of past climate changes determined from radiocarbon dated fossil evidence.

Paleoceanographic Changes on the Farallon Escarpment Off Central California During the Last 16,000 Years – McGann (Quaternary International)
Past climate information is being extracted from marine proxies.

Inferring Precipitation-Anomaly Gradients from Tree Rings – Meko et al. (Quaternary International)
Precipitation is one thing tree rings can indicate – precipitation during recent centuries is being studied here.

Physico-chemical characterization and cytotoxicity of ambient coarse, fine, and ultrafine particulate matters in Shanghai atmosphere – Lu et al. (Atmospheric Environment)
Measurements of air pollution in Sanghai atmosphere.

Impact of emission control strategy on NO2 in urban areas of Korea – Shon & Kim (Atmospheric Environment)
Measurements of nitrogen dioxide in Korea atmosphere.

Elemental mercury in coastal seawater of Yellow Sea, China: Temporal variation and air-sea exchange – Ci et al. (Atmospheric Environment)
Measurements of mercury in Yellow Sea.

Effect of urbanization on lightning over four metropolitan cities of India – Lal & Pawar (Atmospheric Environment)
Urbanization might affect the convection and lightning. “Our analysis shows that both the inland cities show considerable enhancement, where as both the coastal cities do not show enhancement in lightning, in the last 8 years.”

Ichnostratigraphy of middle Cenozoic Coprinisphaera from central Patagonia: Insights into the evolution of dung beetles, herbivores and grass-dominated habitats – Sanchez et al. (Palaeogeography, Palaeoclimatology, Palaeoecology)
The evolution of dung beetles.

Attributes of the wood-boring trace fossil Asthenopodichnium in the Late Cretaceous Wahweap Formation, Utah, USA – Moran et al. (Palaeogeography, Palaeoclimatology, Palaeoecology)
Another biological paper.

Doppler radar observations of mesovortices within a cool-season tornadic squall line over the UK – Clark et al. (Atmospheric Research)
Measurements of a tornado.

As you can see, my comments got shorter towards the end. The sheer volume of scientific research just outweighted me. Not all the papers were about climate due to some journals having rather broad subject areas. At any case, lot of scientific research is being done in climate related fields every day. 29 new papers appeared to my reader while I was writing this. Perhaps a small break before digging into them…

Posted in Climate science | Leave a Comment »

Deep ocean heat

Posted by Ari Jokimäki on September 20, 2010

Newly published research on deep ocean temperatures has found warming during 1990’s and 2000’s. The observed warming is generally stronger in the south and it appears that a large part of the heat in the deep ocean is transferred through the Southern Ocean. The finding is important for global energy budget and for global sea level estimates.

Cross-section from one measurement route. Different colors represent the temperature change.

Earth’s climate has warmed during recent decades. This is most likely due to top of atmosphere energy imbalance caused by the increases in the greenhouse gases in the atmosphere. About 80% of the energy from the imbalance has gone to heating the oceans due to their large heat capacity.

The slow reaction of the oceans to warming also slows the reaction of the surface temperature to the forcing. Even if we would keep greenhouse gases unchanged, the oceans would keep warming for centuries. The amount of heat flux to the deep ocean affects directly the climate sensitivity. This heat flux varies considerably between different models. The insufficient knowledge of the heat flux to the deep ocean might be biggest factor causing variation between different model projections. Because of this, it is important to gain better knowledge on the deep ocean heat flux.

The deep ocean water is ventilated in high latitudes when dense water sinks to the bottom. In North Atlantic it happens in Nordic and Labrador Seas and in Antarctic it happens in Weddell Sea, Ross Sea, and Adelie Coast. There is some previous research showing that deep waters near Antarctic have warmed. Also, nearer the surface the Southern Ocean apparently has warmed faster than world oceans in average.

Sarah Purkey and Gregory Johnson have studied the deep ocean temperatures globally, but concentrating on the role of the Southern Ocean in the matter. Globally deep waters below 4000m were analysed and in Southern Ocean the analysis concentrated to the depths of 1000-4000m.

The measurements used in this study cover the time span from 1990’s to february 2010. Measurements are not evenly distributed, but there are some measurement routes (28 of them were used in this study) that have been measured every now and then from ships. The measurements in these routes cover rather well the whole route both horizontally and vertically, so the measurements form a kind of temperature cross-section along that route (see the figure above for an example). The temporal span between the measurements is for some routes rather large. For example, one route was measured in 1981 and next time in 2010. On the other hand in one route the shortest time span between measurements was three years.

The warming was calculated from the measurements for 24 ocean basins. Additionally the warming was calculated for the Southern Ocean as a whole. For each basin a heat flux was calculated based on the warming in the basin in question. Also a global estimate was derived for the heat flux. Throughout the study the sea level rise from the calculated warming were also derived, but here we’ll concentrate on the warming and heat flux results.

Purkey and Johnson say this about their depth selections in this study:

In many of the basins north of the SAF, warming trends on pressure levels become significantly different from zero at 97.5% confidence below around 4000 m, making this pressure level a natural division for this study. In many of the repeat sections within the Southern Ocean consistently strong warming extends higher in the water column south of the SAF. Hence we also analyze contributions to SLR and heat gain from warming found from 1000–4000 m south of the SAF.

The effect of the heat transferred to deep ocean in the Southern Ocean shows well in the Atlantic, Indian, and Pacific oceans. General trend is that more warming is found towards the south and less warming towards the north. Of all basins few show cooling but only in one the cooling is statistically significant. Most basins show statistically significant warming.

In the global analysis, the effect of Southern Ocean is strong. Between the depths of 1000m and 4000m almost all the warming has happened in the Southern Ocean. Here are their global heat flux results:

The warming below 4000 m is found to contribute 0.027 (±0.009) W m–2. The Southern Ocean between 1000–4000 m contributes an additional 0.068 (±0.062) W m–2, for a total of 0.095 (±0.062) W m–1 to the global heat budget (Table 1).

(I see that there is a typo in the units of the 0.095 number, it should also be W m–2, not W m–1.)

In order to compare their results to other studies, they also calculated heat flux values below 2000m and below 3000m. Deepest earlier global studies have extended to 3000m and currently used Argo reaches depths of 2000m. The total result in this new study for all three analysis (below 2000m, 3000m, and 4000m) is about 0.1 W m–2. They say:

From 1993 to 2008 the warming of the upper 700 m of the global ocean has been reported as equivalent to a heat flux of 0.64 (±0.11) W m–2 applied over the Earth’s surface area (Lyman et al. 2010). Here, we showed the heat uptake by AABW contributes about another 0.10 W m–2 to the global heat budget. Thus, including the global abyssal ocean and deep Southern Ocean in the global ocean heat uptake budget could increase the estimated upper ocean heat uptake over the last decade or so by roughly 16%.

This study seems to suggest that in the warming of the deep world ocean the Southern Ocean plays a remarkably large role. The warming found in this study has been poorly known before, so this study seems to make the ocean heat budget, and even the whole Earth heat budget, more accurate.

Source: Sarah G. Purkey and Gregory C. Johnson, Warming of Global Abyssal and Deep Southern Ocean Waters Between the 1990s and 2000s: Contributions to Global Heat and Sea Level Rise Budgets, Journal of Climate 2010, doi: 10.1175/2010JCLI3682.1. [abstract, full text]

Posted in Climate science | 1 Comment »

NODC ocean heat content

Posted by Ari Jokimäki on September 13, 2010

For some years there has been claims that oceans have cooled after 2003. There has been some flaws identified from the measuring equipment. It has been shown that those flaws caused the original appearance of cooling so the latest scientific research doesn’t seem to give support to the claims of cooling in recent years. The widely used Argo-network is under corrections currently and the situation should be more clear in near future. However, the claims of cooling still continue. I’ll take a brief look at the issue.

The cooling that went away

By now this is quite well known story, so I’ll descibe it just briefly. In 2006, Lyman et al. reported that they had found cooling from the world’s oceans after 2003. This of course generated claims among climate change deniers that global warming has stopped even though the authors of the study didn’t thought so. In 2007, Josh Willis, one of the authors of the original study found out that the cooling they had found didn’t seem to be real. There were problems with some Argo floats and expendable bathythermographs (XBT’s) which both were causing an apparent cooling effect to the data. When the bad Argo floats were excluded and XBT-problem was corrected for, the cooling was no more. [whole story here]

There is also a study from von Schuckmann et al. (2009) suggesting that oceans have actually warmed after 2003 (or 2004 as the current round of claims seem to be). More references on ocean temperatures and on this ocean heat content problem are given in the end of this article.

NODC – the go to place for recent claims

Despite the situation described above, the claims of ocean cooling continue. In some online discussions and blogs I have seen NOAA’s National Oceanographic Data Center (NODC) being used as the source showing that oceans have cooled after 2003 or 2004. As it’s NOAA website, it has authority and therefore seems to be credible reference for backing up the claims. I’m not going to argue that NODC is not credible resource but I’m going to show why it’s not currently the best place to study the issue.

The data in NODC is from their world ocean database, and it is described here. The chapter 6.6 there discusses data problems. Let’s see what it says about the problem Willis identified:

A large number of SOLO floats with FSI CTD packages deployed in the Atlantic Ocean between 2003 and 2006 were found to have a pressure offset problem due to a software error. This error caused pressures to be paired with the temperature measurements from the next lower level, creating the illusion of a cooling ocean. Once the problem was found, a list of such floats was compiled. An effort was made to correct the problem, successful in some floats, not in others. All data from all these problem floats are included in WOD09.

(Bolding mine.) So, this problem causes apparent cooling and the data from problem floats is included. Another problem is also described there:

More recently, in early 2009, a problem with the Druck pressure sensor has been found (J. Willis and D. Roemmich, minutes of 10th meeting of International Argo Steering Team). This problem causes pressure sensor drift after deployment. Deployment of new floats was halted temporarily, until the pressure sensor design could be altered. Already deployed APEX floats are being monitored closely for sensor drift. The full extent of this problem is not yet apparent.

It seems that there are even more problematic Argo floats included in the NODC data. For this one it is not clear to which direction the drift effects.

So clearly, for the last few years the NODC data might not be the most trustworthy. For Argo data, it is best to consult Argo website. There is a section called “>”Advice on Pressure Biases in the Argo Data Set” (UPDATE: direct linking to the page doesn’t seem to work but it can be found through “Argo Information Centre” – additionally, here’s an alternative link from “Argo data management” website giving the same text) that says:

A part of the global Argo data are subject to biases in reported pressures. These biases are usually less than 5db, but occasionally can be larger (> 20db). These bias errors are being steadily removed by the reprocessing of historical Argo data. We expect that by the end of 2010 these errors will be removed from the global Argo data set in both the delayed-mode and real-time data.

So, it seems that we’ll find out more about the ocean temperatures of last few years in next year when they have finished the corrections. NODC will undoubtedly update their data too then. Meanwhile I expect to see lot more claims about oceans cooling after this year or that year, and I doubt it will end even if they would publish corrected Argo dataset showing warming from 2003.


Lyman, J. M., J. K. Willis, and G. C. Johnson (2006), Recent cooling of the upper ocean, Geophys. Res. Lett., 33, L18604, doi:10.1029/2006GL027033. [abstract, full text]

von Schuckmann, K., F. Gaillard, and P.-Y. Le Traon (2009), Global hydrographic variability patterns during 2003–2008, J. Geophys. Res., 114, C09007, doi:10.1029/2008JC005237. [abstract, full text]

Additional information

– More information on ocean heat content problems after 2003 (see especially Willis et al., 2008 and Levitus et al., 2009) and ocean temperatures in general can be found from my list of papers on ocean temperature.
Does ocean cooling prove global warming has ended? – John Cook, Skeptical Science
Pielke Sr and scientific equivocation: don’t beat around the bush, Roger – gpwayne, Skeptical Science

Posted in Climate claims | 10 Comments »

Papers on irrigation and climate

Posted by Ari Jokimäki on September 2, 2010

This is a list of papers on the irrigation effects to climate. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Effects of irrigation on global climate during the 20th century – Puma & Cook (2010) “Various studies have documented the effects of modern-day irrigation on regional and global climate, but none, to date, have considered the time-varying impact of steadily increasing irrigation rates on climate during the 20th century. We investigate the impacts of observed irrigation changes over this century with two ensemble simulations using an atmosphere general circulation model. Both ensembles are forced with transient climate forcings and observed sea surface temperatures from 1902 to 2000; one ensemble includes irrigation specified by a time-varying data set of irrigation water withdrawals. Early in the century, irrigation is primarily localized over southern and eastern Asia, leading to significant cooling in boreal summer (June–August) over these regions. This cooling spreads and intensifies by century’s end, following the rapid expansion of irrigation over North America, Europe, and Asia. Irrigation also leads to boreal winter (December–February) warming over parts of North America and Asia in the latter part of the century, due to enhanced downward longwave fluxes from increased near-surface humidity. Precipitation increases occur primarily downwind of the major irrigation areas, although precipitation in parts of India decreases due to a weaker summer monsoon. Irrigation begins to significantly reduce temperatures and temperature trends during boreal summer over the Northern Hemisphere midlatitudes and tropics beginning around 1950; significant increases in precipitation occur in these same latitude bands. These trends reveal the varying importance of irrigation-climate interactions and suggest that future climate studies should account for irrigation, especially in regions with unsustainable irrigation resources.” Puma, M. J., and B. I. Cook (2010), J. Geophys. Res., 115, D16120, doi:10.1029/2010JD014122. [Full text]

Effects of global irrigation on the near-surface climate – Sacks et al. (2009) “Irrigation delivers about 2,600 km3 of water to the land surface each year, or about 2% of annual precipitation over land. We investigated how this redistribution of water affects the global climate, focusing on its effects on near-surface temperatures. Using the Community Atmosphere Model (CAM) coupled to the Community Land Model (CLM), we compared global simulations with and without irrigation. To approximate actual irrigation amounts and locations as closely as possible, we used national-level census data of agricultural water withdrawals, disaggregated with maps of croplands, areas equipped for irrigation, and climatic water deficits. We further investigated the sensitivity of our results to the timing and spatial extent of irrigation. We found that irrigation alters climate significantly in some regions, but has a negligible effect on global-average near-surface temperatures. Irrigation cooled the northern mid-latitudes; the central and southeast United States, portions of southeast China and portions of southern and southeast Asia cooled by ~0.5 K averaged over the year. Much of northern Canada, on the other hand, warmed by ~1 K. The cooling effect of irrigation seemed to be dominated by indirect effects like an increase in cloud cover, rather than by direct evaporative cooling. The regional effects of irrigation were as large as those seen in previous studies of land cover change, showing that changes in land management can be as important as changes in land cover in terms of their climatic effects. Our results were sensitive to the area of irrigation, but were insensitive to the details of irrigation timing and delivery.” William J. Sacks, Benjamin I. Cook, Nikolaus Buenning, Samuel Levis and Joseph H. Helkowski, Climate Dynamics, Volume 33, Numbers 2-3, 159-175, DOI: 10.1007/s00382-008-0445-z. [Full text]

The impact of agricultural intensification and irrigation on land–atmosphere interactions and Indian monsoon precipitation — A mesoscale modeling perspective – Douglas et al. (2009) “Using the Regional Atmospheric Modeling System (RAMS) we show that agricultural intensification and irrigation can modify the surface moisture and energy distribution, which alters the boundary layer and regional convergence, mesoscale convection, and precipitation patterns over the Indian monsoon region. Four experiments were conducted to simulate a rain event from 16 to 20 July 2002 over the Indian region: (i) a control with Global Land Cover land use and observed Normalized Difference Vegetation Index, (ii) an irrigated crop scenario, (iii) a non-irrigated crop scenario, and (iv) a scenario for potential (natural) vegetation. Results indicate that even under active monsoon conditions, the simulated surface energy and moisture flux over the Indian monsoon region are sensitive to the irrigation intensity and this effect is more pronounced than the impact of land use change from the potential vegetation to the agricultural landscape. When model outputs were averaged over the south Asia model domain, a statistically significant decrease in mean sensible heat flux between the potential vegetation and the irrigated agriculture scenarios of 11.7 Wm− 2 was found. Changes in latent heat fluxes ranging from − 20.6 to + 37.2 Wm− 2 (− 26% to + 24%) and sensible heat fluxes ranging − 87.5 to + 4.4 Wm− 2 (− 77% to + 8%) fluxes were found when model outputs were averaged over Indian states. Decreases in sensible heat in the states of Punjab (87.5 Wm− 2 or 77%) and Haryana (65.3 Wm− 2 or 85%) were found to be statistically significant at the 95% confidence level. Irrigation increased the regional moisture flux which in turn modified the convective available potential energy. This caused a reduction in the surface temperature and led to a modified regional circulation pattern and changes in mesoscale precipitation. These agricultural changes, including irrigation modify the mesoscale convection and rain patterns in the Indian monsoon region. These regional changes in land use need to be considered in improved weather forecasting as well as multi-decadal climate variability and change assessments.” E.M. Douglas, A. Beltrán-Przekurat, D. Niyogi, R.A. Pielke Sr. and C.J. Vörösmarty, Global and Planetary Change, Volume 67, Issues 1-2, May 2009, Pages 117-128, doi:10.1016/j.gloplacha.2008.12.007. [Full text]

Impact of irrigation on the South Asian summer monsoon – Saeed et al. (2009) “The Indian subcontinent is one of the most intensely irrigated regions of the world and state of the art climate models do not account for the representation of irrigation. Sensitivity studies with the regional climate model REMO show distinct feedbacks between the simulation of the monsoon circulation with and without irrigation processes. We find that the temperature and mean sea level pressure, where the standard REMO version without irrigation shows a significant bias over the areas of Indus basin, is highly sensitive to the water used for irrigation. In our sensitivity test we find that removal of this bias has caused less differential heating between land and sea masses. This in turns reduces the westerlies entering into land from Arabian Sea, hence creating conditions favorable for currents from Bay of Bengal to intrude deep into western India and Pakistan that have been unrealistically suppressed before. We conclude that the representation of irrigated water is unavoidable for realistic simulation of south Asian summer monsoon and its response under global warming.” Saeed, F., S. Hagemann, and D. Jacob (2009), Geophys. Res. Lett., 36, L20711, doi:10.1029/2009GL040625.

Regional Differences in the Influence of Irrigation on Climate – Lobell et al. (2009) “A global climate model experiment is performed to evaluate the effect of irrigation on temperatures in several major irrigated regions of the world. The Community Atmosphere Model, version 3.3, was modified to represent irrigation for the fraction of each grid cell equipped for irrigation according to datasets from the Food and Agriculture Organization. Results indicate substantial regional differences in the magnitude of irrigation-induced cooling, which are attributed to three primary factors: differences in extent of the irrigated area, differences in the simulated soil moisture for the control simulation (without irrigation), and the nature of cloud response to irrigation. The last factor appeared especially important for the dry season in India, although further analysis with other models and observations are needed to verify this feedback. Comparison with observed temperatures revealed substantially lower biases in several regions for the simulation with irrigation than for the control, suggesting that the lack of irrigation may be an important component of temperature bias in this model or that irrigation compensates for other biases. The results of this study should help to translate the results from past regional efforts, which have largely focused on the United States, to regions in the developing world that in many cases continue to experience significant expansion of irrigated land.” Lobell, David, Govindasamy Bala, Art Mirin, Thomas Phillips, Reed Maxwell, Doug Rotman, 2009: Regional Differences in the Influence of Irrigation on Climate. J. Climate, 22, 2248–2255, doi: 10.1175/2008JCLI2703.1. [Full text]

Effects of irrigation and vegetation activity on early Indian summer monsoon variability – Lee et al. (2009) “We examined the effects of land cover change over the Indian subcontinent during pre-monsoon season (March, April, and May—MAM) on early Indian summer monsoon (ISM) rainfall using observed Normalized Difference Vegetation Index (NDVI) and July precipitation for the period of 1982–2003. MAM NDVI anomalies have increased in the Indian subcontinent and the increases are significantly correlated with increases in the irrigated area, not preceding rainfall. July rainfall significantly decreased in central and southern India, and the decrease is statistically related to the increase in the preceding MAM NDVI anomalies. Decreased July surface temperature in the Indian subcontinent (an expected result of increased evapotranspiration due to irrigation and increased vegetation) leads to a reduced land–sea thermal contrast, which is one of the factors driving the monsoon, and therefore weakens the monsoon circulation. A weak early ISM appears to be at least partially a result of irrigation and the resultant increased vegetation and crop activity prior to the monsoon.” Eungul Lee, Thomas N. Chase, Balaji Rajagopalan, Roger G. Barry, Trent W. Biggs, Peter J. Lawrence, International Journal of Climatology, Volume 29, Issue 4, pages 573–581, 30 March 2009, DOI: 10.1002/joc.1721. [Full text]

The Role of Irrigation Expansion in Past and Future Temperature Trends – Lobell et al. (2008) “Expansion of irrigated land can cause local cooling of daytime temperatures by up to several degrees Celsius. Here the authors compare the expected cooling associated with rates of irrigation expansion in developing countries for historical (1961–2000) and future (2000–30) periods with climate model predictions of temperature changes from other forcings, most notably increased atmospheric greenhouse gas levels, over the same periods. Indirect effects of irrigation on climate, via methane production in paddy rice systems, were not considered. In regions of rapid irrigation growth over the past 40 yr, such as northwestern India and northeastern China, irrigation’s expected cooling effects have been similar in magnitude to climate model predictions of warming from greenhouse gases. A masking effect of irrigation can therefore explain the lack of significant increases in observed growing season maximum temperatures in these regions and the apparent discrepancy between observations and climate model simulations. Projections of irrigation for 2000–30 indicate a slowing of expansion rates, and therefore cooling from irrigation expansion over this time period will very likely be smaller than in recent decades. At the same time, warming from greenhouse gases will likely accelerate, and irrigation will play a relatively smaller role in agricultural climate trends. In many irrigated regions, therefore, temperature projections from climate models, which generally ignore irrigation, may be more accurate in predicting future temperature trends than their performance in reproducing past observed trends in irrigated regions would suggest.” Lobell, David B., Céline Bonfils, Jean-Marc Faurès, 2008, Earth Interact., 12, 1–11, doi: 10.1175/2007EI241.1.

The Effect of Irrigation on Regional Temperatures: A Spatial and Temporal Analysis of Trends in California, 1934–2002 – Lobell & Bonfils (2008) “The response of air temperatures to widespread irrigation may represent an important component of past and/or future regional climate changes. The quantitative impact of irrigation on daily minimum and maximum temperatures (Tmin and Tmax) in California was estimated using historical time series of county irrigated areas from agricultural censuses and daily climate observations from the U.S. Historical Climatology Network. Regression analysis of temperature and irrigation changes for stations within irrigated areas revealed a highly significant (p < 0.01) effect of irrigation on June–August average Tmax, with no significant effects on Tmin (p > 0.3). The mean estimate for Tmax was a substantial 5.0°C cooling for 100% irrigation cover, with a 95% confidence interval of 2.0°–7.9°C. As a result of small changes in Tmin compared to Tmax, the diurnal temperature range (DTR) decreased significantly in both spring and summer months. Effects on percentiles of Tmax within summer months were not statistically distinguishable, suggesting that irrigation’s impact is similar on warm and cool days in California. Finally, average trends for stations within irrigated areas were compared to those from nonirrigated stations to evaluate the robustness of conclusions from previous studies based on pairwise comparisons of irrigated and nonirrigated sites. Stronger negative Tmax trends in irrigated sites were consistent with the inferred effects of irrigation on Tmax. However, Tmin trends were significantly more positive for nonirrigated sites despite the apparent lack of effects of irrigation on Tmin from the analysis within irrigated sites. Together with evidence of increases in urban areas near nonirrigated sites, this finding indicates an important effect of urbanization on Tmin in California that had previously been attributed to irrigation. The results therefore demonstrate that simple pairwise comparisons between stations in a complex region such as California can lead to misinterpretation of historical climate trends and the effects of land use changes.” Lobell, David B., Céline Bonfils, 2008, J. Climate, 21, 2063–2071, doi: 10.1175/2007JCLI1755.1. [Full text]

Empirical evidence for a recent slowdown in irrigation-induced cooling – Bonfils & Lobell (2007) “Understanding the influence of past land use changes on climate is needed to improve regional projections of future climate change and inform debates about the tradeoffs associated with land use decisions. The effects of rapid expansion of irrigated area in the 20th century has remained unclear relative to other land use changes, such as urbanization, that affected a similar total land area. Using spatial and temporal variations in temperature and irrigation extent observed in California, we show that irrigation expansion has had a large cooling effect on summertime average daily daytime temperatures (−0.14°C to −0.25°C per decade), which corresponds to an estimated cooling of −1.8°C to −3.2°C since the introduction of irrigation practices. Irrigation has negligible effects on nighttime temperatures, leading to a net cooling effect of irrigation on climate (−0.06°C to −0.19°C per decade). Stabilization of irrigated area has occurred in California since 1980 and is expected in the near future for many irrigated regions. The suppression of past human-induced greenhouse warming by increased irrigation is therefore likely to slow in the future, and a potential decrease in irrigation may even contribute to a more rapid warming. Changes in irrigation alone are not expected to influence broad-scale temperatures, but they may introduce large uncertainties in climate projections for irrigated agricultural regions, which provide ≈40% of global food production.” Céline Bonfils and David Lobell, PNAS August 21, 2007 vol. 104 no. 34 13582-13587, doi: 10.1073/pnas.0700144104. [Full text]

Irrigation cooling effect: Regional climate forcing by land-use change – Kueppers et al. (2007) “Regional detection of a greenhouse warming signal relies on extensive, long-term measurements of temperature. The potentially confounding impact of land-cover and land-use change on trends in temperature records has mostly focused on the influence of urban heat islands. Here we use a regional climate model to show that a regional irrigation cooling effect (ICE) exists, opposite in sign to urban heat island effects. The magnitude of the ICE has strong seasonal variability, causing large dry-season decreases in monthly mean and maximum temperatures, but little change in rainy-season temperatures. Our model produced a negligible effect on monthly minimum temperature. In California, the modeled regional ICE is of similar magnitude, but opposite sign, to predictions for future regional warming from greenhouse gases. Given our results for California and the global importance of irrigated agriculture, past expansion of irrigated land has likely affected observations of surface temperature, potentially masking the full warming signal caused by greenhouse gas increases.” Kueppers, L. M., M. A. Snyder, and L. C. Sloan (2007), Geophys. Res. Lett., 34, L03703, doi:10.1029/2006GL028679.

Effects of irrigation on the water and energy balances of the Colorado and Mekong river basins – Haddeland et al. (2006) “An irrigation scheme, based on simulated soil moisture deficit, has been included in the variable infiltration capacity macroscale hydrologic model. Water withdrawals are taken from the nearest river, or, in periods of water scarcity, from reservoirs. Alternatively, water can be assumed freely available. The irrigation scheme successfully simulates crop consumptive water use in large river basins. In general, irrigation leads to decreased streamflow and increased evapotranspiration. The locally significant increases in evapotranspiration (or latent heat) results in lower surface temperatures, and hence decreased sensible heat flux. Simulations performed for a 20-year period for the Colorado and Mekong river basins indicate irrigation water requirements of 10 and 13.4 km3 year−1, respectively, corresponding to streamflow decreases of 37 and 2.3%. The increase in latent heat flux is accompanied by a decrease in annual averaged surface temperatures of 0.04 °C for both river basins. The maximum simulated increase in latent heat flux averaged over the three peak irrigation months for one grid cell is 63 W m−2, where surface temperature decreases 2.1 °C. Simulated actual water use is somewhat less than simulated irrigation water requirements; 8.3 and 12.4 km3 year−1 for the Colorado and Mekong river basin, respectively.” Ingjerd Haddeland, Dennis P. Lettenmaier, and Thomas Skaugen, Journal of Hydrology, Volume 324, Issues 1-4, 15 June 2006, Pages 210-223, doi:10.1016/j.jhydrol.2005.09.028.

Direct human influence of irrigation on atmospheric water vapour and climate – Boucher et al. (2004) “Human activity increases the atmospheric water vapour content in an indirect way through climate feedbacks. We conclude here that human activity also has a direct influence on the water vapour concentration through irrigation. In idealised simulations we estimate a global mean radiative forcing in the range of 0.03 to +0.1 Wm–2 due to the increase in water vapour from irrigation. However, because the water cycle is embodied in the climate system, irrigation has a more complex influence on climate. We also simulate a change in the temperature vertical profile and a large surface cooling of up to 0.8 K over irrigated land areas. This is of opposite sign than expected from the radiative forcing alone, and this questions the applicability of the radiative forcing concept for such a climatic perturbation. Further, this study shows stronger links than previously recognised between climate change and freshwater scarcity which are environmental issues of paramount importance for the twenty first century.” O. Boucher, G. Myhre and A. Myhre, Climate Dynamics, Volume 22, Numbers 6-7, 597-603, DOI: 10.1007/s00382-004-0402-4. [Full text]

Impact of Irrigation on Midsummer Surface Fluxes and Temperature under Dry Synoptic Conditions: A Regional Atmospheric Model Study of the U.S. High Plains – Adegoke et al. (2003) “The impact of irrigation on the surface energy budget in the U.S. high plains is investigated. Four 15-day simulations were conducted: one using a 1997 satellite-derived estimate of farmland acreage under irrigation in Nebraska (control run), two using the Olson Global Ecosystem (OGE) vegetation dataset (OGE wet run and OGE dry run), and the fourth with the Kuchler vegetation dataset (natural vegetation run) as lower boundary conditions in the Colorado State University Regional Atmospheric Modeling System (RAMS). In the control and OGE wet simulations, the topsoil in the irrigated locations, up to a depth of 0.2 m, was saturated at 0000 UTC each day for the duration of the experiment (1–15 July 1997). In the other two runs, the soil was allowed to dry out, except when replenished naturally by rainfall. Identical observed atmospheric conditions were used along the lateral boundary in all four cases. The area-averaged model-derived quantities for the grid centered over Nebraska indicate significant differences in the surface energy fluxes between the control (irrigated) and the “dry” simulations. For example, a 36% increase in the surface latent heat flux and a 2.6°C elevation in dewpoint temperature between the control run and the OGE dry run is shown. Surface sensible heat flux of the control run was 15% less and the near-ground temperature was 1.2°C less compared to the OGE dry run. The differences between the control run and the natural vegetation run were similar but amplified compared to the control run–OGE dry run comparisons. Results of statistical analyses of long-term (1921–2000) surface temperature data from two sites representing locations of extensive irrigated and nonirrigated land uses appear to support model results presented herein of an irrigation-related cooling in surface temperature. Growing season monthly mean and monthly mean maximum temperature data for the irrigated site indicate a steady decreasing trend in contrast to an increasing trend at the nonirrigated site.” Adegoke, Jimmy O., Roger A. Pielke, J. Eastman, Rezaul Mahmood, Kenneth G. Hubbard, 2003, Mon. Wea. Rev., 131, 556–564. [Full text]

Irrigation-Induced Rainfall and the Great Plains – Moore & Rojstaczer (2001) “The post–World War II increase in irrigation in the Great Plains represents the largest human-induced hydrologic impact in North America. Drawn primarily from the High Plains aquifer, water applied as irrigation in the region amounts to billions of cubic meters (2 × 1010 m3 in 1990) annually and is applied to more than 60 000 km2 of farmland. Following studies by Schickedanz and by Barnston and Schickedanz, empirical orthogonal functions and precipitation magnitude comparisons were employed to examine trends in precipitation over the region and to determine if this enormous addition of irrigation water to the surface has had a measurable influence on precipitation during the summer months of June, July, and August. The Barnston and Schickedanz study observed a transition from unirrigated to heavily irrigated conditions; in contrast, this examination focused on a more recent period during which irrigation took place throughout the time of interest. Loading patterns and temporal precipitation trends for 1950–97 show, at best, slight evidence that irrigation induces rainfall. The most prominent evidence of an irrigation effect is found in the Texas Panhandle for 1950–82. If irrigation-induced rainfall exists, its impact is only minor relative to the natural determining factors of plains climate. It also is possible that the chief influence of irrigation on rainfall may take place at some threshold magnitude of irrigation (not explored in this study) that already had been exceeded by 1950.” Moore, Nathan, Stuart Rojstaczer, 2001, J. Appl. Meteor., 40, 1297–1309, doi: 10.1175/1520-0450(2001)0402.0.CO;2. [Full text]

On the Potential Impact of Irrigated Areas in North America on Summer Rainfall Caused by Large-Scale Systems – Segal et al. (1998) “The potential impact of the increase in irrigated areas in North America during the past 100 years on summer rainfall associated with medium- to large-scale precipitation systems is evaluated conceptually and by several illustrative numerical model simulations. The model results for the simulated cases suggest a tendency toward some increase in the continental-average rainfall for the present irrigation conditions compared with those of past irrigation. The maximum increase obtained for several studied cases of 6-day duration each was 1.7%. Rainfall increases typically occur in the location of existing rainfall areas, and the main effect of irrigation is to redistribute rainfall in those preexisting precipitation regions.” Segal, M., Z. Pan, R. W. Turner, E. S. Takle, 1998, J. Appl. Meteor., 37, 325–331, doi: 10.1175/1520-0450-37.3.325. [Full text]

The Effect of Irrigation on Premonsoon Season Precipitation over South West Bengal, India – Lohar & Pal (1995) “The present work is on the modification of climatic variables, such as rainfall, as a result of change in land use during the premonsoon period over the southern part of West Bengal, India. Data analysis supports a decreasing tendency in rainfall during the recent years. As a possible factor behind such change, a significant increase in agricultural activity during recent years in coastal and inland regions has been stressed. The increase in soil moisture as a result of irrigation hinders the development and intensity of the sea-breeze circulation. The low-level moisture supply also decreases, which is an essential criterion for the formation of premonsoon thunderstorms, that is, northwesters. So, the increased vegetation or soil moisture is not always likely to increase rainfall activity; rather, mesoscale effects may be more important in some specific areas.” Lohar, D., B. Pal, 1995, J. Climate, 8, 2567–2570. [Full text]

The Effect of Irrigation on Warm Season Precipitation in the Southern Great Plains – Barnston & Schickedanz (1984) “The synoptic and subsynoptic atmospheric processes that accompany statistically determined periods of irrigation-induced rainfall increases during the warm season in the Texas Panhandle are examined. Major results are as follows. Irrigation appears to increase precipitation only when the synoptic condition provides low-level convergence and uplift, such that the additional moisture produced by irrigation (normally confined to the lowest 10–20 m of the atmosphere) is allowed to ascend to cloud base. Stationary fronts are the most favorable such synoptic condition because they fulfill the requirement for longer time durations than moving fronts or surface low pressure centers. The effect of irrigation is more noticeable during generally rainy periods because such periods often contain the types of significant rainfall events that provide sustained low-level convergence over the irrigated region. Because the mean storm track is closer to north Texas in June than in July and August, the irrigation-produced rainfall anomaly in June (which often is >20% in and somewhat downwind of the irrigation core) is the greatest of these three heavily irrigated months. Irrigation appears to lower the daily surface maximum temperature by 2°C during dry, hot conditions and by 1°C on damp, cooler days. When combining the temperature anomalies with known increases in surface dewpoint, the lifted index is estimated to decrease by up to 1°C, slightly increasing the probability of convection, even in the absence of convergence. Other possible mesoscale effects of irrigation are discussed.” Barnston, Anthony G., Paul T. Schickedanz, 1984, J. Climate Appl. Meteor., 23, 865–888. [Full text]

The Effect of Irrigation on Precipitation in the Great Plains – Schickedanz (1976) “This research addressed the question of whether the extensive irrigation in the Great Plains has had an appreciable effect on the climate of the region. The primary objectives of the research were to examine for a rainfall anomaly due to irrigation and to measure the magnitude of the effect. Another objective was to investigate other associated weather variables for supportive relationships which also could be used to help explain the physical causes. The basic study region included the states of Kansas, Nebraska, and a large portion of the state of Texas. In addition, some data rom the states of Colorado, New Mexico, Wyoming, Iowa, Missouri, and South Dakota were used for extra-area control purposes. The analysis of rainfall trend maps , the factor analysis, the analysis of convariance, and the ratio comparison patterns produced strong evidence for irrigation effects in Nebraska during June, in Texas and Kansas during July, in Kansas during August, and in all three states during summer, (Sims-ISWS).” Schickedanz, PT, 1976, Available from the National Technical Information Service, Springfield VA 22161 as PB-264 921, Report No. NSF/RA-760460, November 1976, 111 p, 29 fig, 9 tab, 30 ref. NSF GI-43871.

The influence of irrigation on the energy balance and the climate near the ground – de Vries (1959) “A theoretical analysis is presented of the influence of irrigation on temperature and humidity of the lower air layers and on the energy balance of the surface. Starting from meteorological data for the dry land (averaged over periods of a few days or longer), the average temperature and moisture profiles in an irrigated area are calculated as functions of the distance downwind from its boundary. The principal simplifying assumption in the analysis is that for each height the eddy diffusivities should have the same values in the irrigated and non-irrigated areas. The theory is applied to and illustrated by measurements of climatic differences between irrigated and non-irrigated pastures in the Australian Riverina. Experimental results of other investigators are briefly discussed. The present developments have led to a theoretical estimate, taking advective energy into account, of the potential evaporation rate for irrigated areas of limited extent on the basis of standard meteorological data for the dry land. The influence of advection decreases rapidly with increasing distance downwind. Under summer conditions in the Australian Riverina, it is considerable up to distances of about 1 km.” de Vries, D. A., 1959, J. Meteor., 16, 256–270. [Full text]

Posted in AGW evidence | Leave a Comment »

Some things I wrote about during summer

Posted by Ari Jokimäki on September 1, 2010

As I noted in february, I’m writing also some newsarticles in Finnish to our blog. I then said that I might publish some of the articles in English in here too. Recently, I have been rather lazy translating the articles to English and I have also thought that there might be not much point in that as the information I write about already exists in English. Here, I’ll just point out some of the research articles I have been reporting:

Six millennia of summer temperature variation based on midge analysis of lake sediments from Alaska – Clegg et al. (2010). Reports about generally cooling July temperatures in Alaska since 4000 BP and to mid 20th century. The abstract doesn’t mention modern temperatures but checking nearby stations suggests that modern temperature might be very close to highest Holocene temperatures that occurred in 6000-4000 BP in that site, and clearly higher than MWP. Both MWP and LIA show up clearly in the reconstruction. (Here’s the reconstruction data and the graph I made. For futher information on the research method – midge remains in lake sediments – in Brodersen & Anderson, 2000.)

Have disaster losses increased due to anthropogenic climate change? – Bouwer (2010). Disaster losses don’t seem to be clearly attributable to climate change yet. (Full text.)

– Two papers on future changes in Europe and in Arctic:

21st century changes in the European climate: uncertainties derived from an ensemble of regional climate model simulations – Kjellström et al. (2010). Europe warms considerably already in next decades. Precipitation increases in northern and decreases in southern Europe. Wind speed decreases in many areas with some exceptions.

Arctic future scenario experiments with a coupled regional climate model – Koenigk et al. (2010). Arctic warms more in their regional model runs than in global model runs. According to IPCC, this is because regional models have more realistic simulation of snow cover.

Collapse of the Maya: Could deforestation have contributed? – Oglesby et al. (2010). The fall of Mayan civilisation might have been aided by Mayan lumberjacks getting carried away…

Wintering French Mallard and Teal Are Heavier and in Better Body Condition than 30 Years Ago: Effects of a Changing Environment? – Guillemain et al. (2010). Are modern ducks so urbanized that they take fitness-classes? Ducks are more massive and more fit than 30 years ago. Probable causes are climate change and improvements in local conditions.

Projected changes in thermal seasons and the growing season in Finland – Ruosteenoja et al. (2010). Seasons will change in Finland during this century. The winter will disappear from southern Finland (where I live – there have been some samples of this already in recent years) and the growth season gets longer by a month in the whole country.

Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event – Pihlatie et al. (2010). Some basic research on peatland emissions. (Full text.)

Arctic marine climate of the early nineteenth century – Brohan et al. (2010). Point here is that they have started digitizing the weather observations from ship logbooks, first results in this paper. (Full textdata from logbooks is available here.)

Response of the ice cap Hardangerjøkulen in southern Norway to the 20th and 21st century climates – Giesen & Oerlemans (2010). In hundred years the Hardangerjøkulen glacier is no more. (Full text.)

Erosion of Lizard Diversity by Climate Change and Altered Thermal Niches – Sinervo et al. (2010). Lizard populations are vanishing before our eyes.

Permanent El Niño and the onset of Northern Hemisphere glaciations: Mechanism and comparison with other hypotheses – Vizcaino et al. (2010). Early Pliocene was warmer than today and there was a permanent El Niño. The fading out of the permanent El Niño is suggested to be one of the causes that lead to northern hemisphere glaciation. Is there a permanent El Niño in our future? (Full text.)

Effects of sea ice on atmospheric pCO2: A revised view and implications for glacial and future climates – Sun & Matsumoto (2010). The carbon dioxide level in atmosphere gets higher when sea ice extent decreases because of gas solubility changes.

Climate change in cities due to global warming and urban effects – McCarthy et al. (2010). Future cities will be really hot due to climate change and urban heating.

Vegetation response to the “African Humid Period” termination in Central Cameroon (7° N) – new pollen insight from Lake Mbalang – Vincens et al. (2010). Ancient pollen sequence describes how certain area in Cameroon changed from rain forest to a savannah. (Full text.)

Volcanic ash as fertiliser for the surface ocean – Langmann et al. (2010). Kasatochi volcano erupted and fertilized the NE Pacific. (Full text. Chlorofyll observations from NE Pacific during the event.)

Posted in Climate science | Leave a Comment »

%d bloggers like this: