AGW Observer

Observations of anthropogenic global warming

New research from last week 26/2011

Posted by Ari Jokimäki on July 4, 2011

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Sun can’t explain temperature change since 1985

Solar activity – climate relations: A different approach – Stauning (2011) “The presentation of solar activity-climate relations is extended with the most recent sunspot and global temperature data series. The extension of data series shows clearly that the changes in terrestrial temperatures are related to sources different from solar activity after ~1985. Based on analyses of data series for the years 1850–1985 it is demonstrated that, apart from an interval of positive deviation followed by a similar negative excursion in Earth’s temperatures between ~1923 and 1965, there is a strong correlation between solar activity and terrestrial temperatures delayed by 3 years, which complies with basic causality principles. A regression analysis between solar activity represented by the cycle-average sunspot number, SSNA, and global temperature anomalies, ΔTA, averaged over the same interval lengths, but delayed by 3 years, provides the relation ΔTA=0.009 (±.002) SSNA. Since the largest ever observed SSNA is ~90 (in 1954–1965), the solar activity-related changes in global temperatures could amounts to no more than ±0.4 °C over the past ~400 years where the sunspots have been recorded. It is demonstrated that the small amplitudes of cyclic variations in the average global temperatures over the ~11 year solar cycle excludes many of the various driver processes suggested in published and frequently quoted solar activity-climate relations. It is suggested that the in-cycle variations and also the longer term variations in global temperatures over the examined 135 years are mainly caused by corresponding changes in the total solar irradiance level representing the energy output from the core, but further modulated by varying energy transmission properties in the active outer regions of the Sun.” P. Stauning, Journal of Atmospheric and Solar-Terrestrial Physics, doi:10.1016/j.jastp.2011.06.011.

Recent Antarctic sea ice increase might be measurement system artifact

Sudden increase in Antarctic sea ice: Fact or artifact? – Screen (2011) “Three sea ice data sets commonly used for climate research display a large and abrupt increase in Antarctic sea ice area (SIA) in recent years. This unprecedented change of SIA is diagnosed to be primarily caused by an apparent sudden increase in sea ice concentrations within the ice pack, especially in the area of the most-concentrated ice (greater than 95% concentration). A series of alternative satellite-derived records do not display any abnormal sudden SIA changes, but do reveal substantial discrepancies between different satellite sensors and sea ice algorithms. Sea ice concentrations in the central ice pack and SIA values derived from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSRE) are consistently greater than those derived from the Special Sensor Microwave Imager (SSMI). A switch in source data from the SSMI to AMSRE in mid-2009 explains most of the SIA increase in all three affected data sets. If uncorrected for, the discontinuity artificially exaggerates the winter Antarctic SIA increase (1979–2010) by more than a factor of 2 and the spring trend by almost a factor of 4. The discontinuity has a weaker influence on the summer and autumn SIA trends, on calculations of Antarctic sea ice extent, and in the Arctic.” Screen, J. A. (2011), Geophys. Res. Lett., 38, L13702, doi:10.1029/2011GL047553.

Highest melt in 4200 years for Canadian Arctic ice caps

Recent melt rates of Canadian Arctic ice caps are the highest in four millennia – Fisher et al. (2011) “There has been a rapid acceleration in ice-cap melt rates over the last few decades across the entire Canadian Arctic. Present melt rates exceed the past rates for many millennia. New shallow cores at old sites bring their melt series up-to-date. The melt-percentage series from the Devon Island and Agassiz (Ellesmere Island) ice caps are well correlated with the Devon net mass balance and show a large increase in melt since the middle 1990s. Arctic ice core melt series (latitude range of 67 to 81 N) show the last quarter century has seen the highest melt in two millennia and The Holocene-long Agassiz melt record shows the last 25 years has the highest melt in 4200 years. The Agassiz melt rates since the middle 1990s resemble those of the early Holocene thermal maximum over 9000 years ago.” David Fisher, James Zheng, David Burgess, Christian Zdanowicz, Christophe Kinnard, Martin Sharp and Jocelyne Bourgeois, Global and Planetary Change, doi:10.1016/j.gloplacha.2011.06.005.

Cold surges are threatening wildlife in warmer climate

Different characteristics of cold day and cold surge frequency over East Asia in a global warming situation – Park et al. (2011) “This study investigates the changes in winter cold extreme events over East Asia in the present and future climates. Two distinct terms to indicate cold extreme events are analyzed: “cold day,” which describes a temperature below a certain threshold value (e.g., simply cold weather), and “cold surge,” which describes an abrupt temperature drop (e.g., relatively colder weather than a previous day). We analyze both observations and long-term climate simulations from 13 atmospheric and oceanic coupled global climate models (CGCMs). The geographical distribution of sea level pressure corresponding to a cold day (cold surge) is represented by a dipole (wave train) feature. Although cold day and cold surge show similar patterns of surface air temperature, they are induced by the out-of-phase sea level pressures. From the results of our analysis of a series of future projections for the mid and late twenty-first century using the 13 CGCMs, cold day occurrences clearly decrease with an increasing mean temperature (a correlation coefficient of −0.49), but the correlation between cold surge occurrences and the mean temperature is insignificant (a correlation coefficient of 0.08), which is supported by the same results in recent observation periods (1980–2006). Thus, it is anticipated that cold surge occurrences will remain frequent even in future warmer climate. This deduction is based on the future projections in which the change in the day-to-day temperature variability is insignificant, although the mean temperature shows significant increase. The present results suggest that living things in the future, having acclimatized to a warmer climate, would suffer the strong impact of cold surges, and hence the issue of vulnerability to cold surges should be treated seriously in the future.” Park, T.-W., C.-H. Ho, S.-J. Jeong, Y.-S. Choi, S. K. Park, and C.-K. Song (2011), J. Geophys. Res., 116, D12118, doi:10.1029/2010JD015369.

New radiosonde analysis shows troposphere warming

A quantification of uncertainties in historical tropical tropospheric temperature trends from radiosondes – Thorne et al. (2011) “The consistency of tropical tropospheric temperature trends with climate model expectations remains contentious. A key limitation is that the uncertainties in observations from radiosondes are both substantial and poorly constrained. We present a thorough uncertainty analysis of radiosonde-based temperature records. This uses an automated homogenization procedure and a previously developed set of complex error models where the answer is known a priori. We perform a number of homogenization experiments in which error models are used to provide uncertainty estimates of real-world trends. These estimates are relatively insensitive to a variety of processing choices. Over 1979–2003, the satellite-equivalent tropical lower tropospheric temperature trend has likely (5–95% confidence range) been between −0.01 K/decade and 0.19 K/decade (0.05–0.23 K/decade over 1958–2003) with a best estimate of 0.08 K/decade (0.14 K/decade). This range includes both available satellite data sets and estimates from models (based upon scaling their tropical amplification behavior by observed surface trends). On an individual pressure level basis, agreement between models, theory, and observations within the troposphere is uncertain over 1979 to 2003 and nonexistent above 300 hPa. Analysis of 1958–2003, however, shows consistent model-data agreement in tropical lapse rate trends at all levels up to the tropical tropopause, so the disagreement in the more recent period is not necessarily evidence of a general problem in simulating long-term global warming. Other possible reasons for the discrepancy since 1979 are: observational errors beyond those accounted for here, end-point effects, inadequate decadal variability in model lapse rates, or neglected climate forcings.” Thorne, P. W., et al. (2011), J. Geophys. Res., 116, D12116, doi:10.1029/2010JD015487.

World’s dry areas have increased and it’s going to get worse

Characteristics and trends in various forms of the Palmer Drought Severity Index during 1900–2008 – Dai (2011) “The Palmer Drought Severity Index (PDSI) has been widely used to study aridity changes in modern and past climates. Efforts to address its major problems have led to new variants of the PDSI, such as the self-calibrating PDSI (sc_PDSI) and PDSI using improved formulations for potential evapotranspiration (PE), such as the Penman-Monteith equation (PE_pm) instead of the Thornthwaite equation (PE_th). Here I compare and evaluate four forms of the PDSI, namely, the PDSI with PE_th (PDSI_th) and PE_pm (PDSI_pm) and the sc_PDSI with PE_th (sc_PDSI_th) and PE_pm (sc_PDSI_pm) calculated using available climate data from 1850 to 2008. Our results confirm previous findings that the choice of the PE only has small effects on both the PDSI and sc_PDSI for the 20th century climate, and the self-calibration reduces the value range slightly and makes the sc_PDSI more comparable spatially than the original PDSI. However, the histograms of the sc_PDSI are still non-Gaussian at many locations, and all four forms of the PDSI show similar correlations with observed monthly soil moisture (r = 0.4–0.8) in North America and Eurasia, with historical yearly streamflow data (r = 0.4–0.9) over most of the world’s largest river basins, and with GRACE (Gravity Recovery and Climate Experiment) satellite-observed water storage changes (r = 0.4–0.8) over most land areas. All the four forms of the PDSI show widespread drying over Africa, East and South Asia, and other areas from 1950 to 2008, and most of this drying is due to recent warming. The global percentage of dry areas has increased by about 1.74% (of global land area) per decade from 1950 to 2008. The use of the Penman-Monteith PE and self-calibrating PDSI only slightly reduces the drying trend seen in the original PDSI. The percentages of dry and wet areas over the global land area and six select regions are anticorrelated (r = −0.5 to −0.7), but their long-term trends during the 20th century do not cancel each other, with the trend for the dry area often predominating over that for the wet area, resulting in upward trends during the 20th century for the areas under extreme (i.e., dry or wet) conditions for the global land as a whole (∼1.27% per decade) and the United States, western Europe, Australia, Sahel, East Asia, and southern Africa. The recent drying trends are qualitatively consistent with other analyses and model predictions, which suggest more severe drying in the coming decades.” Dai, A. (2011), J. Geophys. Res., 116, D12115, doi:10.1029/2010JD015541.

Clouds don’t just cool

Cloud effect of persistent stratus nebulosus at the Payerne BSRN site – Wacker et al. (2011) “This analysis presents radiative transfer calculations of surface downwelling long-wave and short-wave radiation and the corresponding cloud radiative effect of single-layered, completely overcast stratus situations (stratus nebulosus) at the Baseline Surface Radiation Network (BSRN) site Payerne. We found an excellent agreement of 0.6 Wm–2 mean difference between modeled and observed downwelling long-wave radiation with a root mean squared error of 1.5 Wm–2 for 30 carefully selected cases. The discrepancies between modeled and observed diffuse downwelling short-wave radiation are with 2.8 ± 25.4 Wm–2 considerably higher. The net cloud radiative effect of the 30 cases shows a pronounced diurnal variation determined by the diurnal cycle of the short-wave cloud effect and the nearly constant positive long-wave cloud effect. Mean net cloud effect ranges from 80 ± 3 Wm–2 (min.: 75 Wm–2; max.: 85 Wm–2) during nighttime in the absence of solar radiation to − 197 ± 74 Wm–2 (min.: -373 Wm–2; max.: -91 Wm–2) around noon. Mean net cloud effect averaged over 24 hours is 18 ± 20 Wm–2 (min.: -28 Wm–2; max.: + 42 Wm–2) for the 30 casesassuming a persistent, completely overcast stratus cloud. This implies that stratus nebulosus can have a substantial positive radiative effect during the winter half year at this site.” S. Wacker, J. Gröbner, D. Nowak, L. Vuilleumier and N. Kämpfer, Atmospheric Research, doi:10.1016/j.atmosres.2011.06.007.

Measurements of ocean acidification in Japan

Ocean acidification off the south coast of Japan: A result from time series observations of CO2 parameters from 1994 to 2008 – Ishii et al. (2011) “Ocean acidification resulting from increases in present and future atmospheric CO2 levels could seriously affect diverse coastal and oceanic ecosystems. In this work, we determine that a significant trend in ocean acidification is superposed on the large seasonal and interannual variabilities of acidity in surface waters off the south coast of Honshu, Japan, based on our repeated observations of partial pressure of CO2 (pCO2), total inorganic carbon (TCO2), and pH. Multiple regression analysis of TCO2 as a function of temperature, salinity, and timing of observations shows that TCO2 increased at a rate of +1.23 ± 0.40 μmol kg−1 yr−1 for the period 1994–2008, while no long-term change has been determined for total alkalinity calculated from TCO2 and pCO2 in seawater. These results indicate that pH and the aragonite saturation state (Ωarag) are decreasing at a rate of −0.020 ± 0.007 decade−1 and −0.12 ± 0.05 decade−1, respectively. If future atmospheric CO2 levels keep increasing as predicted by the Intergovernmental Panel on Climate Change emission scenario A1FI, which postulates intensive fossil fuel use associated with very rapid economic growth, a further reduction of −0.8 to −1.0 in Ωarag is likely in the next 50 years. Such a rapid reduction of Ωarag could have negative impacts on a variety of calcareous organisms.” Ishii, M., N. Kosugi, D. Sasano, S. Saito, T. Midorikawa, and H. Y. Inoue (2011), J. Geophys. Res., 116, C06022, doi:10.1029/2010JC006831.

Vertical distribution of cloud feedback

The vertical distribution of cloud feedback in coupled ocean-atmosphere models – Soden & Vecchi (2011) “We assess the vertical distribution of cloud feedbacks in coupled climate models, taking care to distinguish between cloud feedbacks and a change in cloud forcing. We show that the effect of cloud changes on the longwave fluxes provides a strong positive feedback that is broadly consistent across models. In contrast, the effect of cloud changes on the shortwave fluxes ranges from a modest negative to a strong positive feedback, and is responsible for most of the intermodel spread in net cloud feedback. The feedback from high clouds is positive in all models, and is consistent with that anticipated by the Proportionately Higher Anvil Temperature hypothesis over the tropics. In contrast, low cloud cover is responsible for roughly three-quarters of the difference in global mean net cloud feedback among models, with the largest contributions from regions associated with low-level subtropical marine cloud systems.” Soden, B. J., and G. A. Vecchi (2011), Geophys. Res. Lett., 38, L12704, doi:10.1029/2011GL047632. [Full text]


One Response to “New research from last week 26/2011”

  1. Thanks for providing us with this intelligence. Very much appreciate these updates and coverage. Just the MSM has to do now a better job in tackling the topic of the century!

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