AGW Observer

Observations of anthropogenic global warming

New research from last week 27/2011

Posted by Ari Jokimäki on July 11, 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:

YD event might have been global and affected mankind

Evidence for Younger Dryas Global Climate Oscillation and Human Response in the American Southwest – Ballenger et al. (2011) “Whether or not abrupt YD climate change affected regional paleoenvironments and late Pleistocene hunter-gatherer populations is an important topic in the archaeology of the American Southwest. This paper reviews multiple, age-resolved proxy evidence to gauge the magnitude and direction of Younger Dryas Chronozone(YDC) environmental changes in different settings and systems. There is no record of YDC pluvial lake highstands in Arizona or New Mexico, but there are impressive records of vegetation, faunal,stable isotope, and geomorphological change coincident with the YDC. These correlate with important adaptive changes in human hunting and land use, as revealed in the analysis of the spatiotemporal distribution of late Pleistocene hunting technologies. Clovis and Folsom projectile point distributions do not support extant models ofpaleoenvironmental conditions in these interpretations. Significant cultural changes that coincide with the YDC include the Clovis-to-Folsom transition, the demise of mammoth hunting and the development of a highly successful emphasis on bison, increased regionalization, and the abandonment of the northwestern Chihuahuan and the Sonoran deserts by mobile, big-game hunters.” Jesse A.M. Ballenger, Vance T. Holliday, Andrew L. Kowler, William T. Reitze, Mary M. Prasciunas, D. Shane Miller and Jason D. Windingstad, Quaternary International, doi:10.1016/j.quaint.2011.06.040.

World War II bombing raids help to study contrail effect on climate

World War II contrails: a case study of aviation-induced cloudiness – Ryan et al. (2011) “Dense and persistent condensation trails or contrails were produced by daytime US Army Air Force (USAAF) bombing raids, flown from England to Europe during World War II (WW2). These raids occurred in years when civilian air travel was rare, giving a predominantly contrail-free background sky, in a period when there were more meteorological observations taken across England than at any time before or since. The aircraft involved in the raids entered formation at contrail-forming altitudes (generally over 16 000 ft, approximately 5 km) over a relatively small part of southeast England before flying on to their target. This formation strategy provides us a unique opportunity to carry out multiple observation-based comparisons of adjacent, same day, well-defined overflown and non-over-flown regions. We compile evidence from archived meteorological data, such as Met Office daily weather reports and individual station meteorological registers, together with historical aviation information from USAAF and Royal Air Force (RAF) tactical mission reports. We highlight a number of potential dates for study and demonstrate, for one of these days, a marked difference in the amount of high cloud cover, and a statistically significant (0.8 °C) difference in the 07:00–13:00 UTC temperature range when comparing data from highly overflown stations to those upwind of the flight path on the same day. Although one event cannot provide firm conclusions regarding the effect of contrails on climate, this study demonstrates that the wealth of observational data associated with WW2 bombing missions allows detailed investigation of meteorological perturbations because of aviation-induced cloudiness.” A. C. Ryan, A. R. MacKenzie, S. Watkins and R. Timmis, International Journal of Climatology, DOI: 10.1002/joc.2392. [Full text]

Not only CO2 but also man-made SOx, NOx and NH3 cause ocean acidification

Impacts of anthropogenic SOx, NOx and NH3 on acidification of coastal waters and shipping lanes – Hunter et al. (2011) “The acidification of the ocean by anthropogenic CO2 absorbed from the atmosphere is now well-recognized and is considered to have lowered surface ocean pH by 0.1 since the mid-18th century. Future acidification may lead to undersaturation of CaCO3 making growth of calcifying organisms difficult. However, other anthropogenic gases also have the potential to alter ocean pH and CO2 chemistry, specifically SOx and NOx and NH3. We demonstrate using a simple chemical model that in coastal water regions with high atmospheric inputs of these gases, their pH reduction is almost completely canceled out by buffering reactions involving seawater HCO3 and CO32− ions. However, a consequence of this buffering is a significant decrease in the uptake of anthropogenic CO2 by the atmosphere in these areas.” Hunter, K. A., et al. (2011), Geophys. Res. Lett., 38, L13602, doi:10.1029/2011GL047720.

King George Island ice cap retreating

Observed glacial changes on the King George Island ice cap, Antarctica, in the last decade – Rückamp et al. (2011) “The Antarctic Peninsula has been identified as a region of rapid on-going climate change with impacts on the cryosphere. The knowledge of glacial changes and freshwater budgets resulting from intensified glacier melt is an important boundary condition for many biological and integrated earth system science approaches. We provide a case study on glacier and mass balance changes for the ice cap of King George Island. The area loss between 2000 and 2008 amounted to about 20 km2 (about 1.6% of the island area) and compares to glacier retreat rates observed in previous years. Measured net accumulation rates for two years (2007 and 2008) show a strong interannual variability with maximum net accumulation rates of 4950mmw.e. a− 1 and 3184mmw.e. a− 1, respectively. These net accumulation rates are at least 4 times higher than reported mean values (1926–95) from an ice core. An elevation dependent precipitation rate of 343mmw.e. a− 1 (2007) and 432mmw.e. a− 1 (2008) per 100m elevation increase was observed. Despite these rather high net accumulation rates on the main ice cap, consistent surface lowering was observed at elevations below 270m above ellipsoid over an 11-year period. These DGPS records reveal a linear dependence of surface lowering with altitude with a maximum annual surface lowering rate of 1.44ma− 1 at 40m and − 0.20ma− 1 at 270m above ellipsoid. These results fit well to observations by other authors and surface lowering rates derived from the ICESat laser altimetry. Assuming that climate conditions of the past 11 years continue, the small ice cap of Bellingshausen Dome will disappear in about 285 years.” M. Rückamp, M. Braun, S. Suckro and N. Blindow, Global and Planetary Change, doi:10.1016/j.gloplacha.2011.06.009.

Cold fronts due to 2010 extreme arctic oscillation caused coral mortality in Florida

Catastrophic mortality on inshore coral reefs of the Florida keys due to severe low-temperature stress – Kemp et al. (2011) “Coral reefs of the Florida Keys typically experience seasonal temperatures of 20–31 °C. Deviation outside of this range causes physiological impairment of reef-building corals, potentially leading to coral colony death. In January and February 2010, two closely spaced cold fronts, apparently driven by an unusually extreme arctic oscillation, caused sudden and severe seawater temperature declines in the Florida Keys. Inshore coral reefs (e.g., Admiral Reef) experienced lower sustained temperatures (i.e., <12 °C) than those further offshore (e.g., Little Grecian Reef, minimum temperature = 17.2 °C). During February and March 2010, we surveyed Admiral Reef and observed a mass die-off of reef-building corals, whereas 12 km away Little Grecian Reef did not exhibit coral mortality. We subsequently measured the physiological effects of low temperature stress on three common reef-building corals (i.e., Montastraea faveolata, Porites astreoides, and Siderastrea siderea) surviving offshore over a range of temperatures that replicated the inshore cold-water anomaly (i.e., from 20 °C to 16 °C to 12 °C and back to 20 °C). Throughout the temperature modulations, coral respiration as well as endosymbiont gross photosynthesis and maximum PSII photosynthetic efficiency were measured. In addition, Symbiodinium genotypic identity, cell densities, and chlorophyll a content were determined at the beginning and conclusion of the experiment. All corals were significantly affected at 12 °C, but species-specific physiological responses were found indicating different coral and/or Symbiodinium cold tolerances. Montastraea faveolata and P. astreoides appeared to be most negatively impacted because, upon return to 20 °C, significant reductions in gross photosynthesis and dark respiration persisted. S. siderea, however readily recovered to pre-treatment rates of dark respiration and gross photosynthesis. Visual surveys of inshore reefs corroborated these results, with S. siderea being minimally affected by the cold-water anomaly whereas M. faveolata and P. astreoides exhibited nearly 100% mortality. This study highlights the importance of understanding the physiological attributes of genotypically distinct coral-Symbiodinium symbioses that contribute to tolerance, recovery and consequences to an environmental perturbation. These data also document effects of a rarely studied environmental stressor, possibly initiated by remote global climate events, on coral-Symbiodinium symbioses and coral reef communities." Dustin W. Kemp, Clinton A. Oakley, Daniel J. Thornhill, Laura A. Newcomb, Gregory W. Schmidt, William K. Fitt, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02487.x.

In warmer climate there will be more cyanobacteria in lakes

Warmer climates boost cyanobacterial dominance in shallow lakes – Kosten et al. (2011) “Dominance by cyanobacteria hampers human use of lakes and reservoirs worldwide. Previous studies indicate that excessive nutrient loading and warmer conditions promote dominance by cyanobacteria, but evidence from global scale field data has so far been scarce. Our analysis, based on a study of 143 lakes along a latitudinal transect ranging from subarctic Europe to southern South America, shows that while warmer climates do not result in higher overall phytoplankton biomass, the percentage of the total phytoplankton biovolume attributable to cyanobacteria increases steeply with temperature. Our results also reveal that the percent cyanobacteria is greater in lakes with high rates of light absorption. This points to a positive feedback because restriction of light availability is often a consequence of high phytoplankton biovolume, which in turn may be driven by nutrient loading. Our results indicate a synergistic effect of nutrients and climate. The implications are that in a future warmer climate, nutrient concentrations may have to be reduced substantially from present values in many lakes if cyanobacterial dominance is to be controlled.” Sarian Kosten, Vera L. M. Huszar, Eloy Bécares, Luciana S. Costa, Ellen van Donk, Lars-Anders Hansson, Erik Jeppesen, Carla Kruk, Gissell Lacerot, Néstor Mazzeo, Luc De Meester, Brian Moss, Miquel Lürling, Tiina Nõges, Susana Romo, Marten Scheffer, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02488.x.

Permafrost warms in Antarctic

A permafrost warming in a cooling Antarctica? – Guglielmin & Cannone (2011) “The magnitude and even direction of recent Antarctic climate change is still debated because the paucity of long and complete instrumental data records. While along Antarctic Peninsula a strong warming coupled with large retreat of glaciers occurred, in continental Antarctica a cooling was recently detected. Here, the first existing permafrost data set longer than 10 years recorded in continental Antarctica is presented. Since 1997 summer ground surface temperature showed a strong warming trend (0.31°C per year) although the air temperature was almost stable. The summer ground surface temperature increase seemed to be influenced mainly by the increase of the total summer radiation as confirmed also by the increase of the summer thawing degree days. In the same period the active layer exhibited a thickening trend (1 cm per year) comparable with the thickening rates observed in several Arctic locations where air warming occurred. At all the investigated depths permafrost exhibited an increase of mean annual temperature of approximately 0.1°C per year. The dichotomy between active layer thickness and air temperature trends can produce large unexepected and unmodelled impacts on ecosystems and CO2 balance.” Mauro Guglielmin and Nicoletta Cannone, Climatic Change, DOI: 10.1007/s10584-011-0137-2.

Extreme emission scenario model projects 2K more warming than IPCC’s highest

The response of the climate system to very high greenhouse gas emission scenarios – Sanderson et al. (2011) “Well informed decisions on climate policy necessitate simulation of the climate system for a sufficiently wide range of emissions scenarios. While recent literature has been devoted to low emissions futures, the potential for very high emissions has not been thoroughly explored. We specify two illustrative emissions scenarios that are significantly higher than the A1FI scenario, the highest scenario considered in past IPCC reports, and simulate them in a global climate model to investigate their climate change implications. Relative to the A1FI scenario, our highest scenario results in an additional 2 K of global mean warming above A1FI levels by 2100, a complete loss of arctic summer sea-ice by 2070 and an additional 43% sea level rise due to thermal expansion above A1FI levels by 2100. Regional maximum temperature increases from late 20th century values are 50–100% greater than A1FI increases, with some regions such as the Central US, the Tibetan plateau and Alaska showing a 300–400% increase above A1FI levels.” Benjamin M Sanderson, Brian C O’Neill, Jeffrey T Kiehl, Gerald A Meehl, Reto Knutti and Warren M Washington, 2011 Environ. Res. Lett. 6 034005, doi: 10.1088/1748-9326/6/3/034005. [Full text]

Waters around Greenland and Antarctica expected to warm at different pace

Different magnitudes of projected subsurface ocean warming around Greenland and Antarctica – Yin et al. (2011) “The observed acceleration of outlet glaciers and ice flows in Greenland and Antarctica is closely linked to ocean warming, especially in the subsurface layer. Accurate projections of ice-sheet dynamics and global sea-level rise therefore require information of future ocean warming in the vicinity of the large ice sheets. Here we use a set of 19 state-of-the-art climate models to quantify this ocean warming in the next two centuries. We find that in response to a mid-range increase in atmospheric greenhouse-gas concentrations, the subsurface oceans surrounding the two polar ice sheets at depths of 200–500 m warm substantially compared with the observed changes thus far. Model projections suggest that over the course of the twenty-first century, the maximum ocean warming around Greenland will be almost double the global mean, with a magnitude of 1.7–2.0 °C. By contrast, ocean warming around Antarctica will be only about half as large as global mean warming, with a magnitude of 0.5–0.6 °C. A more detailed evaluation indicates that ocean warming is controlled by different mechanisms around Greenland and Antarctica. We conclude that projected subsurface ocean warming could drive significant increases in ice-mass loss, and heighten the risk of future large sea-level rise.” Jianjun Yin, Jonathan T. Overpeck, Stephen M. Griffies, Aixue Hu, Joellen L. Russell & Ronald J. Stouffer, Nature Geoscience(2011), doi:10.1038/ngeo1189.


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