Climate News and Blog Recap: 2011 02 21
A simple and coherent framework for partitioning uncertainty in multi-model climate ensembles is presented. The analysis of variance (ANOVA) is used to decompose a measure of total variation additively into scenario uncertainty, model uncertainty and internal variability.
A Simple, Coherent Framework for Partitioning Uncertainty in Climate Predictions (Journal of Climate)
The absence of in-situ pollen and spores in the James Ross Island diamictites cannot be taken as proof of non-existence of vegetation. However, the combined palynological and geological evidence presented in this paper makes the presence of a substantial Pliocene vegetation cover on James Ross Island unlikely and supports previous reconstructions of a permanent ice sheet on the Antarctic Peninsula throughout the Late Neogene.
How likely was a green Antarctic Peninsula during warm Pliocene interglacials? A critical reassessment based on new palynofloras from James Ross Island (Palaeogeography, Palaeoclimatology, Palaeoecology)
The raw observations of winds over the ocean suggest that the winds have grown stronger during the last 60 years. The trend is, however, largely due to a change in the placement of the anemometers, the instruments measuring wind speed. Ships are the main source of wind data over the ocean, and ships have increased in height and so has the anemometer placement. Tokinaga and Xie corrected this wind bias using wind-wave heights.
Using NCEP/NCAR reanalysis data, the China rainfall and surface temperature data of the China Meteorological Administration, and the Arctic Oscillation (AO) indices of NOAA, the author investigates relationships between the AO and the precipitation and temperature over China. There exists a good relationship between the AO index in December and the succeeding January precipitation over South China, indicating that when the December AO index is positive (negative), the January precipitation over South China increases (decreases). A remarkable negative correlation between the December AO index and the January surface temperature also exists over South China, indicating that when the December AO index is positive (negative), the January temperature over South China drops (rises).
The significant relationship between the Arctic Oscillation (AO) in December and the January climate over South China (ADVANCES IN ATMOSPHERIC SCIENCES)
This study examines the mutual interaction between topographically-forced atmospheric stationary waves and continental-scale ice sheets using a thermomechanical ice-sheet model coupled to a linear as well as a fully-nonlinear dry atmospheric primitive equation model. The focus is on how the stationary-wave induced ablation feeds back on the ice sheet.
Studies have indicated that many people misunderstand climate change. Equipped with a limited mental model they inappropriately use a pattern matching heuristics to analyze climate change and mistakenly believe that we can stabilize atmospheric CO2 by keeping anthropogenic emissions at current rates.
Two of the most important topics in Sea Level Science are addressed in this paper. One is concerned with the evidence for the apparent acceleration in the rate of global sea level change between the nineteenth and twentieth centuries and, thereby, with the question of whether the twentieth century sea level rise was a consequence of an accelerated climate change of anthropogenic origin. An acceleration is indeed observed in both tide gauge and saltmarsh data at different locations around the world, yielding quadratic coefficients ‘c’ of order 0.005 mm/year2, and with the most rapid changes of rate of sea level rise occurring around the end of the nineteenth century. The second topic refers to whether there is evidence that extreme sea levels have increased in recent decades at rates significantly different from those in mean levels. Recent results, which suggest that at most locations rates of change of extreme and mean sea levels are comparable, are presented.
These changes follow summer insolation trendsthrough most of the Holocene, but show marked deviations from c. 4 ka to the present day. … Although the absolute d18O values preserved inspeleothems do not precisely reflect the equilibrium values with respect to the waters from which they are precipitated, the tight isotope-longitude correlations indicate that speleothems are reliable recorders of combined rainfall O isotope signals and air temperature
The sky view factor (SVF) describes the surface geometry and is a commonly used and important measure in urban climate investigations whose aim is the exploration of effects of a complex urban surface on climatological processes in built-up areas. A selection of methods and models for calculating the SVF was compared. For this purpose, fish eye images were taken at several locations in the city of Szeged, southern Hungary.
Comparison of models calculating the sky view factor used for urban climate investigations (THEORETICAL AND APPLIED CLIMATOLOGY)
This study indicates that the models could not predict the 2009 drought over India due to the use of less warm SST anomalies over the Pacific in the longer lead runs. Hence, it is proposed that the uncertainties in SST predictions (the lower boundary condition) have to be represented in the model predictions of summer monsoon rainfall over India.
Performance of GCMs for seasonal prediction over India—a case study for 2009 monsoon (THEORETICAL AND APPLIED CLIMATOLOGY)
The results of numerical analysis reveal that the new functional model based on the depth and latitudinal density variations approximates the actual seawater density distribution with a relative accuracy better than 0.45%.
A Mathematical Model of the Global Ocean Saltwater Density Distribution (PURE AND APPLIED GEOPHYSICS)
In order to lower the subpixel temperature estimation error caused by re-sampling of remote sensing data, a disaggregation method for subpixel temperature using the remote sensing endmember index based technique (DisEMI) was established in this study.
Estimation of subpixel land surface temperature using an endmember index based technique: A case examination on ASTER and MODIS temperature products over a heterogeneous area (Remote Sensing of Environment)
The tropical subsurface response in the Atlantic can be twice of that in the Pacific. The maximum subsurface temperature change in the tropical Pacific occurs in the eastern lower thermocline, while that in the tropical Atlantic occurs in the west and well below the lower thermocline. The different responses in the tropical Atlantic and Pacific are closely related to the different changes in the meridional overturning circulations
Impacts of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on Australian rainfall are diagnosed from the perspective of tropical and extratropical teleconnections triggered by tropical sea surface temperature (SST) variations. The tropical teleconnection is understood as the equatorially-trapped, deep baroclinic response to the diabatic (convective) heating anomalies induced by the tropical SST anomalies. These diabatic heating anomalies also excite equivalent barotropic Rossby wavetrains that propagate into the extratropics. The main direct tropical teleconnection during ENSO is the Southern Oscillation (SO), whose impact on Australian rainfall is argued to be mainly confined to near-tropical portions of eastern Australia.
From the marine benthic d18O records it is known that the Earth’s climate has experienced significant variability over the past 40 Million years. In general, a number of assumptions are often needed to disentangle the benthic d18O data into its temperature and ice-volume contributions. In this study, a transient (1-D icesheet) model is used which overcomes these shortcomings by relating temperature to the benthic d18O data, leading to a self-consistent and continuous record of d18O, temperature and sea level.
Transient nature of the Earth’s climate and the implications for the interpretation of benthic d18O records (Palaeogeography, Palaeoclimatology, Palaeoecology)
A set of multi-model 20th-century climate simulations for the phase 3 of the Coupled Model Intercomparison Project (CMIP3) is analyzed to assess the model reproducibility of the Pacific-Japan (PJ) teleconnection pattern. It is the dominant low-frequency anomaly pattern over the summertime western North Pacific (WNP), characterized by a meridional dipole of zonally-elongated vorticity anomalies in the lower troposphere and by anomalous precipitation over the tropical WNP.
The core indicates that surface ocean temperatures at the margins of the peninsula cooled by 3-4?°C over the past 12,000 years, which follows the decline of spring incoming solar radiation (insolation) in the area during that period due to shifts in the Earth’s orbit.
The study also found the cooling is now being offset by the current climate change, and sea temperatures have been rising at around the same rate as land temperatures in the Antarctic, estimated at around 3-4 °C per century
Through a box model of the subpolar North Atlantic, we examine the genesis and predictability of the Atlantic Multidecadal Variability (AMV), posited as a linear perturbation sustained by the stochastic atmosphere.
Large dams could have the potential to significantly alter local rainfall in some regions, according to a team of researchers including Roger Pielke Sr., of the Cooperative Institute for Research in Environmental Sciences (CIRES).
When Was the Last Time Earth’s Atmosphere Was Like Today’s (video interview with Kiehl)
NSF release of Kiehl
The rising level of atmospheric CO2 and consequently the acidification of the surface ocean affect the CO2 absorption rate. However, there are no mathematical models to describe the impacts of acidification on the rate of CO2 absorption. Therefore, the objective of this study was to develop simple mathematical models to describe the dependence of the CO2 absorption rate on the pH of the surface ocean. The developed models predict that the CO2 absorption rate is enhanced with acidification directly proportional to the increase in the abundance of H2CO3 in the surface ocean. In addition, the models predict that the increasing rate of CO2 absorption reflects the increasing rate of increase of CO2 in the atmosphere.
These maps show the rate at which the ice sheet over the British Isles during the last Ice Age melted.
Researchers map out ice sheets shrinking during Ice Age (PhysOrg.com)
Based on reconstructions of Arctic climate variability in the greenhouse world of the Late Cretaceous, Southampton scientists have concluded that man-made global warming probably would not greatly change the climatic influence associated with natural modes of inter-annual climate variability such as the El Niño – Southern Oscillation (ENSO) or the Arctic Oscillation/ North Atlantic Oscillation (AO/ NAO).
“Even in the warm Cretaceous period, the patterns of these climatic oscillations changed over longer decadal timescales,” explained Professor Alan Kemp of the University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre, Southampton. “It is therefore difficult to predict whether anthropogenically driven warming will lead to systematic changes such as persistently milder European winters (a positive AO/ NAO) as some have suggested.
Using new, high-resolution global ocean circulation models, University of Massachusetts Amherst geoscientist Alan Condron, with Peter Winsor at the University of Alaska, report this week that massive glacial meltwaters assumed to have flooded the entire North Atlantic 8,200 years ago, drastically cooling Europe, instead flowed thousands of miles further south. “These results dramatically affect our understanding of what causes climate change,” Condron says.
New model changes view of climate change (PhysOrg.com)