Climate News and Blog Recap: 2011 03 05
Professor Bickmore takes a skeptical look at Dr. Spencer’s The Great Global Warming Blunder: How Mother Nature Fooled the World’s Top Climate Scientists
(also … Roy Spencer’s six trillion degree warming Smith @ Not Spaghetti
Mathematical analysis of Roy Spencer’s climate model Smith @ Not Spaghetti)
Our JGR Paper on Feedbacks is Published
Spencer @ Spencer
On the diagnosis of radiative feedback in the presence of unknown radiative forcing
Spencer and Braswell, 2010
Potential Biases in Feedback Diagnosis from Observational Data: A Simple Model Demonstration
Spencer and Braswell, 2008
Looking back a bit …
Natural Warming Id @ the Air Vent
Warming in Last 50 Years Predicted by Natural Climate Cycles Spencer @ Spencer
Evidence for Natural Climate Cycles in the IPCC Climate Models’ 20th Century Temperature Reconstructions Spencer @ Spencer
Skeptical Science looks at the PDO.
Blaming the Pacific Decadal Oscillation Riccardo @ Skeptical Science
Tamino takes a look at Knudsen et al. 2011: Tracking the Atlantic Multidecadal Oscillation through the last 8,000 years.
8,000 years of AMO? Tamino @ Open Mind
Remiss in my duties, I have not been very systematic in my blog science searches. Some older, but not too old, pieces are included here.
For instance, I missed Two Most Excellent Pieces from The Way Things Break
Greenland and Antarctic ice sheet decay update
Tropical tropospheric temperature, instrumental and proxy trends
Brook looks back at a two year old forecast
A toy model for forecasting global temperatures – 2011 redux, part 1 Barry Brook @ Brave New Climate
Clear Climate Code is sponsoring a Google Summer of Code 2011 project.
Bart touches on the one of the two greatest sources of uncertainty (aside from hand-waving and wand-waving).
Radiative forcing by aerosol used as a wild card: NIPCC vs Lindzen Verheggen @ Our Changing Climate
Spatial patterns of local climate feedback and equilibrium partial temperature responses are produced from eight general circulation models with slab oceans forced by doubling carbon dioxide (CO2). The analysis is extended to other forcing mechanisms with the UK Met Office HadSM3 model. In agreement with previous studies, the greatest inter-model differences are in the tropical cloud feedbacks. However, the greatest inter-model spread in the equilibrium temperature response comes from the water vapour plus lapse rate feedback, not clouds, disagreeing with a previous study. Although the surface albedo feedback contributes most in the annual mean to the greater warming of high latitudes, compared to the tropics (polar amplification), its effect is significantly ameliorated by shortwave cloud feedback. In different seasons the relative importance of the contributions varies considerably, with longwave cloudy sky feedback and horizontal heat transport plus ocean heat release playing a major role during winter and autumn when polar amplification is greatest. The greatest inter-model spread in annual mean polar amplification is due to variations in horizontal heat transport and shortwave cloud feedback. Spatial patterns of local climate feedback for HadSM3 forced with 2×CO2, +2% solar, low-level scattering aerosol and high-level absorbing aerosol are more similar than those for different models forced with 2×CO2. However, the equilibrium temperature response to high-level absorbing aerosol shows considerably enhanced polar amplification compared to the other forcing mechanisms, largely due to differences in horizontal heat transport and water vapour plus lapse rate feedback, with the forcing itself acting to reduce amplification. Such variations in high latitude response between models and forcing mechanisms make it difficult to infer specific causes of recent Arctic temperature change.
A regression-based modeling approach is described for mapping the dependence of atmospheric state variables such as surface air temperature (SAT) on the Madden-Julian Oscillation (MJO). For the special case of a linear model the dependence can be described by two maps corresponding to the amplitude and lag of the mean atmospheric response with respect to the MJO. In this sense the method leads to a more parsimonious description than traditional compositing which usually results in eight maps, one for each MJO phase. Another advantage of the amplitude and phase maps is that they clearly identify propagating signals, and also regions where the response is strongly amplified or attenuated. A straightforward extension of the linear model is proposed to allow the amplitude and phase of the response to vary with the amplitude of the MJO or indices that define the background state of the atmosphere-ocean system. Application of the approach to global SAT for boreal winter clearly shows the propagation of MJO-related signals in both tropics and extra tropics and an enhanced response over eastern North America and Alaska (further enhanced during La Niña years). The SAT response over Alaska and eastern North America is caused mainly by horizontal advection related to variations in shore-normal surface winds which, in turn, can be traced (via signals in the 500 hPa geopotential height) back to MJO-related disturbances in the tropic
A series of simulations have been performed using the Hadley Centre GCM, (HadCM3) to investigate the 8.2ka event. A control simulation with 9ka boundary conditions showed that intrinsic variability in the strength of the N. Atlantic Meridional Overturning Circulation (MOC) was greater than in a comparable pre-industrial simulation but these natural variations were not strong enough to replicate the 8.2ka event at any time, consistent with the idea that the event was ‘forced’ through a freshwater discharge. We therefore investigated the response of the 9ka climate to a freshwater forcing consistent with the final drainage of Lake Agassiz. A 10 member ensemble was performed with 5Sv of Freshwater added to the N. Atlantic ocean for 1 year at various times of the control run, which led to a reduction in the strength of the MOC and the temperature, precipitation and δ18O of precipitation over the N. Atlantic region. The strength and location of the response agreed well with proxy evidence of the 8.2ka event but the duration was too short in all cases. The response to the freshwater forcing was sensitive to the initial state of the ocean, with better agreement with paleodata when the freshwater was added at a time when the Atlantic MOC was relatively weak. The structure and duration of the δ18Op response was consistent over a large region, and appeared in better agreement with regional precipitation than regional temperature, however there were spatial differences between the maximum δ18Op response and both the maximum temperature and precipitation responses
Modelling the 8.2ka event using a coupled atmosphere-ocean GCM (Global and planetary change)
The development of landscapes and morphologies follows initially the tectonic displacement structures of the basement and sediments. Such faults zones or lineaments are often exploited by surface erosional processes and play, therefore, an important role in reconstructing past ice sheet dynamics. Observations of bathymetric features of the continental shelf of the Amundsen Sea Embayment and identification of tectonic lineaments from geophysical mapping indicate that the erosional processes of paleo-ice stream flows across the continental shelf followed primarily such lineaments inherited from the tectonic history since the Cretaceous break-up between New Zealand and West Antarctica. Three major ice flow trends correspond to different tectonic phases in east-west, northwest-southeast and north-south directions. …An understanding of this context helps better constrain the geometries and sea-bed substrate conditions for regional paleo-ice sheet models.
Basement control on past ice sheet dynamics in the Amundsen Sea Embayment, West Antarctica (Palaeogeography, palaeoclimatology, palaeoecology)
The Amundsen Sea Embayment (ASE) drains approximately 35% of the West Antarctic Ice Sheet (WAIS) and is one of the most rapidly changing parts of the cryosphere. In order to predict future ice sheet behaviour, modellers require long-term records of ice-sheet melting to constrain and build confidence in their simulations. Here, we present detailed marine geological and radiocarbon data along three palaeo-ice stream tributary troughs in the western ASE to establish vital information on the timing of deglaciation of the WAIS since the Last Glacial Maximum (LGM). …
Deglacial history of the West Antarctic Ice Sheet in the western Amundsen Sea Embayment (Quaternary science reviews)
Neolithic seafaring across the Taiwan Strait began approximately 5000 years ago and involved open-sea voyages over distances of at least 130 km. Rapid sea-level rise preceded the emergence of open-sea voyaging, but the possible role of environmental change as a stimulus for the development of seafaring is poorly understood. We investigate this problem by presenting a record of Holocene sea-level change and coastal transformation based on sediment cores obtained from the Fuzhou Basin on the coast of Fujian, China. The cores are located in direct proximity to archaeological sites of the Tanshishan Neolithic culture (5000–4300 cal BP), which is significant for its similarity to the earliest Neolithic cultures of Taiwan. Multiple lines of evidence record the early Holocene inundation of the Fuzhou Basin around 9000 cal BP, the mid-Holocene sea-level highstand, and the final Holocene marine transgression. This final transition is precisely documented, with AMS dates showing the change occurred close to 1900 cal BP. Our paleogeographic reconstruction shows that a large estuary filled the Fuzhou Basin during the mid-Holocene. Tanshishan and Zhuangbianshan, two of the major Fuzhou Basin Neolithic sites, are located today on hills nearly 80 km from the modern coastline. However, when the sites were settled around 5500–5000 cal BP, the marine transgression had transformed these hills into islands in the upper estuary. We suggest that the Neolithic era estuary setting, together with the lack of land suitable for rice paddy agriculture, inhibited intensive food production but favored a maritime orientation and the development of seafaring.
Holocene sea-level change and the emergence of Neolithic seafaring in the Fuzhou Basin (Fujian, China) (Quaternary science reviews)
This research uses a quantitative methodology for directly comparing the responses of observed crop yields in the SE USA to ENSO phenomena classified using dissimilar ENSO indices. … Of those tested Multivariate ENSO Index (MEI) was the overall best yield predictor.
As an island nation with some 85% of the population residing within 50 km of the coast, Australia faces significant threats into the future from sea level rise. Further, with over 710,000 addresses within 3 km of the coast and below 6-m elevation, the implication of a projected global rise in mean sea level of up to 100 cm over the 21st century will have profound economic, social, environmental, and planning consequences. In this context, it is becoming increasingly important to monitor trends emerging from local (regional) records to augment global average measurements and future projections. The Australasian region has four very long, continuous tide gauge records, at Fremantle (1897), Auckland (1903), Fort Denison (1914), and Newcastle (1925), which are invaluable for considering whether there is evidence that the rise in mean sea level is accelerating over the longer term at these locations in line with various global average sea level time-series reconstructions. These long records have been converted to relative 20-year moving average water level time series and fitted to second-order polynomial functions to consider trends of acceleration in mean sea level over time. The analysis reveals a consistent trend of weak deceleration at each of these gauge sites throughout Australasia over the period from 1940 to 2000. Short period trends of acceleration in mean sea level after 1990 are evident at each site, although these are not abnormal or higher than other short-term rates measured throughout the historical record.
Is There Evidence Yet of Acceleration in Mean Sea Level Rise around Mainland Australia? (Journal of Coastal Research)
Surface energy fluxes, at averaging times of ten minutes to one hour, are needed as inputs to most state-of-the-art dispersion models. The sensible heat flux is of major priority, since it is combined with the momentum flux to estimate the stability, the wind profile, and the turbulence intensities. Because of recent concerns about dispersion in built-up downtown areas of large cities, there is a need to estimate sensible heat flux in the midst of tall buildings. In this paper we work with some high quality and relevant but arguably underutilized data. The results of analysis of urban heat flux components from ten locations in suburban and built-up downtown areas in Oklahoma City during the Joint Urban 2003 (JU2003) field experiment are presented here. At street level in the downtown area, in the midst of tall skyscrapers, the ground heat flux and the sensible heat flux are relatively large and the latent heat flux is relatively small, when compared with concurrent fluxes observed in the upwind suburban areas. Confirming measurements at other cities, the sensible heat flux in the downtown area is observed to be slightly positive (10 to 20 W m−2) at night, indicating nearly neutral or slightly unstable conditions. Also in agreement with observations in other cities, the ground heat flux in the downtown area has a magnitude three or four times larger than that in suburban or rural areas. These results should permit improved parameterizations of sensible heat fluxes in the urban downtown area with tall buildings.
Urban Energy Fluxes in Built-Up Downtown Areas and Variations across the Urban Area, for Use in Dispersion Models (Journal of Applied Meteorology and Climatology)
Climate change is not only making the planet warmer, it is also making snowstorms stronger and more frequent, US scientists said on Tuesday
Global warming means more snowstorms: scientists (PHYSorg.com: Space & Earth)
Tropical deforestation not only has a large impact on the carbon cycle and climate, but also affects the chemistry of the atmosphere.
Land use affects the composition of the atmosphere (PHYSorg.com: Space & Earth)
Climate researchers at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association (AWI) expand a prevalent theory regarding the development of ice ages. In the current issue of the journal Nature three physicists from AWI’s working group “Dynamics of the Palaeoclimate” present new calculations on the connection between natural insolation and long-term changes in global climate activity. Up to now the presumption was that temperature fluctuations in Antarctica, which have been reconstructed for the last million years on the basis of ice cores, were triggered by the global effect of climate changes in the northern hemisphere. The new study shows, however, that major portions of the temperature fluctuations can be explained equally well by local climate changes in the southern hemisphere.
Ice age rethink puts warming into context Extance @ Simple Climate
The Sun has been in the news a lot lately because it’s beginning to send out more flares and solar storms. Its recent turmoil is particularly newsworthy because the Sun was very quiet for an unusually long time. Astronomers had a tough time explaining the extended solar minimum. New computer simulations imply that the Sun’s long quiet spell resulted from changing flows of hot plasma within it.
A new study released in the scientific journal Ecology Letters offers one of the first confirmations of a wholesale shift in the boreal forest ecosystem due to climate change.
Study illustrates shifting boreal forest ecosystem in Alaska (PHYSorg.com: Space & Earth)
Warming temperatures and melting ice in the Arctic may be behind a progressively earlier bloom of a crucial annual marine event, and the shift could hold consequences for the entire food chain and carbon cycling in the region.
Researchers discover arctic blooms occurring earlier (PHYSorg.com: Space & Earth)
As carbon dioxide levels have risen during the last 150 years, the density of pores that allow plants to breathe has dwindled by 34 percent, restricting the amount of water vapor the plants release to the atmosphere, report scientists from Indiana University Bloomington and Utrecht University in the Netherlands in an upcoming issue of the Proceedings of the National Academy of Sciences (now online)
Rising CO2 is causing plants to release less water to the atmosphere, researchers say (PHYSorg.com: Space & Earth)
Analysis of new data for eight stations in coastal southern Greenland, 1958–2001, shows a significant cooling (trend-line change −1.29°C for the 44 years), as do sea-surface temperatures in the adjacent part of the Labrador Sea, in contrast to global warming (+0.53°C over the same period). The land and sea temperature series follow similar patterns and are strongly correlated but with no obvious lead/lag either way. This cooling is significantly inversely correlated with an increased phase of the North Atlantic Oscillation (NAO) over the past few decades (r = −0.76), and will probably have significantly affected the mass balance of the Greenland Ice Sheet.
The Greenland coastal temperatures have followed the early 20th century global warming trend. Since 1940, however, the Greenland coastal stations data have undergone predominantly a cooling trend. At the summit of the Greenland ice sheet the summer average temperature has decreased at the rate of 2.2 °C per decade since the beginning of the measurements in 1987. This suggests that the Greenland ice sheet and coastal regions are not following the current global warming trend. A considerable and rapid warming over all of coastal Greenland occurred in the 1920s when the average annual surface air temperature rose between 2 and 4 °C in less than ten years (at some stations the increase in winter temperature was as high as 6 °C). This rapid warming, at a time when the change in anthropogenic production of greenhouse gases was well below the current level, suggests a high natural variability in the regional climate. High anticorrelations (r = –0.84 to–0.93) between the NAO (North Atlantic Oscillation) index and Greenland temperature time series suggest a physical connection between these processes. Therefore, the future changes in the NAO and Northern Annular Mode may be of critical consequence to the future temperature forcing of the Greenland ice sheet melt rates.
Global Warming and the Greenland Ice Sheet (Climatic Change)