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This study investigates the causes for, and distribution of, unimodal versus bimodal seasonal cycle of vegetation greenness in the Southwest United States using extensive site observations, climate data, satellite data, and the Lund‐Potsdam‐Jena (LPJ) vegetation model. Peak vegetation greenness is achieved in a clockwise manner across the Southwest, beginning in spring in the Sonoran Desert following winter rains, then in Utah‐Colorado with snowmelt/summer rains, and finally in New Mexico–eastern Arizona with late summer monsoon rains. At high elevations, spring‐summer snowmelt is critical for supplying the necessary soil moisture to trigger vegetation growth. A bimodal seasonal cycle of vegetation greenness is evident in satellite data and LPJ simulations across eastern Arizona and western New Mexico, characterized by peaks during late spring–early summer and late summer–early autumn. This bimodal green‐up remains a pressing paradox for which many competing hypotheses exist. The mechanism for this seasonal pattern is demonstrated using LPJ and observational data and is found to deviate from the traditional pulse‐reserve paradigm. This paradigm states that rainfall events in arid lands produce nearly immediate pulses of vegetation growth and accumulation of reserves but does not consider cold dormancy, time‐lagged vegetation responses, or rainfall seasonality. The following soil moisture based mechanism for bimodal greening is proposed. The initial peak in vegetation greenness during late spring–early summer results from a break in cold dormancy and benefits from the gradual winter‐long accumulation of deep soil moisture from weak synoptic rain events and snowmelt in colder regions. Limited precipitation and ongoing transpiration, from the initial vegetation greening, trigger a midsummer drying of the soil and a consequential minimum in vegetation activity. Later, pulses of monsoon rainfall in late summer–early autumn support the secondary greening, although significant runoff of brief, intense rainstorms and substantial soil evaporation limit moisture to the upper soil layers.

A full global atmosphere-ocean-land vegetation model is used to examine the coupled climate/vegetation changes in the extratropics between modern and mid-Holocene (6,000 year BP) times and to assess the feedback of vegetation cover changes on the climate response. The model produces a relatively realistic natural vegetation cover and a climate sensitivity comparable to that realized in previous studies. The simulated mid-Holocene climate led to an expansion of boreal forest cover into polar tundra areas (mainly due to increased summer/fall warmth) and an expansion of middle latitude grass cover (due to a combination of enhanced temperature seasonality with cold winters and interior drying of the continents). The simulated poleward expansion of boreal forest and middle latitude expansion of grass cover are consistent with previous modeling studies. The feedback effect of expanding boreal forest in polar latitudes induced a significant spring warming and reduced snow cover that partially countered the response produced by the orbitally induced changes in radiative forcing. The expansion of grass cover in middle latitudes worked to reinforce the orbital forcing by contributing a spring cooling, enhanced snow cover, and a delayed soil water input by snow melt. Locally, summer rains tended to increase (decrease) in areas with greatest tree cover increases (decreases); however, for the broad-scale polar and middle latitude domains the climate responses produced by the changes in vegetation are relatively much smaller in summer/fall than found in previous studies. This study highlights the need to develop a more comprehensive strategy for investigating vegetation feedbacks.

The psychological state elicited by the classic psychedelics drugs, such as LSD and psilocybin, is one of the most fascinating and yet least understood states of consciousness. However, with the advent of modern functional neuroimaging techniques, the effect of these drugs on neural activity is now being revealed, although many of the varied phenomenological features of the psychedelic state remain challenging to explain. Integrated information theory (IIT) is one of the foremost contemporary theories of consciousness, providing a mathematical formalization of both the quantity and quality of conscious experience. This theory can be applied to all known states of consciousness, including the psychedelic state. Using the results of functional neuroimaging data on the psychedelic state, the effects of psychedelic drugs on both the level and structure of consciousness can be explained in terms of the conceptual framework of IIT. This new IIT-based model of the psychedelic state provides an explanation for many of its phenomenological features, including unconstrained cognition, alterations in the structure and meaning of concepts and a sense of expanded awareness. This model also suggests that whilst cognitive flexibility, creativity, and imagination are enhanced during the psychedelic state, this occurs at the expense of cause-effect information, as well as degrading the brain's ability to organize, categorize, and differentiate the constituents of conscious experience. Furthermore, the model generates specific predictions that can be tested using a combination of functional imaging techniques, as has been applied to the study of levels of consciousness during anesthesia and following brain injury.

The state of consciousness induced by N,N-dimethyltryptamine (DMT) is one of the most extraordinary of any naturally-occurring psychedelic substance. Users consistently report the complete replacement of normal subjective experience with a novel \"alternate universe,\" often densely populated with a variety of strange objects and other highly complex visual content, including what appear to be sentient \"beings.\" The phenomenology of the DMT state is of great interest to psychology and calls for rigorous academic enquiry. The extremely short duration of DMT effects-less than 20 min-militates against single dose administration as the ideal model for such enquiry. Using pharmacokinetic modeling and DMT blood sampling data, we demonstrate that the unique pharmacological characteristics of DMT, which also include a rapid onset and lack of acute tolerance to its subjective effects, make it amenable to administration by target-controlled intravenous infusion. This is a technology developed to maintain a stable brain concentration of anesthetic drugs during surgery. Simulations of our model demonstrate that this approach will allow research subjects to be induced into a stable and prolonged DMT experience, making it possible to carefully observe its psychological contents, and provide more extensive accounts for subsequent analyses. This model would also be valuable in performing functional neuroimaging, where subjects are required to remain under the influence of the drug for extended periods. Finally, target-controlled intravenous infusion of DMT may aid the development of unique psychotherapeutic applications of this psychedelic agent.

In 1895, after years of growing tension, the prime minister of Britain's South African Cape Colony, Cecil Rhodes, and his friend Dr Leander Starr Jameson, hatched a plot for the latter to embark upon a similar journey, leading a small force into Johannesburg, the capital of the Transvaal, and aiming to spark a revolution among the Uitlanders (non-Boer - mainly British - residents) in the city. Rhodes was given permission (in principle) by the then Liberal government to extend the reach of the Cape Colony (of which he was Prime Minister) all the way north to Rhodesia, which was run by Rhodes's chartered company.

The life cycle and structure of dominant wintertime SST anomalies and associated atmospheric response in the extratropical North Pacific are examined using results from a 100-yr seasonal simulation of a low-resolution atmospheric model with realistic geography coupled to a simple mixed layer ocean. The study focuses on composited SST anomalies produced solely by ocean–atmosphere energy exchange. One key pattern shows a negative (positive) SST anomaly in the central Pacific, denoted CCP (WCP), flanked by opposite signed anomalies in the western and eastern Pacific. For the WCP case, the SST anomaly reaches about 1.0°C in the central Pacific, whereas for the CCP case it is −1.5°C. During the growth phase of the WCP (CCP) SST anomalies, anomalous highs (lows) occur over the western Pacific and over western North America, and an anomalous low (high) is over the east-central Pacific. To the rear of the anomalous low (high), a negative (positive) SST anomaly develops in response to anomalous cold, dry (warm, moist) air. The effect of anomalous wind also contributes but to a lesser extent. The composited SST anomalies primarily develop in 1–2 months. During the decay stage of the WCP SST anomaly, the atmospheric anomalies are essentially of opposite sign than during the growth stage and help to destroy the SST anomaly. In contrast, the atmospheric anomalies during the decay stage of the CCP SST anomaly are of the same sign but weaker than during the growth stage. For this case, a positive SST–atmosphere feedback involving ocean–atmosphere energy exchange helps maintain a more persistent SST anomaly than in the WCP composite case. Comparison of results with prescribed SST anomaly experiments indicate that the ocean is in part forcing the atmosphere during the decay stage of CCP SST anomalies. The magnitude and position of the lower-tropospheric anomalies forced by SST anomalies are similar to those obtained in linear theory, while the vertical structure is more akin to that found in higher-resolution GCMs with realistic geography. The weaker atmospheric anomalies generated by the low-resolution model are likely a consequence of its simulation of weak transients. Differences between the composite and prescribed SST anomaly results (e.g., in position of the atmospheric anomalies relative to the SST anomaly) suggest that the anomalous response of the atmosphere to SST anomalies in a coupled ocean–atmosphere environment may not be the same as in a one-way forced system.

A new modeling concept, referred to as Modeling Surgery, has been recently developed at University of Wisconsin-Madison. It is specifically designed to diagnose coupled feedbacks between different climate components as well as climatic teleconnections within a specific component through systematically modifying the coupling configurations and teleconnective pathways. It thus provides a powerful means for identifying the causes and mechanisms of low-frequency variability in the Earth's climate system. In this paper, we will give a short review of our recent progress in this new area.[PUBLICATION ABSTRACT]

Rising levels of carbon dioxide since the preindustrial era have likely contributed to an observed warming of the global surface, and observations show global greening and an expansion of boreal forests. This study reproduces observed climate and vegetation trends associated with rising CO₂ using a fully coupled atmosphere–ocean–land surface GCM with dynamic vegetation and decomposes the effects into physiological and radiative components. The simulated warming trend, strongest at high latitudes, was dominated by the radiative effect, although the physiological effect of CO₂ on vegetation (CO₂ fertilization) contributed to significant wintertime warming over northern Europe and central and eastern Asia. The net global greening of the model was primarily due to the physiological effect of increasing CO₂, while the radiative and physiological effects combined to produce a poleward expansion of the boreal forests. Observed and simulated trends in tree ring width are consistent with the enhancement of vegetation growth by the physiological effect of rising CO₂.

Two 100-year seasonal simulations, one performed with a low resolution atmospheric general circulation model (GCM) coupled to a mixed-layer ocean formulation and the other made with the GCM forced by prescribed ocean conditions, are compared to assess the effects of an interactive ocean and sea-ice component on the stability and interannual variability of a climate system. Characteristics of the time variation of surface temperature, 700 mb temperature and sea-ice coverage are analyzed for selected land and ocean areas. Both simulations showed stable seasonal cycles of basic variables, although small trends were found. These trends were roughly linear in nature and quite distinct from all other components of variability. Detrended time series were used to describe the other aspects of variability. There was pronounced interannual variability in the simulations from both models as seen in the time series for temperature and sea ice over the entire 100-year time period. Consistent with observations, variations tended to be larger in polar areas and over land. The inclusion of the interactive ocean and sea-ice component produced a red spectrum for surface temperature but not for 700-mb temperature. Using a linearized air–sea model patterned after the coupled models, this result is shown to be linked to the combined effects of the model longwave cooling and ocean-atmosphere energy exchange. The shift towards lower frequency in surface temperature was most evident in polar regions and occurred in conjunction with very low frequency (even decadal-scale) variability in the computed sea-ice coverage. The simulated mean and variability characteristics of sea ice corresponded fairly well with observations. This suggests that the low resolution model is able to represent some relevant aspects of the physics of climate fluctuations and thus provide useful simulations for studies of interannual variability.