A core challenge in global change biology is to predict how species will respond to future environmental change and to manage these responses. To make such predictions and management actions robust ...to novel futures, we need to accurately characterize how organisms experience their environments and the biological mechanisms by which they respond. All organisms are thermodynamically connected to their environments through the exchange of heat and water at fine spatial and temporal scales and this exchange can be captured with biophysical models. Although mechanistic models based on biophysical ecology have a long history of development and application, their use in global change biology remains limited despite their enormous promise and increasingly accessible software. We contend that greater understanding and training in the theory and methods of biophysical ecology is vital to expand their application. Our review shows how biophysical models can be implemented to understand and predict climate change impacts on species' behavior, phenology, survival, distribution, and abundance. It also illustrates the types of outputs that can be generated, and the data inputs required for different implementations. Examples range from simple calculations of body temperature at a particular site and time, to more complex analyses of species' distribution limits based on projected energy and water balances, accounting for behavior and phenology. We outline challenges that currently limit the widespread application of biophysical models relating to data availability, training, and the lack of common software ecosystems. We also discuss progress and future developments that could allow these models to be applied to many species across large spatial extents and timeframes. Finally, we highlight how biophysical models are uniquely suited to solve global change biology problems that involve predicting and interpreting responses to environmental variability and extremes, multiple or shifting constraints, and novel abiotic or biotic environments.
Predictions of how species respond to climate and other global changes should ideally be based explicitly on known processes. Here we review the field of biophysical ecology, which addresses the most fundamental thermodynamic processes by which organisms respond to environmental change. We contend that greater understanding and training in the theory and methods of biophysical models is vital to expand their application.
Ground- and aircraft-based measurements show that the seasonal amplitude of Northern Hemisphere atmospheric carbon dioxide (CO2) concentrations has increased by as much as 50 per cent over the past ...50 years. This increase has been linked to changes in temperate, boreal and arctic ecosystem properties and processes such as enhanced photosynthesis, increased heterotrophic respiration, and expansion of woody vegetation. However, the precise causal mechanisms behind the observed changes in atmospheric CO2 seasonality remain unclear. Here we use production statistics and a carbon accounting model to show that increases in agricultural productivity, which have been largely overlooked in previous investigations, explain as much as a quarter of the observed changes in atmospheric CO2 seasonality. Specifically, Northern Hemisphere extratropical maize, wheat, rice, and soybean production grew by 240 per cent between 1961 and 2008, thereby increasing the amount of net carbon uptake by croplands during the Northern Hemisphere growing season by 0.33 petagrams. Maize alone accounts for two-thirds of this change, owing mostly to agricultural intensification within concentrated production zones in the midwestern United States and northern China. Maize, wheat, rice, and soybeans account for about 68 per cent of extratropical dry biomass production, so it is likely that the total impact of increased agricultural production exceeds the amount quantified here.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The role of surgery for patients with locally advanced and metastatic renal cell carcinoma (RCC) is not precisely defined in our contemporary era of systemic therapies. Research in this field is ...focused on the role of regional lymphadenectomy, along with indications and timing of cytoreductive nephrectomy and metastasectomy. As our understanding of the molecular and immunological basis of RCC continues to develop along with the advent of novel systemic therapies, prospective clinical trials will be critical in defining how surgery should be integrated into the treatment paradigm of advanced RCC.
Sulfur hexafluoride (SF6) is a greenhouse gas with one of the highest radiative efficiencies in the atmosphere as well as an important indicator of transport time scales in the stratosphere. The ...current widely used estimate of the atmospheric lifetime of SF6 is 3200 years. In this study we use in situ measurements in the 2000 Arctic polar vortex that sampled air with up to 50% SF6 loss to calculate an SF6 lifetime. Comparison of these measurements with output from the Whole Atmosphere Community Climate Model (WACCM) shows that WACCM transport into the vortex is accurate and that an important SF6 loss mechanism, believed to be electron attachment, is missing in the model. Based on the measurements and estimates of the size of the vortex, we calculate an SF6 lifetime of 850 years with an uncertainty range of 580–1400 years. The amount of SF6 loss is shown to be consistent with that of HFC‐227ea, which has a lifetime of 670–780 years, adding independent support to our new SF6 lifetime estimate. Based on the revised lifetime the global warming potential of SF6 will decrease only slightly for short time horizons (<100 years) but will decrease substantially for time horizons longer than 2000 years. Also, the use of SF6 measurements as an indicator of transport time scales in the stratosphere clearly must account for potential influence from polar vortex air.
Key Points
Atmospheric lifetime of SF6 reduced by nearly a factor of 3 based on measurements in the stratospheric polar vortex
Consistency of SF6 and HFC‐227ea derived mean age of air gives independent confirmation of SF6 lifetime reduction
The signal of mesospheric loss or production of a trace gas is highly concentrated in the stratospheric polar vortices each winter
Plain Language Summary
We have calculated an atmospheric lifetime of the molecule SF6 based on trace gas measurements in the stratospheric polar vortex. This lifetime is 3 times shorter than the commonly used lifetime over the past 20 years. Since SF6 is a greenhouse gas this adjustment has implications for long‐term climate effects.
Cloud condensation nuclei (CCN) can affect cloud properties and therefore the Earth’s radiative balance. New particle formation (NPF) from condensable vapours in the free troposphere has been ...suggested to contribute to CCN, especially in remote, pristine atmospheric regions, but direct evidence is sparse, and the magnitude of this contribution is uncertain. Here we use in-situ aircraft measurements of vertical profiles of aerosol size distributions to present a global-scale survey of NPF occurrence. We observed intense NPF occurring at high altitude in tropical convective regions over both the Pacific and Atlantic Oceans. Together with the results of chemical-transport models, our findings indicate that NPF persists at all longitudes as a global-scale band in the tropical upper troposphere, covering about 40% of the Earth’s surface. Furthermore, we find that this NPF in the tropical upper troposphere is a globally important source of CCN in the lower troposphere, where they can affect cloud properties. Our findings suggest that the production of CCN, as these new particles descend towards the surface, is currently not adequately captured in global models, because they tend to underestimate both the magnitude of tropical upper tropospheric NPF and the subsequent growth to CCN sizes. This has potential implications for cloud albedo and the global radiative balance.
Summary An international group of multidisciplinary experts on middle-ear and paediatric infections met to explore where consensus exists on the management of acute otitis media. After informal ...discussions among several specialists of paediatric infectious disease, the group was expanded to include a larger spectrum of professionals with complementary expertise in middle-ear disease. Acute otitis media is a very common bacterial infection in children worldwide, leading to excessive antibiotic consumption in children in most countries and to a substantial burden of deafness and suppurative complications in developing countries. The group attempted to move beyond the existing controversies surrounding guidelines on acute otitis media, and to propose to clinicians and public health officials their views on the actions needed to be taken to reduce the disease burden caused by acute otitis media and the microbial antibiotic resistance from the resulting use of antibiotics. Definition of acute otitis media and diagnostic accuracy are crucial steps to identify children who will potentially benefit from treatment with antibiotics and to eliminate unnecessary prescribing. Although the group agreed that antibiotics are distributed indiscriminately, even to children who do not seem to have the disease, no consensus could be reached on whether antibiotics should be given to all appropriately diagnosed children, reflecting the wide range of practices and lack of convincing evidence from observational studies. The major unanimous concern was an urgent need to reduce unnecessary prescribing of antibiotics to prevent further increases in antibiotic resistance. Prevention of acute otitis media with existing and future viral and bacterial vaccines seems the most promising approach to affect disease burden and consequences, both in developed and developing countries.
An enhanced aerosol layer near the tropopause over Asia during the June–September period of the Asian summer monsoon (ASM) was recently identified using satellite observations. Its sources and ...climate impact are presently not well-characterized. To improve understanding of this phenomenon, we made in situ aerosol measurements during summer 2015 from Kunming, China, then followed with a modeling study to assess the global significance. The in situ measurements revealed a robust enhancement in aerosol concentration that extended up to 2 km above the tropopause. A climate model simulation demonstrates that the abundant anthropogenic aerosol precursor emissions from Asia coupled with rapid vertical transport associated with monsoon convection leads to significant particle formation in the upper troposphere within the ASM anticyclone. These particles subsequently spread throughout the entire Northern Hemispheric (NH) lower stratosphere and contribute significantly (∼15%) to the NH stratospheric column aerosol surface area on an annual basis. This contribution is comparable to that from the sum of small volcanic eruptions in the period between 2000 and 2015. Although the ASM contribution is smaller than that from tropical upwelling (∼35%), we find that this region is about three times as efficient per unit area and time in populating the NH stratosphere with aerosol. With a substantial amount of organic and sulfur emissions in Asia, the ASM anticyclone serves as an efficient smokestack venting aerosols to the upper troposphere and lower stratosphere. As economic growth continues in Asia, the relative importance of Asian emissions to stratospheric aerosol is likely to increase.
Black carbon (BC) aerosol loadings were measured during the High‐performance Instrumented Airborne Platform for Environmental Research Pole‐to‐Pole Observations (HIPPO) campaign above the remote ...Pacific from 85°N to 67°S. Over 700 vertical profiles extending from near the surface to max ~14 km altitude were obtained with a single‐particle soot photometer between early 2009 and mid‐2011. The data provides a climatology of BC in the remote regions that reveals gradients of BC concentration reflecting global‐scale transport and removal of pollution. BC is identified as a sensitive tracer of extratropical mixing into the lower tropical tropopause layer and trends toward surprisingly uniform loadings in the lower stratosphere of ~1 ng/kg. The climatology is compared to predictions from the AeroCom global model intercomparison initiative. The AeroCom model suite overestimates loads in the upper troposphere/lower stratosphere (~10×) more severely than at lower altitudes (~3×), with bias roughly independent of season or geographic location; these results indicate that it overestimates BC lifetime.
Key Points
A BC climatology is provided for the remote Pacific and Polar regions
AeroCom overestimates remote BC with strong altitude dependence
Extratropical mixing into the TTL is estimated from BC latitudinal gradients
The Amazon Basin experiences severe droughts that may become more common in the future. Little is known of the effects of such droughts on Amazon forest productivity and carbon allocation. We tested ...the prediction that severe drought decreases litterfall and wood production but potentially has multiple cancelling effects on belowground production within a 7-year partial throughfall exclusion experiment. We simulated an approximately 35-41% reduction in effective rainfall from 2000 through 2004 in a 1 ha plot and compared forest response with a similar control plot. Wood production was the most sensitive component of above-ground net primary productivity (ANPP) to drought, declining by 13% the first year and up to 62% thereafter. Litterfall declined only in the third year of drought, with a maximum difference of 23% below the control plot. Soil CO2 efflux and its 14C signature showed no significant treatment response, suggesting similar amounts and sources of belowground production. ANPP was similar between plots in 2000 and declined to a low of 41% below the control plot during the subsequent treatment years, rebounding to only a 10% difference during the first post-treatment year. Live aboveground carbon declined by 32.5 Mg ha−1 through the effects of drought on ANPP and tree mortality. Results of this unreplicated, long-term, large-scale ecosystem manipulation experiment demonstrate that multi-year severe drought can substantially reduce Amazon forest carbon stocks.
Trend analyses are presented for 30 years (1980–2010) of balloon‐borne stratospheric water vapor measurements over Boulder, Colorado. The data record is broken into four multiple‐year periods of ...water vapor trends, including two that span the well‐examined but unattributed 1980–2000 period of stratospheric water vapor growth. Trends are determined for five 2 km stratospheric layers (16–26 km) utilizing weighted, piecewise regression analyses. Stratospheric water vapor abundance increased by an average of 1.0 ± 0.2 ppmv (27 ± 6%) during 1980–2010 with significant shorter‐term variations along the way. Growth during period 1 (1980–1989) was positive and weakened with altitude from 0.44 ± 0.13 ppmv at 16–18 km to 0.07 ± 0.07 ppmv at 24–26 km. Water vapor increased during period 2 (1990–2000) by an average 0.57 ± 0.25 ppmv, decreased during period 3 (2001–2005) by an average 0.35 ± 0.04 ppmv, then increased again during period 4 (2006–2010) by an average 0.49 ± 0.17 ppmv. The diminishing growth with altitude observed during period 1 is consistent with a water vapor increase in the tropical lower stratosphere that propagated to the midlatitudes. In contrast, growth during periods 2 and 4 is stronger at higher altitudes, revealing contributions from at least one mechanism that strengthens with altitude, such as methane oxidation. The amount of methane oxidized in the stratosphere increased considerably during 1980–2010, but this source can account for at most 28 ± 4%, 14 ± 4%, and 25 ± 5% of the net stratospheric water vapor increases during 1980–2000, 1990–2000, and 1980–2010, respectively.
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