-
Do alternative energy sources displace fossil fuels?
-
A fundamental, generally implicit, assumption of the Intergov- ernmental Panel on Climate Change reports and many energy analysts is that each unit of energy supplied by non-fossil-fuel sources takes the place of a unit of energy supplied by fossil- fuel sources (1–4). However, owing to the complexity of economic systems and human behaviour, it is often the case that changes aimed at reducing one type of resource consumption, either through improvements in efficiency of use or by developing substitutes, do not lead to the intended outcome when net effects are considered (5–9). Here, I show that the average pattern across most nations of the world over the past fifty years is one where each unit of total national energy use from non- fossil-fuel sources displaced less than one-quarter of a unit of fossil-fuel energy use and, focusing specifically on electricity, each unit of electricity generated by non-fossil-fuel sources displaced less than one-tenth of a unit of fossil-fuel-generated electricity. These results challenge conventional thinking in that they indicate that suppressing the use of fossil fuel will require changes other than simply technical ones such as expanding non-fossil-fuel energy production.
Located in
Resources
/
Climate Science Documents
-
Beneficial Biofuels—The Food, Energy, and Environment Trilemma
-
Exploiting multiple feedstocks, under new policies and accounting rules, to balance biofuel production, food security, and greenhouse-gas reduction.
Located in
Resources
/
Climate Science Documents
-
Can Plants Adapt? New Questions in Climate Change Research
-
As it becomes increasingly apparent that human activities are partly responsible for global warming, the focus of climate change research is shifting from the churning out of assessments to the pursuit of science that can test the robustness of existing models. The questions now being addressed are becoming more challenging:The questions now being addressed are becoming more challenging: Can water-use efficiency of plants keep up with rising temperatures? Will we see a greening period for some decades, even a century, before facing a rapid browndown as threshold temperatures are reached? Or could the thresholds be reached much sooner because of interactions of biophysical processes? Is the carbon storage issue missing the point?
Located in
Resources
/
Climate Science Documents
-
A Large-Scale Deforestation Experiment: Effects of Patch Area and Isolation on Amazon Birds
-
As compared with extensive contiguous areas, small isolated habitat patches lack many species. Some species disappear after isolation; others are rarely found in any small patch, regardless of isolation. We used a 13-year data set of bird captures from a large landscape-manipulation experiment in a Brazilian Amazon forest to model the extinction-colonization dynamics of 55 species and tested basic predictions of island biogeography and metapopulation theory. From our models, we derived two metrics of species vulnerability to changes in isolation and patch area. We found a strong effect of area and a variable effect of isolation on the predicted patch occupancy by birds.
Located in
Resources
/
Climate Science Documents
-
Climatic extremes improve predictions of spatial patterns of tree species
-
Understanding niche evolution, dynamics, and the response of species to climate change requires knowledge of the determinants of the environmental niche and species range limits. Mean values of climatic variables are often used in such analyses. In contrast, the increasing frequency of climate extremes suggests the importance of understanding their additional influence on range limits. Here, we assess how measures representing climate extremes (i.e., interannual variability in climate parameters) explain and predict spatial patterns of 11 tree species in Switzerland. We find clear, although comparably small, improvement (20% in adjusted D2, 8% and 3% in cross-validated True Skill Statistic and area under the receiver operating characteristics curve values) in models that use measures of extremes in addition to means. The primary effect of including information on climate extremes is a correction of local overprediction and underprediction. Our results demonstrate that measures of climate extremes are important for understanding the climatic limits of tree species and assessing species niche characteristics. The inclusion of climate variability likely will improve models of species range limits under future conditions, where changes in mean climate and increased variability are expected.
Located in
Resources
/
Climate Science Documents
-
Are there basic physical constraints on future anthropogenic emissions of carbon dioxide?
-
Here, it is shown both theoretically and observationally how the evolution of the human system can be considered from a surprisingly simple thermodynamic perspective in which it is unnecessary to explicitly model two of the emissions drivers: population and standard of living. Specifically, the human system grows through a self-perpetuating feedback loop in which the consumption rate of primary energy resources stays tied to the historical accumulation of global economic production—or p × g—through a time-independent factor of 9.7 ± 0.3 mW per inflation-adjusted 1990 US dollar. This important constraint, and the fact that f and c have historically varied rather slowly, points towards substantially narrowed visions of future emissions scenarios for implementation in GCMs.
Located in
Resources
/
Climate Science Documents
-
Early warning signals of extinction in deteriorating environments
-
During the decline to extinction, animal populations may present dynamical phenomena not exhibited by robust populations (1,2). Some of these phenomena, such as the scaling of demographic variance, are related to small size (3–6) whereas others result from density- dependent nonlinearities (7). Although understanding the causes of population extinction has been a central problem in theoretical biology for decades (8), the ability to anticipate extinction has remained elusive (9). Here we argue that the causes of a population’s decline are central to the predictability of its extinction. Specifically, environmental degradation may cause a tipping point in population dynamics, corresponding to a bifurcation in the underlying population growth equations, beyond which decline to extinction is almost certain. In such cases, imminent extinction will be signalled by critical slowing down (CSD)
critical slowing down
Located in
Resources
/
Climate Science Documents
-
Non-equilibrium succession dynamics indicate continued northern migration of lodgepole pine
-
This study provides evidence of range expansion under current climatic conditions of an indigenous species with strong ecosystem effects. Surveys of stands along the northern distribution limit of lodgepole pine (Pinus contorta var. latifolia) in central Yukon Territory, Canada showed consistent increases in pine dominance following fire. These patterns differed strongly from those observed at sites where pine has been present for several thousand years. Differences in species thinning rates are unlikely to account for the observed increases in pine dominance. Rates of pine regeneration at its range limits were equivalent to those of spruce, indicating a capacity for rapid local population expansion. The study also found no evidence of strong climatic limitation of pine population growth at the northern distribution limit. We interpret these data as evidence of current pine expansion at its range limits and conclude that the northern distribution of lodgepole pine is not in equilibrium with current climate. This study has implications for our ability to predict vegetation response to climate change when populations may lag in their response to climate.
Located in
Resources
/
Climate Science Documents
-
Another reason for concern: regional and global impacts on ecosystems for different levels of climate change
-
Between 1C and 2C increases in global mean temperatures most species, ecosystems and landscapes will be impacted and adaptive capacity will become limited. With the already ongoing high rate of climate change, the decline in biodiversity will therefore accelerate and simultaneously many ecosystem services will become less abundant.
Located in
Resources
/
Climate Science Documents
-
A long-term association between global temperature and biodiversity, origination and extinction in the fossil record
-
We analysed the fossil record for the last 520 Myr against estimates of low latitude sea surface temperature for the same period. We found that global biodiversity (the richness of families and genera) is related to temperature and has been relatively low during warm ‘greenhouse’ phases, while during the same phases extinction and origination rates of taxonomic lineages have been relatively high. These findings are consistent for terrestrial and marine environments and are robust to a number of alternative assumptions and potential biases. Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner. Our findings may have implications for extinction and biodiversity change under future climate warming.
Located in
Resources
/
Climate Science Documents
