A common framework for approaches to extreme event attribution

The extent to which a given extreme weather or climate event is attributable to anthropogenic climate change is a question of considerable public interest. From a scientific perspective, the question can be framed in various ways, and the answer depends very much on the framing. One such framing is a risk-based approach, which answers the question probabilistically, in terms of a change in likelihood of a class of event similar to the one in question, and natural variability is treated as noise. A rather different framing is a storyline approach, which examines the role of the various factors contributing to the event as it unfolded, including the anomalous aspects of natural variability, and answers the question deterministically. It is argued that these two apparently irreconcilable approaches can be viewed within a common framework, where the most useful level of conditioning will depend on the question being asked and the uncertainties involved

Changes in the geographical distribution of plant species and climatic variables on the West Cornwall peninsula (South West UK)

Recent climate change has had a major impact on biodiversity and has altered the geographical distribution of vascular plant species. This trend is visible globally; however, more local and regional scale research is needed to improve understanding of the patterns of change and to develop appropriate conservation strategies that can minimise cultural, health, and economic losses at finer scales. Here we describe a method to manually geo-reference botanical records from a historical herbarium to track changes in the geographical distributions of plant species in West Cornwall (South West England) using both historical (pre-1900) and contemporary (post-1900) distribution records. We also assess the use of Ellenberg and climate indicator values as markers of responses to climate and environmental change. Using these techniques we detect a loss in 19 plant species, with 6 species losing more than 50% of their previous range. Statistical analysis showed that Ellenberg (light, moisture, nitrogen) and climate indicator values (mean January temperature, mean July temperature and mean precipitation) could be used as environmental change indicators. Significantly higher percentages of area lost were detected in species with lower January temperatures, July temperatures, light, and nitrogen values, as well as higher annual precipitation and moisture values. This study highlights the importance of historical records in examining the changes in plant species’ geographical distributions. We present a method for manual geo-referencing of such records, and demonstrate how using Ellenberg and climate indicator values as environmental and climate change indicators can contribute towards directing appropriate conservation strategies

Nocturnal cerebral oxygenation in relation to vital parameters in acute stroke.

Background: Stroke is the third leading cause of death in the world. Admittance to a specialized hospital ward (so called Stroke Unit) is proven beneficial for outcome after acute stroke. So far it is unclear what exactly the rationale behind this specialized care is. Damaged brain tissue and vessels cannot compensate for drops in blood pressure and oxygenation (so called impaired cerebral autoregulation). Vital parameters are frequently measured and corrected on the Stroke Unit to optimize brain perfusion and oxygenation. Near-infrared spectroscopy (NIRS) provides a non invasive method of continuously monitoring cerebral oxygenation. The aim was to measure nocturnal vital parameters and cerebral oxygenation in the frontal areas in acute stroke patients to see whether nocturnal fluctuations of NIRS (rSO2) occur and differ between hemispheres. Furthermore we investigated whether fluctuations are related to variations in vital parameters. Method: Observational ‘pilot’ study. 8 acute anterior stroke patients were monitored within 24 hours after onset overnight. The NIRS optodes were attached bifrontally. Saturation and mean arterial pressure (Map) were measured continuously, Map was recorded with an ambulatory blood pressure device (Portapres). Statistics: Pearson or Spearman correlations are applied to evaluate the degree of association (NIRS L and R with Map (Mx) and SpO2 (Sx)). The Wilcoxon signed rank test is used to compare vital parameters (Mx and Sx analysis) with NIRS to see if there are hemispherical differences (non affected versus affected hemisphere, non-lacunar versus lacunar infarction). Results: In our patients Mx was slightly higher in the affected hemispheres, however the difference was not significant. The Sx was non-significantly higher in the non affected hemispheres. Subgroup analysis showed a slight higher trend for type of infarction, atrium fibrillation and hypertension in the non affected hemisphere. Creating subgroups with or without hypertension, diabetes and atrium fibrillation did not provide any new insights. Patients with a higher NIHSS displayed a wider difference between affected and non affected hemisphere in the Mx. In older patients a lower Mx was observed. The Sx analysis follows in opposite direction of Mx, especially in non lacunar infarctions (Mx high, Sx low). Studying the Mx and Sx of each patient separate, it seems that with lacunar infarctions both correlation indices follow one another with a narrow range. For the non lacunar infarctions this was less clear. Conclusions: NIRS offers a continuous, non invasive monitoring measurement of cerebral oxygenation in real time at bedside in acute stroke patients. Combining NIRS with other vital parameters offers new insights in cerebral autoregulation after acute stroke. In this pilot correlation study with a diversity of patients, we found small differences between affected and non affected hemispheres, infarct type and stroke severity, which needs further inclusion of patients. The correlation indices Mx and Sx seem promising ways to evaluate the state of cerebral autoregulation in two hemispheres in acute stroke patients over time.