Climate change: No warming hiatus for extreme hot temperatures

Extremely hot temperatures over land have dramatically and unequivocally increased in number and area despite claims that the rise in global average temperatures has slowed over the past 10 to 20 years during what some public commentators have called a global warming hiatus period.Scientists from UNSW’s ARC Centre of Excellence for Climate System Science and international colleagues made the finding when they focused their research on the rise of temperatures at the extreme end of the spectrum where impacts are felt the most.”It quickly became clear, the ‘hiatus’ in global average temperatures did not stop the rise in the number, intensity and area of extremely hot days,” said one of the paper’s authors, Dr Lisa Alexander.”Our research has found a steep upward tendency in the temperatures and number of extremely hot days over land and the area they impact, despite the complete absence of a strong El Nio since 1998.”The researchers examined the extreme end of the temperature spectrum because this is where global warming impacts are expected to occur first and are most clearly felt. As Australians saw this summer and the last, extreme temperatures in inhabited areas have powerful impacts on our society.The observations also showed that extremely hot events are now affecting, on average, more than twice the area when compared to similar events 30 years ago.To get their results, which are published today in the journal Nature Climate Change, the researchers examined hot days starting from 1979. Temperatures of every day throughout the year were compared against temperatures on that exact same calendar day from 1979-2012. The hottest 10 per cent of all days over that period were classified as hot temperature extremes.Globally, on average, regions normally expect around 36.5 extremely hot days in a year. The observations showed that during the period from 1997-2012, regions that experienced 10, 30 or 50 extremely hot days above this average saw the greatest upward trends in extreme hot days over time and the area they impacted.The consistently upward trend persisted right through the “hiatus” period from 1998-2012.”Our analysis shows there has been no pause in the increase of warmest daily extremes over land and the most extreme of the extreme conditions are showing the largest change,” said Dr Markus Donat.”Another interesting aspect of our research was that those regions that normally saw 50 or more excessive hot days in a year saw the greatest increases in land area impact and the frequency of hot days. In short, the hottest extremes got hotter and the events happened more often.”While global annual average near-surface temperatures are a widely used measure of climate change, this latest research reinforces that they do not account for all aspects of the climate system.A stagnation in the increase of global annual mean temperatures, over a relatively short period of 10 to 20 years, does not imply that global warming has stopped. Other measures, such as extreme temperatures, ocean heat content and the disappearance of land-based ice all show continuous changes that are consistent with a warming world.”It is important when we take global warming into account, that we use measures that are useful in determining the impacts on our society,” said Professor Sonia Seneviratne from ETH Zurich, who led the study while on sabbatical at the ARC Centre.”Global average temperatures are a useful measurement for researchers but it is at the extremes where we will most likely find those impacts that directly affect all of our lives. Clearly, we are seeing more heat extremes over land more often as a result of enhanced greenhouse gas warming.”Story Source:The above story is based on materials provided by University of New South Wales. Note: Materials may be edited for content and length.

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Smokers who survive to 70 still lose four years of life

Aug. 31, 2013 — Smokers who survive to 70 still lose an average of 4 years of life, according to findings from the Whitehall study.Dr Emberson said: “Despite recent declines in the numbers of people smoking and tar yields of cigarettes, smoking remains the leading preventable cause of death in Europe.”He added: “Previous studies had demonstrated that prolonged cigarette smoking from early adult life was associated with about 10 years loss of life expectancy, with about one quarter of smokers killed by their habit before the age of 70. Stopping at ages 60, 50, 40 or 30 years gained back about 3, 6, 9 or the full 10 years. However, the hazards of continuing to smoke and the benefits of stopping in older people had not been widely studied.”In the current study, scientists tracked the health of 7,000 older men (mean age 77 years, range 66 to 97) from 1997 to 2012 who took part in the Whitehall study of London civil servants. Hazard ratios (HRs) for overall mortality and various causes of death in relation to smoking habits were calculated after adjustment for age, last known employment grade and previous diagnoses of vascular disease or cancer.During the 15-year study 5,000 of the 7,000 men died. Deaths in current smokers were about 50% higher than in never smokers (HR=1.50), due chiefly to vascular disease (HR=1.34), cancer (HR=1.74) and respiratory disease (HR=2.39).Deaths in former smokers were 15% higher than in never smokers (HR=1.15), due chiefly to cancer (HR=1.24) and respiratory disease (HR=1.58). Compared with never smokers, men who had quit smoking within the previous 25 years (median 14 years) had a 28% higher mortality rate (HR=1.28) while men who quit >25 years ago (median 35 years) had no significant excess risk (HR=1.05).Dr Emberson said: “Our results clearly show that active smoking continues to increase the risk of death in old age. Risk in former smokers decreases as the time since quitting gets longer and, if one survives long enough, eventually reaches levels of never smokers.”Average life expectancy from age 70 was about 18 years in men who had never regularly smoked, 16 years for men who gave up smoking before age 70 but only about 14 years in men still smoking at age 70. Two-thirds of never smokers (65%), but only half of current smokers (48%), survived from age 70 to age 85.Dr Emberson said: “This study shows that even if you were to ignore all the deaths caused by smoking before the age of 70, older smokers still do considerably worse than older non-smokers, losing a considerable amount of subsequent lifespan.”Dr Robert Clarke (UK), coordinator of the study, concluded: “We have shown that even if a smoker is fortunate enough to survive to age 70 they still lose, on average, about 4 years of subsequent lifespan compared with men who do not smoke. Quitting is beneficial at any age and it really is never too late to stop.”

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Single gene change increases mouse lifespan by 20 percent

Aug. 29, 2013 — By lowering the expression of a single gene, researchers at the National Institutes of Health have extended the average lifespan of a group of mice by about 20 percent — the equivalent of raising the average human lifespan by 16 years, from 79 to 95. The research team targeted a gene called mTOR, which is involved in metabolism and energy balance, and may be connected with the increased lifespan associated with caloric restriction.A detailed study of these mice revealed that gene-influenced lifespan extension did not affect every tissue and organ the same way. For example, the mice retained better memory and balance as they aged, but their bones deteriorated more quickly than normal.This study appears in the Aug. 29 edition of Cell Reports.”While the high extension in lifespan is noteworthy, this study reinforces an important facet of aging; it is not uniform,” said lead researcher Toren Finkel, M.D., Ph.D., at NIH’s National Heart, Lung, and Blood Institute (NHLBI). “Rather, similar to circadian rhythms, an animal might have several organ-specific aging clocks that generally work together to govern the aging of the whole organism.”Finkel, who heads the NHLBI’s Laboratory of Molecular Biology in the Division of Intramural Research, noted that these results may help guide therapies for aging-related diseases that target specific organs, like Alzheimer’s. However, further studies in these mice as well as human cells are needed to identify exactly how aging in these different tissues is connected at the molecular level.The researchers engineered mice that produce about 25 percent of the normal amount of the mTOR protein, or about the minimum needed for survival. The engineered mTOR mice were a bit smaller than average, but they otherwise appeared normal.The median lifespan for the mTOR mice was 28.0 months for males and 31.5 months for females, compared to 22.9 months and 26.5 months for normal males and females, respectively. The mTOR mice also had a longer maximal lifespan; seven of the eight longest-lived mice in this study were mTOR mice. This lifespan increase is one of the largest observed in mice so far.While the genetically modified mTOR mice aged better overall, they showed only selective improvement in specific organs. …

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July 30, 2013 — Higher variability in visit-to-visit blood pressure readings, independent of average blood pressure, could be related to impaired cognitive function in old age in those already at high risk of cardiovascular disease, suggests a a new article.There is increasing evidence that vascular factors contribute in development and progression of dementia. This is of special interest as cardiovascular factors may be amendable and thus potential targets to reduce cognitive decline and the incidence of dementia. Visit-to-visit blood pressure variability has been linked to cerebrovascular damage (relating to the brain and its blood vessels). It has also been shown that this variability can increase the risk of stroke.It has been suggested that higher blood pressure variability might potentially lead to cognitive impairment through changes in the brain structures.Researchers from the Leiden University Medical Center (Netherlands), University College Cork (Ireland) and the Glasgow University (UK) therefore investigated the association of visit-to-visit blood pressure variability (independent of average blood pressure) with cognitive function in older subjects at high risk of cardiovascular disease.All data were obtained from the PROSPER study, which investigated the effect of statins in prevention of vascular events in older men and women. This study took data on 5,461 individuals aged 70-82 years old in Ireland, Scotland and the Netherlands. Average follow-up was three years.Both systolic (peak pressure) and diastolic (minimum pressure) blood pressures were measured every three months in the same clinical setting. The variability between these measurements were calculated and used in the analyses.The study used data on cognitive function where the following was tested: selective attention and reaction time; general cognitive speed; immediate and delayed memory performance.Results showed that visit-to-visit blood pressure variability was associated with worse performance on all cognitive tests. The results were consistent after adjusting for cardiovascular disease and other risk factors.The main findings of the study were: higher visit-to-visit blood pressure variability is associated with worse performance in different cognitive tests; higher variability is associated with higher risk of stroke and both these associations are independent of various cardiovascular risk factors, in particular, average blood pressure.Researcher Simon Mooijaart, (Leiden University Medical Centre, Leiden, the Netherlands) says that by using a population of “over five thousand participants and over three years of blood pressure measurements, we showed that high visit-to-visit systolic and diastolic blood pressure variability associates with worse performance in different domains of cognitive function including selection attention, processing speed, immediate verbal memory and delayed verbal memory.” The researchers do add though that it is still unclear whether higher blood pressure variability is a cause or consequence of impaired cognitive function.They suggest several explanations for their findings: firstly that blood pressure variability and cognitive impairment could stem from a common cause, with cardiovascular risk factors being the most likely candidate; secondly that variability might reflect a long term instability in the regulation of blood pressure and blood flow to the key organs in the body; thirdly that exaggerated fluctuations in blood pressure could result in the brain not receiving enough blood, which can cause brain injury, leading to impairment of cognitive function.The researchers conclude that “higher visit-to-visit blood pressure variability independent of average blood pressure might be a potential risk factor with worse cognitive performance in older subjects at high risk of cardiovascular disease.” Given that dementia is a major public health issue, they say that further interventional studies are warranted to establish whether reducing blood pressure variability can decrease the risk of cognitive impairment in old age.

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