Category: Environment

{Scientists at The Australian National University (ANU) say the early Earth was likely to be barren, flat and almost entirely under water with a few small islands, following their analysis of tiny mineral grains as old as 4.4 billion years.}

Lead researcher Dr Antony Burnham said the team studied zircon mineral grains that were preserved in sandstone rocks in the Jack Hills of Western Australia and which were the oldest fragments of the Earth ever found.

“The history of the Earth is like a book with its first chapter ripped out with no surviving rocks from the very early period, but we’ve used these trace elements of zircon to build a profile of the world at that time,” said Dr Burnham from the ANU Research School of Earth Sciences.

“Our research indicates there were no mountains and continental collisions during Earth’s first 700 million years or more of existence — it was a much more quiet and dull place.

“Our findings also showed that there are strong similarities with zircon from the types of rocks that predominated for the following 1.5 billion years, suggesting that it took the Earth a long time to evolve into the planet that we know today.”

Dr Burnham said the zircon grains that eroded out of the oldest rocks were like skin cells found at a crime scene.

“We used the granites of southeast Australia to decipher the link between zircon composition and magma type, and built a picture of what those missing rocks were,” he said.

The first known form of life emerged some time later, around 3.8 billion years ago.

Dr Burnham said the zircon formed by melting older igneous rocks rather than sediments.

“Sediment melting is characteristic of major continental collisions, such as the Himalayas, so it appears that such events did not occur during these early stages of Earth’s history,” he said.

Dr Burnham said scientists in the field were able to build on each other’s work to gain a better understanding of early Earth.

“The samples of zircon from Jack Hills have been collected over the course of several decades by many people, while chemical analyses carried out by an ANU research group 20 years ago have proved invaluable,” he said.

Source:Science Daily

{A new analysis of decades of data on oceans across the globe has revealed that the amount of dissolved oxygen contained in the water — an important measure of ocean health — has been declining for more than 20 years.}

Researchers at Georgia Institute of Technology looked at a historic dataset of ocean information stretching back more than 50 years and searched for long term trends and patterns. They found that oxygen levels started dropping in the 1980s as ocean temperatures began to climb.

“The oxygen in oceans has dynamic properties, and its concentration can change with natural climate variability,” said Taka Ito, an associate professor in Georgia Tech’s School of Earth and Atmospheric Sciences who led the research. “The important aspect of our result is that the rate of global oxygen loss appears to be exceeding the level of nature’s random variability.”

The study, which was published April in Geophysical Research Letters, was sponsored by the National Science Foundation and the National Oceanic and Atmospheric Administration. The team included researchers from the National Center for Atmospheric Research, the University of Washington-Seattle, and Hokkaido University in Japan.

Falling oxygen levels in water have the potential to impact the habitat of marine organisms worldwide and in recent years led to more frequent “hypoxic events” that killed or displaced populations of fish, crabs and many other organisms.

Researchers have for years anticipated that rising water temperatures would affect the amount of oxygen in the oceans, since warmer water is capable of holding less dissolved gas than colder water. But the data showed that ocean oxygen was falling more rapidly than the corresponding rise in water temperature.

“The trend of oxygen falling is about two to three times faster than what we predicted from the decrease of solubility associated with the ocean warming,” Ito said. “This is most likely due to the changes in ocean circulation and mixing associated with the heating of the near-surface waters and melting of polar ice.”

The majority of the oxygen in the ocean is absorbed from the atmosphere at the surface or created by photosynthesizing phytoplankton. Ocean currents then mix that more highly oxygenated water with subsurface water. But rising ocean water temperatures near the surface have made it more buoyant and harder for the warmer surface waters to mix downward with the cooler subsurface waters. Melting polar ice has added more freshwater to the ocean surface — another factor that hampers the natural mixing and leads to increased ocean stratification.

“After the mid-2000s, this trend became apparent, consistent and statistically significant — beyond the envelope of year-to-year fluctuations,” Ito said. “The trends are particularly strong in the tropics, eastern margins of each basin and the subpolar North Pacific.”

In an earlier study, Ito and other researchers explored why oxygen depletion was more pronounced in tropical waters in the Pacific Ocean. They found that air pollution drifting from East Asia out over the world’s largest ocean contributed to oxygen levels falling in tropical waters thousands of miles away.

Once ocean currents carried the iron and nitrogen pollution to the tropics, photosynthesizing phytoplankton went into overdrive consuming the excess nutrients. But rather than increasing oxygen, the net result of the chain reaction was the depletion oxygen in subsurface water.

That, too, is likely a contributing factor in waters across the globe, Ito said.

Source:Science Daily

{One of the last dinosaurs living in Africa before their extinction 66 million years ago has been discovered in a phosphate mine in northern Morocco. A study of the fossil, led by the Milner Centre for Evolution at the University of Bath, suggests that following the breakup of the supercontinent Gondwana in the middle of the Cretaceous period, a distinct dinosaur fauna evolved in Africa.}

The new species, Chenanisaurus barbaricus, was of one of the last dinosaurs on Earth and among those species wiped out when an asteroid hit 66 million years ago
It is the smaller African contemporary of the North American T. rex
Fossil is evidence of distinct fauna in southern hemisphere at this time
Almost nothing is known about the dinosaurs that lived in Africa at the end of the Cretaceous period 66 million years ago, just before they were wiped out by the impact of a giant asteroid. At this time sea levels were high, and so most of the fossils come from marine rocks.

Among these are the phosphate deposits of Morocco — remains of an ancient seabed, laid down 66 million years ago. The phosphate is harvested from vast strip mines and is used in everything from fertilizer to cola drinks.

Last year, Dr Nick Longrich, from the Milner Centre for Evolution and the Department of Biology & Biochemistry at the University of Bath, studied a rare fragment of a jaw bone that was discovered in the mines at Sidi Chennane in the Oulad Abdoun Basin, Morocco. In collaboration with colleagues based in Morocco, France, and Spain, Longrich identified it as belonging to an abelisaur.

Abelisaurs were two-legged predators like T. rex and other tyrannosaurs, but with a shorter, blunter snout, and even tinier arms. While the tyrannosaurs dominated in North America and Asia, the abelisaurs were the top predators at the end of the Cretaceous in Africa, South America, India, and Europe.

Dr Longrich explained: “This find was unusual because it’s a dinosaur from marine rocks — it’s a bit like hunting for fossil whales, and finding a fossil lion. It’s an incredibly rare find — almost like winning the lottery. But the phosphate mines are so rich, it’s like buying a million lottery tickets, so we actually have a chance to find rare dinosaurs like this one.”

“We have virtually no dinosaur fossils from this time period in Morocco — it may even be the first dinosaur named from the end-Cretaceous in Africa. It’s also one of the last dinosaurs in Africa before the mass extinction that wiped out the dinosaurs.

“It’s an exciting find because it shows just how different the fauna was in the Southern hemisphere at this time.”

Named Chenanisaurus barbaricus, the newly discovered dinosaur stood on two legs and had stumpy arms. Dr Longrich added: “Abelisaurs had very short arms. The upper arm bone is short, the lower arm is shorter, and they have tiny little hands.”

The teeth from the fossil were worn as if from biting into bone, suggesting that like T. rex, Chenanisaurus was a predator. However, unlike the partially feathered T. rex, Chenanisaurus had only scales, its brain was smaller, and its face was shorter and deeper.

The research project was carried out as part of an international scientific collaboration that is helping create and study paleontology collections in Morocco with the aim of conserving the country’s rich fossil heritage. The specimens used for this study are conserved in the Office Chérifien de Phosphates paleontological collection in Morocco.

Source:Science Daily

{In sparrowhawks diversity in frailty and robustness helps females live longer}

Females often live longer than men — this is true for humans and for many other animal species.

The phenomenon exists even when you adjust for male risky behavior which leads to more early male deaths than female (car accidents, wars, homocides, etc).

Scientists don’t know why. Females are not better at withstanding certain viruses or bacteria for instance — there seems to be no obvious physiological reasons.

{{More robust females}}

A new study in Journal of Ecology has looked at sex differences and mortality in the Eurasian sparrowhawk. It turns out that heterogeneity is what drives longer lives in female sparrowhawks.

Heterogeneity in this context means that female sparrowhawk physiology is more diverse and less average than the males. There are more frail females than frail males, but there are also more robust females than robust males.

The females have a wider range and when it comes to ageing it gives them an advantage, says study author, Associate Professor Fernando Colchero from Department of Mathematics and Computer Science, University of Southern Denmark. Other authors are biologists Owen Jones og Dalia Conde from Department of Biology.
Surprised researchers

With more frail females, there will of course be more early female deaths than male. But this is more than weighed up by the larger number of robust females than males.

According to the study, the life expectancy for the most robust adult females reach up to 4.23 years, while for the most robust adult males it was 2.68 years.

{{The results are a surprise to the researchers.}}

This shows us that sexual differences in mortality are not only due to factors like physical size or how much time an individual invests in reproducing. It is also unusual to see shorter life spans in the smaller sex, as we do here; Male sparrowhawks are smaller than the females. Our results contribute a novel perspective to the ongoing debate about the mechanisms that drive sex differences in vital rates in vertebrates, said Fernando Colchero.
It is possible that this phenomenon can be found in other animal species, but it is still uncertain. I suggest that when studying sex differences in mortality, researchers should consider accounting for heterogeneity.

{{The study also concludes}}

Individuals who spend more energy on reproducing and raising chicks live longer.
Bigger females are better at reproduction than smaller females.

Smaller males have better chances for surviving than bigger males.

Source:Science Daily

{EPEE has called for a swift ratification of the Kigali Amendment to the Montreal Protocol following approval by the EU’s council of ministers and the appointment of the team of rapporteurs.}

The European Commission’s proposal for the EU to ratify the Kigali amendment, which seeks a global phase-down of HFCs under the mechanism of the Montreal Protocol, was adopted in February. The EU has already taken action to reduce HFCs under the F-gas regulations, and it is now encouraging other countries to take early action as well.

EPEE (The European Partnership for Energy and the Environment) supports the gradual reduction of HFC use by 80-85% as agreed by the Montreal Protocol parties, with the first reductions by the most developed countries expected in 2019.

“This is an important milestone in the EU ratification process and demonstrates that there is political will to bring this to a conclusion as soon as possible,” said Andrea Voigt, director general of EPEE.

“Following the UN Paris Agreement on Climate Change and the EU F-gas phase-down, this global deal on HFCs will send a strong signal and will unite our industry even more in its efforts to achieve HFC reduction targets,” EPEE said in a statement.

For the amendment to enter into force on 1 January 2019, 20 parties to the Montreal Protocol need to ratify it. Therefore, ratification by the EU and its Member States could trigger the entry into force of the Amendment and demonstrate the EU’s leadership in this field as happened with the 2015 F-gas regulation.

Source:Cooling Post

{After an unusually intense heat wave, downpour or drought, Noah Diffenbaugh and his research group inevitably receive phone calls and emails asking whether human-caused climate change played a role.}

“The question is being asked by the general public and by people trying to make decisions about how to manage the risks of a changing climate,” said Diffenbaugh, a professor of Earth system science at Stanford’s School of Earth, Energy & Environmental Sciences. “Getting an accurate answer is important for everything from farming to insurance premiums, to international supply chains, to infrastructure planning.”

In the past, scientists typically avoided linking individual weather events to climate change, citing the challenges of teasing apart human influence from the natural variability of the weather. But that is changing.

“Over the past decade, there’s been an explosion of research, to the point that we are seeing results released within a few weeks of a major event,” said Diffenbaugh, who is also the Kimmelman Family Senior Fellow at the Stanford Woods Institute for the Environment.

In a new study, published in this week’s issue of Proceedings of the National Academy of Sciences, Diffenbaugh and a group of current and former Stanford colleagues outline a four-step “framework” for testing whether global warming has contributed to record-setting weather events. The new paper is the latest in a burgeoning field of climate science called “extreme event attribution,” which combines statistical analyses of climate observations with increasingly powerful computer models to study the influence of climate change on individual extreme weather events.

Climate change fingerprints

In order to avoid inappropriately attributing an event to climate change, the authors began with the assumption that global warming had played no role, and then used statistical analyses to test whether that assumption was valid. “Our approach is very conservative,” Diffenbaugh said. “It’s like the presumption of innocence in our legal system: The default is that the weather event was just bad luck, and a really high burden of proof is required to assign blame to global warming.”

The authors applied their framework to the hottest, wettest and driest events that have occurred in different areas of the world. They found that global warming from human emissions of greenhouse gases has increased the odds of the hottest events across more than 80 percent of the surface area of the globe for which observations were available. “Our results suggest that the world isn’t quite at the point where every record hot event has a detectable human fingerprint, but we are getting close,” Diffenbaugh said.

For the driest and wettest events, the authors found that human influence on the atmosphere has increased the odds across approximately half of the area that has reliable observations. “Precipitation is inherently noisier than temperature, so we expect the signal to be less clear,” Diffenbaugh said. “One of the clearest signals that we do see is an increase in the odds of extreme dry events in the tropics. This is also where we see the biggest increase in the odds of protracted hot events — a combination that poses real risks for vulnerable communities and ecosystems.”

The Stanford research team, which includes a number of former students and postdocs who have moved on to positions at other universities, has been developing the extreme event framework in recent years, focusing on individual events such as the 2012-2017 California drought and the catastrophic flooding in northern India in June 2013. In the new study, a major goal was to test the ability of the framework to evaluate events in multiple regions of the world, and to extend beyond extreme temperature and precipitation, which have been the emphasis of most event attribution studies.

Test cases

One high-profile test case was Arctic sea ice, which has declined by around 40 percent during the summer season over the past three decades. When the team members applied their framework to the record-low Arctic sea ice cover observed in September 2012, they found overwhelming statistical evidence that global warming contributed to the severity and probability of the 2012 sea ice measurements. “The trend in the Arctic has been really steep, and our results show that it would have been extremely unlikely to achieve the record-low sea ice extent without global warming,” Diffenbaugh said.

Another strength of a multi-pronged approach, the team said, is that it can be used to study not only the weather conditions at the surface, but also the meteorological “ingredients” that contribute to rare events. “For example, we found that the atmospheric pressure pattern that occurred over Russia during the 2010 heat wave has become more likely in recent decades, and that global warming has contributed to those odds,” said co-author Daniel Horton, an assistant professor at Northwestern University in Evanston, Illinois, and a former postdoc in Diffenbaugh’s lab who has led research on the influence of atmospheric pressure patterns on surface temperature extremes. “If the odds of an individual ingredient are changing — like the pressure patterns that lead to heat waves — that puts a thumb on the scales for the extreme event.”

Diffenbaugh sees the demand for rigorous, quantitative event attribution growing in the coming years. “When you look at the historical data, there’s no question that global warming is happening and that extremes are increasing in many areas of the world,” he said. “People make a lot of decisions — short term and long term — that depend on the weather, so it makes sense that they want to know whether global warming is making record-breaking events more likely. As scientists, we want to make sure that they have accurate, objective, transparent information to work with when they make those decisions.”

Source:Science Daily

{What is the volume of water in lakes on Earth? Using a mathematical analysis, researcher David Seekell, at Umeå University in Sweden, and his American collaborators now suggest that the mean depth of lakes is 30 per cent lower than previously estimated. Shallower lakes implies less fresh water and has consequences for our understanding of climate change and the carbon cycle. The results have been published in Geophysical Research Letters.}

“Our estimations measure around 190,000 km3, which is a very small amount of water. In comparison, the ocean contains 1.3 billion km3 of water. If we poured the water of all lakes on Earth together into one big lake, the mean depth of the lake would be 42 metres. The mean depth of the ocean is 3,682 metres,” says David Seekell, associate professor at the Department of Ecology and Environmental Sciences and the Climate Impacts Research Centre (CIRC) at Umeå University in Sweden.

A possible conclusion is if lakes are shallower, they release more methane into the atmosphere than previously estimated.

Measuring the volume of the lakes on Earth seems like a simple task. Nevertheless, the challenges to carry out a measurement on a global scale are huge. Satellites can measure the volume of very large lakes, such as for instance Lake Vättern in Sweden or Lake Superior in the United States and Canada, but measuring the tens of millions of small lakes spread across the surface of Earth requires time-consuming field work. A commonly used method is GPS positioning and depth sounder by boat. The researcher is required to row around on the lake until he or she has collected a large number of depths. The depths and coordinates are later used to build bathymetric maps which the volume and mean depth can be derived from. The approach works well for small lakes, but is expensive due to the time-consuming process and only a small number of lakes can be mapped.

So far, there have been few estimates of the volume of fresh water in lakes on Earth, and those that exist vary greatly and are typically presented without any data or methods.

“We decided to use a theory driven approach. We assumed that the surface of Earth is self-affine. This basically means that if you zoomed in and out of a cross-section of Earth’s surface, the statistical characteristics of the vertical topography are predictable based upon a stretching factor,” says David Seekell.

The researchers evaluated their model with measured volumes from thousands of lakes from diverse landscapes. The presumptions proved accurate and based upon this model, the researchers were able to deduce a theoretical volume-area relationship.

“We were able to use the model to estimate the mean volume of lakes at each given lake surface area, but also for variations in volume of lakes with the same surface area. Given the total lake surface area on Earth — which can actually be accurately recorded by satellite, even for small lakes — we were now able to estimate the total volume and assess the uncertainty in the estimate,” says David Seekell.

The research team assessed that there are 184,000-199,000 km3 of lake water. The reason behind the variation can be explained by how lakes are counted and how their surface area is measured, particularly the smaller ones.

The majority of lake water can be found in a few very large lakes such as the Caspian Sea, Lake Superior, and Lake Baikal. In fact, about 80 percent of lake water can be found in the 20 largest lakes alone.

The quality and quantity of lake water can rapidly change due to human activities. For example, in some regions many ponds and reservoirs have been built for ornamental purposes, for irrigation, to generate electricity, or to store drinking water, which increasing the volume of fresh water.

On the other hand, some large lakes have dried up and disappeared. For example, Lake Poopo in Bolivia previously had a surface area of about 3,000 km2 and was one of the largest lakes in Bolivia. Due to climate change and water diversions for agricultural production, there is almost no water left, which greatly affects local communities. A very similar story can be told about the Aral Sea — once the fourth largest lake on Earth — where climate change and water diversions for agriculture have left only a tiny fraction of its former surface.

It is not only quantity that is of great concern at the moment. The water quality of the largest lakes on Earth are subject to degradation due to human activities. For example, Lake Erie in the United States and Canada with a surface area of about 25,667 km2 has been exposed to nutrient pollution and harmful algae blooms. This has rendered the lake an unreliable source for drinking water for communities along the shoreline. As a consequence, over 400,000 people even lost access to drinking water due to neurotoxins in the lake water associated with algae bloom in 2014.

“Our study emphasizes the relative scarcity of lake water, and how rapidly human activities can change the quality and quantity of water resources,” says David Seekell.

Source:Science Daily