Global warming skeptics unmoved by extreme weather

What will it take to convince skeptics of global warming that the phenomenon is real? Surely, many scientists believe, enough droughts, floods and heat waves will begin to change minds. Credit: © lightmemorystock / Fotolia

What will it take to convince skeptics of global warming that the phenomenon is real? Surely, many scientists believe, enough droughts, floods and heat waves will begin to change minds.

But a new study led by a Michigan State University scholar throws cold water on that theory.
Only 35 percent of U.S. citizens believe global warming was the main cause of the abnormally high temperatures during the winter of 2012, Aaron M. McCright and colleagues report in a paper published online today in the journal Nature Climate Change.

"Many people already had their minds made up about global warming and this extreme weather was not going to change that," said McCright, associate professor in MSU's Lyman Briggs College and Department of Sociology.

Winter 2012 was the fourth warmest winter in the United States dating back to at least 1895, according to the National Oceanic and Atmospheric Administration. Some 80 percent of U.S. citizens reported winter temperatures in their local area were warmer than usual.

The researchers analyzed March 2012 Gallup Poll data of more than 1,000 people and examined how individuals' responses related to actual temperatures in their home states. Perceptions of warmer winter temperatures seemed to track with observed temperatures.

"Those results are promising because we do hope that people accurately perceive the reality that's around them so they can adapt accordingly to the weather," McCright said.

But when it came to attributing the abnormally warm weather to global warming, respondents largely held fast to their existing beliefs and were not influenced by actual temperatures.

As this study and McCright's past research shows, political party identification plays a significant role in determining global warming beliefs. People who identify as Republican tend to doubt the existence of global warming, while Democrats generally believe in it.

The abnormally warm winter was just one in an ongoing series of severe weather events -- including the 2010 Russian heat wave, Hurricane Sandy in 2012 and the 2013 typhoon in the Philippines -- that many believed would help start convincing global warming skeptics.

"There's been a lot of talk among climate scientists, politicians and journalists that warmer winters like this would change people's minds," McCright said. "That the more people are exposed to climate change, the more they'll be convinced. This study suggests this is not the case."

Source: Michigan State University

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Managing coasts under threat from climate change, sea-level rise

Sea levels are rising. Experts say that we need to address human-led and other non-climatic changes. Credit: Image courtesy of University of Southampton

Coastal regions under threat from climate change and sea-level rise need to tackle the more immediate threats of human-led and other non-climatic changes, according to a team of international scientists.

The team of 27 scientists from five continents, led by Dr Sally Brown at the University of Southampton, reviewed 24 years of Intergovernmental Panel on Climate Change (IPCC) assessments (the fifth and latest set being published in 2013 and 2014). They focused on climate change and sea-level rise impacts in the coastal zone, and examined ways of how to better manage and cope with climate change.

They found that to better understand climate change and its impacts, scientists need to adopt an integrated approach into how coasts are changing. This involves recognising other causes of change, such as population growth, economic development and changes in biodiversity. Dr Brown emphasised that: "Over the last two and half decades, our scientific understanding of climate change and sea-level rise, and how it will affect coastal zones has greatly increased. We now recognise that we need to analyse all parts of our human and natural environments to understand how climate change will affect the world."

The scientists also acknowledged that long-term adaptation to climate change can greatly reduce impacts, but further research and evaluation is required to realise the potential of adaptation. "Many parts of the coast can, with forward planning, adapt to sea-level rise, but we need to better understand environments that will struggle to adapt, such as developing countries with large low-lying river deltas sensitive to salinisation, or coral reefs and particularly small, remote islands or poorer communities," said Dr Brown.

For example, in the Maldives, many small, remote low-lying islands are at risk from climate change and will struggle to adapt. But around the densely populated capital city and airport, adaptation has already occurred as land claim is a common practice in order to relive population pressure. Sea-level rise has already been considered into newly claimed land. 

Thus in decades to come, potential climate change impacts, such as flooding, will be reduced for this island, benefiting both the local population and economy.

Dr Jochen Hinkel from Global Climate Forum in Germany, who is a co-author of this paper and a Lead Author of the coastal chapter for the 2014 IPCC Assessment Report added: "The IPCC has done a great job in bringing together knowledge on climate change, sea-level rise and is potential impacts but now needs to complement this work with a solution-oriented perspective focusing on overcoming barriers to adaptation, mobilising resources, empowering people and discovering opportunities for strengthening coastal resilience in the context of both climate change as well as existing coastal challenges and other issues."

This new research, published as a commentary in Nature Climate Change, will help in the understanding of the impacts of climate change and how to reduce impacts via adaptation. Its multi-disciplinary approach could be useful if future IPCC assessment reports are commissioned.

Source: University of Southampton

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New insights into origins of agriculture could help shape future of food

Wheat field (stock image). Agricultural decisions made by our ancestors more than 10,000 years ago could hold the key to food security in the future, according to new research by the University of Sheffield. Credit: © igor / Fotolia

Agricultural decisions made by our ancestors more than 10,000 years ago could hold the key to food security in the future, according to new research by the University of Sheffield.

Scientists, looking at why the first arable farmers chose to domesticate some cereal crops and not others, studied those that originated in the Fertile Crescent, an arc of land in western Asia from the Mediterranean Sea to the Persian Gulf.

They grew wild versions of what are now staple foods like wheat and barley along with other grasses from the region to identify the traits that make some plants suitable for agriculture, including how much edible seed the grasses produced and their architecture.

Dr Catherine Preece, who worked on the study with colleagues from the University's Department of Animal and Plant Sciences and Department of Archaeology, said: "Our results surprised us because numerous other grasses that our ancestors ate, but we do not, can produce just as much seed as wild wheat and barley. It is only when these plants are grown at high densities, similar to what we would find in fields, that the advantage of wild wheat and barley is revealed."

The study identified two key characteristics shared by the wild relatives of current crop plants. Firstly they have bigger seeds, which means they grow into bigger seedlings and are able to get more than their fair share of light and nutrients, and secondly, as adult plants they are less bushy than other grasses and package their big seeds onto fewer stems. This means crop wild relatives perform better than the other wild grasses that they are competing with and are better at growing close together in fields, making them ideal for using in agriculture.

"The results are important because our expanding human population is putting increasing demands on food production," said Dr Preece.

"Before humans learnt how to farm, our ancestors ate a much wider variety of grasses. If we can understand what traits have made some grasses into good crops then we can look for those characteristics in other plants and perhaps identify good candidates for future domestication."

She added: "To shape the future we must understand the past, so the more we can discover about the origins of agriculture, the more information we will have to help us tackle the challenges that face modern day food production."

So far the researchers have been conducting their experiments in greenhouses and their results indicate that the traits affecting how plants compete with each other are crucial factors to determining the success of a crop.

The team now plan to observe how the plants interact in their natural environment by growing them in experimental fields in Turkey, the heart of the Fertile Crescent. They hope that their experiments will yield another crop of important results.

"Cereal breeders are taking an increasing interest in modern crops' wild relatives as a source of useful traits that may help to increase yields or increase resilience to climate change, and our work should help in this process," said Dr Preece.

Dr Preece presented the results of this study to the joint British Ecological Society and the French Ecological Society 11 December 2014 in the Grand Palais, Lille.

Source: University of Sheffield

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Clearing tropical rainforests distorts Earth's wind and water systems, packs climate wallop beyond carbon

The world without tropical rainforests. Credit: Image courtesy of ClimateFocus

A new study released today presents powerful evidence that clearing trees not only spews carbon into the atmosphere, but also triggers major shifts in rainfall and increased temperatures worldwide that are just as potent as those caused by current carbon pollution. Further, the study finds that future agricultural productivity across the globe is at risk from deforestation-induced warming and altered rainfall patterns.

The report, "Effects of Tropical Deforestation on Climate Change and Agriculture," published today in Nature Climate Change and released in collaboration with Climate Focus provides the most comprehensive analysis to date of the climate impacts of tropical forest destruction on agriculture in the tropics and thousands of miles away. Specifically, the study finds that deforestation in South America, Southeast Asia and Africa may alter growing conditions in agricultural areas in the tropics and as far away as the US Midwest, Europe and China.

The study is also the only global synthesis of research based on cutting-edge climate models and empirical data on the direct local, regional and global impacts of cutting down tropical forests, which regulate interactions between the earth and the atmosphere. It predicts that atmospheric impacts resulting from complete tropical deforestation could lead to a rise in global temperature of 0.7 degrees Celsius (on top of the impact from greenhouse gases), which would double the observed global warming since 1850. Currently, climate change negotiators are shaping policies that focus on greenhouse gases, in particular carbon. To date, they have overlooked policy responses that address other ways that forests affect climate.

"Tropical deforestation delivers a double whammy to the climate -- and to farmers," said Deborah Lawrence, Professor of Environmental Sciences at the University of Virginia, the study's lead author. "Most people know that climate change is a dangerous global problem, and that it's caused by pumping carbon into the atmosphere. But it turns out that removing forests alters moisture and air flow, leading to changes -- from fluctuating rainfall patterns to rises in temperatures -- that are just as hazardous, and happen right away. The impacts go beyond the tropics -- the United Kingdom and Hawaii could see an increase in rainfall while the US Midwest and Southern France could see a decline."

The report presents compelling evidence that tropical deforestation is already affecting local and regional climates. Meteorological data, for example, show that in Thailand, the beginning of the dry season is experiencing less rainfall due to deforestation. And in parts of the Amazon, the world's largest stretch of rainforest, the timing of once-predictable rainfall has shifted due to deforestation. In deforested regions, the wet season is delayed by two weeks; in forested regions, there are no changes.

"The study not only compiles highly relevant scientific literature, it will also help guide policy makers working on climate change. Tropical deforestation impacts weather patterns globally, which makes addressing deforestation one of the most important mitigation strategies," adds Dr. Charlotte Streck, Director of Climate Focus.

Globalized Impacts of Deforestation

"Teleconnections," associated with the mass movement of air and conditions in the upper atmosphere, have the potential to extend the impacts of tropical deforestation on climate globally. An increase in temperature in the tropics due to deforestation generates large upward-moving air masses. When these hit the upper atmosphere they cause ripples, or teleconnections, that flow outward in various directions, similar to the way in which an underwater earthquake can create a tsunami.

Models examined in the study showed that increased or complete deforestation could put the climate in some of the world's most important agriculture regions off kilter. These variations in rainfall and spikes in temperature could occur across the world, according to the report.

For example, complete deforestation of the Amazon Basin would likely reduce rainfall in the US Midwest, Northwest and parts of the south during the agricultural season. The complete deforestation of Central Africa would likely cause declines in rainfall in the Gulf of Mexico and parts of the US Midwest and Northwest and increase it on the Arabian Peninsula. There could also be precipitation declines in Ukraine and Southern Europe.

"While complete deforestation is unlikely to occur, over the course of history, deforestation has continued as countries develop," Lawrence said. "Further, this study fills gaps in our understanding of deforestation tipping points -- and what could happen if we continue down this path."

Turning up the heat, turning down the rain

Across the board, the study reports, deforestation poses risks to agriculture by causing an increase in average temperature, a decline in average rainfall and a change in the location and timing of rainfall. Deforestation, for example, would lead to a reduction in rainfall between 10-15 percent in the region surrounding where the deforestation took place.

According to Lawrence, there is almost always an increase in temperature with deforestation. "This does not change, no matter what you do -- no matter what kind of model you use, temperature increases occur -- whether it's half a degree, a full degree or two degrees."

"That's a very big deal," said Lawrence. "In the last few centuries, the average global temperature has never varied by more than about one degree. Once we go above one degree -- to 1.5 degrees or more -- we're talking about conditions that are very different from anything humanity has ever experienced." Because crops are highly sensitive to changes in temperature and moisture, she added, they would suffer in hotter conditions. Increased floods or decreases in soil moisture would further add to stress on crops.

"Farmers, so reliant on consistent and reliable growing conditions, could lose their bearings and even their incomes, when facing these ups and downs in temperature and rainfall," Lawrence said. "While farmers may ultimately adapt to shifts in the season, it's difficult -- if not impossible -- for farmers to adapt to increased floods or parched soils."

Forests: Not Lungs but Sweat Glands

Because forests turn water from soil into moisture in the air, they cool the atmosphere above them. Tropical forests move more water than any other ecosystem on land. They are central to the earth's process of generating and regenerating moisture, so clearing ever-larger swathes of forest eventually leads to a drying and warming effect. By disturbing the movement of air in remote parts of the atmosphere, tropical deforestation throws temperature and rainfall patterns worldwide out of whack.

The impact of deforestation is diverse and varies across regions and scales -- from small plots of farmland in the midst of the rainforest to large swathes of cattle pasture bordered by forests -- but the more deforestation that occurs, the greater the impact.

"Tropical forests are often talked about as the 'lungs of the earth,' but they're more like the sweat glands," said Lawrence. "They give off a lot of moisture, which helps keep the planet cool. That crucial function is lost -- and even reversed -- when forests are destroyed."

The study found that relatively small plots of deforestation can actually increase rainfall at a local scale. There is, however, a critical clearing size above which rainfall declines dramatically.

Models studied in the report show that in the Amazon and, possibly, in the Congo Basin, 30-50 percent may be the deforestation tipping point. Any additional forest clearing would lead to rainfall reductions that could significantly change ecosystems, and compound the risk of additional dangers, such as an increase in forest fires.

The location of deforested areas can also affect their impacts on regional climates, the study finds. Deforesting West Africa or the Congo could reduce rainfall across the region by 40-50% and increase temperatures there up to 3°C. Regional scale models project that in the Amazon Basin, clearing 40% of the forest would decrease wet-season rainfall by 12% and dry-season rainfall by 21%. It would also reduce by 4% rainfall in the Rio de la Plata Basin, a center for soy, corn and wheat production, thousands of miles south of the Amazon. Because Southeast Asia is surrounded by oceans, the impact of deforestation on regional temperatures and rainfall may be less severe.

To reduce the effects of deforestation on climate change, the data suggest it would be best to retain large swathes of forest across the tropical forest belt and to avoid large-scale deforestation in any single location.

Lawrence added that climate-change negotiators and other policymakers should take the impacts of deforestation seriously. "What happens on the surface of the earth (in terms of changes in vegetation) is a big factor in climate change. We ignore it at our own peril."

Source: ClimateFocus

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New study explains the role of oceans in 'global warming hiatus'

Warming hiatus illustrated.
Credit: Image courtesy of University of Southampton

New research shows that ocean heat uptake across three oceans is the likely cause of the ‘warming hiatus’ – the current decade-long slowdown in global surface warming. Using data from a range of state-of-the-art ocean and atmosphere models, the research shows that the increased oceanic heat drawdown in the equatorial Pacific, North Atlantic and Southern Ocean basins has played a significant role in the hiatus.

Using data from a range of state-of-the-art ocean and atmosphere models, the research shows that the increased oceanic heat drawdown in the equatorial Pacific, North Atlantic and Southern Ocean basins has played a significant role in the hiatus.

The new analysis has been published in Geophysical Research Letters by Professor Sybren Drijfhout from the University of Southampton and collaborators from the National Oceanography Centre (NOC) Dr Adam Blaker, Professor Simon Josey, Dr George Nurser and Dr Bablu Sinha, together with Dr Magdalena Balmaseda from the European Centre for Medium Range Weather Forecasting (ECMWF).

Professor Drijfhout said: "This study attributes the increased oceanic heat drawdown in the equatorial Pacific, North Atlantic and Southern Ocean to specific, different mechanisms in each region. This is important as current climate models have been unable to simulate the hiatus. Our study gives clues to where the heat is drawn down and by which processes. This can serve as a benchmark for climate models on how to improve their projections of future global mean temperature."

Previously, the drawdown of heat by the Equatorial Pacific Ocean over the hiatus period, due to cool sea-surface temperatures associated with a succession of cool-surface La Nina episodes, was thought to be sufficient to explain the hiatus.

However, this new analysis reveals that the northern North Atlantic, the Southern Ocean and Equatorial Pacific Ocean are all important regions of ocean heat uptake. Each basin contributes a roughly equal amount to explaining the hiatus, but the mechanisms of heat drawdown are different and specific in each basin.

In the North Atlantic, more heat has been retained at deep levels as a result of changes to both the ocean and atmospheric circulations, which have led to the winter atmosphere extracting less heat from the ocean.

In the Southern Ocean, the extra drawdown of heat had gone unnoticed and is increasing on a much longer timescale (multi-decadal) than the other two regions (decadal). Here, gradual changes in the prevailing westerly winds have modified the ocean-atmosphere heat exchange, particularly in the Southern Indian Ocean.

The team calculated the change in the amount of heat entering the ocean using a state-of-the-art high resolution ocean model developed and run by NOC scientists that is driven by surface observations. This estimate was compared with results from an ocean model-data synthesis from ECMWF and a leading atmospheric model-data synthesis produced in the US. Professor Josey said: "It is the synthesis of information from models and observational data that provides a major strength of our study."

Dr Sinha concluded: "The deeper understanding gained in this study of the processes and regions responsible for variations in oceanic heat drawdown and retention will improve the accuracy of future climate projections."

Source: University of Southampton

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Scientists caution against exploitation of deep ocean

A new OSU study looks at how exploiting the ocean's vast resources have put it in peril. 
Credit: Image courtesy of Oregon State University

The world's oceans are vast and deep, yet rapidly advancing technology and the quest for extracting resources from previously unreachable depths is beginning to put the deep seas on the cusp of peril, an international team of scientists warned this week.

In an analysis in Biogeosciences, which is published by the European Geosciences Union, the researchers outline "services" or benefits provided by the deep ocean to society. Yet using these services, now and in the future, is likely to make a significant impact on that habitat and what it ultimately does for society, they point out in their analysis.

"The deep sea is the largest habitat on Earth, it is incredibly important to humans and it is facing a variety of stressors from increased human exploitation to impacts from climate change," said Andrew Thurber, an Oregon State University marine scientist and lead author on the study. "As we embark upon greater exploitation of this vast environment and start thinking about conserving its resources, it is imperative to know what this habitat already does for us."

"Our analysis is an effort to begin to summarize what the deep sea provides to humans because we take it for granted or simply do not know that the deep sea does anything to shape our daily lives," he added. "The truth is that the deep sea affects us, whether we live on the coast or far from the ocean -- and its impact on the globe is pervasive."

The deep sea is important to many critical processes that affect Earth's climate, including acting as a "sink" for greenhouse gases -- helping offset the growing amounts of carbon dioxide emitted into the atmosphere. It also regenerates nutrients through upwelling that fuel the marine food web in productive coastal systems such as the Pacific Northwest of the United States, Chile and others. Increasingly, fishing and mining industries are going deeper and deeper into the oceans to extract natural resources.

"One concern is that many of these areas are in international waters and outside of any national jurisdiction," noted Thurber, an assistant professor (senior research) in Oregon State's College of Earth, Ocean, and Atmospheric Sciences. "Yet the impacts are global, so we need a global effort to begin protecting and managing these key, albeit vast, habitats."

Fishing is an obvious concern, the scientists say. Advances in technology have enabled commercial fisheries to harvest fish at increasing depths -- an average of 62.5 meters deeper every decade, according to fisheries scientists. This raises a variety of potential issues.

"The ability to fish deeper is shifting some fisheries to deeper stocks, and opening up harvests of new species," Thurber said. "In some local cases, individual fisheries are managed aggressively, but due to how slow the majority of the fish grow in the deep, some fish populations are still in decline -- even with the best management practices."

The orange roughy off New Zealand, for instance, is both a model of effective and conservation-based management, yet its populations continue to decline, though at a slower rate than they would have experienced without careful management, Thurber noted.

"We also have to be concerned about pollution that makes its way from our continental shelves into the deep sea," he added. "Before it was 'out of sight, out of mind.' However, some of the pollution can either make it into the fish that we harvest, or harm the fishers that collect the fish for us. It is one of the reasons need to identify how uses of the deep sea in the short term can have long-term consequences. Few things happen fast down there."

Mining is a major threat to the deep sea, the researchers point out in their analysis. In particular, the quest for rare earth and metal resources, which began decades ago, has skyrocketed in recent years because of their increased use in electronics, and because of dwindling or limited distribution of supplies on land. Mining the deep ocean for manganese nodules, for example -- which are rich in nickel -- requires machines that may directly impact large swaths of the seafloor and send up a sediment plume that could potentially affect an even larger area, the scientists note.

These mining resources are not limited to muddy habitats, Thurber pointed out. Massive sulfides present at hydrothermal vents are another resource targeted by mining interests.

"The deep sea has been an active area for oil and gas harvesting for many years," he said, "yet large reservoirs of methane and other potential energy sources remain unexploited. In addition to new energy sources, the potential for novel pharmaceuticals is also vast.

"There are additional threats to these unique habitats, including ocean acidification, warming temperatures and possible changes to ocean circulation through climate change."

The next step, the researchers say, is to attach an economic value to both the services provided by the deep sea -- and the activities that may threaten those services.

"What became clear as we put together this synopsis is that there is vast potential for future resources but we already benefit greatly through this environment," Thurber said. ""What this means is that while the choices to harvest or mine will be decided over the coming decades, it is important to note that the stakeholders of this environment represent the entire world's population."

"The Bible, the Koran, the Torah, and early Greek texts all reference the deep sea," he added. "Maybe it's time for all of us to take a closer look at what it has to offer and decide if and how we protect it."

Source: Oregon State University

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Hydraulic fracturing linked to earthquakes in Ohio

Seismograph (stock image). Hydraulic fracturing triggered a series of small earthquakes in 2013 on a previously unmapped fault in Harrison County, Ohio, according to a study. Credit: © hakandogu / Fotolia

Hydraulic fracturing triggered a series of small earthquakes in 2013 on a previously unmapped fault in Harrison County, Ohio, according to a study published in the journal Seismological Research Letters (SRL).

Nearly 400 small earthquakes occurred between Oct. 1 and Dec. 13, 2013, including 10 "positive" magnitude earthquake, none of which were reported felt by the public. The 10 positive magnitude earthquakes, which ranged from magnitude 1.7 to 2.2, occurred between Oct. 2 and 19, coinciding with hydraulic fracturing operations at nearby wells.

This series of earthquakes is the first known instance of seismicity in the area.
Hydraulic fracturing, or fracking, is a method for extracting gas and oil from shale rock by injecting a high-pressure water mixture directed at the rock to release the gas inside. The process of hydraulic fracturing involves injecting water, sand and chemicals into the rock under high pressure to create cracks. The process of cracking rocks results in micro-earthquakes. Hydraulic fracturing usually creates only small earthquakes, ones that have magnitude in the range of negative 3 (−3) to negative 1 (-1).

"Hydraulic fracturing has the potential to trigger earthquakes, and in this case, small ones that could not be felt, however the earthquakes were three orders of magnitude larger than normally expected," said Paul Friberg, a seismologist with Instrumental Software Technologies, Inc. (ISTI) and a co-author of the study.

The earthquakes revealed an east-west trending fault that lies in the basement formation at approximately two miles deep and directly below the three horizontal gas wells. The EarthScope Transportable Array Network Facility identified the first earthquakes on Oct. 2, 2013, locating them south of Clendening Lake near the town of Uhrichsville, Ohio. A subsequent analysis identified 190 earthquakes during a 39-hour period on Oct. 1 and 2, just hours after hydraulic fracturing began on one of the wells.

The micro-seismicity varied, corresponding with the fracturing activity at the wells. The timing of the earthquakes, along with their tight linear clustering and similar waveform signals, suggest a unique source for the cause of the earthquakes -- the hydraulic fracturing operation. The fracturing likely triggered slip on a pre-existing fault, though one that is located below the formation expected to confine the fracturing, according to the authors.

"As hydraulic fracturing operations explore new regions, more seismic monitoring will be needed since many faults remain unmapped." Friberg co-authored the paper with Ilya Dricker, also with ISTI, and Glenda Besana-Ostman originally with Ohio Department of Natural Resources, and now with the Bureau of Reclamation at the U.S. Department of Interior.

Source: Seismological Society of America

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Geoengineering could disrupt rainfall patterns

Volcanic eruptions, such as the one of the Karymsky volcano (Russia) in 2004, release sulphur dioxide to the atmosphere, which has a cooling effect. Geoengineering an ‘artificial volcano’ to mimic this release has been proposed as a solution to global warming.

A geoengineering solution to climate change could lead to significant rainfall reduction in Europe and North America, a team of European scientists concludes. The researchers studied how models of Earth in a warm, CO2-rich world respond to an artificial reduction in the amount of sunlight reaching the planet's surface.

The study is published June 6 in Earth System Dynamics, an Open Access journal of the European Geosciences Union (EGU).

Tackling climate change by reducing the solar radiation reaching our planet using climate engineering, known also as geoengineering, could result in undesirable effects for Earth and humankind. In particular, the work by the team of German, Norwegian, French, and UK scientists shows that disruption of global and regional rainfall patterns is likely in a geoengineered climate.

"Climate engineering cannot be seen as a substitute for a policy pathway of mitigating climate change through the reduction of greenhouse gas emissions," they conclude in the paper.

Geoengineering techniques to reduce the amount of solar radiation reaching Earth's surface range from mimicking the effects of large volcanic eruptions by releasing sulphur dioxide into the atmosphere to deploying giant mirrors in space. Scientists have proposed these sunlight-reflecting solutions as last-ditch attempts to halt global warming.

But what would such an engineered climate be like?
To answer this question, the researchers studied how four Earth models respond to climate engineering under a specific scenario. This hypothetical scenario assumes a world with a CO2 concentration that is four times higher than preindustrial levels, but where the extra heat caused by such an increase is balanced by a reduction of radiation we receive from the Sun.
"A quadrupling of CO2 is at the upper end, but still in the range of what is considered possible at the end of the 21st century," says Hauke Schmidt, researcher at the Max Planck Institute for Meteorology in Germany and lead author of the paper.

Under the scenario studied, rainfall strongly decreases -- by about 15 percent (some 100 millimetres of rain per year) of preindustrial precipitation values -- in large areas of North America and northern Eurasia. Over central South America, all models show a decrease in rainfall that reaches more than 20 percent in parts of the Amazon region. Other tropical regions see similar changes, both negative and positive. Overall, global rainfall is reduced by about five percent on average in all four models studied.

"The impacts of these changes are yet to be addressed, but the main message is that the climate produced by geoengineering is different to any earlier climate even if the global mean temperature of an earlier climate might be reproduced," says Schmidt.

The authors note that the scenario studied is not intended to be realistic for a potential future application of climate engineering. But the experiment allows the researchers to clearly identify and compare basic responses of Earth's climate to geoengineering, laying the groundwork for more detailed future studies.

"This study is the first clean comparison of different models following a strict simulation protocol, allowing us to estimate the robustness of the results. Additionally we are using the newest breed of climate models, the ones that will provide results for the Fifth IPCC [Intergovernmental Panel on Climate Change] Report," explains Schmidt.

The scientists used climate models developed by the UK Met Office's Hadley Centre, the Institut Pierre Simon Laplace in France, and the Max Planck Institute in Germany. Norwegian scientists developed the fourth Earth model used.


Source: European Geosciences Union

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Sunshade geoengineering more likely to improve global food security, research suggests

New research examines the potential effects that geoengineering the climate could have on global food production and concludes that sunshade geoengineering would be more likely to improve rather than threaten food security. Credit: © Igor Chaikovskiy / Fotolia

Carbon dioxide emissions from the burning of coal, oil, and gas have been increasing over the past decades, causing Earth to get hotter and hotter. There are concerns that a continuation of these trends could have catastrophic effects, including crop failures in the heat-stressed tropics. This has led some to explore drastic ideas for combating global warming, including the idea of trying to counteract it by reflecting sunlight away from Earth. However, it has been suggested that reflecting sunlight away from Earth might itself threaten the food supply of billions of people.

New research led by Carnegie's Julia Pongratz examines the potential effects that geoengineering the climate could have on global food production and concludes that sunshade geoengineering would be more likely to improve rather than threaten food security. Their work is published online by Nature Climate Change Jan. 22.

Big volcanoes cool the planet by placing lots of small particles in the stratosphere, but the particles fall out within a year and the planet heats back up. One proposal for cooling the planet is to use high-flying airplanes to constantly replenish a layer of small particles in the stratosphere that would scatter sunlight back to space. But such so-called sunshade geoengineering could have unintended consequences for climate, and especially for precipitation.

Although scientists know that climate change in recent decades has negatively impacted crop yields in many regions, the study by Pongratz and colleagues is the first to examine the potential effect of geoengineering on food security. Pongratz's team, which included Carnegie's Ken Caldeira and Long Cao, as well as Stanford University's David Lobell, used models to assess the impact of sunshade geoengineering on crop yields.

Using two different climate models, they simulated climates with carbon dioxide levels similar to what exists today. A second set of simulations doubled carbon-dioxide levels -- levels that could be reached in several decades if current trends in fossil-fuel burning continue unabated. A third set of simulations posited doubled carbon dioxide, but with a layer of sulfate aerosols in the stratosphere deflecting about 2% of incoming sunlight away from Earth. The simulated climate changes were then applied to crop models that are commonly used to project future yields.

The team found that, in the model, sunshade geoengineering leads to increased crop yields in most regions, both compared with current conditions and with the future projection of doubled carbon dioxide on its own. This is because deflecting sunlight back to space reduces temperatures, but not CO2. "In many regions, future climate change is predicted to put crops under temperature stress, reducing yields. This stress is alleviated by geoengineering," Pongratz said. "At the same time, the beneficial effects that a higher CO2 concentration has on plant productivity remain active."

Even if the geoengineering would help crop yields overall, the models predict that some areas could be harmed by the geoengineering. And there are other risks that go beyond the direct impact on crop yields. For example, deployment of such systems might lead to political or even military conflict. Furthermore, these approaches do not solve the problem of ocean acidification, which is also caused by carbon dioxide emissions.

"The real world is much more complex than our climate models, so it would be premature to act based on model results like ours," Caldeira said. "But desperate people do desperate things. Therefore, it is important to understand the consequences of actions that do not strike us as being particularly good ideas."

"The climate system is not well enough understood to exclude the risks of severe unanticipated climate changes, whether due to our fossil-fuel emissions or due to intentional intervention in the climate system," Pongratz said. "Reducing greenhouse gas emissions is therefore likely a safer option than geoengineering to avert risks to global food security."

Source:  Carnegie Institution

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The Massive debris pile reveals risk of huge tsunamis in Hawaii

The researchers simulated earthquakes with magnitudes between 9.0 and 9.6 originating at different locations along the Aleutian-Alaska subduction zone, and found that the unique geometry of the eastern Aleutians would direct the largest post-earthquake tsunami energy directly toward the Hawaiian Islands. The red circles are centered on Kaua‘i and encircle the Big Island. Credit: Rhett Butler

A mass of marine debris discovered in a giant sinkhole in the Hawaiian islands provides evidence that at least one mammoth tsunami, larger than any in Hawaii's recorded history, has struck the islands, and that a similar disaster could happen again, new research finds. Scientists are reporting that a wall of water up to nine meters (30 feet) high surged onto Hawaiian shores about 500 years ago. A 9.0-magnitude earthquake off the coast of the Aleutian Islands triggered the mighty wave, which left behind up to nine shipping containers worth of ocean sediment in a sinkhole on the island of Kauai.

The tsunami was at least three times the size of a 1946 tsunami that was the most destructive in Hawaii's recent history, according to the new study that examined deposits believed to have come from the extreme event and used models to show how it might have occurred. Tsunamis of this magnitude are rare events. An earthquake in the eastern Aleutian Trench big enough to generate a massive tsunami like the one in the study is expected to occur once every thousand years, meaning that there is a 0.1 percent chance of it happening in any given year -- the same probability as the 2011 Tohoku earthquake that struck Japan, according to Gerard Fryer, a geophysicist at the Pacific Tsunami Warning Center in Ewa Beach, Hawaii.

Nevertheless, the new research has prompted Honolulu officials to revise their tsunami evacuation maps to account for the possibility of an extreme tsunami hitting the county of nearly 1 million people. The new maps would more than double the area of evacuation in some locations, according to Fryer.
"You're going to have great earthquakes on planet Earth, and you're going to have great tsunamis," said Rhett Butler, a geophysicist at the University of Hawaii at Manoa and lead author of the new study published online in Geophysical Research Letters, a journal of the American Geophysical Union. "People have to at least appreciate that the possibility is there."

Hawaiians have told stories about colossal tsunamis hitting the islands for generations, but possible evidence of these massive waves was only first detected in the late 1990s when David Burney, a paleoecologist at the National Tropical Botanical Garden in Kalaheo, was excavating the Makauwahi sinkhole, a collapsed limestone cave on the south shore of Kauai.

Two meters (six and a half feet) below the surface he encountered a layer of sediment marked by coral fragments, mollusk shells and coarse beach sand that could only have come from the sea. But the mouth of the sinkhole was separated from the shore by 100 meters (328 feet) of land and seven-meter (23-foot) high walls. Burney speculated that the deposit could have been left by a massive tsunami, but he was unable to verify the claim.

The deposits remained a mystery until the Tohoku earthquake hit Japan in 2011. It caused water to surge inland like a rapidly rising tide, reaching heights up to 39 meters (128 feet) above the normal sea level. After that tsunami deluged the island nation, scientists began to question Hawaii's current tsunami evacuation maps. The maps are based largely upon the 1946 tsunami, which followed a magnitude 8.6 earthquake in the Aleutian Islands and caused water to rise only two and a half meters (8 feet) up the side of the Makauwahi sinkhole.

"[The Japan earthquake] was bigger than almost any seismologist thought possible," said Butler. "Seeing [on live TV] the devastation it caused, I began to wonder, did we get it right in Hawaii? Are our evacuation zones the correct size?"

To find out, the study's authors used a wave model to predict how a tsunami would flood the Kauai coastline. They simulated earthquakes with magnitudes between 9.0 and 9.6 originating at different locations along the Aleutian-Alaska subduction zone, a 3,400-kilometer (2,113-mile) long ocean trench stretching along the southern coast of Alaska and the Aleutian Islands where the Pacific tectonic plate is slipping under the North American plate.

The researchers found that the unique geometry of the eastern Aleutians would direct the largest post-earthquake tsunami energy directly toward the Hawaiian Islands. Inundation models showed that an earthquake with a magnitude greater than 9.0 in just the right spot could produce water levels on the shore that reached eight to nine meters (26 to 30 feet) high, easily overtopping the Makauwahi sinkhole wall where the ocean deposits were found.

The authors used radiocarbon-dated marine deposits from Sedanka Island off the coast of Alaska and along the west coasts of Canada and the United States dating back to the same time period as the Makauwahi deposit to show that all three sediments could have come from the same tsunami and provide some evidence that the event occurred, according to the study.

"[The authors] stitched together geological evidence, anthropological information as well as geophysical modeling to put together this story that is tantalizing for a geologist but it's frightening for people in Hawaii," said Robert Witter, a geologist at the U.S. Geological Survey in Anchorage, Alaska who was not involved in the study.

According to Witter, it is possible that a massive tsunami hit Hawaii hundreds of years ago, based on the deposits found in the Kauai sinkhole, but he said it is difficult to determine if all three locations experienced the same event based on radiocarbon dating alone.

Radiocarbon dating only gives scientists a rough estimate of the age of a deposit, he said. All three locations offer evidence of a great tsunami occurring between 350 and 575 years ago, but it is hard to know if it was the same tsunami or ones that occurred hundreds of years apart.

"An important next thing to do is to look for evidence for tsunamis elsewhere in the Hawaiian island chain," said Witter.

Fryer, of the Pacific Tsunami Warning Center, is confident that more evidence of the massive tsunami will be found, confirming that events of this magnitude have rocked the island chain in the not-so-distant past.

"I've seen the deposit," said Fryer, who was not involved in the study. "I'm absolutely convinced it's a tsunami, and it had to be a monster tsunami."

Fryer is so convinced that he has worked with the city and county of Honolulu to update their tsunami evacuation maps to include the possibility of a massive tsunami the size of the one detailed in the new study hitting the islands. The county hopes to have the new maps distributed to residents by the end of the year, he said.

"We prepared ourselves for the worst tsunami that's likely to happen in one hundred years," Fryer said of the current tsunami evacuation maps based on the 1946 event. "What hit Japan was a thousand-year event … and this scenario [in the eastern Aleutians] is a thousand year event."

Source: American Geophysical Union

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The Hydraulic fracturing linked to earthquakes in Ohio

Seismograph (stock image). Hydraulic fracturing triggered a series of small earthquakes in 2013 on a previously unmapped fault in Harrison County, Ohio, according to a study. Credit: © hakandogu / Fotolia

Hydraulic fracturing triggered a series of small earthquakes in 2013 on a previously unmapped fault in Harrison County, Ohio, according to a study published in the journal Seismological Research Letters (SRL).

Nearly 400 small earthquakes occurred between Oct. 1 and Dec. 13, 2013, including 10 "positive" magnitude earthquake, none of which were reported felt by the public. The 10 positive magnitude earthquakes, which ranged from magnitude 1.7 to 2.2, occurred between Oct. 2 and 19, coinciding with hydraulic fracturing operations at nearby wells.

This series of earthquakes is the first known instance of seismicity in the area.
Hydraulic fracturing, or fracking, is a method for extracting gas and oil from shale rock by injecting a high-pressure water mixture directed at the rock to release the gas inside. The process of hydraulic fracturing involves injecting water, sand and chemicals into the rock under high pressure to create cracks. The process of cracking rocks results in micro-earthquakes. Hydraulic fracturing usually creates only small earthquakes, ones that have magnitude in the range of negative 3 (−3) to negative 1 (-1).
"Hydraulic fracturing has the potential to trigger earthquakes, and in this case, small ones that could not be felt, however the earthquakes were three orders of magnitude larger than normally expected," said Paul Friberg, a seismologist with Instrumental Software Technologies, Inc. (ISTI) and a co-author of the study.

The earthquakes revealed an east-west trending fault that lies in the basement formation at approximately two miles deep and directly below the three horizontal gas wells. The EarthScope Transportable Array Network Facility identified the first earthquakes on Oct. 2, 2013, locating them south of Clendening Lake near the town of Uhrichsville, Ohio. A subsequent analysis identified 190 earthquakes during a 39-hour period on Oct. 1 and 2, just hours after hydraulic fracturing began on one of the wells.

The micro-seismicity varied, corresponding with the fracturing activity at the wells. The timing of the earthquakes, along with their tight linear clustering and similar waveform signals, suggest a unique source for the cause of the earthquakes -- the hydraulic fracturing operation. The fracturing likely triggered slip on a pre-existing fault, though one that is located below the formation expected to confine the fracturing, according to the authors.

"As hydraulic fracturing operations explore new regions, more seismic monitoring will be needed since many faults remain unmapped." Friberg co-authored the paper with Ilya Dricker, also with ISTI, and Glenda Besana-Ostman originally with Ohio Department of Natural Resources, and now with the Bureau of Reclamation at the U.S. Department of Interior.

Source: Seismological Society of America

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Storm-triggered landslides: Examining causes of devastating debris flow

Storm-triggered landslides cause loss of life, property damage, and landscape alterations. For instance, the remnants of Hurricane Camille in 1969 caused 109 deaths in central Virginia, after 600 mm of rain fell in mountainous terrain in 6 hours. More recently, on 8 August 2010, a rainstorm-induced landslide devastated the Chinese county of Zhouqu, causing more than 1000 deaths. A new modeling study by Ren examines the multiple factors, both natural and human caused, that came together to produce this event. The triad of storm-triggered landslides is geological condition, surface loading and vegetation roots, and extreme precipitation.

Extreme precipitation can be explained by three factors: low-level moisture buildup, conditional instability, and a lifting mechanism. When several factors (e.g., El Niño years, hurricane remnants, lifting mechanisms (e.g., orography, cold fronts, jets, and differential heating from land cover contrast), and weather pattern phase-lock) work in synergy in a region, extreme precipitation may occur.

Using a multiple-phase scalable and extensible geofluid model, the author considered geological features of the region, as well as an earthquake, drought, deforestation, and topsoil erosion before the triggering storm. Previously, drought conditions created cracks and crevices in the surface; these cracks and crevices were deepened by the 2008 M7.9 Wenchuan earthquake.

Another key factor in setting up the conditions for the landslide was human-induced deforestation and topsoil erosion, the study found. The results "underscore the urgency for a high priority program of re-vegetation of Zhouqu County, without which the region will remain exposed to future disastrous, progressive bulking type landslides," the author reports.

Source: Wiley

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