Solar activity not a key cause of climate change, study shows

Dec. 22, 2013 — Climate change has not been strongly influenced by variations in heat from the sun, a new scientific study shows.

The findings overturn a widely held scientific view that lengthy periods of warm and cold weather in the past might have been caused by periodic fluctuations in solar activity.

Research examining the causes of climate change in the northern hemisphere over the past 1000 years has shown that until the year 1800, the key driver of periodic changes in climate was volcanic eruptions. These tend to prevent sunlight reaching Earth, causing cool, drier weather. Since 1900, greenhouse gases have been the primary cause of climate change.

The findings show that periods of low sun activity should not be expected to have a large impact on temperatures on Earth, and are expected to improve scientists' understanding and help climate forecasting.

Scientists at the University of Edinburgh carried out the study using records of past temperatures constructed with data from tree rings and other historical sources. They compared this data record with computer-based models of past climate, featuring both significant and minor changes in the sun.

They found that their model of weak changes in the sun gave the best correlation with temperature records, indicating that solar activity has had a minimal impact on temperature in the past millennium.

The study, published in Nature GeoScience, was supported by the Natural Environment Research Council.

Dr Andrew Schurer, of the University of Edinburgh's School of GeoSciences, said: "Until now, the influence of the sun on past climate has been poorly understood. We hope that our new discoveries will help improve our understanding of how temperatures have changed over the past few centuries, and improve predictions for how they might develop in future. Links between the sun and anomalously cold winters in the UK are still being explored."

View the original article here

Some plants may not adapt quickly to future climate change

Dec. 22, 2013 — Using the largest dated evolutionary tree of flowering plants ever assembled, a new study suggests how plants developed traits to withstand low temperatures, with implications that human-induced climate change may pose a bigger threat than initially thought to plants and global agriculture.

The study appearing Sunday (Dec. 22) in the journal Nature and co-authored by University of Florida scientists shows many angiosperms, or flowering plants, evolved mechanisms to cope with freezing temperatures as they radiated into nearly every climate during pre-historic times. Researchers found the plants likely acquired many of these adaptive traits prior to their movement into colder regions. The study also suggests some modern angiosperms, including most flowering plants, trees and agricultural crops, may not have the traits needed to rapidly respond to human-induced climate change, said study co-author Pam Soltis, a distinguished professor and curator of molecular systematics and evolutionary genetics at the Florida Museum on the UF campus.

"Only some plants were able to make the adjustments to survive in cold climates," said Soltis, who also is a member of the UF Genetics Institute. "In fact, some had traits used for other purposes that they co-opted for cold tolerance. The results have implications for plant response to climate change -- some plant lineages, including many crops, will not have the underlying genetic attributes that will allow for rapid responses to climate change."

Early flowering plants are thought to have been woody -- meaning they maintain a prominent stem above ground across years and changing weather conditions, such as a maple tree -- and restricted to warm, wet, tropical environments. But they have since put down roots in colder climates, dominating large swaths of the globe where freezing occurs. How they managed this expansion has long vexed researchers searching for plants' equivalent to the winter parka.

"Until now, we haven't had a compelling narrative about how leaf and stem traits have evolved to tolerate cold temperatures," said lead author Amy Zanne, assistant professor of biology in George Washington University's Columbian College of Arts and Sciences who earned her doctorate at UF. "Our research gives us this insight, showing us the 'whens,' 'hows' and 'whys' behind plant species' trait evolution and movements around the globe."

Zanne continued: "Freezing is a challenge for plants. Their living tissues can be damaged. It's like a plant's equivalent to frostbite. Their water-conducting pipes can also be blocked by air bubbles as water freezes and thaws. So over time, if plants moved into colder climates, they've had to figure out how to get around these problems."

Identifying evolutionary adaptations to these problems and likely paths to them required the team to build two sets of data. Researchers first created a database of 49,064 species, recording whether each maintains a stem aboveground over time, loses or keeps its leaves, has been exposed to freezing, and the width of its water-carrying pathways. Researchers combined the information with a dated evolutionary tree of 32,223 plant species and modeled the evolution of species' traits and climate over time, which identified the order of evolutionary events.

"We can determine the relative order of events without a dated tree, but the dated tree allows us to say exactly when something happened, so that we can correlate the events with geological events, like big changes in Earth's temperature," Soltis said.

Using this "timetree," researchers identified three repeated evolutionary shifts they believe flowering plants made to fight the cold. Plants either dropped their leaves seasonally, shutting down the pathways that would normally carry water between roots and leaves; developed thinner water-conducting pathways, allowing them to keep their leaves while reducing the risk of air bubbles developing during freezing and thawing; or avoided the cold seasons altogether as herbs, losing aboveground stems and leaves and retreating as seeds, or storing organs underground, such as tulips or potatoes.

"Angiosperms were not successful until they got the adaptation to drop their leaves," said study co-author Doug Soltis, a Florida Museum distinguished professor with appointments in UF's biology department and the UF Genetics Institute. "Sometimes the trait evolves for some other purpose, and then the organism is able to adapt and use it for something new."

Researchers found that woody plants most often became herbs or developed thinner pathways before moving into freezing climates, while plants that dropped their leaves usually did so after moving into freezing climates. But the changes did not occur rapidly, Pam Soltis said.

"Some of these changes were probably not as simple as we once thought," she said. "Adjusting to big shifts in their environments is probably not easy for plants to do."

The researchers plan to use the findings to explore other aspects of plants' evolutionary history, including examining how they respond to environmental changes other than freezing temperatures.

"The onset of freezing temperatures did not affect the entire world, but only certain habitats became colder," Pam Soltis said. "Certain lineages could not move into the cold, but were able to persist unaffected by the cold in warmer areas. With climate change that is human-induced, all habitats will be affected over a short period of time, and plants and other organisms will have to adapt quickly if they are to survive."

View the original article here

Human influence on climate clear, IPCC report says

Sep. 27, 2013 — Human influence on the climate system is clear. This is evident in most regions of the globe, a new assessment by the Intergovernmental Panel on Climate Change (IPCC) concludes.

It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. The evidence for this has grown, thanks to more and better observations, an improved understanding of the climate system response and improved climate models.

Warming in the climate system is unequivocal and since 1950 many changes have been observed throughout the climate system that are unprecedented over decades to millennia. Each of the last three decades has been successively warmer at Earth's surface than any preceding decade since 1850, reports the Summary for Policymakers of the IPCC Working Group I assessment report, Climate Change 2013: the Physical Science Basis, approved on Friday by member governments of the IPCC in Stockholm, Sweden.

"Observations of changes in the climate system are based on multiple lines of independent evidence. Our assessment of the science finds that the atmosphere and ocean have warmed, the amount of snow and ice has diminished, the global mean sea level has risen and the concentrations of greenhouse gases have increased," said Qin Dahe, Co-Chair of IPCC Working Group I.

Thomas Stocker, the other Co-Chair of Working Group I said: "Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions."

"Global surface temperature change for the end of the 21st century is projected to be likely to exceed 1.5°C relative to 1850 to 1900 in all but the lowest scenario considered, and likely to exceed 2°C for the two high scenarios," said Co-Chair Thomas Stocker. "Heat waves are very likely to occur more frequently and last longer. As Earth warms, we expect to see currently wet regions receiving more rainfall, and dry regions receiving less, although there will be exceptions," he added.

Projections of climate change are based on a new set of four scenarios of future greenhouse gas concentrations and aerosols, spanning a wide range of possible futures. The Working Group I report assessed global and regional-scale climate change for the early, mid-, and later 21st century.

"As the ocean warms, and glaciers and ice sheets reduce, global mean sea level will continue to rise, but at a faster rate than we have experienced over the past 40 years," said Co-Chair Qin Dahe. The report finds with high confidence that ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010.

Co-Chair Thomas Stocker concluded: "As a result of our past, present and expected future emissions of CO2, we are committed to climate change, and effects will persist for many centuries even if emissions of CO2 stop."

Rajendra Pachauri, Chair of the IPCC, said: "This Working Group I Summary for Policymakers provides important insights into the scientific basis of climate change. It provides a firm foundation for considerations of the impacts of climate change on human and natural systems and ways to meet the challenge of climate change." These are among the aspects assessed in the contributions of Working Group II and Working Group III to be released in March and April 2014. The IPCC Fifth Assessment Report cycle concludes with the publication of its Synthesis Report in October 2014.

"I would like to thank the Co-Chairs of Working Group I and the hundreds of scientists and experts who served as authors and review editors for producing a comprehensive and scientifically robust summary. I also express my thanks to the more than one thousand expert reviewers worldwide for contributing their expertise in preparation of this assessment," said IPCC Chair Pachauri.

The Summary for Policymakers of the Working Group I contribution to the IPCC Fifth Assessment Report (WGI AR5) is available at www.climatechange2013.org or www.ipcc.ch.

View the original article here

Study provides insights on protecting world's poor from climate change

Sep. 11, 2013 — The worst impacts of climate change on the world's poorest fishing communities can likely be avoided by careful management of the local environment and investing in the diversification of options for local people, according to the Wildlife Conservation Society and James Cook University.

Climate change is already putting pressure on fishers who depend on nature for their livelihoods. In a new study, scientists found large differences in the potential to adapt based on the local mixture of social and environmental characteristics, requiring a variety of management approaches for each situation.

The paper appears today in the online journal PLOS ONE. The authors include: Joshua E. Cinner, Cindy Huchery, Nicholas Graham, and Christina Hicks of the ARC Centre of Excellence for Coral Reef Studies, James Cook University; Emily Darling of Simon Fraser University and Austin Humphries of Rhodes University; Nadine Marshall of CSIRO; and Tim McClanahan of the Wildlife Conservation Society.

The study undertaken by an international team of scientists, focused on 12 poor fishing communities along the coast of Kenya -- a poor country that has been identified as one of the most vulnerable to the impacts of climate change. The scientists found that, even among the poor, there were considerable differences in how climate change was likely to affect the communities based on the existing social conditions and how each community cared for its marine resources.

"Despite the fact that all of the communities we studied were geographically close, they were vulnerable in very different ways," said lead author Dr. Joshua Cinner. "Some communities really lacked the assets to invest in new opportunities; others lacked the diversity of livelihood opportunities and skills to make a change, while some lacked the social networks and connections that people can rely on in times of need."

The team also looked at how the local coral reefs were holding up to a changing climate. "There are a number of studies that look at how climate change will affect either ecosystems or society, but in this study we really brought both of these together to get a more complete picture" says co-author Dr. Tim McClanahan, a Senior Conservation Zoologist from the Wildlife Conservation Society. "We conducted rigorous studies of reef ecology, the types of fish people were catching, and local socioeconomic conditions." Consequently, the study provides the most detailed and comprehensive examination of both social and ecological aspects of climate change impacts on coral reef fisheries to date.

The authors noted that climate change is already exerting significant pressure on the fishing communities of coastal Kenya; the 1998 El Nino Southern Oscillation resulted in widespread coral mortality along the coast. In areas where overfishing was rampant, communities lacked the potential to recover quickly from disturbances. These same areas tended to have fish species that were more sensitive to coral loss than areas that were protected from fishing by local communities and the government.

Overall, the authors found that communities and coastal managers can find ways of reducing the impacts of climate change on fragile coral reef ecosystems. Just as important, the authors maintain, will be formulating adaptation solutions combining ecological and socio-economic factors.

View the original article here