A number of NASA instruments captured detailed images of this coronal mass ejection on August 31, 2012. Although CMEs can damage sensitive technological systems, this one just struck a glancing blow to Earth's atmosphere. New research has identified quasi-annual variations in solar activity, which may help experts better forecast CMEs and potentially damaging space weathers. (Image courtesy NASA Goddard Space Flight Center.)

The Sun undergoes a type of seasonal variability, with its activity waxing and waning over the course of nearly two years, according to a new study by a team of researchers led by the National Center for Atmospheric Research (NCAR). This behavior affects the peaks and valleys in the approximately 11-year solar cycle, sometimes amplifying and sometimes weakening the solar storms that can buffet Earth’s atmosphere.

The quasi-annual variations appear to be driven by changes in the bands of strong magnetic fields in each solar hemisphere. These bands also help shape the approximately 11-year solar cycle that is part of a longer cycle that lasts about 22 years.

“What we’re looking at here is a massive driver of solar storms,” said Scott McIntosh, lead author of the new study and director of NCAR’s High Altitude Observatory. “By better understanding how these activity bands form in the Sun and cause seasonal instabilities, there’s the potential to greatly improve forecasts of space weather events.”

The overlapping bands are fueled by the rotation of the Sun’s deep interior, according to observations by the research team. As the bands move within the Sun’s northern and southern hemispheres, activity rises to a peak over a period of about 11 months and then begins to wane.

The quasi-annual variations can be likened to regions on Earth that have two seasons, such as a rainy season and a dry season, McIntosh said.

The study, published this week in Nature Communications, can help lead to better predictions of massive geomagnetic storms in Earth’s outer atmosphere that sometimes disrupt satellite operations, communications, power grids, and other technologies.

The research was funded by NASA and the National Science Foundation, which is NCAR’s sponsor.

A “JET STREAM” IN THE SUN

The new study is one of a series of papers by the research team that examines the influence of the magnetic bands on several interrelated cycles of solar magnetism. In a paper last year in Astrophysical Journal, the authors characterized the approximately 11-year sunspot cycle in terms of two overlapping parallel bands of opposite magnetic polarity that slowly migrate over almost 22 years from high solar latitudes toward the equator, where they meet and terminate.

McIntosh and his co-authors detected the twisted, ring-shaped bands by drawing on a host of NASA satellites and ground-based observatories that gather information on the structure of the Sun and the nature of solar flares and coronal mass ejections (CMEs). These observations revealed the bands in the form of fluctuations in the density of magnetic fuel that rose from the solar interior through a transition region known as the tachocline and on to the surface, where they correlated with changes in flares and CMEs.

In the new paper, the authors conclude that the migrating bands produce seasonal variations in solar activity that are as strong as the more familiar 11-year counterpart. These quasi-annual variations take place separately in both the northern and southern hemispheres.

“Much like Earth’s jet stream, whose warps and waves have had severe impact on our regional weather patterns in the past couple of winters, the bands on the Sun have very slow-moving waves that can expand and warp it too,” said co-author Robert Leamon, a scientist at Montana State University. “Sometimes this results in magnetic fields leaking from one band to the other. In other cases, the warp drags magnetic fields from deep in the solar interior, near the tachocline, and pushes them toward the surface.”

The surges of magnetic fuel from the Sun’s interior catastrophically destabilize the corona, the Sun’s outermost atmosphere. They are the driving force behind the most destructive solar storms.

“These surges or ‘whomps’ as we have dubbed them, are responsible for over 95 percent of the large flares and CMEs—the ones that are really devastating,” McIntosh said.

The quasi-annual variability can also help explain a cold-war era puzzle: why do powerful solar flares and CMEs often peak a year or more after the maximum number of sunspots? This lag is known as the Gnevyshev Gap, after the Soviet scientist who first reported it in the 1940s. The answer appears to be that seasonal changes may cause an upswing in solar disturbances long after the peak in the solar cycle.

Researchers can turn to advanced supercomputer simulations and more detailed observations to learn more about the profound influence of the bands on solar activity. McIntosh said this could be assisted by a proposed network of satellites observing the Sun, much as the global networks of satellites around Earth has helped to advance terrestrial weather models since the 1960s.

“If you understand what the patterns of solar activity are telling you, you’ll know whether we’re in the stormy phase or the quiet phase in each hemisphere,” McIntosh said. “If we can combine these pieces of information, forecast skill goes through the roof.”

Floodwaters from Lake Mendota and Lake Monona could reach clear across central Madison's isthmus. If Lake Mendota breaks its banks, officials would be forced to close down Dane County Regional Airport.

How society should respond to climate change may be a global-scale debate, but University of Wisconsin-Madison researchers know that preparing for climate change's impact on weather is a profoundly local problem.

Professor of Civil and Environmental Engineering Kenneth Potter and David S. Liebl, a UW-Madison faculty associate in Engineering Professional Development, are combining strengths in water resource management and outreach to help local communities better understand their vulnerabilities to large storms stoked by climate change. The two have developed a computer-modeling tool that essentially transposes rainfall data from a recent damaging storm in one area to a nearby area that might reasonably be expected to share the same weather and climate conditions.

In a prototype recently showcased in the National Oceanic and Atmospheric Administration U.S. Climate Resilience Toolkit, Potter and Liebl took the storm that caused the disastrous Baraboo River flood of 2008 and shifted it southeast to Madison. By computationally slamming heavy rains into the topography of Madison and the structure of the Yahara River Watershed, the model went beyond statistics to yield concrete predictions.

"It turns out that many people who influence public decisions are not very comfortable with statistically based predictions," Potter says. "But a storm that occurred recently, where people witnessed a lot of damage, they know that could have happened 30 miles further south, so they tune in better."

Potter and Liebl worked with professional engineers and officials at cities and counties around the state, along with state officials and scientists at the Wisconsin Department of Natural Resources. The ultimate goal is to build a computing tool that officials around the country could use to better plan infrastructure projects that account for storm predictions.

Potter says most statistical and modeling approaches to precipitation aren't that useful to city- or county-level planners. Some global circulation models divide the entire state up into three grid areas, providing averages that would be a bit crude for, say, civil engineers plotting out worst-case storm scenarios in Dane County - and, just as importantly, such relatively crude data isn't a great starting point for a conversation about climate readiness.

"Rainfall can be very local," Potter says. "There are a lot of variables, and we felt that it would be difficult for decision makers to act on that kind of information."

The key challenge, in both scientific and outreach terms, is to build something that will resonate on the local level for communities with varying needs, resources, weather patterns and geography. A truly flexible storm-prediction tool would require a database of transposable storms, and likely buy-in from federal agencies to develop computing tools that many cities and counties around the country couldn't afford to develop themselves.

"We've used this 2008 Baraboo storm pretty effectively, but it's limited in that it's mostly going to be relevant to communities in the region and people who are aware of what happened in that storm, know the locality, know the Baraboo River and how it flooded the Interstate," Liebl says. "Once you get further afield, you need to find storms that people can relate to elsewhere in the country. The character of storms and the type of rainfall we get here in the upper Midwest isn't necessarily characteristic of other parts of the country."

Even in Dane County, Potter says, the researchers want to refine their modeling by incorporating richer detail about the pathways water can take through the local landscape.

"Water can go through storm sewers connecting areas that from the topography you wouldn't think are connected," Potter says. "I've been working for a long time on statistical characterization of storms, and I'm convinced this is going to be a lot easier for people to understand and appreciate their vulnerability."

Potter and Liebl's research was funded by the NOAA Sectoral Applications Research Program and the Northeast Climate Science Center.

There's a carbon showdown brewing in the Arctic as Earth's climate changes. On one side, thawing permafrost could release enormous amounts of long-frozen carbon into the atmosphere. On the opposing side, as high-latitude regions warm, plants will grow more quickly, which means they'll take in more carbon from the atmosphere.

Whichever side wins will have a big impact on the carbon cycle and the planet's climate. If the balance tips in favor of permafrost-released carbon, climate change could accelerate. If the balance tips in favor of carbon-consuming plants, climate change could slow down.

Turns out the result will be lopsided. There will be a lot more carbon released from thawing permafrost than the amount taken in by more Arctic vegetation, according to new supercomputer simulations conducted by scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab).

The findings are from an Earth system model that is the first to represent permafrost processes as well as the dynamics of carbon and nitrogen in the soil. Simulations using the model showed that by the year 2300, if climate change continues unchecked, the net loss of carbon to the atmosphere from Arctic permafrost would range from between 21 petagrams and 164 petagrams. That's equivalent to between two years and 16 years of human-induced CO2 emissions.

The scientists included nitrogen dynamics in the model because, as permafrost thaws, nitrogen trapped in deeper soil layers (below one meter underground) will decompose and become available to fertilize plants. At the same time, organic carbon frozen in deeper soil layers will decompose and enter the atmosphere.

"The big question has been: Which side wins? And we found the rate of permafrost thaw and its effect on the decomposition of deep carbon will have a much bigger impact on the carbon cycle than the availability of deep nitrogen and its ability to spark plant growth," says Charles Koven of Berkeley Lab's Earth Sciences Division.

Koven conducted the research with fellow Berkeley Lab scientist William Riley and David Lawrence of the National Center for Atmospheric Research. They recently  in the Proceedings of the National Academy of Sciences.

The scientists believe that nitrogen's relatively small impact on the carbon cycle is due to the fact that deeper layers of permafrost won't thaw until the fall or even early winter, when summer's warmth finally reaches more than one meter below ground. At that stage in the growing season, the deep nitrogen that decomposes and becomes available will have few plants to fertilize.

The model's output also highlights uncertainties in the science. After all, the simulations found that between 21 petagrams and 164 petagrams of carbon will be released to the atmosphere, which is a big range. The scientists say that more field and lab research is needed to determine how carbon-decomposition dynamics work in deep layers of permafrost versus at the surface, including the role of microbes, minerals, and plant roots.

"These simulations allow us to identify processes that seem to have a lot of leverage on climate change, and which we need to explore further," says Koven.

The terrestrial ecosystem portion of the Earth system model simulations were conducted at the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility located at Berkeley Lab.

Photo credit: Hugo Glendinning

Multi-institutional effort led by Berkeley Lab, called NGEE-Tropics, will couple field research with the development of a new ecosystem model

Tropical forests play major roles in regulating Earth's climate, but there are large uncertainties over how they'll respond over the next 100 years as the planet's climate warms. An expansive new project led by scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) aims to bring the future of tropical forests and the climate system into much clearer focus.

The project is called the Next Generation Ecosystem Experiments-Tropics, or NGEE-Tropics. Its goal is the development of a model that represents how tropical forests interact with Earth's climate in much greater ecological detail than ever before. This will help scientists explore, more accurately than is possible today, how rising temperatures, shifting precipitation patterns, increasing greenhouse gas levels, and other natural and human-induced changes affect tropical forests' influence on Earth's climate.

The planned ten-year, $100 million project is supported by the Department of Energy's Office of Science. The Department of Energy approved and supported NGEE-Tropics in early March.

"Tropical forests cycle more carbon and water than any other biome, and as such they're a critical player in the planet's energy balance and in climate change. But there's a lot we don't know. Through NGEE-Tropics, we plan to dramatically reduce this uncertainty to improve future climate projections," says Jeff Chambers, an ecologist in Berkeley Lab's Earth Sciences Division and the Principal Investigator and Project Director of NGEE-Tropics.

In addition to Berkeley Lab researchers, the effort includes collaborators from Brookhaven, Los Alamos, Oak Ridge, and Pacific Northwest national laboratories. The study also includes researchers from the Smithsonian Tropical Research Institute, the U.S. Forest Service, the National Center for Atmospheric Research, NASA, and several institutions from other nations, including Brazil's National Institute of Amazonian Research.

More than a dozen other scientists in Berkeley Lab's Earth Sciences and Computational Research divisions are involved in NGEE-Tropics, including Lara Kueppers, the Deputy Project Director.

Over the next decade, NGEE-Tropics scientists will collaborate with other researchers to carry out experiments in tropical forests around the globe. This research will fuel the development of a first-of-its-kind tropical forest ecosystem model that extends from the bedrock to the top of the forest canopy. The model will capture myriad soil and vegetation processes at a resolution better than ten kilometers. This is the resolution that next-generation Earth system models will achieve during the project's lifetime.

During the first phase of the project, which spans the next three years, scientists will assess what's known about tropical forest ecosystems and how well these processes are represented in models. Several pilot field studies will also be developed in phase one that link modeling advances with field observations.

One high-priority activity in phase one will explore how tropical forests respond to reduced precipitation, which is expected in some tropical regions. The study, in Manaus, Brazil, will investigate changes in the forest carbon cycle resulting from low water supply during the dry season from June through September. This is important for understanding whether tropical forests will respond to drought by releasing instead of accumulating carbon.

In another phase one activity in Puerto Rico, NGEE-Tropics scientists will study how soil fertility affects the regrowth of forests on abandoned agricultural land. These so-called secondary forests are known to take up CO2 from the atmosphere and store it for decades, but the rate of uptake is thought to depend on soil fertility. The research will involve measurements of phosphorus and nitrogen across different soil types. It will also involve airborne instruments, such as LiDAR to measure the forest structure and optical sensors to study the chemistry of the forest canopy.

And in Panama, scientists will use detailed datasets of species by species differences across regions to understand which characteristics enable some species to thrive under warmer or drier conditions, while others perish. The research will shed light on how forests dynamically respond to a warming climate.

The NGEE team includes DOE's Pacific Northwest National Laboratory researchers. PNNL's Ruby Leung will lead a team to understand and model how surface and subsurface water varies geographically and over time, and how that variability influences water and nutrients available to plants in a changing climate. The PNNL team will also participate in other research to develop a way to represent the dynamics of tropical forests in models, and to improve understanding and modeling of vegetation when it's disturbed by nature and humans and then recovers. PNNL will receive $2.2 million over the first three years.

Ultimately, the scientists will integrate what they learn from the pilot studies, and the more extensive field investigations in phases two and three, into their new tropical forest model.

"Our process-rich model will be applied within an Earth system model, and will greatly improve our understanding of how tropical forests respond to changes coming over the next century," says Chambers.

The rate of temperature change is rising and will continue to do so, as seen here with the thick gray line. This model depicts rates measured in 40-year windows of time, a time frame that reflects lifespans of people.

The speed with which temperatures change will continue to increase over the next several decades, intensifying the impacts of climate change

An analysis of changes to the climate that occur over several decades suggests that these changes are happening faster than historical levels and are starting to speed up. The Earth is now entering a period of changing climate that will likely be faster than what's occurred naturally over the last thousand years, according to a new paper in Nature Climate Change, committing people to live through and adapt to a warming world.

In this study, interdisciplinary scientist Steve Smith and colleagues at the Department of Energy's examined historical and projected changes over decades rather than centuries to determine the temperature trends that will be felt by humans alive today.

"We focused on changes over 40-year periods, which is similar to the lifetime of houses and human-built infrastructure such as buildings and roads," said lead author Smith. "In the near term, we're going to have to adapt to these changes."

See CMIP run

Overall, the Earth is getting warmer due to increasing greenhouse gases in the atmosphere that trap heat. But the rise is not smooth — temperatures bob up and down. Although natural changes in temperature have long been studied, less well-understood is how quickly temperatures changed in the past and will change in the future over time scales relevant to society, such as over a person's lifetime. A better grasp of how fast the climate might change could help decision-makers better prepare for its impacts.

To examine rates of change, Smith and colleagues at the Joint Global Change Research Institute, a collaboration between PNNL and the University of Maryland in College Park, turned to the Coupled Model Intercomparison Project. The CMIP combines simulations from over two-dozen climate models from around the world to compare model results.

All the CMIP models used the same data for past and future greenhouse gas concentrations, pollutant emissions, and changes to how land is used, which can emit or take in greenhouse gases. The more models in agreement, the more confidence in the results.

The team calculated how fast temperatures changed between 1850 and 1930, a period when people started keeping records but when the amount of fossil fuel gases collecting in the atmosphere was low. They compared these rates to temperatures reconstructed from natural sources of climate information, such as from tree rings, corals and ice cores, for the past 2,000 years.

Taken together, the shorter time period simulations were similar to the reconstructions over a longer time period, suggesting the models reflected reality well.

While there was little average global temperature increase in this early time period, Earth's temperature fluctuated due to natural variability. Rates of change over 40-year periods in North America and Europe rose and fell as much as 0.2 degrees Celsius per decade. The supercomputer models and the reconstructions largely agreed on these rates of natural variability, indicating the models provide a good representation of trends over a 40-year scale.

Now versus then

Then the team performed a similar analysis using CMIP but calculated 40-year rates of change between 1971 to 2020. They found the average rate of change over North America, for example, to be about 0.3 degrees Celsius per decade, higher than can be accounted for by natural variability. The CMIP models show that, at the present time, most world regions are almost completely outside the natural range for rates of change.

The team also examined how the rates of change would be affected in possible . Climate change picked up speed in the next 40 years in all cases, even in scenarios with lower rates of future greenhouse gas emissions. A scenario where greenhouse gas emissions remained high resulted in high rates of change throughout the rest of this century.

Still, the researchers can't say exactly what impact faster rising temperatures will have on the Earth and its inhabitants.

"In these climate model simulations, the world is just now starting to enter into a new place, where rates of temperature change are consistently larger than historical values over 40-year time spans," said Smith. "We need to better understand what the effects of this will be and how to prepare for them."

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