TOPIC | Climate Change


August 3, 2021, 07:07 PDT

Flip Flop: Why Variations in Earth's Magnetic Field Aren't Causing Today's Climate Change

By Alan Buis,
NASA's Jet Propulsion Laboratory

magnetosphere
Earth is surrounded by a system of magnetic fields, called the magnetosphere. The magnetosphere shields our home planet from harmful solar and cosmic particle radiation, but it can change shape in response to incoming space weather from the Sun. Credit: NASA's Scientific Visualization Studio
conceptual animation of solar wind
A constant outflow of solar material streams out from the Sun, depicted here in an artist's rendering. This solar wind is always passing by Earth. Credit: NASA Goddard's Conceptual Image Lab/Greg Shirah

Earth is surrounded by an immense magnetic field, called the magnetosphere. Generated by powerful, dynamic forces at the center of our world, our magnetosphere shields us from erosion of our atmosphere by the solar wind, particle radiation from coronal mass ejections (eruptions of large clouds of energetic, magnetized plasma from the Sun’s corona into space), and from cosmic rays from deep space. Our magnetosphere plays the role of gatekeeper, repelling these forms of energy that are harmful to life, trapping most of it safely away from Earth’s surface. You can learn more about Earth’s magnetosphere here.

Since the forces that generate our magnetic field are constantly changing, the field itself is also in continual flux, its strength waxing and waning over time. This causes the location of Earth’s magnetic north and south poles to gradually shift, and to even completely flip locations every 300,000 years or so. That might be somewhat important if you use a compass, or for certain animals like birds, fish and sea turtles, whose internal compasses use the magnetic field to navigate.

Some people have claimed that variations in Earth’s magnetic field are contributing to current global warming and can cause catastrophic climate change. However, the science doesn’t support that argument. In this blog, we’ll examine a number of proposed hypotheses regarding the effects of changes in Earth’s magnetic field on climate. We’ll also discuss physics-based reasons why changes in the magnetic field can’t impact climate.

Image showing changes in Earth's magnetic field between January 1 and June 20, 2014
Launched in November 2013 by the European Space Agency (ESA), the three-satellite Swarm constellation is providing new insights into the workings of Earth’s global magnetic field. Generated by the motion of molten iron in Earth’s core, the magnetic field protects our planet from cosmic radiation and from the charged particles emitted by our Sun. It also provides the basis for navigation with a compass.

Based on data from Swarm, the top image shows the average strength of Earth’s magnetic field at the surface (measured in nanotesla) between January 1 and June 30, 2014. The second image shows changes in that field over the same period. Though the colors in the second image are just as bright as the first, note that the greatest changes were plus or minus 100 nanotesla in a field that reaches 60,000 nanotesla. Credit: European Space Agency/Technical University of Denmark (ESA/DTU Space)

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Hypotheses:

1. Shifts in Magnetic Pole Locations

The position of Earth’s magnetic north pole was first precisely located in 1831. Since then, it’s gradually drifted north-northwest by more than 600 miles (1,100 kilometers), and its forward speed has increased from about 10 miles (16 kilometers) per year to about 34 miles (55 kilometers) per year. This gradual shift impacts navigation and must be regularly accounted for. However, there is little scientific evidence of any significant links between Earth’s drifting magnetic poles and climate.

2. Magnetic Pole Reversals

Supercomputer models of Earth's magnetic field
Supercomputer models of Earth's magnetic field. On the left is a normal dipolar magnetic field, typical of the long years between polarity reversals. On the right is the sort of complicated magnetic field Earth has during the upheaval of a reversal. Credit: University of California, Santa Cruz/Gary Glatzmaier

During a pole reversal, Earth’s magnetic north and south poles swap locations. While that may sound like a big deal, pole reversals are common in Earth’s geologic history. Paleomagnetic records tell us Earth’s magnetic poles have reversed 183 times in the last 83 million years, and at least several hundred times in the past 160 million years. The time intervals between reversals have fluctuated widely, but average about 300,000 years, with the last one taking place about 780,000 years ago.

Geomagnetic polarity over the past 169 million years, trailing off into the Jurassic Quiet Zone. Dark areas denote periods of normal polarity, light areas denote reverse polarity.
Geomagnetic polarity over the past 169 million years, trailing off into the Jurassic Quiet Zone. Dark areas denote periods of normal polarity, light areas denote reverse polarity. Credit: Public domain

During a pole reversal, the magnetic field weakens, but it doesn’t completely disappear. The magnetosphere, together with Earth’s atmosphere, continue protecting Earth from cosmic rays and charged solar particles, though there may be a small amount of particulate radiation that makes it down to Earth’s surface. The magnetic field becomes jumbled, and multiple magnetic poles can emerge in unexpected places.

No one knows exactly when the next pole reversal may occur, but scientists know they don’t happen overnight: they take place over hundreds to thousands of years.

In the past 200 years, Earth’s magnetic field has weakened about nine percent on a global average. Some people cite this as “evidence” a pole reversal is imminent, but scientists have no reason to believe so. In fact, paleomagnetic studies show the field is about as strong as it’s been in the past 100,000 years, and is twice as intense as its million-year average. While some scientists estimate the field’s strength might completely decay in about 1,300 years, the current weakening could stop at any time.

The Sun expels a constant outflow of particles and magnetic fields known as the solar wind and vast clouds of hot plasma and radiation called coronal mass ejections. This solar material streams across space and strikes Earth’s magnetosphere, the space occupied by Earth’s magnetic field, which acts like a protective shield around the planet.
The Sun expels a constant outflow of particles and magnetic fields known as the solar wind and vast clouds of hot plasma and radiation called coronal mass ejections. This solar material streams across space and strikes Earth’s magnetosphere, the space occupied by Earth’s magnetic field, which acts like a protective shield around the planet. Credit: NASA Goddard/Bailee DesRocher

Plant and animal fossils from the period of the last major pole reversal don’t show any big changes. Deep ocean sediment samples indicate glacial activity was stable. In fact, geologic and fossil records from previous reversals show nothing remarkable, such as doomsday events or major extinctions.

3. Geomagnetic Excursions

Recently, there have been questions and discussion about “geomagnetic excursions:” shorter-lived but significant changes in the magnetic field’s intensity that last from a few centuries to a few tens of thousands of years. During the last major excursion, called the Laschamps event, radiocarbon evidence shows that about 41,500 years ago, the magnetic field weakened significantly and the poles reversed, only to flip back again about 500 years later.

Earth's magnetic field
Earth’s magnetic field. Credit: NASA

While there is some evidence of regional climate changes during the Laschamps event timeframe, ice cores from Antarctica and Greenland don’t show any major changes. Moreover, when viewed within the context of climate variability during the last ice age, any changes in climate observed at Earth’s surface were subtle.

Bottom line: There’s no evidence that Earth’s climate has been significantly impacted by the last three magnetic field excursions, nor by any excursion event within at least the last 2.8 million years.

Physical Principles

1. Insufficient Energy in Earth’s Upper Atmosphere

Electromagnetic currents exist within Earth’s upper atmosphere. But the energy driving the climate system in the upper atmosphere is, on global average, a minute fraction of the energy that drives the climate system at Earth’s surface. Its magnitude is typically less than one to a few milliwatts per square meter. To put that into context, the energy budget at Earth’s surface is about 250 to 300 watts per square meter. In the long run, the energy that governs Earth’s upper atmosphere is about 100,000 times less than the amount of energy driving the climate system at Earth’s surface. There is simply not enough energy aloft to have an influence on climate down where we live.

2. Air Isn’t Ferrous

Finally, changes and shifts in Earth’s magnetic field polarity don’t impact weather and climate for a fundamental reason: air isn’t ferrous.

Ferrous? Say what?? Bueller? Bueller?

Ferrous means “containing or consisting of iron.” While iron in volcanic ash is transported in the atmosphere, and small quantities of iron and iron compounds generated by human activities are a source of air pollution in some urban areas, iron isn’t a significant component of Earth’s atmosphere. There’s no known physical mechanism capable of connecting weather conditions at Earth’s surface with electromagnetic currents in space.

Thermal and compositional structure of the atmosphere.
Thermal and compositional structure of the atmosphere. The upper atmosphere, comprising the mesosphere, thermosphere, and embedded ionosphere, absorbs all incident solar radiation at wavelengths less than 200 nanometers (nm). Most of that absorbed radiation is ultimately returned to space via infrared emissionsfrom carbon dioxide (CO2) and nitric oxide (NO) molecules. The stratospheric ozone layer absorbs radiation between 200 and 300 nm.

The plot on the left shows the typical global-average thermal structure of the atmosphere when the flux of solar radiation is at the minimum and maximum values of its 11-year cycle. The plot on the right shows the density of nitrogen (N2), oxygen (O2), and atomic oxygen (O), the three major neutral species in the upper atmosphere, along with the free electron (e−) density, which is equal to the combined density of the various ion species. The F, E, and D regions of the ionosphere are also indicated, as is the troposphere, the atmosphere’s lowest region. Credit: Naval Research Laboratory/J. Emmert

Solar storms and their electromagnetic interactions only impact Earth’s ionosphere, which extends from the lowest edge of the mesosphere (about 31 miles or 50 kilometers above Earth’s surface) to space, around 600 miles (965 kilometers) above the surface. They have no impact on Earth’s troposphere or lower stratosphere, where Earth’s surface weather, and subsequently its climate, originate.

In short, when it comes to climate, variations in Earth’s magnetic field are nothing to get charged up about.

Related Feature

Earth's Magnetosphere: Protecting Our Planet from Harmful Space Energy

April 21, 2021, 15:34 PDT

NASA Technologies Spin off to Fight Climate Change

By Mike DiCicco,
NASA’s Spinoff Publication

An orbital sunrise is pictured from the International Space Station (ISS) as it orbited 260 miles (418 kilometers) above the Pacific Ocean, about 500 miles (805 kilometers) southwest of Mexico. As Earth's climate changes, the ISS watches from above, helping to provide unique insights to keep our planet safe. Credit: NASA

An orbital sunrise is pictured from the International Space Station (ISS) as it orbited 260 miles (418 kilometers) above the Pacific Ocean, about 500 miles (805 kilometers) southwest of Mexico. As Earth's climate changes, the ISS watches from above, helping to provide unique insights to keep our planet safe. Credit: NASA

NASA’s work has generated countless spinoffs that are now on the front lines of the fight against climate change. That shouldn’t be a surprise, since the agency’s missions include studying Earth and improving aircraft efficiency.

But that’s not the only way NASA’s innovations make an impact. Many advances to meet the harsh demands of space travel are also helping to reduce greenhouse gases, improve alternative energy sources, and increase our understanding of the causes and effects of climate change.

Read on for a few examples, and head over to spinoff.nasa.gov/climate-change for a roundup of dozens more.

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Trapping Greenhouse Gases

Carbon dioxide, a greenhouse gas, is the most prominent driver of climate change on Earth. On Mars, however, where most of the atmosphere is CO2, the gas could come in handy. Under NASA contracts, one engineer helped develop technology to capture Martian carbon dioxide and break it into carbon and oxygen for other uses, from life support to fuel for a journey home.

Although it never flew, Perseverance will test out a similar idea, using an experimental system called MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment). Meanwhile, the earlier technology led to a system that now captures natural gases at oil wells, instead of wastefully burning them off and dumping the resulting CO2 into the atmosphere.

And another version of the system helps beer breweries go “greener” by capturing carbon dioxide from the brewing process, rather than venting it, and using it for carbonation instead of buying more.

Conserving Energy

Conserving energy is a crucial consideration for space travel, and many innovations NASA has come up with in that arena are now widespread in improving energy efficiency on Earth.

For example, NASA helped create a type of reflective insulation to efficiently maintain a comfortable temperature within spacecraft and spacesuits. In the decades since, this insulation has been adapted and used in homes and buildings around the world.

Another material pioneered to insulate cryogenic rocket fuel against the balmy weather around the launch pad at Cape Canaveral, Florida, now saves energy by preserving temperatures at industrial facilities. And a coating invented to protect spacecraft during the extreme heat of atmospheric entry improves the efficiency of incinerators, boilers, and refractories, ovens, and more.

Infographic: More NASA Tech Helping to Solve Climate Challenges
NASA research and innovations have led to many environment-saving spinoffs, and this graphic highlights a few. Credit: NASA
Click for PDF version

Shrinking Air Travel’s Carbon Footprint

Air travel is a major contributor to human-made greenhouse gases. Designing aircraft to fly more efficiently reduces the amount of fuel they burn, and in turn, their resulting emissions. And many of the improvements that make modern aircraft more efficient come straight from NASA.

In fact, some of the agency’s most significant contributions to aeronautic fuel efficiency can be traced back to the work of a single NASA engineer in the 1960s and ’70s. Richard Whitcomb designed and tested an entirely new wing shape – the supercritical wing – that significantly increased efficiency at high speeds and eliminated weight.

He then designed upturned wingtips that make use of air vortices that would otherwise create drag. Now incorporated into nearly all commercial planes, these advances combined save billions of dollars’ worth of fuel, along with associated CO2 emissions, every year.

In the decades since, NASA has continued to work with industry partners to improve airplane efficiency, and the agency is now supporting the cutting edge of all-electric flight.

Advancing Renewable Energy

Because there are no fossil fuels on Mars, NASA became interested in wind energy to power future Martian operations. So, the space agency helped a company develop a wind turbine that could operate in a similarly harsh environment – the South Pole. Rugged and designed for easy maintenance and efficiency at extremely low temperatures, more than 800 of the resulting turbines are now generating power on Earth.

Unexpectedly, software NASA supported for improved aircraft design and maintenance has also led to more efficient, long-lasting wind turbines. And several solar panel manufacturers have benefited from the agency’s long reliance on the sun for energy.

Understanding Climate Change

Mountains of data from a fleet of Earth-observing NASA satellites help countless other agencies, researchers, and companies better understand the causes and effects of climate change. The agency has worked with commercial partners to make this data manageable and easier to mine for information. Other companies have benefited from NASA’s support for technology to monitor conditions on the ground and in the oceans and atmosphere, including innovative devices to sense local greenhouse gases and ocean conditions. The resulting data helps to verify and enrich the agency’s models of Earth weather and climate, which span decades, circle the globe, and peer into the future.

NASA has a long history of transferring technology to the private sector. The agency’s Spinoff publication profiles NASA technologies that have transformed into commercial products and services, demonstrating the broader benefits of America’s investment in its space program. Spinoff is a publication of the Technology Transfer program in NASA’s Space Technology Mission Directorate.

For more information on how NASA brings space technology down to Earth, visit:

spinoff.nasa.gov

July 14, 2020, 08:47 PDT

Sea Level 101, Part Two: All Sea Level is ‘Local'

By Alan Buis,
NASA's Jet Propulsion Laboratory

Global sea level rise impacts all coastlines differently due to numerous factors. The height of the ocean relative to the land along a coastline is referred to as relative sea level. Credit: joiseyshowaa/Flickr CC BY-SA 2.0

Global sea level rise impacts all coastlines differently due to numerous factors. The height of the ocean relative to the land along a coastline is referred to as relative sea level. Credit: joiseyshowaa/Flickr CC BY-SA 2.0

As discussed in our last Sea Level 101 blog post, we know sea level on the open ocean isn’t really flat. A number of factors combine to determine the topography of the ocean surface.

Global sea level rise is complex as well. To begin with, it has multiple causes, including the thermal expansion of the ocean as it warms, runoff of meltwater from land-based ice sheets and mountain glaciers, and changes in water that’s stored on land. These factors combine to raise the height of our global ocean about 3.3 millimeters (0.13 inches) every year. That rate is accelerating by another 1 millimeter per year (0.04 inches per year) every decade or so.

Factors that contribute to sea level change.
Factors that contribute to sea level change. Credit: Intergovernmental Panel on Climate Change 2001

Another factor that makes sea level rise complex is that it’s not uniform around the globe. If you look at a global map of sea level rise, you’ll find it’s happening rapidly in some places and more slowly in others. This means that although sea level rise affects coastal areas all over our ocean planet, some regions feel its effects sooner and more severely than others. This is reflected in future projections of sea level rise, with many cities in Asia expected to be among the hardest hit localities. Here in the United States, cities expected to see the worst impacts include New York, Miami and New Orleans, to name but a few.

Total sea level change between 1992 and 2014, based on data collected from the U.S./European Topex/Poseidon, Jason-1, and Jason-2 satellites.
Total sea level change between 1992 and 2014, based on data collected from the U.S./European Topex/Poseidon, Jason-1, and Jason-2 satellites. Credit: NASA’s Scientific Visualization Studio

Indeed, at any given place and time around our planet, sea level rise varies. But why is that? It turns out that when it comes to sea level rise, it’s all local. And it’s all relative.

Relative Sea Level

“Relative sea level” refers to the height of the ocean relative to land along a coastline. Common causes of relative sea level change include:

  • Changes due to heating of the ocean, and changes in ocean circulation
  • Changes in the volume of water in the ocean due to the melting of land ice in glaciers, ice caps, and ice sheets, as well as changes in the global water cycle
  • Vertical land motion (up or down movements of the land itself at a coastline, such as sinking caused by the compaction of sediments, or the rise and fall of land masses driven by the movement of continental or oceanic tectonic plates)
  • Normal, short-term, frequent variations in sea level that have always existed, such as those associated with tides, storm surges, and ocean waves (swell and wind waves). These variations can be on the order of meters or more (discussed in more detail in our previous blog post).

Let’s look at these factors more closely.

When you heat up water, it expands and takes up more space. How much it expands depends on how deep the warming occurs as well as the temperature of the water to begin with. For example, in Earth’s tropics, a 1-degree Celsius (1.8 degrees Fahrenheit) warming in the temperature of the top 100 meters (328 feet) of the ocean raises sea level there by about 3 centimeters (1.2 inches). This thermal expansion of the ocean is responsible for between one-third and one-half of the overall global sea level rise observed over the last two decades. Because Earth’s ocean isn’t warming at the same rate everywhere, it results in regional differences in relative sea level rise, with areas that are warming faster seeing faster sea level rise.

Diagram explaining the concept of thermal expansion of the ocean.
Diagram explaining the concept of thermal expansion of the ocean. Credit: Roseanne Smith / CC BY 4.0
Ocean heat content in 2018 compared to the 1955-2006 average.
Ocean heat content in 2018 compared to the 1955-2006 average. Orange and blue areas show where the upper 700 meters (2,300 feet) of the global ocean gained or lost up to 3 gigajoules (109 joules) of heat energy per square meter compared to the long-term average. Warming of ocean water is raising global sea level because water expands when it warms. Credit: NOAA

Changes in ocean circulation also contribute to regional sea level differences. For example, in the United States, El Niño, a cyclical, naturally-occurring ocean circulation pattern of warming (in the central and eastern tropical Pacific Ocean) and cooling (in the western tropical Pacific Ocean) can temporarily raise relative sea level along the West Coast by more than a foot for up to a couple of years. Similarly, along the U.S. East Coast, the speedup or slowdown of the major ocean current known as the Gulf Stream can temporarily add or subtract as much as 5 centimeters (2 inches) of sea level height to local coastlines.

The El Niño of 2015-2016 was the biggest, so far, of the 21st century.
The El Niño of 2015-2016 was the biggest, so far, of the 21st century. This image shows a side-by-side comparison of Pacific Ocean sea surface height anomalies during the 2015-16 event with the famous 1997-1998 El Niño. The images were made from data collected by the U.S./European Topex/Poseidon (1997-1998) and OSTM/Jason-2 (2015-2016) satellites. Credit: NASA-JPL/Caltech

Next, there’s melting land ice in the Greenland and Antarctic ice sheets and Earth’s glaciers and ice caps. The largest contribution is from Greenland, which loses hundreds of billions of tons of ice a year and is a major contributor to sea level rise across the globe. As Greenland loses ice, the land beneath its ice sheet rises as the weight of the ice sheet is removed. As a result, Greenland itself doesn’t see any local sea level rise.

But all of its melted ice — currently averaging 281 gigatons a year, as measured by the U.S./German Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on (GRACE-FO) satellite missions — has to go somewhere. Gravity causes it to flow into the ocean, causing sea level to rise thousands of miles away. Data from GRACE-FO tell us that melting land ice in glaciers, ice caps, and ice sheets contributed about two-thirds of global sea level rise during the last decade.

The mass of the Greenland ice sheet has rapidly declined in the last several years due to surface melting and iceberg calving. Research based on observations from the NASA/German Aerospace Center’s twin Gravity Recovery and Climate Experiment (GRACE) satellites indicates that between 2002 and 2016, Greenland shed approximately 280 gigatons of ice per year, causing global sea level to rise by 0.8 millimeters (0.03 inches) per year.

These images, created from GRACE data, show changes in Greenland ice mass since 2002. Orange and red shades indicate areas that lost ice mass, while light blue shades indicate areas that gained ice mass. White indicates areas where there was very little or no change in ice mass since 2002. In general, higher-elevation areas near the center of Greenland experienced little to no change, while lower-elevation and coastal areas experienced up to 4 meters (13.1 feet) of ice mass loss (expressed in equivalent-water-height; dark red) over a 14-year period. The largest mass decreases of up to 30 centimeters (11.8 inches) (equivalent-water-height) per year occurred along the West Greenland coast. The average flow lines (grey; created from satellite radar interferometry) of Greenland’s ice converge into the locations of prominent outlet glaciers, and coincide with areas of high mass loss. Credit: NASA

As land ice in Greenland, Antarctica and elsewhere melts, it changes Earth’s gravity field and slightly shifts the direction of Earth’s rotation. This causes uneven changes in sea level across the globe. Each melting ice mass around the world creates its own unique pattern of sea level change in the global ocean. For example, when ice melts in Antarctica, the amount of sea level rise it generates in California and Florida is up to 52 percent greater in those locations than if the global ocean just filled up uniformly, like water in a bathtub. Scientists use gravity data from the GRACE-FO mission to calculate patterns of sea level change associated with the loss of ice from glaciers, ice caps and ice sheets, as well as from changes in land water storage.

An animation showing “sea level fingerprints,” or patterns of rising and falling sea levels across the globe in response to changes in Earth’s gravitational and rotational fields. The movement of water across our planet can cause localized bumps and dips in gravity, sometimes with counterintuitive effects. Melting glaciers, for example, actually cause nearby sea level to drop; as they lose mass, their gravitational pull slackens, and sea water migrates away.

In this animation, computed from data gathered by the twin GRACE satellites since 2002, sea level is dropping around rapidly melting Greenland (orange, yellow). But near coastlines at a sufficient distance, the added water causes sea levels to rise (blue). The computational method is described in Adhikari et al. (2016, Geoscientific Model Development). These solutions are presented in Adhikari and Ivins (2016, Science Advances). Credit: NASA-JPL/Caltech

Then there’s vertical land motion along coastlines. When land sinks (a process known as subsidence), it causes a relative increase in sea levels. When land rises (known as uplift), it results in a relative decrease in sea levels.

A number of factors, both natural and human-produced, cause land to rise or sink, including:

  • Adjustments related to the rebound of land during and following the retreat of past ice sheets in North America and Eurasia at the end of the last Ice Age (known as isostatic, or post-glacial, rebound). The retreat of the ice sheets lightened the load of mass on the underlying mantle deep below Earth’s surface, causing Earth’s surface there to slowly rise. Land areas that were once near the edge of these ancient ice sheets, such as along the U.S. eastern seaboard, are today falling, exacerbating sea level rise there.
    A model of present-day vertical land motion due to post-glacial rebound and the reloading of the ocean basins with seawater.
    A model of present-day vertical land motion due to post-glacial rebound and the reloading of the ocean basins with seawater. Blue and purple areas indicate rising due to the removal of the ice sheets. Yellow and red areas indicate falling as mantle material moved away from these areas in order to supply the rising areas, and because of the collapse of the forebulges around the ice sheets. Credit: NASA-JPL/Caltech
  • Plate tectonics. Earth is divided into multiple slowly moving tectonic plates that interact with each other along plate boundaries. At some plate boundaries, the motion of one plate under, over, or past another results in vertical uplift or subsidence of the land surface above.

  • Natural or human-produced compaction of sediments, such as those caused by pumping groundwater, or oil and gas. Subsidence related to groundwater withdrawal can be especially pronounced in areas with large populations and extensive agriculture. Sediments can also be compacted by construction activities by humans or by the natural settling of new soils. In the United States, subsidence is a major factor in relative sea level rise along parts of the Gulf and East Coasts.

The ruins of a Civil War-era structure, Fort Beauregard, lie partially submerged east of New Orleans.
The ruins of a Civil War-era structure, Fort Beauregard, lie partially submerged east of New Orleans. Researchers say many large coastal cities around the world sink faster than sea levels rise at their location. Credit: Frank McMains

Oceanographer and climate scientist Josh Willis of NASA’s Jet Propulsion Laboratory in Southern California says that when it comes to relative sea level rise at any particular coastal location, subsidence is the most immediate consideration.

“People in coastal areas need to know what the land is doing right now where they live,” he said. “Is it sinking? If so, how fast? When you combine a sinking coastline with sea level rise caused by other contributing factors, you’re in trouble. Remember, scientists are projecting feet of global-mean sea level rise in this century. But in some places, land can sink by one foot in a decade. We have to understand all of these pieces before we can project future sea level rise at a beach near you.”

June 23, 2020, 09:33 PDT

Sea Change: Why Long Records of Coastal Climate Matter

A Monitoring Station off the Coast of Spain Is Giving Scientists a Front-Row Seat to Understanding the Region’s Long-Term Climate Change

By Alan Buis,
NASA's Jet Propulsion Laboratory

L'Estartit, a small Spanish coastal town in the Catalan Costa Brava region of the northwestern Mediterranean Sea. A half-century of continuous data from a meteorological and oceanographic coastal station here are giving scientists important insights into the region's long-term climate trends. Credit: Cnestartit / CC BY-SA

L'Estartit, a small Spanish coastal town in the Catalan Costa Brava region of the northwestern Mediterranean Sea. A half-century of continuous data from a meteorological and oceanographic coastal station here are giving scientists important insights into the region's long-term climate trends. Credit: Cnestartit / CC BY-SA

Climate scientists will tell you a key challenge in studying climate change is the relative dearth of long-term monitoring sites around the world. The oldest continuously operating station — the Mauna Loa Observatory on Hawaii’s Big Island, which monitors carbon dioxide and other key constituents of our atmosphere that drive climate change — has only been in operation since the late 1950s.

This obstacle is even more profound in the world’s coastal areas. In the global open ocean, the international Argo program’s approximately 4,000 drifting floats have observed currents, temperature, salinity and other ocean conditions since the early 2000s. But near coastlines, the situation is different. While coastal weather stations are plentiful, their focus is to produce weather forecasts for commercial and recreational ocean users, which aren’t necessarily useful for studying climate. The relative lack of long-term records of surface and deep ocean conditions near coastlines has limited our ability to make accurate oceanographic forecasts.

A meteorological and oceanographic coastal station in the small Spanish coastal town of L’Estartit is a notable exception. Located in the Catalan Costa Brava region of the northwest Mediterranean Sea, the L’Estartit station has collected inland data on air temperature, precipitation, atmospheric pressure and humidity since 1969, and has also made oceanographic observations at least weekly since 1973. This makes L’Estartit the longest available uninterrupted oceanographic data time series in the Mediterranean. A new NASA-funded study presents a detailed analysis of the site, revealing climate trends for its Mediterranean coastal environment spanning nearly a half century.

“The long-term data set from L’Estartit is a treasure trove that’s useful for assessing the regional impacts of climate change and how it’s evolved over time."
- JPL oceanographer Jorge Vazquez

The study, led by Jordi Salat of the Institut de Ciències del Mar (CSIC) in Barcelona, provides estimates of annual trends in sea and atmospheric temperature and sea level, along with seasonal trends. It also compares data from the site with previous and other estimates of climate trends in the region. Co-authors include Josep Pascual, also with CSIC; oceanographers Jorge Vazquez and Mike Chin of NASA’s Jet Propulsion Laboratory in Southern California; and Mar Flexas of Caltech, also in Southern California.

The Evolution of Modern Ocean Monitoring

The existence of the L’Estartit station reflects the results of decades of scientific research dating back to the 20th century. This body of work has established the vital role the ocean plays, in conjunction with our atmosphere, in shaping Earth’s global weather and climate. While sea level and sea state have been monitored regularly for some time, other measurements of oceanic conditions haven’t been as well-chronicled. In order to reconstruct the climate history of the ocean, scientists have typically relied on data from coastal tide gauges and stationary mooring stations, along with oceanographic cruises that weren’t generally part of any coordinated monitoring program.

By the 1980s, however, as Earth’s global climate warming trend became evident, scientists began to establish international programs to conduct long-term studies of the ocean. As a result, in recent years, scientists have increasingly acknowledged the value of having the oceanographic equivalent of weather forecasts. Maintaining regular, long-term records of air temperature, water temperatures at the surface and at various depths, winds, sea level, salinity, and other key oceanographic parameters gives scientists valuable information on long-term average values, how variable our climate is and on long-term changes and trends. Moreover, they help scientists better evaluate how humans are contributing to climate change.

Over the past 20 to 30 years, new technologies have given scientists the ability to monitor the ocean all the way from the sea surface to the ocean floor. These include satellites, drifters, gliders, moorings, buoys, Argo profilers and ship data. These data are used as inputs to computer models to estimate the state of the ocean, make ocean forecasts and estimate climate trends.

L’Estartit: Monitoring a Climate Hot Spot

Maintained by voluntary observer Josep Pascual in collaboration with CSIC and the authority of the marine protected area, the L’Estartit station is well positioned to monitor the Mediterranean, a region of our planet that’s significantly impacted by climate change. It lies at the southern end of a relatively narrow offshore continental shelf and along the coastal side of the Northern Current, the main along-slope ocean current in the northwestern Mediterranean.

L'Estartit station location 1
Ocean observations for the L'Estartit station are collected from a fixed point located about 4 kilometers offshore (the orange circle in the right center of the image).Credit: Adapted from Figure 1 of Salat et al. (2019)
L'Estartit location 2
The locations of the L'Estartit station's meteorological box (magenta circle), sea level gauge (red triangle) and wind station (blue diamond) are depicted on a map (b), and on a photo (c). Credit: Adapted from Figure 1 of Salat et al. (2019)

You can think of the Mediterranean as sort of a miniature ocean, since most of the processes that take place in the global ocean also take place here, albeit at different time scales in some instances. Its relatively small size also makes it more accessible to monitoring than many other regions of the global ocean. Because it’s located in Earth’s mid latitudes, it experiences significant seasonal variations, which affect the way it exchanges heat with the atmosphere.

The L’Estartit site collects a broad array of oceanographic data. In addition to the data mentioned previously, the site began continuous measurements of potential daily evaporation in 1976; and has measured sea state, along with wind speed and direction, since 1988. With the installation of a tide gauge in the harbor in 1990, continuous sea level data have been collected. Also added in the 1990s were conductivity-temperature-depth (CTD) profiles and water samples to analyze the temperature and salinity of the water column.

L’Estartit’s long-term data record makes it possible for scientists to calculate trends for a variety of atmospheric and oceanic climate attributes, including air temperature, sea surface and sub-surface temperature to a depth of 80 meters (262 feet), air pressure, relative humidity, relative cloudiness, wind, salinity, changes in ocean stratification, estimates of favorable conditions for evaporation, sea level and precipitation.

“The long-term data set from L’Estartit is a treasure trove that’s useful for assessing the regional impacts of climate change and how it’s evolved over time,” said Vazquez. “The data can be used as reference for other areas in the Mediterranean. The strong agreement between the site’s measurements of sea surface temperatures and satellite data of sea surface temperatures demonstrates how L’Estartit can serve as both a long-term ground truth site to validate satellite observations and as a regional monitoring site for climate change.”

Vazquez says data from the site have been used in numerous climate research studies and have also been used to document a variety of extreme events, from cold spells and heat waves to storms.

A Half-Century of Climate Trends

The researchers’ analysis of the nearly 50-year data set reveals numerous climate trends. For example, air temperature has increased by an average of 0.05 degrees Celsius (0.09 degrees Fahrenheit) per year during this time. Sea surface temperature has increased by an average of 0.03 degrees Celsius (0.05 degrees Fahrenheit) per year, while the temperature of the ocean at a depth of 80 meters (262 feet) has increased by an average of 0.02 degrees Celsius (0.04 degrees Fahrenheit) per year.

Monthly temperature anomalies - air, sea surface, sea 80 m
a) Time series of monthly air temperature anomalies (line), annual mean (squares) and linear trend. b) Time series of monthly sea surface temperature anomalies (line), annual mean (blue squares), winter (pink triangles), spring (small green squares), summer (red squares) and autumn (brown circles). Seasonal trend lines are colored according to the symbols. c) Time series of monthly sea temperature anomalies at a depth of 80 meters (line), annual mean (squares), autumn values (brown circles) and their linear trends. Credit: Figure 6 of Salat et al. (2019)
L'Estartit mean sea level anomaly (cm)
Time series of monthly sea level anomalies at the L'Estartit station, with trend lines for mean, maximum and minimum values. Credit: Figure 8 of Salat et al. (2019)

While sea level in the Mediterranean decreased from the 1960s to the 1990s due to changes in the North Atlantic Oscillation (a multi-decadal cyclical fluctuation of atmospheric pressure over the North Atlantic Ocean that strongly influences winter weather in Europe, Greenland, northeastern North America, North Africa and northern Asia), it’s been on the rise since the mid-1990s. The L’Estartit data show that sea level at that site is currently rising at a rate of 3.1 millimeters (0.12 inches) per year.

The researchers found that some of the long-term climate trends they observed were more pronounced during some seasons than in others. For example, trends in air temperature and sea surface temperature were significantly stronger during spring, while the trend for ocean temperature at 80 meters was greatest during autumn. Among their other findings, they noted a small increase in the number of days per year that experience summer-like sea conditions. They also found an almost two day per year drop in conditions favorable for marine evaporation, which may be related to an observed decrease in springtime coastal precipitation.

Vazquez says the good statistical comparison between sea surface temperature values and trends from the L’Estartit data set and data from available satellite products is encouraging. “The long-term consistency of the direct measurements with our satellite data gives scientists the opportunity to validate climate trends across multiple decades,” he said. “Data from L’Estartit should serve as a wake-up call to the global climate science community to immediately begin similar initiatives and ensure their continuity over time.”

The L’Estartit data are available to the public free of charge. The digitized data are accessible at http://meteolestartit.cat/. The remote sensing data used in the study may be retrieved through NASA’s Physical Oceanography Distributed Active Archive Center (PO.DAAC) at http://podaac.jpl.nasa.gov.

May 6, 2020, 10:16 PDT

Fire and Ice: Why Volcanic Activity Is Not Melting the Polar Ice Sheets

By Alan Buis,
NASA's Jet Propulsion Laboratory

Mount Waesche is a 10,801-foot-high (3,292 meters) possibly active volcano at the southern end of the Executive Committee Range in Marie Byrd Land, Antarctica. Credit: NASA/Michael Studinger

Mount Waesche is a 10,801-foot-high (3,292 meters) possibly active volcano at the southern end of the Executive Committee Range in Marie Byrd Land, Antarctica. Credit: NASA/Michael Studinger

Few natural phenomena are as impressive or awesome to behold as glaciers and volcanoes. I’ve seen both with my own eyes. I’ve marveled at the enormous power of flowing ice as I trekked across a glacier on Washington’s Mount Rainier — an active, but dormant, volcano. And I’ve hiked a rugged lava field on Hawaii’s Big Island alone on a moonless night to witness the surreal majesty of a lava stream from Kilauea volcano spilling into the sea — its orange-red lava meeting the waves in billowing steam — while still more glowing ribbons of lava snaked down the mountain slopes behind me.

There are many places on Earth where fire meets ice. Volcanoes located in high-latitude regions are frequently snow- and ice-covered. In recent years, some have speculated that volcanic activity could be playing a role in the present-day loss of ice mass from Earth’s polar ice sheets in Greenland and Antarctica. But does the science support that idea?

Illustration of flowing water under the Antarctic ice sheet
Illustration of flowing water under the Antarctic ice sheet. Blue dots indicate lakes, lines show rivers. Marie Byrd Land is part of the bulging "elbow" in the left center of the image. Credit: NSF/Zina Deretsky

In short, the answer is a definitive “no,” though recent studies have shed important new light on the matter. For example, a 2017 NASA-led study by geophysicists Erik Ivins and Helene Seroussi of NASA’s Jet Propulsion Laboratory added evidence to bolster a longstanding hypothesis that a heat source called a mantle plume lies deep below Antarctica's Marie Byrd Land, explaining some of the melting that creates lakes and rivers under the ice sheet. While the study may help explain why the ice sheet collapsed rapidly in an earlier era of rapid climate change and why it’s so unstable today, the researchers emphasized that the heat source isn't a new or increasing threat to the West Antarctic ice sheet, but rather has been going on over geologic timescales, and therefore represents a background contribution to the melting of the ice sheet.

I checked in with Ivins and Seroussi to get a deeper understanding of this question, which our readers frequently ask about. Here's what I learned…

Greenland Has a Long-Departed “Hot Spot” but Is Now Quiet

Since 2002, the U.S./German Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) satellite missions have recorded a rapid loss of ice mass from Greenland — at a rate of approximately 281 gigatonnes per year.

Greenland mass variation since 2002
Data from the U.S./German GRACE and GRACE Follow-On satellite missions show the Greenland ice sheet is losing ice mass at a rate of approximately 281 gigatonnes per year since 2002. Credit: NASA

There’s plenty of evidence of volcanism in regions now covered by the Greenland ice sheet and the mountains around it, but this volcanic activity occurred in the distant past. Many of Greenland’s mountains are eroded flood basalts — high-volume lava eruptions that cover broad regions. Flood basalts are the biggest type of lava flows known on Earth.

A glacier between mountains in Greenland's Geikie Peninsula
A glacier between mountains on Greenland's Geikie Peninsula. The mountains here consist mostly of flood basalts formed during the opening of the North Atlantic Ocean millions of years ago. Credit: NASA/Michael Studinger

But volcanic activity isn’t responsible for the current staggering loss of Greenland’s ice sheet, says Ivins. There are no active volcanoes in Greenland, nor are there any known mapped, dormant volcanoes under the Greenland ice sheet that were active during the Pliocene period of geological history that began more than 5.3 million years ago (volcanoes are considered active if they’ve erupted within the past 50,000 years). In fact, he says, the history of the Greenland ice sheet is probably more connected to atmospheric and ocean heat than it is to heat from the solid Earth. Ten million years ago, there was actually very little ice present in Greenland. The whole age of ice sheet waxing and waning in the Northern Hemisphere didn’t really get going until about five million years ago.

This visualization shows the Greenland geothermal heat flux map, the track of the Iceland hotspot through Greenland, and the plate tectonic motion of Greenland over the hotspot during the past 100 million years. Credit: NASA’s Scientific Visualization Studio

While there are no active volcanoes in Greenland, scientists are confident a “hot spot” — an area where heat from Earth’s mantle rises up to the surface as a thermal plume of buoyant rock — existed long ago beneath Greenland because they can see the residual heat in Earth’s crust, Ivins says. While mantle plumes can drive some forms of volcanoes, Ivins says they aren’t a factor in the current melting of the ice sheet. Researchers hypothesize however that this residual heat may drive the flow of the Northeast Greenland Ice Stream, which penetrates hundreds of kilometers inland (an ice stream is a faster-flowing current of ice within a larger and more stagnant ice sheet). Recent modeling experiments show that if enough residual heat is present, it can initiate an ice stream. GPS measurements also provide evidence that a hot spot once existed beneath Greenland.

Northeast Greenland Ice Stream
Ice in the Northeast Greenland Ice Stream can travel more than 1,640 feet (500 meters) each year. Credit: NASA's Goddard Space Flight Center

That hot spot subsequently moved, however, and now lies beneath Iceland — home to about 130 volcanoes, of which roughly 30 are active. The hot spot is at least partially responsible for the island’s high volcanic activity. Iceland also lies along the tectonically active Mid-Atlantic Ridge.

Overview of the second fissure on Iceland's Fimmvörðuháls volcano
Overview of the second fissure on Iceland’s Fimmvörðuháls volcano, close to Eyjafjallajökull volcano, as the lava flows down toward the north, turning snow into steam. Credit: Boaworm / CC BY

Antarctica Has Volcanoes, but There's No Link to its Current Ice Loss

Antarctica mass variation since 2002
Data from the U.S./German GRACE and GRACE Follow-On satellite missions show the Antarctic ice sheet is losing ice mass at a rate of approximately 146 gigatonnes per year since 2002. Credit: NASA

The GRACE missions have also observed a rapid loss of ice mass in Antarctica, at a rate of approximately 146 gigatonnes per year since 2002. Unlike Greenland, however, there’s substantial evidence of volcanoes under the Antarctic Ice Sheet, some of which are currently active or have been in the recent geologic past. While the exact number of volcanoes in Antarctica is unknown, a recent study found 138 volcanoes in West Antarctica alone. Many of the active volcanoes are located in Marie Byrd Land. However, there’s no evidence of a dramatic volcanic eruption in Antarctica in the recent geologic past. Seroussi says details about the volcanism of many parts of Antarctica (particularly in East Antarctica) remain uncertain, both because they’re covered by ice and because their remoteness makes surveying them difficult.

Map of Antarctica showing the distribution of volcanoes aged between c. 11 Ma and present. Only a small number are active.
Map of Antarctica showing the distribution of volcanoes aged between c. 11 Ma (million years) and present. Only a small number are active. Credit: Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0)
Locations of recently discovered West Antarctic volcanoes
Map of the location of cone-shaped structures (circles) identified from the British Antarctic Survey's Bedmap2 ice thickness and subglacial topographic model of Antarctica (greyscale background) across the West Antarctic Rift System. The color of the circles represents the degree of confidence the researchers have that the cones are subglacial volcanoes, and the circle size is proportional to the size of the cone’s base diameter. Circles with black rims represent volcanoes that have been confirmed in other studies (LeMasurier et al. 1990; Smellie & Edwards 2016); generally those with tips that protrude above the ice surface. Credit: Attribution 3.0 Unported (CC BY 3.0)

Multiple additional lines of evidence point to Antarctica’s past and present volcanism. For example, topographic maps of the bedrock beneath the Antarctic ice sheet give scientists clues to suspected volcanic locations. Analyses of volcanic rock samples reveal numerous volcanic eruptive events within the last 100,000 years, as do ash layers in ice cores. In their 2017 study of Marie Byrd Land, Seroussi and Ivins estimated the intensity of the heat produced by the hypothesized mantle plume by studying the meltwater produced under the ice sheet and its motion by measuring changes in the elevation of the ice surface.

Antarctica's Bedrock

These images depict the differences between Antarctica's ice sheet with its underlying topography. Click and drag the white bar to compare the images. (Vertical scale has been magnified by a factor of 17 to make terrain features such as mountains and valleys more visible.)

The topography map, called Bedmap2, was compiled by the British Antarctic Survey and incorporates millions of new measurements, including substantial data sets from NASA's ICESat satellite and an airborne mission called Operation IceBridge. Credit: NASA's Goddard Space Flight Center
Ice core
The dark band in this ice core from West Antarctica is a layer of volcanic ash that settled on the ice sheet approximately 21,000 years ago. Credit: Heidi Roop, National Science Foundation (NSF)

An intriguing paper by Loose et al. published in Nature Communications in 2018 provides additional evidence. The researchers measured the composition of isotopes of helium detected in glacial meltwater flowing from the Pine Island Glacier Ice Shelf. They found evidence of a source of volcanic heat upstream of the ice shelf. Located on the West Antarctic ice sheet, Pine Island Glacier is the fastest melting glacier in Antarctica, responsible for nearly a quarter of all Antarctic ice loss. By measuring the ratio between helium’s two naturally-occurring isotopes, scientists can tell whether the helium taps into Earth’s hot mantle or is a product of crust that is relatively passive tectonically.

The team found the helium originated in Earth’s mantle, pointing to a volcanic heat source that may be triggering melting beneath the glacier and feeding the water network beneath it. However, the researchers concluded that the volcanic heat is not a significant contributor to the glacial melt observed in the ocean in front of Pine Island Glacier Ice Shelf. Rather, they attributed the bulk of the melting to the warm temperature of the deep-water mass Pine Island Glacier flows into, which is melting the glacier from underneath.

Antarctica's Pine Island Glacier meets the ocean.
Antarctica’s Pine Island Glacier meets the ocean. Credit: Galen Dossin, NSF

Seroussi notes the changes happening now, especially in West Antarctica, are along the coast, which suggests the changes taking place in the ice sheet have nothing to do with volcanism, but are instead originating in the ocean. Ice streams reaching inland begin to flow and accelerate as ice along the coast disappears.

In addition, Seroussi says the tectonic plate that Antarctica rests upon is one of the most immobile on Earth. It’s surrounded by activity, but that activity also tends to keep it locked in position. There’s no reason to believe it would change today to impact the melting of the Antarctic ice sheet.

So, in conclusion, while Antarctica’s known volcanism does cause melting, Ivins and Seroussi agree there’s no connection between the loss of ice mass observed in Antarctica in recent decades and volcanic activity. The Antarctic ice sheet is at least 30 million years old, and volcanism there has been going on for millions of years. It's having no new effect on the current melting of the ice sheet.

March 10, 2020, 13:38 PDT

How Climate Change May Be Impacting Storms Over Earth's Tropical Oceans

By Alan Buis,
NASA's Jet Propulsion Laboratory

Hurricane Lorenzo moving through the eastern North Atlantic Ocean, as seen from NASA's Terra satellite. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS).

Hurricane Lorenzo moving through the eastern North Atlantic Ocean, as seen from NASA's Terra satellite. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS).

When NASA climate scientists speak in public, they’re often asked about possible connections between climate change and extreme weather events such as hurricanes, heavy downpours, floods, blizzards, heat waves and droughts. After all, it seems extreme weather is in the news almost every day of late, and people are taking notice. How might particular extreme weather and natural climate phenomena, such as El Niño and La Niña, be affected by climate change, they wonder?

There’s no easy answer, says Joao Teixeira, co-director of the Center for Climate Sciences at NASA’s Jet Propulsion Laboratory in Pasadena, California, and science team leader for the Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite. “Within the scientific community it’s a relatively well-accepted fact that as global temperatures increase, extreme precipitation will very likely increase as well,” he says. “Beyond that, we’re still learning.”

“Within the scientific community it’s a relatively well-accepted fact that as global temperatures increase, extreme precipitation will very likely increase as well. Beyond that, we’re still learning.”
- Joao Teixeira

While there’s not yet a full consensus on the matter, in recent years a body of evidence linking extreme weather with climate change has begun to emerge. Evidence from satellites, aircraft, ground measurements and climate model projections are increasingly drawing connections. Quantifying those interconnections is a big challenge.

“All our available tools have pros and cons,” says Teixeira. “Rain gauges, for example, provide good measurements, but they’re local and spread far apart. In contrast, satellites typically measure climate variables (such as precipitation, temperature and humidity) indirectly and don’t yet have long enough data records to establish trends, though that’s beginning to change. In addition, representing small-scale processes of the atmosphere that are key to extreme weather events in climate models, such as turbulence, convection and cloud physics, is notoriously difficult. So, we’re in a bit of a conundrum. But great progress is being made as more studies are conducted.”

A simple analogy describes how difficult it is to attribute extreme weather to climate change. Adding fossil fuel emissions to Earth’s atmosphere increases its temperature, which adds more energy to the atmosphere, supercharging it like an athlete on steroids. And just as it’s difficult to quantify how much of that athlete’s performance improvement is due to steroid use, so too it’s difficult to say whether extreme weather events are definitively due to a warmer atmosphere.

Are Supercharged Atlantic Hurricane Seasons a Case in Point?

Take hurricanes, for example. A hot topic in extreme weather research is how climate change is impacting the strength of tropical cyclones. A look at the 2019 Atlantic hurricane season provides a case in point.

After a quiet start to the 2019 season, Hurricane Dorian roared through the Atlantic in late August and early September, surprising many forecasters with its unexpected and rapid intensification. In just five days, Dorian grew from a minimal Category 1 hurricane to a Category 5 behemoth, reaching a peak intensity of 185 miles (295 kilometers) per hour when it made landfall in The Bahamas. In the process, Dorian tied an 84-year-old record for strongest landfalling Atlantic hurricane and became the fifth most intense recorded Atlantic hurricane to make landfall, as measured by its barometric pressure.

visible hurricane dorian
Hurricane Dorian as seen by the four visible/near-infrared channels of the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA's Aqua satellite at 2 p.m. EDT (11 a.m. PDT) on Sept. 1, 2019, as the storm made landfall in The Bahamas. At the time of landfall, Dorian had reached its peak intensity of 185 miles (295 kilometers) per hour, tying an 84-year-old record for strongest landfalling Atlantic hurricane. Credit: NASA/JPL-Caltech
false-color infrared hurricane dorian
A false-color infrared image of Hurricane Dorian, as seen by the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA's Aqua satellite at 2 p.m. EDT (11 a.m. PDT) on Sept. 1, 2019. Hurricanes are large collections of severe, deep thunderstorms. Purple shades denote the coldest cloud top temperatures and most severe convective activity. Blues and greens show warmer areas with less rain clouds, while oranges and reds represent mostly cloud-free air. Each square pixel represents the measurements from a 10-by-10-mile (16-by-16-kilometer) area. Credit: NASA/JPL-Caltech

Two weeks later the remnants of Tropical Storm Imelda swamped parts of Texas under more than 40 inches (102 centimeters) of rain, enough to make it the fifth wettest recorded tropical cyclone to strike the lower 48 states. Fueled by copious moisture from a warm Gulf of Mexico, the slow-moving Imelda’s torrential rains and flooding wreaked havoc over a wide region.

Then in late September, Hurricane Lorenzo became the most northerly and easterly Category 5 storm on record in the Atlantic, even affecting the British Isles as an extratropical cyclone.

Earth’s atmosphere and oceans have warmed significantly in recent decades. A warming ocean creates a perfect cauldron for brewing tempests. Hurricanes are fueled by heat in the top layers of the ocean and require sea surface temperatures (SSTs) greater than 79 degrees Fahrenheit (26 degrees Celsius) to form and thrive.

Since 1995 there have been 17 above-normal Atlantic hurricane seasons, as measured by NOAA’s Accumulated Cyclone Energy (ACE) Index. ACE calculates the intensity of a hurricane season by combining the number, wind speed and duration of each tropical cyclone. That’s the largest stretch of above-normal seasons on record.

So while there aren’t necessarily more Atlantic hurricanes than before, those that form appear to be getting stronger, with more Category 4 and 5 events.

NASA Research Points to an Increase in Extreme Storms Over Earth’s Tropical Oceans

What does NASA research have to say about extreme storms? One NASA study from late 2018 supports the notion that global warming is causing the number of extreme storms to increase, at least over Earth’s tropical oceans (between 30 degrees North and South of the equator).

A team led by JPL’s Hartmut Aumann, AIRS project scientist from 1993 to 2012, analyzed 15 years of AIRS data, looking for correlations between average SSTs and the formation of extreme storms. They defined extreme storms as those producing at least 0.12 inches (3 millimeters) of rain per hour over a certain-sized area. They found that extreme storms formed when SSTs were hotter than 82 degrees Fahrenheit (28 degrees Celsius). The team also saw that for every 1.8 degrees Fahrenheit (1 degree Celsius) that SST increased, the number of extreme storms went up by about 21 percent. Based on current climate model projections, the researchers concluded that extreme storms may increase 60 percent by the year 2100.

Thanks to weather satellites, scientists have identified possible correlations between the extremely cold clouds seen in thermal infrared satellite images (called deep convective clouds) and extreme storms observed on the ground under certain conditions, especially over the tropical oceans. When precipitation from these clouds hits the top of Earth’s lowest atmospheric layer, the troposphere, it produces torrential rain and hail.

AIRS can’t measure precipitation directly from space, but it can measure the temperature of clouds with extraordinary accuracy and stability. Its data can also be correlated with other climate variables such as SSTs, for which scientists maintain long data records.

To determine the number of extreme storms, Aumann’s team plotted the number of deep convective clouds each day against measurements of sea surface temperature. They found that the number of these clouds correlated with increases in sea surface temperature.

The results of this study reflect a long line of AIRS research and three previously published papers. The researchers say large uncertainties and speculations remain regarding how extreme storms may change under future climate scenarios, including the possibility that a warming climate may result in fewer but more intense storms. But the results of this study point to an intriguing direction for further research.

What Lies Ahead?

Aumann is confident future studies will reveal additional insights into how severe storms detected as individual deep convective clouds coalesce to form tropical storms and hurricanes. He notes that if you look at these clouds over the global ocean, they frequently occur in clusters.

“AIRS sees hurricanes as hundreds of these clusters,” he said. “For example, it saw Hurricane Dorian as a cluster of about 150 deep convective clouds, while Hurricane Katrina contained about 500. If you look at a weather satellite image, you’ll see the severe storms that make up a hurricane are not actually contiguous. In fact, they’re uncannily similar to the stars within the spiral arms of a galaxy. It’s one severe thunderstorm after another, each dumping a quantity of rain on the ground.

“AIRS has 2,400 different frequency channels, so it’s a very rich data set,” he said. “In fact, there’s so much data, our computer capabilities aren’t able to explore most of it. We just need to ask the right questions.”

February 13, 2020, 14:02 PST

There Is No Impending 'Mini Ice Age'

By NASA Global Climate Change 

Image of the Sun showing a solar prominence (a large, bright feature extending outward from the Sun's surface). Credit: ESA/NASA

Image of the Sun showing a solar prominence (a large, bright feature extending outward from the Sun's surface). Credit: ESA/NASA

"Pink elephant in the room" time: There is no impending “ice age” or "mini ice age" if there's a reduction in the Sun’s energy output in the next several decades.

Through its lifetime, the Sun naturally goes through changes in energy output. Some of these occur over a regular 11-year period of peak (many sunspots) and low activity (fewer sunspots), which are quite predictable.

Temperature vs Solar Activity 2020
The above graph compares global surface temperature changes (red line) and the Sun's energy that Earth receives (yellow line) in watts per square meter since 1880. The lighter/thinner lines show the yearly levels while the heavier/thicker lines show the 11-year average trends. Eleven-year averages are used to reduce the year-to-year natural noise in the data, making the underlying trends more obvious.

The amount of solar energy that Earth receives has followed the Sun’s natural 11-year cycle of small ups and downs with no net increase since the 1950s. Over the same period, global temperature has risen markedly. It is therefore extremely unlikely that the Sun has caused the observed global temperature warming trend over the past half-century. Credit: NASA/JPL-Caltech

But every so often, the Sun becomes quieter for longer periods of time, experiencing much fewer sunspots and giving off less energy. This is called a "Grand Solar Minimum," and the last time this happened, it coincided with a period called the "Little Ice Age" (a period of extremely low solar activity from approximately AD 1650 to 1715 in the Northern Hemisphere, when a combination of cooling from volcanic aerosols and low solar activity produced lower surface temperatures).

Anomalous periods like a Grand Solar Minimum show that magnetic activity and energy output from the Sun can vary over decades, although the space-based observations of the last 35 years have seen little change from one cycle to the next in terms of total irradiance. Solar Cycle 24, which began in December 2008 and is likely to end in 2020, was smaller in magnitude than the previous two cycles.

On occasion, researchers have predicted that coming solar cycles may also exhibit extended periods of minimal activity. The models for such predictions, however, are still not as robust as models for our weather and are not considered conclusive.

But if such a Grand Solar Minimum occurred, how big of an effect might it have? In terms of climate forcing – a factor that could push the climate in a particular direction – solar scientists estimate it would be about -0.1 W/m2, the same impact of about three years of current carbon dioxide (CO2) concentration growth.

Thus, a new Grand Solar Minimum would only serve to offset a few years of warming caused by human activities.

What does this mean? The warming caused by the greenhouse gas emissions from the human burning of fossil fuels is six times greater than the possible decades-long cooling from a prolonged Grand Solar Minimum.

Even if a Grand Solar Minimum were to last a century, global temperatures would continue to warm. The reason for this is because more factors than just variations in the Sun’s output change global temperatures on Earth, the most dominant of those today is the warming coming from human-induced greenhouse gas emissions.


Related post: What Is the Sun's Role in Climate Change?

The Sun powers life on Earth; it helps keep the planet warm enough for us to survive. It also influences Earth’s climate: We know subtle changes in Earth’s orbit around the Sun are responsible for the comings and goings of the past ice ages. But the warming we’ve seen over the last few decades is too rapid to be linked to changes in Earth’s orbit, and too large to be caused by solar activity.

The Sun doesn’t always shine at the same level of brightness; it brightens and dims slightly, taking approximately 11 years to complete one solar cycle. During each cycle, the Sun undergoes various changes in its activity and appearance. Levels of solar radiation go up or down, as does the amount of material the Sun ejects into space and the size and number of sunspots and solar flares. These changes have a variety of effects in space, in Earth’s atmosphere and on Earth’s surface.

The current solar cycle, Solar Cycle 24, began in December 2008 and is less active than the previous two. It’s expected to end sometime in 2020. Scientists don’t yet know with confidence how strong the next solar cycle may be.

What Effect Do Solar Cycles Have on Earth’s Climate?

According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC), the current scientific consensus is that long and short-term variations in solar activity play only a very small role in Earth’s climate. Warming from increased levels of human-produced greenhouse gases is actually many times stronger than any effects due to recent variations in solar activity.

For more than 40 years, satellites have observed the Sun's energy output, which has gone up or down by less than 0.1 percent during that period. Since 1750, the warming driven by greenhouse gases coming from the human burning of fossil fuels is over 50 times greater than the slight extra warming coming from the Sun itself over that same time interval.

Are We Headed for a ‘Grand Solar Minimum’? (And Will It Slow Down Global Warming?)

As mentioned, the Sun is currently experiencing a lower level of sunspot activity. Some scientists speculate that this may be the beginning of a Grand Solar Minimum — a decades-to-centuries-long period of low solar activity — while others say there is insufficient evidence to support that position. During a grand minimum, solar magnetism diminishes, sunspots appear infrequently and less ultraviolet radiation reaches Earth.

The largest recent event -- the “Maunder Minimum,” which lasted from 1645 and 1715 — overlapped with the “Little Ice Age” (13th to mid-19th century). While scientists continue to research whether an extended solar minimum could have contributed to cooling the climate, there is little evidence that the Maunder Minimum sparked the Little Ice Age, or at least not entirely by itself (notably, the Little Ice Age began before the Maunder Minimum). Current theories on what caused the Little Ice Age consider that a variety of events could have contributed, with natural fluctuations in ocean circulation, changes in land use by humans and cooling from a less active sun also playing roles; overall, cooling caused by volcanic aerosols likely played the title role.

Several studies in recent years have looked at the effects that another Grand Solar Minimum might have on global surface temperatures. These studies have suggested that while a grand minimum might cool the planet as much as 0.3 degrees C, this would, at best, slow down but not reverse human-caused global warming. There would be a small decline of energy reaching Earth; however, just three years of current carbon dioxide concentration growth would make up for it. In addition, the Grand Solar Minimum would be modest and temporary, with global temperatures quickly rebounding once the event concluded.

Moreover, even a prolonged Grand Solar Minimum or Maunder Minimum would only briefly and minimally offset human-caused warming.

More about solar cycles:

https://scijinks.gov/solar-cycle/

September 6, 2019, 11:24 PDT

What Is the Sun's Role in Climate Change?

From NASA's Global Climate Change Website

The Sun powers life on Earth; it helps keep the planet warm enough for us to survive. It also influences Earth’s climate: We know subtle changes in Earth’s orbit around the Sun are responsible for the comings and goings of the past ice ages. But the warming we’ve seen over the last few decades is too rapid to be linked to changes in Earth’s orbit, and too large to be caused by solar activity.1

The Sun doesn’t always shine at perpetually the same level of brightness; it brightens and dims slightly, taking 11 years to complete one solar cycle. During each cycle, the Sun undergoes various changes in its activity and appearance. Levels of solar radiation go up or down, as does the amount of material the Sun ejects into space and the size and number of sunspots and solar flares. These changes have a variety of effects in space, in Earth’s atmosphere and on Earth’s surface.

The current solar cycle began January 4, 2008, and appears to be headed toward the lowest level of sunspot activity since accurate recordkeeping began in 1750. It’s expected to end sometime between now and late 2020. Scientists don’t yet know with confidence how strong the next solar cycle may be.

What Effect Do Solar Cycles Have on Earth’s Climate?

According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC), the current scientific consensus is that long and short-term variations in solar activity play only a very small role in Earth’s climate. Warming from increased levels of human-produced greenhouse gases is actually many times stronger than any effects due to recent variations in solar activity.

For more than 40 years, satellites have observed the Sun's energy output, which has gone up or down by less than 0.1 percent during that period. Since 1750, the warming driven by greenhouse gases coming from the human burning of fossil fuels is over 50 times greater than the slight extra warming coming from the Sun itself over that same time interval.

Are We Headed for a ‘Grand Minimum’? (And Will It Slow Down Global Warming?)

solar irradiance with branding
The above graph compares global surface temperature changes (red line) and the Sun's energy that Earth receives (yellow line) in watts (units of energy) per square meter since 1880. The lighter/thinner lines show the yearly levels while the heavier/thicker lines show the 11-year average trends. Eleven-year averages are used to reduce the year-to-year natural noise in the data, making the underlying trends more obvious.

The amount of solar energy that Earth receives has followed the Sun’s natural 11-year cycle of small ups and downs with no net increase since the 1950s. Over the same period, global temperature has risen markedly. It is therefore extremely unlikely that the Sun has caused the observed global temperature warming trend over the past half-century. Credit: NASA/JPL-Caltech

As mentioned, the Sun is currently experiencing a low level of sunspot activity. Some scientists speculate that this may be the beginning of a periodic solar event called a “grand minimum,” while others say there is insufficient evidence to support that position. During a grand minimum, solar magnetism diminishes, sunspots appear infrequently and less ultraviolet radiation reaches Earth. Grand minimums can last several decades to centuries. The largest recent event happened during the “Little Ice Age” (13th to mid-19th century): the “Maunder Minimum,” an extended period of time between 1645 and 1715, when there were few sunspots.

Several studies in recent years have looked at the effects that another grand minimum might have on global surface temperatures.2 These studies have suggested that while a grand minimum might cool the planet as much as 0.3 degrees C, this would, at best, slow down (but not reverse) human-caused global warming. There would be a small decline of energy reaching Earth, and just three years of current carbon dioxide concentration growth would make up for it. In addition, the grand minimum would be modest and temporary, with global temperatures quickly rebounding once the event concluded.

Some people have linked the Maunder Minimum’s temporary cooling effect to decreased solar activity, but that change was more likely influenced by increased volcanic activity and ocean circulation shifts.3

Moreover, even a prolonged “Grand Solar Minimum” or “Maunder Minimum” would only briefly and minimally offset human-caused warming.

More about solar cycles:

https://scijinks.gov/solar-cycle/

References

1 Fourth National Climate Assessment, Volume 1, Chapter 2

2 Feulner & Rahmstorf (2010), Jones et al. (2012), Anet et al. (2013), Meehl et al. (2013), Ineson et al (2015), Maycock et al (2015), Lubin et al. (2017)

3 IPCC Assessment Report 1, Working Group 1, Chapter 5

November 6, 2018, 10:06 PST

We are the land and the land is us: Indigenous women accompany NASA campaign studying Arctic climate change

By Mandy Bayha

A lake located just off the Ingraham Trail, a few kilometers outside of Yellowknife in Canada’s Northwest Territories, where data was collected that will help in the creation of algorithms to capture and interpret wetland and inundated sites via satellite and remote sensing. Credit: Mandy Bayha

A lake located just off the Ingraham Trail, a few kilometers outside of Yellowknife in Canada’s Northwest Territories, where data was collected that will help in the creation of algorithms to capture and interpret wetland and inundated sites via satellite and remote sensing. Credit: Mandy Bayha

My name is Mandy Bayha, and I am from a small community called Délįnę [pronounced De-lee-nay] in Canada’s Northwest Territories. With a population of about 500, the community is nestled on the shores of the southwest Keith arm of the beautiful Great Bear Lake. The Sahtúotįnę (which means “people of Great Bear Lake”) have been its only inhabitants since time immemorial. The community is rich in culture and language and has a deep sense of love and connection to the land, especially the lake.

I am an environmental science and conservation biology student and the indigenous healing coordinator (an initiative called “Sahtúotįnę Nats’eju”) for the Délįnę Got’įnę government. Under the guidance and mentorship of the elders, knowledge holders, and my community's leadership, I have been tasked to facilitate and implement a pilot project that aims to bridge the gap between traditional knowledge and western knowledge to create a seamless and holistic approach to health and wellness.

University environmental science students Joanne Spearman and Mandy Bayha, from the Northwest Territories in Canada, inside NASA's Gulfstream III jet during an ABoVE flight.
University environmental science students Joanne Spearman (left) and Mandy Bayha, from the Northwest Territories in Canada, inside NASA’s Gulfstream III jet during an ABoVE flight. Credit: NASA

Traditional knowledge is relevant to everything we do, from healing, governance, and environmental management to early childhood development and education. Traditional knowledge encompasses virtually every human relationship and dynamic and outlines our relationships with each another, our Mother Earth, and our creator. As our elders say, “We are the land and the land is us. The land provides everything to us and is like a mother to us all and we all come from her.” We believe everything is interconnected and in a constant relationship, forever and always.

On August 20, I traveled to Yellowknife to participate in the Arctic-Boreal Vulnerability Experiment, or ABoVE. Currently in its second year, this 10-year project is focused on the Arctic's vulnerability and resilience and on understanding climate change's effects on such a delicate ecosystem. ABoVE is important because it can provide a holistic view of climate change in the north by bringing together two knowledge systems: western science and the traditional knowledge of my ancestors. In fact, the project’s first guiding principle is to “recognize the value of traditional knowledge as a systematic way of thinking [that] will enhance and illuminate our understanding of the Arctic environment and promote a more complete knowledge base.”

I was able to participate in this incredible opportunity with a fellow Délįnę woman named Joanne Speakman, who is also an environmental science student. Our first day started on August 22, bright and early at 8 o’clock in the morning. We met the flight team at the Adlair Aviation hanger to undergo a safety briefing and egress training. It was like walking into a scene from the movie Armageddon.

The two ex-U.S. Air Force test pilots were speaking a technical language riddled in codes, and the remote sensing engineers were spouting their checks and balances. I was thrilled to be surrounded by NASA employees all adorned in patches, jumpsuits, and ball caps. Afterward, Dr. Peter Griffith, the project lead, explained everything to Joanne and me in plain language. We then took a tour of the plane and learned how to exit in the unlikely event of an emergency. We were treated so nicely, and I felt more than welcome to participate.

We were invited to sit in a jump seat situated right behind the pilots during take-off and landing. Joanne got take-off and I got landing. What an experience that was! During our four-hour flight, which took us from Yellowknife to Scotty Creek (a permafrost research site near Fort Simpson), Kakisa, Fort Providence, and back to Yellowknife, Dr. Griffith sat with us and explained the ABoVE project. He gave us background on how the “lines”—the strips of areas that were scanned by the radar—were chosen and filled us in on research done in those areas previously, such as major burn sites, permafrost melt, carbon cycling, and methane levels. He referred to pictures while explaining how certain equipment as well as ground data calibration and validation techniques were used.

At work in the Gulfstream jet were flight engineer and navigator Sam Choi from NASA’s Armstrong Flight Research Center and radar operator Tim Miller from NASA’s Jet Propulsion Laboratory.
At work in the Gulfstream jet were flight engineer and navigator Sam Choi from NASA’s Armstrong Flight Research Center and radar operator Tim Miller from NASA’s Jet Propulsion Laboratory. Credit: Joanne Speakman

We also chatted with engineers from NASA’s Jet Propulsion Laboratory in Pasadena, California, who manned the remote sensing station on the flight. They explained that the remote sensing equipment, which was welded to the bottom of the Gulfstream III jet, is made of many tiny sensors that send signals to the ground that bounce back to a receiving antenna on the aircraft.

The resulting data tell a story of what is happening on Earth’s surface, revealing features such as inundation (marshy areas where vegetation is saturated with water) and the rocky topography from the great Canadian shield, for example. The sensor they’re using is called an L-band synthetic aperture radar (SAR), which has a long wavelength ideal for penetrating the active layer in the soil. This is important for many reasons but mainly for indicating soil moisture.

Mandy Bayha gets a pilot's view from the jump seat as the NASA Gulfstream III comes in for landing, the town of Yellowknife on the shores of Great Slave Lake in view.
Mandy Bayha gets a pilot’s view from the jump seat as the NASA Gulfstream III comes in for landing, the town of Yellowknife on the shores of Great Slave Lake in view. Credit: Mandy Bayha

When flying above target areas, the pilots had to position the plane precisely on the designated lines to trigger the L-band SAR on the bottom of the plane, which would put the aircraft on autopilot mode and allow the sensor to “fly” the plane for the entire length of scanning the line. Once the scan was complete, the pilots would then take control of the plane again. The precision and accuracy for all those things to work in tandem was extraordinary to witness.

After the last scan, I hopped into the jump seat directly behind the pilots and watched them land the plane. Once on the ground, we were greeted by reporters with Cabin Radio (a local NWT radio station) who interviewed us and took our pictures with the Gulfstream III jet in the background. It was an absolute honor and a once-in-a-lifetime experience that I will never forget.

Fortunately, our incredible journey with NASA wasn’t yet complete. Joanne and I tagged along with two scientists, Paul Siqueira and Bruce Chapman, who are helping to build an Earth-orbiting satellite called the NASA-ISRO Synthetic Aperture Radar, or NISAR. We met up with Paul and Bruce early on the morning of August 24 and identified two lakes located just off the Ingraham Trail, a few kilometers outside of Yellowknife, to collect data that will help in the creation of algorithms to capture and interpret wetland and inundated sites via satellite and remote sensing.

We reached the shores of the first lake and split into two groups, one scientist and one student per group. We walked in separate directions in areas of inundation between the open water and the treeline surrounding the lake and took measurements using an infrared laser for accurate distances between the treeline and open water and made estimations and diagrams to fully detail the ground view.

University of Massachusetts Amherst scientist Paul Siqueira enjoyed the last canoe ride of the day with Joanne Speakman and Mandy Bahya.
University of Massachusetts Amherst scientist Paul Siqueira enjoyed the last canoe ride of the day with Joanne Speakman and Mandy Bahya. Credit: NASA/Bruce Chapman

We tackled the second lake with a canoe and could not have asked for better weather. We enjoyed our afternoon bathed in the sun. The waterfowl and minnows shared their home with us for a time. During our canoe ride, we learned a lot more about our scientist friends. They were part of a launch that carried some of the first remote sensing technology into space. This technology was then used to study the surface of Venus and Mars. How fortunate were Joanne and I to be able to listen and learn from such a brilliant crew of scientists who have had amazing careers.

It was an enriching and humbling experience to participate in the ABoVE project. If an organization such as NASA realizes that indigenous traditional knowledge is both valid and important, then I am hopeful for our next generation of indigenous people. I believe that this is the first step in reconciliation: acknowledgment and appreciation. I would be honoured to participate again; however, I am more than grateful to know that there is this collaboration happening and that it includes the indigenous Dene of the north.

Mahsi Cho (thank you)!

This piece was adapted from NASA's Earth Expeditions blog.