Tag Archives: carbon dioxide

NASA’s Webb Detects Carbon Dioxide in Exoplanet Atmosphere

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NASA’s James Webb Space Telescope has captured the first clear evidence for carbon dioxide in the atmosphere of a planet outside the solar system. This observation of a gas giant planet orbiting a Sun-like star 700 light-years away provides important insights into the composition and formation of the planet. The finding, accepted for publication in Nature, offers evidence that in the future Webb may be able to detect and measure carbon dioxide in the thinner atmospheres of smaller rocky planets.

WASP-39 b is a hot gas giant with a mass roughly one-quarter that of Jupiter (about the same as Saturn) and a diameter 1.3 times greater than Jupiter. Its extreme puffiness is related in part to its high temperature (about 1,600 degrees Fahrenheit or 900 degrees Celsius). Unlike the cooler, more compact gas giants in our solar system, WASP-39 b orbits very close to its star – only about one-eighth the distance between the Sun and Mercury – completing one circuit in just over four Earth-days. The planet’s discovery, reported in 2011, was made based on ground-based detections of the subtle, periodic dimming of light from its host star as the planet transits, or passes in front of the star.

Previous observations from other telescopes, including NASA’s Hubble and Spitzer space telescopes, revealed the presence of water vapor, sodium, and potassium in the planet’s atmosphere. Webb’s unmatched infrared sensitivity has now confirmed the presence of carbon dioxide on this planet as well.

NASA Prepares Webb Telescope /NASA

NASA Prepares Webb Telescope /NASA

Filtered Starlight

Transiting planets like WASP-39 b, whose orbits we observe edge-on rather than from above, can provide researchers with ideal opportunities to probe planetary atmospheres.

During a transit, some of the starlight is eclipsed by the planet completely (causing the overall dimming) and some is transmitted through the planet’s atmosphere.

Because different gases absorb different combinations of colors, researchers can analyze small differences in brightness of the transmitted light across a spectrum of wavelengths to determine exactly what an atmosphere is made of. With its combination of inflated atmosphere and frequent transits, WASP-39 b is an ideal target for transmission spectroscopy.

First Clear Detection of Carbon Dioxide

The research team used Webb’s Near-Infrared Spectrograph (NIRSpec) for its observations of WASP-39b. In the resulting spectrum of the exoplanet’s atmosphere, a small hill between 4.1 and 4.6 microns presents the first clear, detailed evidence for carbon dioxide ever detected in a planet outside the solar system.

“As soon as the data appeared on my screen, the whopping carbon dioxide feature grabbed me,” said Zafar Rustamkulov, a graduate student at Johns Hopkins University and member of the JWST Transiting Exoplanet Community Early Release Science team, which undertook this investigation. “It was a special moment, crossing an important threshold in exoplanet sciences.”

No observatory has ever measured such subtle differences in brightness of so many individual colors across the 3 to 5.5-micron range in an exoplanet transmission spectrum before. Access to this part of the spectrum is crucial for measuring abundances of gases like water and methane, as well as carbon dioxide, which are thought to exist in many different types of exoplanets.

“Detecting such a clear signal of carbon dioxide on WASP-39 b bodes well for the detection of atmospheres on smaller, terrestrial-sized planets,” said Natalie Batalha of the University of California at Santa Cruz, who leads the team.

Understanding the composition of a planet’s atmosphere is important because it tells us something about the origin of the planet and how it evolved. “Carbon dioxide molecules are sensitive tracers of the story of planet formation,” said Mike Line of Arizona State University, another member of this research team. “By measuring this carbon dioxide feature, we can determine how much solid versus how much gaseous material was used to form this gas giant planet. In the coming decade, JWST will make this measurement for a variety of planets, providing insight into the details of how planets form and the uniqueness of our own solar system.”

Is the Earth warming? The ocean gives you the answer

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Humans have released carbon dioxide and other greenhouse gases, and the result is an accumulation of heat in the Earth’s climate system, commonly referred to as “global warming”. “How fast is the Earth’s warming?” is a key question for decision makers, scientists and general public.

Previously, the global mean surface temperature has been widely used as a key metric of global warming. However, a new study published in AGU’s Eos proposed a better way of measuring global warming: monitoring ocean heat content change and sea level rise. The authors come from a variety of international communities including China (Institute of Atmospheric Physics, Chinese Academy of Sciences), U.S.A. (NCAR, NOAA, and University of St. Thomas) and France (Mercator Ocean).

To determine how fast the Earth is accumulating heat, scientists focus on the Earth’s energy imbalance (EEI): the difference between incoming solar radiation and outgoing longwave (thermal) radiation. Increases in the EEI are directly attributable to human activities that increase carbon dioxide and other greenhouse gases in the atmosphere. Extra heat trapped by increasing greenhouse gases mainly ends up in the oceans (more than 90% is stored there). Hence, to measure global warming, we have to measure ocean warming!

On the other hand, the amplitude of the global warming signal compared with natural variability (noise) defines how well a metric tracks global warming. This study shows that the temporal evolution of ocean heat content has relatively high signal-to-noise ratio; therefore, it requires 3.9 years to separate the global warming trend from natural variability. Similarly, for sea level rise, 4.6 years are sufficient to detect the climate change signal. By contrast, owing to weather, El Niño – Southern Oscillation and other natural variability embedded in the global mean surface temperature record, scientists need at least 27 years of data to detect a robust trend. An excellent example is the 1998-2013 period, when energy was redistributed within the Earth’s system and the rise of global mean surface temperature slowed – sometimes call a “hiatus”.

This study suggests that changes in ocean heat content, the dominant component of Earth’s energy imbalance, should be a fundamental metric along with sea level rise. Based on the recent improvements of ocean monitoring technologies, especially after 2005 through autonomous floats called Argo, and advanced methodologies to reconstruct the historical ocean temperature record, scientists have been able to quantify ocean heat content changes back to 1960, even though there is a much sparser historical instrument record prior to 2005. Sea level rise is best known since 1993 when altimeters were first launched on satellites to enable sea level change observations to millimeter accuracy.

According to the most up-to-date estimates, the top-10 warmest years of the ocean (indicated by OHC change at upper 2000m) are all in the most recent decade after 2006, with 2015-2016 the warmest period among the past 77 years. The heat storage in the ocean amounts to an increase of 30.4×1022 Joules (J) since 1960, equal to a heating rate of 0.33 Watts per square meter (W m-2) averaged over the entire Earth’s surface– and 0.61 W m-2 after 1992. For comparison, the increase in ocean heat content observed since 1992 in the upper 2000 meters is about 2000 times the total net generation of electricity by U.S. utility companies in 2015.

It is evident that scientists and modelers who seek global warming signals should track how much heat the ocean has stored at any given time, i.e. ocean heat content, as well as sea level rise. Locally, in the deep tropics, ocean heat content directly relates to hurricane activity. Ocean heat content is a vital sign of our planet and informs societal decisions about adaptation to and mitigation of climate change.

Millions may face protein deficiency because of carbon dioxide emissions by Humans

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Human-caused carbon dioxide emissions lower the nutritional value of staple crops, increasing the risk for dietary deficiencies among the world’s most vulnerable people.
This study provides further evidence for the need to curb human-caused CO2 emissions.
Boston, MA – If CO2 levels continue to rise as projected, the populations of 18 countries may lose more than 5% of their dietary protein by 2050 due to a decline in the nutritional value of rice, wheat, and other staple crops, according to new findings from Harvard T.H. Chan School of Public Health. Researchers estimate that roughly an additional 150 million people may be placed at risk of protein deficiency because of elevated levels of CO2 in the atmosphere. This is the first study to quantify this risk.

“This study highlights the need for countries that are most at risk to actively monitor their populations’ nutritional sufficiency, and, more fundamentally, the need for countries to curb human-caused CO2 emissions,” said Samuel Myers, senior research scientist in the Department of Environmental Health.

The study will be published online August 2, 2017 in Environmental Health Perspectives.

Globally, 76% of the population derives most of their daily protein from plants. To estimate their current and future risk of protein deficiency, the researchers combined data from experiments in which crops were exposed to high concentrations of CO2 with global dietary information from the United Nations and measures of income inequality and demographics.

They found that under elevated CO2 concentrations, the protein contents of rice, wheat, barley, and potatoes decreased by 7.6%, 7.8%, 14.1%, and 6.4%, respectively. The results suggested continuing challenges for Sub Saharan Africa, where millions already experience protein deficiency, and growing challenges for South Asian countries, including India, where rice and wheat supply a large portion of daily protein. The researchers found that India may lose 5.3% of protein from a standard diet, putting a predicted 53 million people at new risk of protein deficiency.

A companion paper co-authored by Myers, which will be published as an Early View article August 2, 2017 in GeoHealth, found that CO2-related reductions in iron content in staple food crops are likely to also exacerbate the already significant problem of iron deficiency worldwide. Those most at risk include 354 million children under 5 and 1.06 billion women of childbearing age–predominantly in South Asia and North Africa–who live in countries already experiencing high rates of anemia and who are expected to lose more than 3.8% of dietary iron as a result of this CO2 effect.

These two studies, taken alongside a 2015 study co-authored by Myers showing that elevated CO2 emissions are also likely to drive roughly 200 million people into zinc deficiency, quantify the significant nutritional toll expected to arise from human-caused CO2 emissions.

“Strategies to maintain adequate diets need to focus on the most vulnerable countries and populations, and thought must be given to reducing vulnerability to nutrient deficiencies through supporting more diverse and nutritious diets, enriching the nutritional content of staple crops, and breeding crops less sensitive to these CO2 effects. And, of course, we need to dramatically reduce global CO2 emissions as quickly as possible,” Myers said.