nsf.gov - National Science Foundation - How much fertilizer is too much for Earth's climate?

Helping farmers around the globe combat greenhouse gas emissions and climate change

Applying nitrogen fertilizer to corn at the NSF Kellogg Biological Station LTER site. Credit and Larger Version

June 9, 2014

The following is part fifteen in a series on the National Science Foundation's Long-Term Ecological Research (LTER) Network. Visit parts one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, and fourteen.

Helping farmers around the globe apply more precise amounts of fertilizer nitrogen can combat climate change.

That's the conclusion of a study published this week in the journal Proceedings of the National Academy of Sciences. In the paper, researchers at Michigan State University (MSU) provide an improved prediction of nitrogen fertilizer's contribution to greenhouse gas emissions from agricultural fields.

The study uses data from around the world to show that emissions of nitrous oxide (N₂O), a greenhouse gas produced in soil following nitrogen addition, rise faster than previously expected when fertilizer rates exceed crop needs.

Nitrogen-based fertilizers spur greenhouse gas emissions by stimulating microbes in the soil to produce more nitrous oxide.

Nitrous oxide is the third most important greenhouse gas, behind carbon dioxide and methane.

Agriculture accounts for about 80 percent of human-caused nitrous oxide emissions worldwide, which have increased substantially in recent years due to increased nitrogen fertilizer use.

"Our motivation is to learn where to best target agricultural efforts to slow global warming," says MSU scientist Phil Robertson. Robertson is also director of the National Science Foundation (NSF) Kellogg Biological Station Long-term Ecological Research (LTER) site, one of 25 such NSF LTER sites around the globe, and senior author of the paper.

"Agriculture accounts for 8 to 14 percent of all greenhouse gas production globally. We're showing how farmers can help reduce this number by applying nitrogen fertilizer more precisely."

The production of nitrous oxide can be greatly reduced if the amount of fertilizer needed by crops is exactly the amount that's applied to farmers' fields.

When plants' nitrogen needs are matched with the nitrogen that's supplied, fertilizer has substantially less effect on greenhouse gas emissions, Robertson says.

"These results vastly improve the ability of research to inform climate change, food security and the economic health of the world's farmers," says Saran Twombly, a program director in NSF's Division of Environmental Biology, which funded the research through the LTER Program.

Lead author and MSU researcher Iurii Shcherbak notes that the research is especially applicable to fertilizer practices in under-fertilized areas such as sub-Saharan Africa.

"Because nitrous oxide emissions won't be accelerated by fertilizers until crops' nitrogen needs are met, more nitrogen fertilizer can be added to under-fertilized crops without much affecting emissions," says Shcherbak.

Adding less nitrogen to over-fertilized crops elsewhere, however, would deliver major reductions to greenhouse gas emissions in those regions.

The study provides support for expanding the use of carbon credits to pay farmers for better fertilizer management and offers a framework for using this credit system around the world.

Carbon credits for fertilizer management are now available to U.S. corn farmers, says Robertson.

The research was also funded by MSU, the U.S. Department of Energy's Great Lakes Bioenergy Research Center and the Electric Power Research Institute.

--	Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
--	Layne Cameron, MSU (517) 353-8819 layne.cameron@cabs.msu.edu

Investigators Douglas Landis
Thomas Schmidt
Katherine Gross
Stephen Hamilton
G. Philip Robertson

Related Institutions/Organizations Michigan State University

Locations Michigan

Related Programs Long-Term Ecological Research

Related Awards #1027253 The KBS LTER Project: Long-term Ecological Research in Row-crop Agriculture

Total Grants $4,103,781

Related WebsitesNSF Kellogg Biological Station Long-Term Ecological Research (LTER) Site:

 http://lter.kbs.msu.edu/
NSF Long-Term Ecological Research (LTER) Network:

 http://www.lternet.edu
NSF News: Scientists Develop New Carbon Accounting Method to Reduce Farmers' Use of Nitrogen Fertilizer:

 http://www.nsf.gov/news/news_summ.jsp?cntn_id=123848
NSF News: Marginal Lands Are Prime Fuel Source for Alternative Energy:

 http://www.nsf.gov/news/news_summ.jsp?cntn_id=126498
NSF Publication: Discoveries in Long-Term Ecological Research:

 http://www.nsf.gov/pubs/2013/nsf13083/nsf13083.pdf

A Michigan corn field east of the Kellogg Biological Station LTER site.
Credit and Larger Version

View of a Kellogg Biological Station LTER experiment to test how crops respond to nitrogen.
Credit and Larger Version

Good crop: Corn in mid-August at the Kellogg Biological Station LTER site.
Credit and Larger Version

Researcher AJ Ozanich collects greenhouse gas samples in a Kellogg Biological Station corn field.
Credit and Larger Version

LTER scientist Kevin Kahmark analyzes greenhouse gas samples in the lab.
Credit and Larger Version

the National Science Foundation (NSF)

Guillermo GOnzalo Sánchez Achutegui

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NASA : Long-Term Warming Likely to Be Significant Despite Recent Slowdown

Five new NASA Earth science missions are launching in 2014 to expand our understanding of Earth’s changing climate and environment.

Feature Link:

NASA's "Earth Right Now" website

A new NASA study shows Earth's climate likely will continue to warm during this century on track with previous estimates, despite the recent slowdown in the rate of global warming.

This research hinges on a new and more detailed calculation of the sensitivity of Earth's climate to the factors that cause it to change, such as greenhouse gas emissions. Drew Shindell, a climatologist at NASA's Goddard Institute for Space Studies in New York, found Earth is likely to experience roughly 20 percent more warming than estimates that were largely based on surface temperature observations during the past 150 years.

Shindell's paper on this research was published March 9 in the journal Nature Climate Change.

A new NASA study suggests that projections of Earth's future warming should be more in line with previous estimates that indicated a higher sensitivity to increasing greenhouse gas emissions.

Image Credit: NASA SVS/NASA Center for Climate Simulation

Global temperatures have increased at a rate of 0.22 Fahrenheit (0.12 Celsius) per decade since 1951. But since 1998, the rate of warming has been only 0.09 F (0.05 C) per decade -- even as atmospheric carbon dioxide continues to rise at a rate similar to previous decades. Carbon dioxide is the most significant greenhouse gas generated by humans.

Some recent research, aimed at fine-tuning long-term warming projections by taking this slowdown into account, suggested Earth may be less sensitive to greenhouse gas increases than previously thought. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), which was issued in 2013 and was the consensus report on the state of climate change science, also reduced the lower range of Earth's potential for global warming.

To put a number to climate change, researchers calculate what is called Earth's "transient climate response." This calculation determines how much global temperatures will change as atmospheric carbon dioxide continues to increase – at about 1 percent per year -- until the total amount of atmospheric carbon dioxide has doubled. The estimates for transient climate response range from near 2.52 F (1.4 C) offered by recent research, to the IPCC's estimate of 1.8 F (1.0 C). Shindell's study estimates a transient climate response of 3.06 F (1.7 C), and determined it is unlikely values will be below 2.34 F (1.3 C).

Shindell's paper further focuses on improving our understanding of how airborne particles, called aerosols, drive climate change in the Northern Hemisphere. Aerosols are produced by both natural sources – such as volcanoes, wildfire and sea spray – and sources such as manufacturing activities, automobiles and energy production. Depending on their make-up, some aerosols cause warming, while others create a cooling effect. In order to understand the role played by carbon dioxide emissions in global warming, it is necessary to account for the effects of atmospheric aerosols.

While multiple studies have shown the Northern Hemisphere plays a stronger role than the Southern Hemisphere in transient climate change, this had not been included in calculations of the effect of atmospheric aerosols on climate sensitivity. Prior to Shindell's work, such calculations had assumed aerosol impacts were uniform around the globe.

This difference means previous studies have underestimated the cooling effect of aerosols. When corrected, the range of likely warming based on surface temperature observations is in line with earlier estimates, despite the recent slowdown.

One reason for the disproportionate influence of the Northern Hemisphere, particularly as it pertains to the impact of aerosols, is that most man-made aerosols are released from the more industrialized regions north of the equator. Also, the vast majority of Earth's landmasses are in the Northern Hemisphere. This furthers the effect of the Northern Hemisphere because land, snow and ice adjust to atmospheric changes more quickly than the oceans of the world.

"Working on the IPCC, there was a lot of discussion of climate sensitivity since it's so important for our future," said Shindell, who was lead author of the IPCC Fifth Assessment Report's chapter on Anthropogenic and Natural Radiative Forcing. "The conclusion was that the lower end of the expected warming range was smaller than we thought before. That was a big discussion. Yet, I kept thinking, we know the Northern Hemisphere has a disproportionate effect, and some pollutants are unevenly distributed. But we don't take that into account. I wanted to quantify how much the location mattered."

Shindell's climate sensitivity calculation suggests countries around the world need to reduce greenhouse gas emissions at the higher end of proposed emissions reduction ranges to avoid the most damaging consequences of climate change. "I wish it weren't so," said Shindell, "but forewarned is forearmed."

For more information about the Goddard Institute for Space Studies, visit:

http://www.giss.nasa.gov

NASA

Guillermo GOnzalo Sánchez Achutegui

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NASA - Tropical Ecosystems Boost Carbon Dioxide as Temperature Rises

Temperature and Vegetation Seasonality Diminishment over Northern Lands

The research finding reports that decreasing temperature difference between the seasons in the North is increasing plant growth and blurring the distinction between the normally more-seasonal North and abutting less-seasonal South.

A greenhouse effect initiated by increased atmospheric concentration of heat-trapping gasses, such as water vapor, carbon dioxide, methane, etc., causes the Earth’s surface and nearby air to warm. The warming reduces the extent of polar sea ice and snow cover on the large land mass girdling the Arctic ocean, which increases the amount of solar energy absorbed by the now somewhat less-white surface. This sets in motion a cycle of positive reenforcement between warming and loss of sea ice and snow cover – the amplified greenhouse effect.

This amplified warming in the North, roughly above the border between Canada and the USA for example, is reducing temperature seasonality over time because the colder seasons are warming more rapidly than the summer.

Consequently, the total amount of heat available for plant growth in these cold climes is increasing from enhanced level of warming overall and a lengthening thaw season. The result is numerous large patches of vigorously productive vegetation, totaling more than a third of the Northern landscape, in resemblance of their lusher and less-seasonal Southern counterparts.

This linked diminishment of temperature and vegetation seasonality is reported by an international team of 21 authors from 17 institutions in 7 countries. They used a new 30-year satellite data set of vegetation greenness developed by coauthors Drs. Compton Tucker and Jorge Pinzon of NASA Goddard Space Flight Center in Greenbelt, USA, in addition to two independent data sets of temperature. To determine the growing season, the authors used 20 years of twice-daily satellite observations of freeze/thaw state of the ground developed under NASA’s auspices.

The study cast seasonality changes using latitude as a yardstick because total growing season warmth and plant growth of circumpolar belts of land monotonically decrease poleward from about 50°N latitude. This allowed definition of reference latitudinal profiles of these quantities and translation of their changes over time as shifts along these reference profiles.

As an example, consider the Arctic, the far northern tree-less circumpolar belt of shrubs, grass and sedge meadows. Arctic plant growth during the early 1980s, the reference period, equaled that of lands north of 64°N, while now, 30 years later, it equals that of lands north of 57°N during the reference period – a reduction in vegetation seasonality of about 7°N in latitude. This manner of analyses suggested a decline in temperature and vegetation seasonality of about 4 to 7° latitude over the past 30 years.

The diminishment of vegetation seasonality, or increased greenness, in the Arctic is visually evident on the ground as increasing abundance of shrubs, their height and also tree incursions in several locations. The greening in the adjacent Boreal areas is much less conspicuous in North America than in Eurasia, reasons for which are not known, but likely involve increasingly divergent precipitation patterns between the continents.

Indeed a key finding of this study is the accelerating decline of vegetation seasonality, that is, increasing greening rate over time, in the Arctic and a decelerating decline of vegetation seasonality in the Boreal region, in the face of nearly-constant rate of temperature seasonality diminishment in these regions over the past 30 years. Perhaps this portends a decoupling between growing season warmth and vegetation productivity in the North, as the ramifications of amplified greenhouse effect, such as permafrost thawing, increased risks of fires and pest infestations, summer time aridity, etc., come in to play.

The future does indeed look disturbing. The authors report diminishment of temperature seasonality in the North of over 20° latitude during the last decade of this century, relative to the reference period 1951-1980, based on analysis of 17 state-of-the-art climate model simulations. The prediction of temperature seasonality decline by these models for the decade 2001-2010 is actually less than the observed decline. As we do not know the actual trajectory of atmospheric concentration of various agents capable of forcing a change in climate, such projections should of course be interpreted cautiously.

The soils in the North can release significant amount of greenhouse gases, such as carbon dioxide and methane, which are currently locked up in the permanently frozen ground. Any large-scale deep-thawing of these soils has the potential to further amplify the overall greenhouse effect.

The way of life of many organisms on Earth is tightly linked to seasonal changes in temperature and availability of food, and all food on land comes first from plants. Think of migration of birds to the Arctic in the summer and hibernation of bears in the winter. Any significant alterations to temperature and vegetation seasonality are likely to impact life not only in the North but elsewhere in ways that we do not yet know.

Attachments

34-temp-ssnlty-dim-globe-large.jpg temperature seasonality diminishment	753.8 KB
39-plant-growth_large.jpg plant growth change	1.2 MB
07-temp-veg-ssnlty.jpg vegetation seasonality is tightly coupled to temperature seasonality in the North.	1.2 MB
38-veg-map.jpg Arctic and Boreal Vegetated Lands	981.5 KB
36-plant-growth-changes.jpg Trend in Arctic and Boreal Region with respect to 1982 (% per decade)	1.0 MB
15-avg-ndvi-large.jpg Climatological NDVI derived from 30-years of AVHRR data	1.0 MB

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Tropical Ecosystems Boost Carbon Dioxide as Temperature Rises

WASHINGTON -- NASA scientists and an international team of researchers have found tropical ecosystems can generate significant carbon dioxide when temperatures rise, unlike ecosystems in other parts of the world.

The researchers discovered a temperature increase of just 1 degree Celsius in near-surface air temperatures in the tropics leads to an average annual growth rate of atmospheric carbon dioxide equivalent to one-third of the annual global emissions from combustion of fossil fuels and deforestation combined. In tropical ecosystems carbon uptake is reduced at higher temperatures. This finding provides scientists with a key diagnostic tool to better understand the global carbon cycle.
"What we learned is that in spite of droughts, floods, volcano eruptions, El Niño and other events, the Earth system has been remarkably consistent in regulating the year-to-year variations in atmospheric carbon dioxide levels," said Weile Wang, a research scientist at NASA's Ames Research Center in Moffett Field, Calif., and lead author of a paper published Wednesday, July 24, in the Proceedings of the National Academy of Sciences.
The study provides support for the "carbon-climate feedback" hypothesis proposed by many scientists. This hypothesis asserts a warming climate will lead to accelerated carbon dioxide growth in the atmosphere from vegetation and soils. Multiple Earth system processes, such as droughts and floods, also contribute to changes in the atmospheric carbon dioxide growth rate. The new finding demonstrates observed temperature changes are a more important factor than rainfall changes in the tropics.
The team used a state-of-the-art, high-performance computing and data access facility called NASA Earth Exchange (NEX) at Ames to investigate the mechanisms underlying the relationship between carbon dioxide levels and increased temperatures. The NEX facility allowed scientists to analyze widely available data of atmospheric carbon dioxide concentrations and global air temperatures between 1959 and 2011, while studying outputs from several global dynamic vegetation models.
"Climate warming is what we know with certainty will happen under climate change in the tropics," said Josep G. Canadell, executive director of the Global Carbon Project in Canberra, Australia, and co-author on the paper. "This implies the release of carbon dioxide from the tropical ecosystems will very likely be accelerated with future warming."
Events that can temporarily influence climate, such as volcanic eruptions, may disturb the strength of the relationship between annual temperature and carbon dioxide growth for a few years, but the coupling always recovers after such events.
"The study really highlights the importance of long-term Earth observations for improving our understanding of the Earth system," said Rama Nemani, principal scientist at Ames for the NEX project. "Conclusions drawn from analysis of shorter records could be misleading."
The study was supported by the Earth Science Division in the Science Mission Directorate at NASA Headquarters in Washington.
For more information about the NEX program, visit:

http://nex.nasa.gov

 

For more information about NASA and agency programs, visit:

http://www.nasa.gov

 

NASA

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