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Link to PLANKTOS web site based on "The idea of stimulating plankton production with iron grew out of the fertile mind of the late John H. Martin, an oceanographer at the Moss Landing Marine Laboratory near Monterey, California.

Terrestrial ecosystem feedbacks to global climate change
DA Lashof, BJ DeAngelo, SR Saleska, J Harte - Ann. Rev. Energy Environ, 1997 - energy.annualreviews.org
... Human enhancement of the greenhouse effect (referred to here as global warming or
global climate change), however, introduces two unprecedented issues ...
Cited by 7 - Web Search - plant.annualreviews.org - soc.annualreviews.org - plant.annualreviews.org - all 5 versions »

 

Vegetation Increased in Last 20 Years, Satellite Data Show

By JASON BATES
Space News Staff Writer
posted:
02:38 pm ET, 14 July 2003

 

Climate changes, including warming temperatures, have led to increased global vegetation production over the last 20 years, according to a U.S. government-funded study based on data from environmental satellites.

"The higher latitude areas have gotten warmer," said Steve Running, a professor of ecology at the University of Montana at Missoula. "Some of the drier parts of the world have gotten wetter. Some of the tropical areas have gotten sunnier. Add all those together, and you have an increase in global productivity."

Running was one of the lead authors of the study, which drew its conclusions about vegetation trends based on weather satellite data dating back to 1982. The study culminated in a report dubbed "Climate-Driven Increases in Global Terrestrial Net Primary Production," which was released June 6 by NASA, the University of Boston and the University of Montana.

Scientists hope to continue the research for several more decades using data from a variety of new satellite sensors, Running said in an interview.

The origins of the study date back to work performed in the mid-1990s by Charles Keeling, a scientist at the Scripps Institute of Oceanography in La Jolla, Calif. Working independently, Keeling determined that atmospheric carbon dioxide did not reach predicted levels during the 1980s and 1990s. He theorized that this was due to more active vegetation growth worldwide, because plants consume carbon dioxide.

Keeling then approached researchers at NASA and the two universities to help confirm his theory, said Ranga Myneni, an associate professor in the department of geography at Boston University.

NASA and Boston University prepared global vegetation maps using data from the Advanced Very High Resolution Radiometer (AVHRR) sensors aboard U.S. government polar-orbiting weather satellites. In addition to tracking clouds, storms and other weather phenomena, AVHRR sensors aboard the two civilian U.S. polar-orbiting weather satellites measure global vegetation levels on a weekly basis, Myneni said.

The data were analyzed by the University of Montana.

Initially, the study concentrated on the higher latitudes of the Earth’s Northern Hemisphere, Myneni said. But as the scientists began to notice changes, they expanded their work to the entire Northern Hemisphere and eventually the globe, he said.

Many leading scientists theorize that fossil-fuel burning and other human activities release chemicals into the atmosphere that have caused it to retain heat, leading to rising global temperatures. The theory is commonly known as global warming.

Some have seized upon the vegetation report as evidence that global warming is good for the planet, Running said. But he warned that such conclusions are premature.

"This [the vegetation increase] is one aspect of global change that does happen to be positive," Running said. "But other aspects, particularly in water resources, are not as rosy. It would be a real oversimplification to take these results and widely claim that global warming is good overall."

The only way to answer the questions being raised by the report is to continue the study for several more decades using new sources of data, Running said.

In 2000, the team began incorporating data from the Moderate Resolution Imaging Spectroradiometer, or Modis, instruments, into their work, Running said. The sensors are carried aboard NASA’s Aqua and Terra Earth observing satellites.

Modis instruments collect data in more spectral bands than the AVHRR sensors, allowing more in-depth studies of the vegetation, Myneni said. The Modis sensor also can be calibrated in space — something that cannot be done with AVHRR — making it easier to produce usable data, he said.

"The AVHRR data is a historical analysis; the future will be the Modis data set," Running said. "It’s continuing the same analysis with a newer, better satellite."

While the team still is in the process of incorporating Modis into the study, plans already are being made to move to the next generation of sensors, Running said.

Modis data eventually will be replaced by data from the planned National Polar orbiting Operational Environmental Satellite System, which is being jointly developed by the U.S. National Oceanic and Atmospheric Administration and the U.S. Air Force. The launch of the first spacecraft is scheduled for around the end of the decade.

"This really is the inauguration of a global vegetation monitoring system," Running said. "We did the historical look backward, and now we have an ongoing stream in the future. We hope this is the start of a permanent biosphere monitor." 

 

 

 

Public release date: 12-Jul-2004

Contact:
Krishna Ramanujan
krishna_ramanujan@ssaihq.com
607-273-2561
NASA/Goddard Space Flight Center--EOS Project Science Office

 

When sun's too strong, plankton make clouds

People say size doesn't matter, and that may be true for tiny plankton, those free-floating ocean plants that make up the bottom of the marine food-chain. Little plankton may be able to change the weather, and longer term climate, in ways that serve them better.

It's almost hard to believe, but new NASA-funded research confirms an old theory that plankton can indirectly create clouds that block some of the Sun's harmful rays. The study was conducted by Dierdre Toole of the Woods Hole Oceanographic Institution (WHOI) and David Siegel of the University of California, Santa Barbara (UCSB).

 

The study finds that in summer when the Sun beats down on the top layer of ocean where plankton live, harmful rays in the form of ultraviolet (UV) radiation bother the little plants. When they are bothered, or stressed, plankton try to protect themselves by producing a compound called dimethylsulfoniopropionate (DMSP). Though no one knows for sure, some scientists believe DMSP helps strengthen the plankton's cell walls. This chemical gets broken down in the water by bacteria, and it changes into another substance called dimethylsulfide (DMS).

 

DMS then filters from the ocean into the air, where it reacts with oxygen, to form different sulfur compounds. Sulfur in the DMS sticks together in the air and creates tiny dust-like particles. These particles are just the right size for water to condense on, which is the beginning of how clouds are formed. So, indirectly, plankton help create more clouds, and more clouds mean less direct light reaches the ocean surface. This relieves the stress put on plankton by the Sun's harmful UV rays.

 

For years now scientists have been studying related processes in the lab, but this is the first time scientists have shown how variations in light impact plankton in a natural environment. The research was done in the Sargasso Sea, off the coast of Bermuda.

 

Previous research also found that the cloud producing compound peaks in the summer in the ocean, when UV rays are high, but plankton numbers are at their lowest.

"Plankton levels are at a minimum in the summer but DMS is at its peak," said Toole.

 

In the warmest months, the top layer of the ocean warms as well. This heating of the top 25 meters (around 80 feet) creates a contrast with cooler deeper layers. The deeper layers hold many of the nutrients that plankton need to live on. Like how oil separates from water, the warmer upper layer creates almost a barrier from the cooler lower layers and less mixing occurs. Also, the shallow upper layer exposes the plankton to more UV light. Under conditions where there are low nutrients in the water and levels of UV light are high, plankton create more DMS.

 

DMS levels peak from June through the end of September. During the season, the study found that a whopping 77 percent of the changes in amounts of DMS were due to exposure to UV radiation. The researchers found it amazing that a single factor could have such a big affect on this process.

 

"For someone studying marine biology and ecology, this type of variation is absolutely incredible," Siegel said.

 

The researchers were also surprised to find that the DMS molecules completely refresh themselves after only three to five days. That means the plankton may react to UV rays quickly enough to impact their own weather. Toole and Siegel were surprised by the lightning-fast rate of turnover for DMS. To give an example for comparison, when carbon dioxide gets into the atmosphere where it acts as a greenhouse gas and traps heat, it may last for decades. Toole adds that the cycles that break down DMS scream along at these very fast rates, even though overall amounts over the course of the year remain pretty stable with a slow increase over summer and a gradual decline over winter.

 

The next step for the researchers will be to see how much the added clouds from plankton actually impact climate. By figuring out how plankton react to light, scientists now have the information they need to use computer models to recreate the impacts of plankton on cloud cover. Since the white clouds can reflect sunlight back out to space, the researchers believe the plankton-made clouds may have some affect on global temperatures.

 

This is important in light of man-made greenhouse gas production that warms the planet, and ozone depletion that allows more life-threatening UV radiation to strike Earth.

 

"There is the potential that this cycle could slow global warming," said Siegel. "But right now we have no idea of the size of it or even what it means."

 

In order to measure how much plankton may alter the climate, computer models would need to simulate different scenarios. One scenario would show our climate without clouds due to plankton, and another would show the climate with the increased cloud cover. Then researchers could begin to compare the differences between each scenario.

 

The researchers add that this effect may help to slow or lessen climate change, but would in no way reverse the trend or stop it altogether.

 

The research took place in the Sargasso Sea, where a wide range ocean data has been collected since the 1950s. A 1998 study relying on data from this area contained a 1992 to 1994 time series that focused on the cycling of organic sulfur from DMS in the ocean. Siegel has also been collecting data of changes in sea surface temperatures over seasons, variations in both visible light and UV light in the water, and the relationships between these solar variations and DMS levels. All of these measurements have been taken from research vessels and buoys in the Sargasso Sea.

 

In the future, the paper's authors look forward to incorporating satellite data from NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS) mission into this line of research. SeaWIFS will provide comprehensive data on shifts in visible light reaching the ocean's surface.

 

###

The study was funded by NASA. Studies of DMS have been funded by the National Science Foundation.

 

NASA Satellite Sees Ocean Plants Increase, Coasts Greening

 

 

Greenbelt MD (SPX) Mar 04, 2005
A few years ago, NASA researcher Watson Gregg published a study showing that tiny free-floating ocean plants called phytoplankton had declined in abundance globally by 6 percent between the 1980s and 1990s. A new study by Gregg and his co-authors suggests that trend may not be continuing, and new patterns are taking place.

Why is this important? Well, the tiny ocean plants help regulate our atmosphere and the health of our oceans. Phytoplankton produce half of the oxygen generated by plants on Earth.

They also can soften the impacts of climate change by absorbing carbon dioxide, a heat-trapping greenhouse gas. In addition, phytoplankton serve as the base of the ocean food chain, so their abundance determines the overall health of ocean ecosystems.

Given their importance, it makes sense that scientists would want to closely track trends in phytoplankton numbers and in how they are distributed around the world.

Gregg and his colleagues published their new study in a recent issue of Geophysical Research Letters. The researchers used NASA satellite data from 1998 to 2003 to show that phytoplankton amounts have increased globally by more than 4 percent.

These increases have mainly occurred along the coasts. No significant changes were seen in phytoplankton concentrations within the global open oceans, but phytoplankton levels declined in areas near the center of the oceans, the mid-ocean gyres.

Mid-ocean gyres are "ocean deserts", which can only support low amounts of phytoplankton. When viewed by satellite, these phytoplankton-deprived regions look deep-blue, while in aquatic regions where plant life thrives, the water appears greener.

"The ocean deserts are getting bluer and the coasts are getting greener," said Gregg, an oceanographer at NASA's Goddard Space Flight Center (GSFC), Greenbelt, Md. "The study suggests there may be changes occurring in the biology of the oceans, especially in the coast regions."

Phytoplankton amounts have increased by 10.4 percent along global coast regions, where the ocean floor is less than 200 meters (656 feet) deep. Ocean plant life has greened the most in the Patagonian Shelf and the Bering Sea, and along the coasts of the Eastern Pacific Ocean, Southwest Africa, and near Somalia.

Both the Patagonian Shelf and the California/Mexican Shelf showed large increases in phytoplankton concentrations of over 60 percent.

Meanwhile, the researchers observed declines in phytoplankton amounts in five mid-ocean gyres over the six-year study period, including the North and South Atlantic, and North and South Pacific oceans, and a possible new gyre region in the North Central Indian ocean.

At the same time, for all but the North Atlantic gyre, sea surface temperatures increased in at least one season.

"In the mid-ocean gyres, the downward trends in phytoplankton concentrations do appear related to mid-ocean sea surface temperatures," said Gregg.

Phytoplankton growth is largely dependent on amounts of nutrients and light available to the plants. Warmer water temperatures can create distinct layers in the ocean surface, which allows less of the nutrient-rich, colder deeper water to rise up and mix with sunny surface layers where phytoplankton live.

Winds churn and mix the ocean water, carrying nutrient-rich waters to the sunny surface layer, so when winds decline mixing declines, and phytoplankton can suffer.

In a number of open ocean regions, increases in phytoplankton levels countered the declines found in the gyres and other areas. For example, a 72 percent increase in phytoplankton abundance occurred in the Barents Sea.

The researchers observed a smaller 17 percent increase in phytoplankton amounts in the Western Central Pacific near Indonesia and the Philippines. The waters cooled in the Western Pacific, while wind stresses increased by 26 percent over the study period. The cooling water and increasing winds are consistent with climate conditions that lead to greater mixing of water.

The six full years of data used in this analysis came from NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS), which detects ocean colors.

Chlorophyll is the substance or pigment in plants that appears green and captures energy from sunlight. The sunlight, along with carbon dioxide and water, are processed by the phytoplankton to form carbohydrates for building cells. SeaWiFS measures this greenness.

While the study refers to the measurement of chlorophyll a concentrations in the ocean, researchers use the measures of chlorophyll a to estimate amounts of phytoplankton.

While declines in phytoplankton abundance in mid-ocean gyres appear related to warming oceans, a number of factors requiring more study to may be contributing to the coastal increases in plant life.

"We don't know the causes of these coastal increases," said Gregg. "The trends could indicate improved health of the ecosystems as a whole, or they could be a sign of nutrient stress."

Causes of nutrient stress include land run-off that deposits agricultural fertilizers and other nutrients in the oceans. The run-off can promote large algal blooms that can deplete the water of oxygen.

Gregg and coauthors caution that the length of time the data cover is too short to answer questions about long term trends, but for the time being the phytoplankton declines in the global oceans observed between the 1980s and 1990s appear to have subsided.

Co-authors on the study include Nancy Casey of Science Systems Applications, who works at NASA GSFC, and Charles McClain, also a researcher at NASA GSFC.

 

 

From:  (http://www.greeningearthsociety.org/wca/2003/wca_1aa.html )

Lush Life

There’s trouble a’brewing for the climate-change-is-bad crowd. The news is this: As a result of a changing climate and enhanced atmospheric carbon dioxide levels during the past two decades, the world has become a better place for plants. This from a paper published in the June 6 edition of Science by Ramakrishna Nemani of the University of Montana School of Forestry and seven colleagues. While this may be news to some, it’s hardly news to us.
     We have been reporting for years that satellite observations of plant growth patterns – research primarily led by Boston University’s Ranga Myneni – have indicated that the earth has been “greening” since the early 1980s. That’s when such satellite observations first became available. There’s been much speculation as to the reasons for the greening of planet Earth. Some credited carbon dioxide fertilization, others the extended growing season brought on by global warming. Nemani’s research team, which includes Myneni and six other collaborators, sets out to end the speculation and determine the root cause. What they’ve found should chill the blood of those who insist humans are destroying the earth.
     The authors begin by declaring that the past two decades (1982 to 1999) have been two of the warmest on record based on the ground-based historical temperature record. There have been three intense and/or persistent El Nino events, changes in tropical cloudiness and monsoon dynamics, just under a ten percent increase in atmospheric carbon dioxide levels, and a population increase of thirty-seven percent. All of these factors have combined to produce “dramatic environmental changes.”
     To assess how those and other changes impact plant life, Nemani’s team calculated net primary productivity (NPP), basically the amount of carbon produced by plants while growing minus the amount they lose through respiration, within 0.5º latitude by 0.5º longitude grid cells across the world’s land masses. The greater the NPP, the more productive is plant life.
Figure 1 shows what they found.
     Globally, there has been a statistically significant rise in NPP of 6.17 percent between 1982 and 1999. More than twenty-five percent of the world’s vegetated areas show statistically significant increases. Statistically significant declines are limited to about seven percent of the earth’s land area. As the authors note, a change in NPP integrates “climate, ecological, geochemical, and human influences on the biosphere.” In other words, everything that has affected terrestrial plant growth from 1982 to 1999 is accounted for in NPP.
     The authors identify increased air temperatures as responsible for enhanced growth in the temperature-limiting environments of North America and northwestern Europe. Increased precipitation led to enhanced growth in the water-limited ecosystems of Australia, Africa, and India. Decreased cloudiness (read that, increased sunshine) led to better growing conditions in the radiation-constrained area of western Europe and in the equatorial tropics, especially Amazonia. Decreased precipitation was responsible for a decline in NPP in Mexico. Cooling (!) temperatures were the cause of the decline in NPP in far northern Siberia. While the authors identify these climate changes as important to the observed NPP trends, they find that fertilization from the atmosphere’s increasing atmospheric carbon dioxide concentration also played a role in the increases, although they don’t believe that carbon dioxide fertilization is solely responsible.
     This means that for the past twenty years the net sum of all of the environmental changes that have occurred over earth’s surface has produced a global environment that is better for plant life. This poses an interesting dilemma for global warming doomsayers who seek to link adverse environmental changes with human activity, including those changes they believe lead to global warming. If they continue to link climate change with human activity, they are forced to admit that human activity has resulted in large-scale beneficial effects. If they deny the linkage, they’re left with – nothing. If they choose to straddle the dilemma’s horns by pushing their gloom-and-doom scenario out to some future date, besides getting gored, they’re left without any observed support for their scenario and remain completely reliant on the climate models that seem incapable of squaring reality with their output. But what’s new in that posture, inquiring minds ask?


Reference:

Nemani, R.R., et al., 2003. Climate-driven increases in global terrestrial net primary production from 1982 to 1999. Science, 300: 1560-1563.




Figure 1. The spatial pattern of change in net primary productivity from 1982 to 1999 (source: Nemani et al., 2003, Science).

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April 23, 2001

NR-01-04-08

Past Cooling Trend Caused By Move From Forests To Agriculture

LIVERMORE, Calif. - Researchers in Lawrence Livermore National Laboratory’s Atmospheric Science Division have demonstrated a cooling of up to 2-degree Fahrenheit over land between 1000 and 1900 AD as a result of changes from natural vegetation, such as forests, to agriculture.

Through climate model simulations, the LLNL research team made up of Bala Govindasamy, Ken Caldeira and Philip Duffy, determined that a previously recognized cooling trend up to the last century could, in part, be attributed to the land-use change.

Previous studies had attributed cooling to natural climate variations. The Livermore research, however, suggests that much of this cooling could have been the result of human activity.

Forests tend to look dark from the sky, but agricultural lands, with their amber waves of grain, tend to look much lighter. Dark colors tend to absorb sunlight, and light colors tend to reflect sunlight back out to space. Changing from forests to crops results in more sunlight reflected back to space. This reflection of solar energy to space tends to cool the Earth, especially in regions such as the eastern and mid-western United States, where huge tracts of land have been converted to crops. In the 20th century, some of this cropland has been reverting back to forest, especially in the eastern United States.

Greenhouse gas emissions in the 20th century likely overcame any cooling trends that took place up to that time. Growing more trees has been suggested as a way to soak up carbon dioxide, a greenhouse gas, from the atmosphere. However, earlier studies demonstrate that growing dark forests could actually heat the earth’s surface more because dark colors tend to absorb more sunlight, despite the uptake of carbon dioxide.

"The Earth land surface has cooled by about 0.41 K (= by about 3/4 of a degree Fahrenheit) due to the replacement of dark forests by lighter farms growing wheat, corn, etc.," said Caldeira, a climate model researcher who also is co-director for the Department of Energy’s Center for Research on ocean carbon sequestration. "This is an example of inadvertent geoengineering -- we changed the reflectivity of the Earth and have probably caused a global cooling in the past. This is now probably being overwhelmed by our greenhouse gas emissions."

The research, published in the Geophysical Research Letters, also shows a slight increase in the annual means of global and Northern Hemisphere sea ice volumes in association with the cooling. The simulated annual average cooling due to land-use change during this period is almost a half a degree Fahrenheit globally, 0.66 °F for the Northern Hemisphere and .74 °F over land.

In the simulations, land use data for 1000 AD uses potential natural vegetation, made up mainly of forests, while data for the 1900 AD period uses standard current vegetation data, which is a mix of forest and croplands, taken from the Community Climate Model developed at the National Center for Atmospheric Research. The greenhouse gas levels in both simulations are in concentrations taken at pre-industrial levels.

"The estimated temperature change in the continental United States as a result of change from forests to agriculture is up to a 2-degree Fahrenheit cooling," Caldeira said. "So, when we talk about global warming, we can no longer take for granted that this global warming is starting from some natural climate state, undisturbed by human activities."

Founded in 1952, Lawrence Livermore National Laboratory is a national nuclear security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. The National Nuclear Security Administration’s Lawrence Livermore National Laboratory is managed by the University of California.

Contact:
Anne M. Stark
Phone: 925/422-9799
E-mail:
stark8@llnl.gov

This text derived from http://www.llnl.gov/llnl/06news/NewsReleases/2001/NR-01-04-08.html

 

 

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Title:
Impact of Geoengineering Schemes on the Terrestrial Biosphere
Authors:
Govindasamy, B.; Thompson, S. L.; Duffy, P. B.; Caldeira, K. G.; Delire, C.
Affiliation:
AA(Lawrence Livermore National Lab, 7000 East Ave. L-103, Livermore, CA 94550 United States ; Bala@llnl.gov), AB(Lawrence Livermore National Lab, 7000 East Ave. L-103, Livermore, CA 94550 United States ; thompson59@llnl.gov), AC(Lawrence Livermore National Lab, 7000 East Ave. L-103, Livermore, CA 94550 United States ; pduffy@llnl.gov), AD(Lawrence Livermore National Lab, 7000 East Ave. L-103, Livermore, CA 94550 United States ; kenc@llnl.gov), AE(University of Wisconsin-Madison, 1225 W. Dayton St., Madison, WI 53706 United States ; cldelire@facstaff.wisc.edu)
Journal:
American Geophysical Union, Fall Meeting 2002, abstract #A12A-0131
Publication Date:
12/2002
Origin:
AGU
AGU Keywords:
0315 Biosphere/atmosphere interactions, 1600 GLOBAL CHANGE (New category), 1615 Biogeochemical processes (4805), 1620 Climate dynamics (3309), 3309 Climatology (1620)
Abstract Copyright:
(c) 2002: American Geophysical Union
Bibliographic Code:
2002AGUFM.A12A0131G

Abstract

Climate stabilization via "Geoengineering" schemes seek to mitigate climate change due to increased greenhouse gases by compensating reduction in solar radiation incident on earth's surface. Though the spatial and temporal pattern of radiative forcing from greenhouse gases differs from that of sunlight, it was shown in recent studies that these schemes would largely mitigate regional or seasonal climate change for a doubling and quadrupling of the atmospheric CO2 content. In this study, we address the impact of these climate stabilization schemes on terrestrial biosphere using equilibrium simulations from a coupled atmosphere-terrestrial biosphere model (CCM3-IBIS). Geoengineering schemes would tend to limit changes in vegetation distribution brought on by climate change, but would not prevent CO2 -induced changes in NPP or biomass; indeed, if CO2 fertilization is significant, then a climate-stabilized world could have higher net primary productivity NPP than our current world. Nevertheless, there are many reasons why geoengineering is not a preferred option for climate stabilization.Impact of Geoengineering Schemes on the Terrestrial Biosphere
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Title:
Global response of the terrestrial biosphere to CO2 and climate change using a coupled climate-carbon cycle model
Authors:
Berthelot, M.; Friedlingstein, P.; Ciais, P.; Monfray, P.; Dufresne, J. L.; Le Treut, H.; Fairhead, L.
Journal:
Global Biogeochemical Cycles, Volume 16, Issue 4, pp. 31-1, CiteID 1084, DOI 10.1029/2001GB001827 (GBioC Homepage)
Publication Date:
11/2002
Origin:
AGU
AGU Keywords:
Atmospheric Composition and Structure: Biosphere/atmosphere interactions, Global Change: Biogeochemical processes (4805), Global Change: Impact phenomena,
Abstract Copyright:
(c) 2002: American Geophysical Union
DOI:
10.1029/2001GB001827
Bibliographic Code:
2002GBioC..16d..31B

Abstract

We study the response of the land biosphere to climate change by coupling a climate general circulation model to a global carbon cycle model. This coupled model was forced by observed CO2 emissions for the 1860-1990 period and by the IPCC SRES-A2 emission scenario for the 1991-2100 period. During the historical period, our simulated Net Primary Production (NPP) and net land uptake (NEP) are comparable to the observations in term of trend and variability. By the end of the 21st century, we show that the global NEP is reduced by 56% due to the climate change. In the tropics, increasing temperature, through an increase of evapotranspiration, acts to reduce the soil water content, which leads to a 80% reduction of net land CO2 uptake. As a consequence, tropical carbon storage saturates by the end of the simulation, some regions becoming sources of CO2. On the contrary, in northern high latitudes, increasing temperature stimulates the land biosphere by lengthening the growing season by about 18 days by 2100 which in turn leads to a NEP increase of 11%. Overall, the negative climate impact in the tropics is much larger than the positive impact simulated in the extratropics, therefore, climate change reduce the global land carbon uptake. This constitutes a positive feedback in the climate-carbon cycle system.
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Title:
Using Linear and Non-Linear Methods to Study Precipitation-Vegetation Dynamics at Global Scales
Authors:
Lotsch, A.; Friedl, M. A.
Affiliation:
AA(Boston University Deptartment of Geography, 675 Commonwealth Ave, Boston, MA 02215 United States ; alotsch@crsa.bu.edu), AB(Boston University Deptartment of Geography, 675 Commonwealth Ave, Boston, MA 02215 United States ; friedl@bu.edu)
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American Geophysical Union, Fall Meeting 2002, abstract #B21B-0730
Publication Date:
12/2002
Origin:
AGU
AGU Keywords:
1615 Biogeochemical processes (4805), 1620 Climate dynamics (3309), 1630 Impact phenomena, 1640 Remote sensing, 1694 Instruments and techniques
Bibliographic Code:
2002AGUFM.B21B0730L

Abstract

Large areas of the Earth's land surface experience significant spatio-temporal variability in precipitation regimes. This variability can result in important perturbations to ecosystem processes. In recent years remote sensing observations have been used to examine large-scale dynamics in ecosystem response to climate. However, because of the complexity of both the processes and data sets involved, analysis of coupled spatio-temporal variability in remote sensing and other earth science data poses a challenging problem. In this paper, linear and non-linear statistical learning techniques are used to perform automated feature extraction and unsupervised data analysis of precipitation and remotely sensed vegetation index data sets at global and inter-annual scales. To examine the joint variability of precipitation and vegetation, canonical correlation analysis (CCA) and maximum covariance analysis (MCA) are used. These techniques are designed to isolate coupled modes of different variables in both space and time. Unfortunately, MCA and CCA require fairly strict assumptions concerning the statistical distribution of the input variables. When such assumptions are not met, non-linear techniques can provide additional information that cannot be retrieved using linear techniques. In particular, independent component analysis (ICA) has recently emerged as a novel technique to isolate non-Gaussian signals from multivariate data. While many linear techniques rely on the variance/covariance information contained in a dataset, ICA uses higher order statistical moments to isolate patterns. ICA is particularly powerful for identifying spatial and temporal artifacts that are commonly contained in Earth science data sets and for isolating anomalous events that arise from perturbations in the atmosphere-biosphere system such as droughts and floods associated with El-Niño (and other) events. In this paper, ICA is used to extract information related to the spatial and temporal variability of atmospheric and terrestrial data that is complementary to results from CCA and MCA. Specifically, we apply ICA and CCA to time series of precipitation and normalized difference vegetation index data sets at continental and global scales. Results reveal interesting space-time patterns that are diagnostic of climate-biosphere interactions.
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The Economic Impact of Climate, CO2, and Tropospheric Ozone Effects on Crop Yields in China, the US, and Europe
Authors:
Reilly, J. M.; Felzer, B. S.; Paltsev, S.; Melillo, J. M.; Prinn, R. G.; Wang, C.; Sokolov, A. P.; Wang, X.
Affiliation:
AA(Joint Program on the Science and Policy of Global Change Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States ; jreilly@mit.edu), AB(The Ecosystems Center Marine Biological Laboratory, 7 MBL St., Woods Hole, MA 02543 United States ; bfelzer@mbl.edu), AC(Joint Program on the Science and Policy of Global Change Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States ; paltsev@mit.edu), AD(The Ecosystems Center Marine Biological Laboratory, 7 MBL St., Woods Hole, MA 02543 United States ; jmelillo@mbl.edu), AE(Joint Program on the Science and Policy of Global Change Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States ; rprinn@mit.edu), AF(Joint Program on the Science and Policy of Global Change Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States ; wangc@mit.edu), AG(Joint Program on the Science and Policy of Global Change Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States ; sokolov@mit.edu), AH(Joint Program on the Science and Policy of Global Change Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States ; dulles@mit.edu)
Journal:
American Geophysical Union, Fall Meeting 2004, abstract #B33A-0239
Publication Date:
12/2004
Origin:
AGU
AGU Keywords:
6304 Benefit-cost analysis, 6309 Decision making under uncertainty, 1615 Biogeochemical processes (4805), 0315 Biosphere/atmosphere interactions, 0345 Pollution: urban and regional (0305)
Bibliographic Code:
2004AGUFM.B33A0239R

Abstract

Multiple environmental changes that may occur over the next century will affect crop productivity. Some of these effects are likely to be positive (CO2 fertilization), some negative (tropospheric ozone damage), and some may be either positive or negative (temperature and precipitation). Climate effects may operate in either direction because the direction of change may differ across regions (more precipitation in some areas and less in others) and warming may increase growing season lengths in cold-limited growing areas while acting as a detriment to productivity in areas with already high temperatures. Previous work has shown the effects of these combined environmental changes on carbon sequestration in natural and managed systems, and valued these effects in terms of avoided costs of fossil fuel carbon abatement. The more direct and obvious economic effect, however, is the changes in crop yields implied by these vegetation effects. Here we use the MIT Integrated Global Systems Model (IGSM) to analyze the potential economic impact of changes in crop yields. For this work we have augmented the Emissions Prediction and Policy Analysis (EPPA) model by further disaggregating the agricultural sector. This allows us to simulate economic effects of changes in yield (i.e. the productivity of cropland) on the regional economies of the world, including impacts on agricultural trade. The EPPA model includes multiple channels of market-based adaptation, including input substitution and trade. We are thus able to examine the extent to which market forces contribute toward adaptation and thus modify the initial yield effects. We examine multiple scenarios where tropospheric ozone precursors are controlled or not, and where greenhouse gas emissions are abated or not. This allows us to consider how these policies interact. We focus on China, the US, and Europe which are currently regions with high levels of tropospheric ozone damage. We find significant negative effects of tropospheric ozone on crop yields and the agricultural economy under current conditions. Our results compare favorably with other methods that show damages of the same level. Our future simulations depend highly on whether tropospheric ozone precursors are controlled in the future. While policies exist in countries to limit tropospheric ozone as a local/regional pollutant, a growing problem particularly in the northern latitudes that include our focus regions, will be that background levels of ozone could reach levels such that it will be difficult for any one country to control its ozone levels without similar control efforts in other regions. This preliminary work highlights the importance of these policy interactions, and emphasizes the need for improved modeling of the atmospheric transport of pollutants.
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