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Ning
Zeng
Associate Professor
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In the News
Research Opportunities
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My general research interests are in the
field of climate change and climate variability on time scales ranging
from seasonal-interannual to
glacial-interglacial cycles. My approach is to study the Earth system
as a whole, focusing on the interactions among various components, in
particular, the atmosphere, the hydrosphere and the biosphere.
Currently my research covers two different but inter-connected areas:
carbon cycle-climate interaction and the modeling of
atmosphere-land-vegetation-ocean system. I also conduct research in the
technical solutions and policy implications of climate change.
Research
Examples
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 Expansion
of the world's deserts due to vegetation-albedo feedback under global
warming
Many subtropical
regions are expected to become drier due to climate change. This will
lead to reduced vegetation which may in turn amplify the initial
drying. Using a coupled atmosphere-ocean-land model with a dynamic
vegetation component that predicts surface albedo change, here we
simulate the climate change from 1901 to 2099 with CO2 and other
forcings. In a standard IPCC-style simulation, the model simulated an
increase in the world's ‘warm desert’ area of 2.5 million km
squared or 10% at the end of the 21st century. In a more
realistic simulation where the vegetation-albedo feedback was allowed
to interact, the ‘warm desert’ area expands by 8.5 million km2 or 34%.
This occurs mostly as an expansion of the world's major subtropical
deserts such as the Sahara, the Kalahari, the Gobi, and the Great Sandy
Desert. It is suggested that vegetation-albedo feedback should be fully
included in IPCC future climate projections. Zeng
and Yoon (2009)
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 Carbon sequestration via wood burial and
storage (WBS)
To mitigate global
climate change, a portfolio of strategies will be needed to keep the
atmospheric CO2 concentration below a dangerous level. I propose a
carbon sequestration strategy in which certain dead or live trees are
harvested via collection or selective cutting, then buried in trenches
or stowed away in above-ground shelters. The largely anaerobic
condition under a sufficiently thick layer of soil will prevent the
decomposition of the buried wood. Because a large flux of CO2 is
constantly being assimilated into the world’s forests via
photosynthesis, cutting off its return pathway to the atmosphere forms
an effective carbon sink. I estimated that a theoretical
potential for sustainable
long-term
carbon sequestration using WBS is 10 GtC/y, but the
practical potential is likely between 1-5 GtC/y. The cost is lower than
the typical cost for power plant CO2 capture
with geological storage. The technique is low tech, distributed, easy
to monitor, safe, and reversible, thus an attractive option for
large-scale implementation in a world-wide carbon market. Zeng (2008).
See In
the News for media
stories and comments. Further discussion can be found at biocarbonsinks.org.
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 Midlatitude drought and anomalous CO2 growth
A rare drought occurred from 1998 to 2002
across much of the Northern Hemisphere midlatitude regions. Using observational data
and numerical models, we analyze the impact of this event on
terrestrial ecosystem and the global carbon cycle. The biological
productivity in these regions were found to decrease by 0.9 PgC/y or 5% compared to the average of the
previous two decades, in conjunction with significantly reduced
vegetation greenness. The drought led to a land carbon release that is
large enough to significantly modify the canonical tropically dominated
ENSO response. This large CO2 source explains the consecutive
large increase in atmospheric CO2 growth rate of about 2 ppmv/y
in recent years, as well as the anomalous timing of events. Zeng,
Qian, Roedenbeck and Heimann
(2005).
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 Glacial-interglacial
Cycles
Only 21,000 years ago, large parts of the
Northern Hemisphere were covered under giant icesheets. Today, the mystery of the
glacial-interglacial cycles remains unsolved. Apart from important
roles astronomical orbital forcing may play, it is becoming
increasingly clear that CO2-climate interaction is a key component. Zeng
(2003) hypothesized a mechanism in which organic carbon buried
under the icesheets may be a `missing link' in the ice-age
story. Zeng
(2007) further proposed a mechanism where internally
generated quasi-100ky cycles could be triggered by subglacial burial carbon release as large icesheets such as the Laurentide grow long and large enough and the basal
melting ejects burial carbon into the atmosphere, thus starting a
carbon-climate-icesheet feedback that could explain such as the deglaciation at Termination II.
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 Drought
in the Sahel
The Sahel, a
semiarid region in West Africa between the Sahara desert and the Guinea coast
rainforest, has experienced an unprecedented drought in recorded
history since the late 1960s. The drought had a devastating impact on
this ecologically vulnerable region and was a major impetus in the
establishment of the United Nations Convention on Combating
Desertification and Drought. In a perspective article in the journal
Science, Zeng
(2003) explains our current understanding of the problem.
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