My recent peer-reviewed publications
Assessment of "Dangerous" Climate Change
and Emissions Pathways (2005)
S.H. Schneider, M.D. Mastrandrea, PNAS 102,
Climate policy decisions driving future greenhouse gas mitigation efforts will strongly influence the success of compliance with Article 2 of the United Nations Framework Convention on Climate Change, avoiding “dangerous anthropogenic interference with the climate system” (DAI). However, success will be measured in very different ways by different stakeholders, suggesting a spectrum of possible definitions for DAI. The likelihood of avoiding a given threshold for DAI is dependent in part upon uncertainties in the climate systemnotably, the range of uncertainty in climate sensitivity. We combine a set of probabilistic global average temperature metrics for DAI with probability distributions of future climate change produced from a combination of several published climate sensitivity distributions and a range of proposed concentration stabilization profiles differing in both stabilization level and approach trajectoryincluding overshoot profiles. These analyses present a “likelihood framework” to differentiate future emissions pathways with regard to their potential for preventing DAI. Our analysis of overshoot profiles in comparison with non-overshoot profiles demonstrates that overshoot of a given stabilization target can significantly increase the likelihood of exceeding “dangerous” climate impact thresholds, even though equilibrium warming in our model is identical for non-overshoot concentration stabilization profiles having the same target.
temperatures induce species changes: Joint attribution
T.L. Root, D.P. MacMynowski, M.D. Mastrandrea,
S.H. Schneider, PNAS 102,
Average global surface-air temperature is increasing.
Contention exists over relative contributions
by natural and anthropogenic forcings. Ecological
studies attribute plant and animal changes to
observed warming. Until now, temperature–species
connections have not been statistically attributed
directly to anthropogenic climatic change. Using
modeled climatic variables and observed species
data, which are independent of thermometer records
and paleoclimatic proxies, we demonstrate statistically
significant "joint attribution," a two-step
linkage: human activities contribute significantly
to temperature changes and human-changed temperatures
are associated with discernible changes in plant
and animal traits. Additionally, our analyses
provide independent testing of grid-box-scale
temperature projections from a general circulation
Integrated: Assessment of "Dangerous"
Climate Change (2004)
M.D. Mastrandrea, S.H. Schneider, Science
Climate policy decisions are being made despite
layers of uncertainty. Such decisions directly
in.uence the potential for "dangerous anthropogenic
interference with the climate system." We
mapped a metric for this concept, based on Intergovernmental
Panel on Climate Change assessment of climate
impacts, onto probability distributions of future
climate change produced from uncertainty in key
parameters of the coupled social-natural system—climate
sensitivity, climate damages, and discount rate.
Analyses with a simple integrated assessment model
found that, under midrange assumptions, endogenously
calculated, optimal climate policy controls can
reduce the probability of dangerous anthropogenic
interference from ~45% under minimal controls
to near zero.
of Climate and Ecosystem Coupling: Abrupt Changes
and Multiple Equilibria (2002)
P.A.T. Higgins, M.D. Mastrandrea, S.H. Schneider,
Philosophical Transactions of the Royal Society
of London Series B-Biological Sciences 357(1421),
Interactions between subunits of the global climate–biosphere
system (e.g. atmosphere, ocean, biosphere and
cryosphere) often lead to behaviour that is not
evident when each subunit is viewed in isolation.
This newly evident behaviour is an emergent property
of the coupled subsystems. Interactions between
thermohaline circulation and climate illustrate
one emergent property of coupling ocean and atmospheric
circulation. The multiple thermohaline circulation
equilibria that result caused abrupt climate changes
in the past and may cause abrupt climate changes
in the future. Similarly, coupling between the
climate system and ecosystem structure and function
produces complex behaviour in certain regions.
Assessment of Abrupt Climate Change (2001)
M.D. Mastrandrea, S.H. Schneider, Climate
Policy 1, 433-449.
One of the most controversial
conclusions to emerge from many of the first generation
of integrated assessment models (IAMs) of climate
policy was the perceived economic optimality of
negligible near-term abatement of greenhouse gases.
Typically, such studies were conducted using smoothly
varying climate change scenarios or impact responses.
Abrupt changes observed in the climatic record
and documented in current models could substantially
alter the stringency of economically optimal IAM
policies. Such abrupt climatic changes—or
consequent impacts—would be less foreseeable
and provide less time to adapt, and thus would
have far greater economic or environmental impacts
than gradual warming.We extend conventional, smooth
IAM analysis by coupling a climate model capable
of one type of abrupt change to a well-established
energy–economy model (DICE).