Michael R. Raupach talks with
ScienceWatch.com and answers a few questions about
this month's Emerging Research Front Paper in the field of
Article: Global and regional drivers of accelerating
Authors: Raupach, MR;Marland, G;Ciais, P;Le Quere, C;Canadell,
JG;Klepper, G;Field, CB
Journal: PROC NAT ACAD SCI USA, 104 (24): 10288-10293 JUN 12
Addresses: Commonwealth Sci & Ind Res Org, Global Carbon
Project, Canberra, ACT 2601, Australia.
Commonwealth Sci & Ind Res Org, Global Carbon Project,
Canberra, ACT 2601, Australia. (addresses have been
Why do you think your paper is highly
This paper made five contributions, each of which contributed to its high
First, it showed that the annual growth rate of CO2 emissions
from fossil fuels accelerated since 2000 to well over 3% per year, a large
increase above the growth rate in the 1990s (just over 1% per year) and
well above the long-term historic growth rate, over two centuries, of just
under 2% per year.
Second, the paper compared observed growth rates in emissions to scenario
predictions made around 2000 in the Special Report on Emissions Scenarios
(SRES) of the Intergovernmental Panel on Climate Change (IPCC), showing
that actual emissions growth rates lie well above average growth rates for
all six SRES scenario families.
Third, the paper showed that the drivers of increasing emissions over the
last several decades were approximately equally partitioned at global scale
between growth in population and growth in per-capita Gross World Product
(GWP), offset by improvement in the carbon intensity of the global
economy—but the recent post-2000 increase in emissions growth rate
was driven mainly by increased growth in GWP.
Fourth, the paper identified a decrease in the rate of improvement in the
carbon intensity of the global economy in the first few years following
2000, which made an additional contribution to the increased emissions
Finally, the paper analyzed the regional contributions to these trends,
showing the dominant roles of developing regions and China in particular.
The paper received significant press comment because of the massive
interest and policy significance of trends in CO2 emissions as
drivers of climate change, and the implications of current trends for the
task of reducing emissions. An acceleration in emissions makes the task of
mitigation that much harder. These factors contributed to its high citation
rate in subsequent papers analyzing the global mitigation challenge.
"A new and fundamental challenge for science (and
society) in this century will be to understand the nature
of these limits, and to identify and follow the pathways in
which humanity can develop which are consistent with the
finite nature of our planet."
This work was an initial contribution to a series of updates of the state
and trends of the global carbon cycle, including both natural and human
factors, by the Global Carbon Project (GCP) of the Earth System
Science Partnership. Companion papers focus on the overall atmospheric
CO2 budget (Canadell, et al., 2007, Le Quere, et
Does it describe a new discovery, methodology, or
synthesis of knowledge?
The paper was among the first to point out the rapid recent acceleration in
human perturbation of the global carbon cycle. It synthesized the human,
economic, and technological drivers of CO2 emissions using basic
metrics: population, GWP (or its domestic equivalent) per person, the
energy intensity of GWP, and the carbon intensity of energy.
The methods were very simple, involving an algebraic identity called the
Kaya identity (Kaya and Yokobori, 1997) which expresses emissions as the
product of these four metrics. The Kaya identity is an algebraic truism,
but nevertheless provides a useful decomposition of emissions drivers in a
form which enables diagnosis of underlying trends. This enables a synthesis
of drivers of CO2 emissions drivers and the responses of the
earth system, a theme initiated in this paper and developed in later work
(Raupach et al., 2008, Canadell et al., 2009).
The resulting synthesis opened a path for a number of subsequent analyses,
which led, in turn, to new evaluations of requirements for climate
Would you summarize the significance of your paper
in layman's terms?
CO2 emissions are rising, faster than most estimates from a few
years ago. Every region is contributing to this. Relative emissions growth
in developing regions is faster than in developed (rich) regions, but both
energy use and CO2 emissions per person in developing regions
are much less than in developed regions.
There are close relationships between wealth, energy use, and
CO2 emissions, which are showing no signs of changing, also
changes in these relationships (particularly the amount of CO2
emitted per dollar of wealth generated) are essential if global wealth
generation is to continue while emissions are reduced to reduce the risks
of adverse impacts from climate change.
How did you become involved in this research and
were any particular problems encountered along the way?
I started my scientific career as a biophysical scientist, working on fluid
mechanics in atmospheric boundary layers and on the exchanges of carbon,
energy, water, and other entities between land surfaces and the atmosphere.
My work was first focused at small scales, such as vegetation canopies and
small areas of land. Searching for interactions in the biophysical world, I
have been drawn to study progressively larger environmental systems
including the global carbon cycle and the interactions between the carbon,
climate, and human societies.
The inclusion of humans is necessary to understand the way Earth's system
works in the present "Anthropocene" epoch, in which human activities are
significantly altering the cycles of carbon, energy, water, and other
entities, with implications for climate and ecosystems everywhere. The
research in this paper and related work with colleagues are steps in this
There have been challenges, before, during, and since the work reported in
First, the work is strongly transdisciplinary and requires a synthesis of
insights from the natural sciences, economics, and the social sciences.
Concepts and worldviews vary widely across this spectrum, as do narratives
and languages. The task of understanding is therefore challenging.
Second, work on carbon-climate-human interactions is subject to high media
interest and scrutiny. This is so because of direct policy implications,
for example for emissions mitigation, and also for deeper reasons
associated with the contrasting demands of economic growth and global
Third, the trends examined in this paper are changing rapidly and the
picture needs regular updating, for example to assess the effects of the
global financial crisis (Le Quere et al., 2009).
Where do you see your research leading in the
Work on carbon-climate-human interactions, for which this paper forms one
quantitative foundation, will merge with work in other disciplines which
contribute to the study of what could be called the ecology of a finite
This is the new ecology confronting humankind in the Anthropocene epoch
where human activities are altering the dynamics of the Earth's system, and
consequently where the natural world imposes limits on human activities
through resource constraints and the finite biogeochemical capacity of the
A new and fundamental challenge for science (and society) in this century
will be to understand the nature of these limits, and to identify and
follow the pathways in which humanity can develop which are consistent with
the finite nature of our planet.
Do you foresee any social or political
implications for your research?
There are profound implications, as indicated in all preceding sections.
Michael R Raupach, Ph.D.
Global Carbon Project
CSIRO Marine and Atmospheric Research
Canadell JG, et al., "Contributions
to accelerating atmospheric CO2 growth from economic activity, carbon
intensity, and efficiency of natural sinks," PNAS
Canadell JG, et al., "Anthropogenic
CO2 emissions in Africa," Biogeosciences 6:468,
Kaya Y, Yokobori K, "Environment, Energy, and
Economy: strategies for sustainability," United Nations University
Press, New York, Paris, 331 pp, 1997.
Le Quere C, et al., "Trends in the
sources and sinks of carbon dioxide," Nature Geoscience
Raupach MR, et al., "Anthropogenic
and biophysical contributions to increasing atmospheric CO2 growth rate
and airborne fraction," Biogeosciences 5:1601-1613,
KEYWORDS: CARBON INTENSITY OF ECONOMY; CARBON INTENSITY OF ENERGY;
EMISSIONS SCENARIOS; FOSSIL FUELS; KAYA IDENTITY; ATMOSPHERIC CO2;