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The historic increase in anthropogenic CO2 emissions since
Figure 3. Global Greenhouse Gas Emissions by Gas. Source: IPCC (2014;
https://www.ipcc.ch/report/ar5/wg3/) based on global emissions from
2010. Details about the sources included in these estimates can be found
in the “Contribution of Working Group III to the Fifth Assessment Report
of the Intergovernmental Panel on Climate Change.”
terms, this implies a 40% increase in fossil fuel burning over
those 28 years as a result of the increase in total energy demand.
Petroleum liquids consumption continues to decrease as a per-
centage of the global mix, but in absolute terms is projected to still
increase through 2040, primarily as a transportation fuel as a
function of increased demand in China and India. Natural gas
consumption slightly increases in the mix from 23% to 26%, prin-
cipally as a fuel for electric power generation and for industrial
use. Coal as a percent of total energy has continued to slowly rise
to 28% today, but is projected to flatten out toward 2040 (22%).
Renewable energy resources are projected to grow from 11% of
total global power generation in 2012 to 16% in 2040, which is
more than a doubling of the 2012 generation capacity. Nuclear
power, which emits no direct greenhouse gases, but has serious
public acceptance challenges, is projected to also increase. The
mix of energy sources and their magnitudes that are predicted to
meet current and growing energy demand will greatly influence
the economy, environment, national security, and public health of
the world’s citizens. These projected energy sources needed to
fulfill future energy demand will increase the rate of CO2 emis-
sions. The CO2 emissions from the burning of fossil fuels consti-
tuted 65% of the overall anthropogenic greenhouse emissions in
2010 (Fig. 3, “Fifth Assessment Report” [AR5] of the United
Nations Intergovernmental Panel on Climate Change [IPCC])8.
www.geosociety.org/gsatoday
the late nineteenth century, and the cumulative amount of
anthropogenic CO2 emissions, are illustrated in Figure 4 and
show the dominant contributions from fossil fuel burning.
Human-sourced emissions of CO2 and other greenhouse
gases have strongly impacted those earth processes that regu-
late the terrestrial climate, ecosystems, and seawater composi-
tion (e.g., pH). The IPCC “Climate Change 2014 Synthesis
Report” (p. 8)9 states:
Continued emission of greenhouse gases will cause Position Statement Draft
further warming and long-lasting changes in all com-
ponents of the climate system, increasing the like-
lihood of severe, pervasive and irreversible impacts
for people and ecosystems. Limiting climate change
would require substantial and sustained reductions in
greenhouse gas emissions which, together with adap-
tation, can limit climate change risks.
The United States, together with 173 other nations, signed the
UN Paris Agreement on Climate Change10 on 22 April 2016.
Under the terms of this agreement, the signatories have com-
mitted to reduce their carbon output “as soon as possible” to do
their best to keep global warming “to well below 2 °C.” The
short summary above of CO2 fluxes from the past 100 years and
the associated rise in atmospheric CO2 and projected energy use
for future demand are incompatible with requirements for
reductions in carbon outputs.
THE POLICY CHALLENGE
There is a clear policy rationale and a United Nations man-
date to reduce global carbon and other greenhouse gas emis-
sions in order to mitigate the impact of climate change.
However, forecasts by the United States Energy Information
Agency11, the International Energy Agency12, and industry fore-
casts, such as those published by ExxonMobil13 and BP14, all
indicate a significant increase in fossil fuel consumption
through 2040. The challenge for policy makers and scientific
innovators is to find a way to reduce carbon emissions and
accelerate the transition to renewable energy without adversely
impacting global standards of living.
GSA has recommended in its position paper on climate, that
Strategies for reducing greenhouse‐gas emissions
should be evaluated based on their impacts on climate,
on costs to global and national economies, and on
Figure 4. Global Anthropogenic CO Emissions.
2
Source: “Climate Change 2014 Synthesis Report,”
IPCC 2015, p. 3.
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