(The author is a Reuters columnist. The opinions expressed are
By Gerard Wynn
LONDON Oct 23 Both European Union and U.S.
carbon emissions have fallen sharply over the past five years,
but working out whether that will continue requires teasing out
short-term and one-off factors, and pinpointing lasting
Some causes are temporary or one-off: clearly, over the last
several years energy demand was lower as a result of the
financial crisis; while the weather can have a large impact,
including a mild 2011/2012 winter in the United States.
The U.S. shift to natural gas from coal, as a result of the
shale energy revolution, has a few years to play out but will
taper off and so could be seen as a medium-term factor.
Two trends are longer term: first, a shift towards renewable
power, especially in the EU for the rest of this decade, and
also in the United States if costs continue to fall; and second,
a trend towards more energy efficiency.
Continuing, falling emissions have implications for fossil
fuel demand, and where driven by efficiency, for
They may also allow developed countries to offer modest
targets to curb greenhouse gases at long-running U.N.-backed
climate talks, and so keep these ticking over.
The long-term trend for global greenhouse gases - and for
expected climate change - will depend on emerging economies and
how far investment in energy efficiency and low-carbon energy
balance spending in oil and coal.
U.S. carbon emissions reached an 18-year low last year, the
U.S. Energy Information Administration (EIA) government data
body said on Monday, in its report: "U.S. Energy-Related Carbon
Dioxide Emissions, 2012". (Chart 1)
Carbon dioxide (CO2) emissions have fallen in five out of
the last seven years, and are now 12 percent below their highest
level in 2007, suggesting that they may have peaked.
Most of the falls in the past five years were due to slower
economic growth and a switch to natural gas and renewable power
Significantly, last year emissions fell even as the economy
grew strongly, by 2.8 percent, and the biggest single factor was
a decline in energy consumption, rather than a switch from coal
to gas, according to the EIA.
In the European Union, greenhouse gas emissions including
CO2 peaked three decades ago before east European countries
switched to liberalised market economies, crushing their
industrial output as a result.
More recently, emissions were flat until a sharp fall in
2007 as a result of the financial crisis and a shift to
Chart 1: (page 2) goo.gl/yrtCUL
Chart 2: (page 11) goo.gl/yrtCUL
Chart 3: (page 51) goo.gl/NrHkpu
Carbon intensity of energy supply is a measure of the
emissions per unit of energy, and will be much lower in an
economy powered by natural gas rather than coal.
Energy intensity measures the amount of energy consumed per
dollar of economic output, and reflects the efficiency of and
share of heavy industry in the economy.
The main reason for last year's drop in U.S. emissions was a
decline in energy intensity.
Together, falls in energy and carbon intensity offset the
effects of a rising population and higher economic output (GDP).
Energy consumption fell for both short and long-term
The biggest cause was a one-off, a mild winter through March
last year, accounting for half the decline.
The value for heating degree-days (which measures the
average temperature difference below a relatively warm
benchmark) fell 20 percent compared with the decade average.
But there were also efficiency gains.
Grid and generating efficiency reduced electricity system
losses sharply last year (by 4.8 percent).
And more efficient vehicles reduced road transport emissions
even as the number of miles travelled was unchanged.
EIA data show U.S. road transportation energy consumption is
on a firmer downward trend than any other sector (compared with
residential, commercial and industrial). (Chart 2)
In the last five years one of the dominant factors in
falling U.S. CO2 emissions has been the shift from coal in the
electricity supply, whose carbon intensity fell 13 percent from
2007 to 2012.
A shift to natural gas as a result of the shale energy
revolution accounted for about two thirds of a drop in carbon
intensity, and renewable energy the rest, according to the EIA.
Both trends may continue, with renewable power taking over
in the longer term.
In the EU, emissions have fallen faster over the past four
years among installations participating in the EU emissions
trading scheme (ETS), compared with the rest of the economy (by
12 percent compared with 7 percent). (Chart 3)
Sectors including cement, iron and steel were more affected
by the financial crisis than those outside the EU ETS, such as
agriculture and transport.
In addition, a shift to renewable power cut fossil fuel
demand in the energy combustion sector, the European Environment
Agency said two weeks ago.
"Achieving emission (cuts) in the non-ETS sectors appeared
more difficult," it said in its report, "Trends and projections
in Europe 2013".
The trend towards renewable power is certain to continue in
Net power generating capacity will rise by 250 gigawatts
over the next decade, of which 220 GW will be from renewable
sources, according to the European Network of Transmission
System Operators for Electricity.
In the United States, that trend is less sure, but there is
strong impetus towards energy efficiency.
As the EIA said on Monday: "Specific circumstances such as
the very warm first quarter of 2012 and the large increase in
natural gas-fired generation relative to coal contributed to the
significant decline in emissions in 2012. Other factors, such as
improvements in vehicle fuel efficiency and increased use of
renewable generation, however, could play a continuing role in
It should be noted that the EIA has cut its long-term U.S.
CO2 emissions forecast (25 years ahead) in each of its last
three annual energy outlooks.
(Editing by Keiron Henderson)