Shipping was estimated
to have emitted 1046 million tonnes of CO2
in 2007, which corresponded to 3.3% of the global emissions during 2007.
was estimated to have emitted 870 million tonnes, or about 2.7% of the global
emissions of CO2
Exhaust gases were the
primary source of emissions from ships. Carbon dioxide was the most important
GHG emitted by ships. Both in terms of quantity and of global warming
potential, other GHG emissions from ships were less important.
· Mid-range emissions
scenarios showed that, by year 2050, in the
absence of policies, ship emissions could grow by 200% to 300%
(compared to the emissions in 2007) as a result of the growth in world trade.
· A significant potential
for reduction of GHG emissions through
technical and operational measures had been identified.
Together, if implemented, these measures could increase efficiency and reduce
the emissions rate by 25% to
75% below the current levels.
Many of these measures appeared to be cost-effective, although non-financial
barriers may discourage their implementation.
A number of policies to
reduce GHG emissions from ships were conceivable. The report analysed options
relevant to the current IMO debate. The report found that market-based measures
were cost-effective policy instruments with a high environmental effectiveness.
Such instruments captured the largest amount of emissions under the scope,
allowed both technical and operational measures in the shipping sector to be
used, and could offset emissions in other sectors. A mandatory limit on the
Energy Efficiency Design Index for new ships was a cost-effective solution that
could provide an incentive to improve the design efficiency of new ships.
However, its environmental effect was limited because it only applied to new
ships and because it only incentivized design improvements and not improvements
Shipping had been shown,
in general, to be an energy-efficient means of transportation compared to other
The emissions of CO2
from shipping lead to positive “radiative forcing” (a metric of climate change)
and to long-lasting global warming. In the shorter term, the global mean radiative
forcing from shipping was negative and implied cooling; however, regional
temperature responses and other manifestations of climate change may
nevertheless occur. In the longer term, emissions from shipping would result in
a warming response as the long-lasting effect of CO2
would overwhelm any shorter-term cooling effects.
If the climate was to be
stabilized at no more than 2°C warming over pre industrial levels by 2100 and
emissions from shipping continue as projected in the scenarios that were given
in the report, then they would constitute between 12% and 18% of the global
emissions in 2050 that would be required to achieve stabilization (by 2100)
with a 50% probability of success.