Environmental Engineering Reference
In-Depth Information
Table 2.1
Main messages of the IPCC 2013 5th Assessment. (IPCC
2013
)
Warming of the climate system is unequivocal, and since the 1950s, many of the observed
changes are unprecedented over decades to millennia
Each of the last three decades has been successively warmer at the Earth's surface than any
preceding decade since 1850
Ocean warming dominates the increase in energy stored in the climate system, accounting for
more than 90 % of the energy accumulated between 1971 and 2010
Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, gla-
ciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere
spring snow cover have continued to decrease in extent
The atmospheric concentrations of CO
2
, methane, and nitrous oxide have increased to levels
unprecedented in at least the last 800,000 years. Human influence has been detected in warm-
ing of the atmosphere and the ocean, in changes in the global water cycle, in reductions in
snow and ice, in global mean sea level rise, and in changes in some climate extremes. It is
extremely likely
that human influence has been the dominant cause of the observed warming
since the mid-Twentieth century
Global surface temperature change for the end of the Twenty-first century is
likely
to exceed
1.5 ºC relative to 1850-1900 for all RCP scenarios except RCP2.6. It is
likely
to exceed 2 ºC
for RCP6.0 and RCP8.5, and
more likely than not
to exceed 2 ºC for RCP4.5. Warming will
continue beyond 2100 under all RCP scenarios except RCP2.6. It is
very likely
that the Arctic
sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow cover
will decrease during the Twenty-first century as global mean surface temperature rises. Global
glacier volume will further decrease
Global mean sea level will continue to rise during the Twenty-first century. Under all RCP
scenarios the rate of sea level rise will
very likely
exceed that observed during 1971-2010 due
to increased ocean warming and increased loss of mass from glaciers and ice sheets
Cumulative emissions of CO
2
largely determine global mean surface warming by the late
Twenty-first century and beyond. Most aspects of climate change will persist for many centu-
ries even if emissions of CO
2
are stopped. This represents a substantial multi-century climate
change commitment created by past, present and future emissions of CO
2
Associated with each of these problems are some common factors; they all result
from the rapid growth in human numbers and activity, in the rapid growth in the
exploitation of resources, and the lack of any balance between consumption and its
consequences. We have been attempting to deal with such pollution problems now
for many years- particularly since the 1950s, and now know a lot about the environ-
mental impacts of different types of emissions, how they spread and may or may
not be degraded by the environment, how to measure and calculate toxic impacts,
and how to mitigate the harmful effects of pollutants. Some of these major problems
are under some degree of control (for instance the ozone layer depletion seems to
have stabilised), but others such as deforestation, desertification and global warm-
ing show no signs of being placed under effective control. Only recently, the IPCC
released the summary for policymakers in its 5th Assessment (IPCC
2013
) which
confirmed that global temperatures are rising as a result of emissions of greenhouse
gases from human activities, that a further rise in temperature of up to 4.8 ºC can be
expected by the end of the century (depending on the degree of success in reducing
emissions), together with a sea level rise of 26-82 cm (Table
2.1
). A critical fact
