Geoscience Reference
In-Depth Information
attributed solely to global warming). The Intergovernmental Panel on Climate
Change (IPCC), a scienti
c body set up by WMO and UNEP in the same year to
advise the world
s governments on the topic, later reported that twentieth-century
temperature increases were unusually rapid when compared with those for the
previous two millennia. Over the last century, average global temperatures have
risen by 0.3
'
0.6
°
C, and they are projected to pass the critical threshold of 2
°
Cby
-
changes in climate).
64
Left unchecked,
human-induced global warming will result in a whole range of
2100 (the
'
tipping point
'
for
'
dangerous
'
'
natural disasters
'
that include: deserti
cation, droughts, forest
res, species extinctions, sea-level rise,
and a destructive change in weather patterns.
By living off the accumulated energy capital of the past (fossil fuels) instead of
'
(renewable energies), humankind released huge quantities of CO
2
that had been securely locked up underground, profoundly altering the global
carbon cycle. Ice core data from Greenland and Antarctica show conclusively that
atmospheric concentrations of the main
current income
'
CO
2
now far exceed
preindustrial values, up from around 280 to more than 390 parts per million, with
most of this increase coming after 1950 (well above the 350 parts per million mark
that many scientists say is the highest
'
greenhouse gas
'
level for carbon dioxide in the
atmosphere). Concentration levels exceeded the symbolic 400 parts per million
threshold at several Arctic monitoring stations for the
'
safe
'
rst time in 2012.
65
Other
anthropogenic greenhouse gas emissions have also increased substantially since
1750, particularly methane from irrigated agriculture, livestock, decomposing
garbage, gas pipelines and coal mining, as well as nitrous oxide from agricultural
fertilisers, car exhausts and industrial smokestacks. In addition, CFCs and HFCs
account for a small percentage of human-generated warming (see above).
According to the World Resources Institute, in the year 2005 agriculture was
responsible for almost 14 % of greenhouse gas emissions; transport (especially
private automobile use) emitted just over 14 %; industry and industrial processes
produced 19 %; changing land use (primarily deforestation) just over 12 %; while
energy consumption for electricity and heating (particularly in residential and
commercial buildings) generated almost 25 % of the total. Because most humans
now live and work in cities, and the world
'
s urban population will continue to grow
in the future, they are the
'
front lines
'
in the battle to halt dangerous climate
change.
66
At the global level, between 1850 and 2000 the United States, Britain, Germany,
Japan and other industrialised countries accounted for about 75 % of greenhouse
gas emissions. But industrialising countries like China and India
—
with their rapidly
growing populations and booming economies
will drive carbon dioxide build-up
in the atmosphere for decades to come. Effective international policies and
—
64
Weart (
2003
) and Intergovernmental Panel on Climate Change (
2013
).
65
Mosley (
2010
) and World Meteorological Organization (
2013
).
66
Penna (
2010
), World Greenhouse Gas Emissions (
2005
), Worldwatch Institute (
2009
) and UN-
HABITAT (
2008
).
