冲澡水土保持专业英语

2021年1月20日发(作者：wald)
W2

Greenhouse gases and global warming

Key note

Carbon dioxide concentration in the atmosphere

Carbon dioxide(CO
2
) is the main vehicle of carbon flux between atmosphere, oceans and biota.
Fossil fuels(coal,oil and natural gas) present in the atmosphere lay dormant until recent centuries.
The concentration of CO
2
in the atmosphere has increased from about 280 parts per million(ppm)
in 1750 to about 350 ppm in 1990 and is still rising , with the main reason for the increase being
the
combustion
of
fossil
fuels.
Estimates
of
future
CO
2
emissions,
and
the
combustion
to
be
expected in the atmosphere vary, but it appears likely that the concentration will rise to a mean
about 500 ppm by the year 2050.
The greenhouse effect

The
greenhouse
effect
is
a
theory
which
proposes
that
pollution
by
common
anthropogenic(d
by
humans)pollutants
such
as
CO
2

and
methane
may
lead
to
an
increased global temperature. Over the last century , CO
2
concentrations have risen and global air
temperatures
have
increased
by
0.4-0.7
℃
,
which
supports
this
theory .
The
atmosphere
formed
around
the
earth
insulates
the
planet
from
full
effects
of
heats
loss
by
trapping
heat
in
the
atmosphere
using
greenhouse
gases
,which
include
water
vapor
as
well
as
CO
2

and
other
anthropogenic pollutants . Doubling of the atmospheric CO
2
concentration from its present level is
predicted to lead to a further warming of around 3.5
℃
.
Related topics

Solar radiation and climate(C1)



Ozone depletion(W3)



Air, water and soil pollutants(W1)

Carbon dioxide concentrations in the atmosphere

Photosynthesis and respiration are the two opposing processes driving the global carbon cycle. It
is
predominantly
a
gaseous
cycle,
with
CO
2

as
the
main
vehicle
of
flux
between
atmosphere
,
oceans
and
ically,
the
lithosphere
played
only
a
minor
role;
fossil
fuels(coal,oil
and
natural gas) lay dormant until recent centuries. The concentration of CO
2
in the atmosphere has
increased from about 280(ppm) in 1750 to about 350 ppm in 1990 and is still rising. Since 1958
the
atmosphere
CO
2
concentration
has
risen
from
315
ppm
to
350
ppm
in
1990(Fig.1).
The
principal
cause
of
the
increase
in
atmospheric
CO
2

in
recent
years
has
been
the
combustion
of
fossil fuels, which in 1990 released about 5.5
×
10
9
tons of carbon into the atmosphere.

The
exploitation
of
rain
forest
has
also
caused
a
significant
release
of
CO
2
.
The
burning
that
follows
most
forest
clearance
quickly
converts
some
of
the
vegetation
to
CO
2
,
while
decomposition of the remaining vegetation releases CO
2
over a longer period. If forests have been
cleared
to
provide
for
permanent
agriculture,
the
carbon
content
of
the
soil
is
reduced
through
decomposition of soil organic matter and/or by erosion. In total it is estimated that about 1.0
×
10
9

tons
year
-1
of
carbon
released
through
changes
in
tropic
land
use .
The
total
amount
of
carbon
released each year to the atmosphere as a result of man's activities around 6.5
×
10
9
tons compared