Environmental Engineering Reference
In-Depth Information
Climate basics
This topic will not enter into the science of climate change in great depth
- there is a list of recommended topics given in the Resources section,
among them the
Rough Guide to Climate Change
. But in order to relate
climate change to the energy crisis, a few very basic points need to be
recapped.
The sun's rays pass through the Earth's atmosphere and warm the plan-
et. These rays would then escape almost entirely back into outer space,
leaving us freezing at night, or whenever we were out of direct sunshine,
were it not for greenhouse gases (GHGs), which trap some of the infrared
radiation in, acting as a kind of blanket. So the greenhouse effect is a natu-
ral phenomenon, which happens to maintain Earth's surface at around
30˚C warmer than it would otherwise be. This gives Earth a Goldilocks
temperature - not too hot and not too cold. Mars has no GHGs and is
freezing; Venus is a seething mass of GHGs and is boiling.
Most greenhouse gases are products both of the natural ecosystem and
of mankind (thereby giving rise to the ongoing argument over what the
precise human contribution to global warming is). The main GHGs are
water vapour, carbon dioxide, methane and nitrous oxide. Overall, these
greenhouse gases make up a very small part of earth's atmosphere, which
is mainly composed of nitrogen and oxygen, and which interposes no
barrier to heat escaping the planet.
The biggest greenhouse gas by volume is carbon dioxide, and so the
other gases tend to be measured for their greenhouse-warming effect in
terms of carbon dioxide equivalent, or CO
2
e. When they are measured
as a ratio of the whole atmosphere, they come out small - today's level of
CO
2
e is around 435ppm (parts per million), or ppm, of the atmosphere.
But with regard to climate change, small numbers make a big difference.
And this number is increasing: it has already increased significantly dur-
ing the period for which we have records. So the blanket is getting thicker,
and those under it - the Earth and all that dwell on it - are getting hotter.
Carbon dioxide is by far the most voluminous of greenhouse gases,
amounting to 75 percent of them, and the burning of hydrocarbons in
energy production is by far the biggest contributor to it. According to the
2007 report of the Intergovernmental Panel on Climate Change (IPCC)
energy production accounted for nearly two-thirds of global greenhouses
gases in terms of CO
2
e. This figure is a global average and it is impor-
tant to note the considerable difference in the contributions to it from
industrialized and agricultural economies. In the US, energy-related CO
2
