Geoscience Reference
In-Depth Information
Climate
is usually defi ned as the statistical average and variability of
temperature, wind, humidity, cloudiness, precipitation, and other
quantities over a period of time ranging from months to thousands of
years.
Climate change
is a change in these statistical properties when
considered over long periods of time. Climate is distinguished from
weather,
which is the realization of the climatic process for a short
period of time. The distinction between weather and climate can be
seen because the climate is what you expect (such as cold winters)
and weather is what you get (as in an occasional blizzard).
In this topic, I generally use the terms “global warming” and “climate
change” interchangeably. Accuracy would require a long and awkward
phrase such as “the impacts of rising CO
2
and other related gases and fac-
tors.” The term “climate change” is perhaps closer because the issues in-
clude much more than warming—for example, sea-level rise, droughts,
increased storm intensity, and health impacts. But even climate change
does not capture the impact of ocean carbonization. Some have proposed
“global change,” but that term is hopelessly vague. So I just use the two
terms—global warming and climate change—with the understanding
that these words represent a complex set of forces that are under way as a
result of the buildup of CO
2
and other greenhouse gases.
I generally use the centigrade (°C) scale as that is the standard scien-
tifi c convention. Americans usually hear about the Fahrenheit scale (°F).
As a rough guide, you can multiply any °C change by 2 to get the °F
change. If you want to be absolutely accurate, you should multiply by 9/5.
FROM EMISSIONS TO CONCENTRATIONS
Chapter 3 analyzed the emissions of CO
2
, past and future. These emis-
sions are not themselves the source of concern. If they were to quickly
disappear or to be transformed into some innocuous rock, this topic
would not need to be written, and people could worry about other issues.
It is the concentrations of CO
2
and other GHGs in the atmosphere,
not emissions, that are the concern of scientists. So there is an inter-
mediate step from emissions to climate change in Chapter 4—the link
between emissions and concentrations.
