Botkin Environmental Science Earth as Living Planet 8th txtbk

20.2 Weather and Climate 431
390
380
370
360
CO 2 (ppm)
350
340
330
320
(a)
310
1960 1970 1980 1990 2000 2010
Year
(b)
FIGURE 20.3 (a) Carbon dioxide concentrations in the
air above Mauna Loa, Hawaii; (b) the NOAA Observatory
on Mauna Loa, where these measurements were made.
(Sources: (a) Encyclopedia of Earth, http://www.eoearth.org/
article/Climate_change; taken from C.D. Keeling and
T.P. Whorf, 2005. “Atmospheric CO 2 records from sites in
the SIO air sampling network,” in Trends: A Compendium of
Data on Global Change. Carbon Dioxide Information Analysis
Center, Oak Ridge National Laboratory, U.S. Department of
Energy, Oak Ridge, TN).
20.2 Weather and Climate
Weather is what’s happening now or over some short time
period—this hour, today, this week—in the atmosphere
near the ground: its temperature, pressure, cloudiness, precipitation,
winds. Climate is the average weather and usually
refers to average weather conditions over long periods,
at least seasons, but more often years or decades. When
we say it’s hot and humid in New York today or raining
in Seattle, we are speaking of weather. When we say Los
Angeles has cool, wet winters and warm, dry summers, we
are referring to the Los Angeles climate.
Since climates are characteristic of certain latitudes
(and other factors that we will discuss later), they are
classified mainly by latitude—tropical, subtropical,
midlatitudinal (continental), sub-Arctic (continental),
and Arctic—but also by wetness/dryness, such as humid
continental, Mediterranean, monsoon, desert, and tropical
wet–dry (Figure 20.4). Recall from the discussion of
biogeography in Chapter 7 that similar climates produce
similar kinds of ecosystems. Therefore, knowing the climate,
we can make pretty good predictions about what
kinds of life we will find there and what kinds could survive
there if introduced.