Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 117
Page 117
14
The Climate Record
Temperature
The clearest signal of an enhanced greenhouse effect, or
greenhouse warming, that is projected by climate models is a
widespread and substantial increase of surface temperature,
especially over continental areas. For this reason, special
attention has been given to the observed temporal and spatial
variations of land surface temperatures (typically measured 1 to 2
m (3.3 to 6.6 feet) above ground level) and sea surface
temperatures (typically measured in the layer from the surface to
several meters below the ocean's surface). Estimates of global
temperature change are credible only for measurements that have
been taken since the late nineteenth century. Earlier temperature
data are available, but their spatial distribution and their
sparseness seriously compromise the attempts to infer global
averages. Additional difficulties arise because measurements were
not taken with an eye to the small and gradual global average
changes that are characteristic of climate change. This problem is
exacerbated when regional changes are at issue simply because the
statistical amelioration of offsetting bias is not very helpful
when the data are sparse.
The most comprehensive assessment of the instrumental record of
surface temperature has recently been completed by the
Intergovernmental Panel on Climate Change (1990). A significant
warming has been observed since the late nineteenth century.
Uncertainties underlie the interpretation of the data, but there is
consensus that the actual rise probably lies within the range of
0.3° to 0.6°C (0.5° to 1.1°F) (see Figure 14.1).
Qualitatively, an inference of global warming is supported by
several independent sources of information: (1) land and sea
surface temperatures are independently measured, and both depict
significant warming (Figure 14.2), (2) the collective
OCR for page 118
Page 118
FIGURE 14.1 Combined land air and sea surface
temperature relative to 1951 to 1980
average temperatures. Land air temperatures are typically measured
1 to 2 m above
ground level. Sea surface temperatures are typically measured in
the layer from the ocean's surface
to several meters below. Smoothed curves are 11-year bimodal
filters with the first and
last 5 years drawn by projecting the endpoints of the series.
SOURCES: Land air
temperatures are updated from Jones et al.(1986a,b), and sea
surface
temperatures are from Farmer et al. (1989).
behavior of many glaciers is likely to be sensitive to
large-scale temperature variations, and many mountain glaciers have
retreated since the end of the nineteenth century, some of them
markedly, and (3) estimates of sea level variations over the past
century indicate a general rise in sea level that is qualitatively
consistent with the global increase of surface temperature.
OCR for page 119
Page 119
FIGURE 14.2 IPCC global sea surface (solid),
night marine air (dashed), and land air (line-dots)
temperature anomalies, relative to 1951 to 1980. Smoothed curves
are 11-year bimodal filters
with the first and last 5 years drawn by projecting the endpoints
of the series.
SOURCES: Sea
surface temperatures are averages from Farmer et al.(1989) and the
U.K.
Meteorological Office. Night marine air temperatures are from the
U.K.Meteorological Office.
Land temperatures are equally weighted averages of data from Jones
et al. (1986a,b), Hansen
and Lebedeff (1988), and Vinnikov et al.(1990).
Uncertainties in the Record
Despite the fact that there is virtually unanimous agreement
that global temperatures have increased since the nineteenth
century, the exact magnitude is still somewhat uncertain for a
variety of reasons. For land-based surface temperatures, these
uncertainties arise for the following reasons:
• Station locations have changed and thereby have
introduced uncertainties into the interpretation of the temporal
record.
• Many stations are located in and around cities that have
increased in size and population density, thereby introducing a
systematic increase in the local temperature record that is
unrelated to global climate change.
Additional uncertainties for both land and sea surface
temperatures include the following:
• The spatial coverage of the data is neither globally
comprehensive nor optimally sited, and the degree of coverage
changes over time.
• Changes have occurred in instruments, exposures of
thermometers, observing schedules, observing practices, and other
factors including land use, thus introducing artificial changes in
the temperature record, sometimes of a systematic nature.
Most of these uncertainties have been assessed in various
studies, as reviewed by Karl et al. (1989). Arguably the most
serious of these uncertainties
OCR for page 120
Page 120
are the changes in observation practices related to sea surface
temperature measurements. Changes in these practices have resulted
in systematic biases as large as the observed warming depicted in
Figure 14.1. The sea surface temperature has been measured by the
use of various types of buckets lowered from the ship's deck, and
more recently by the water flowing to the ship's engine intake.
Various researchers have addressed this problem (Farmer et al.,
1989; Bottomley et al., 1990; Folland and Parker, 1990).
Differences in the assumptions, in approaches used to correct for
these systematic biases, and in the input data lead to an
uncertainty associated with the warming since the nineteenth
century of about ±0.1°C (±0.18°F).
Urbanization effects in the thermometric record have now been
assessed by various researchers for many, but by no means all,
regions of the globe. Studies by Hansen and Lebedeff (1987, 1988),
Balling and Idso (1989), Karl et al. (1988), Karl and Jones (1989,
1990), and Jones et al. (1989, 1990) suggest that the bias
introduced into the observed warming of the land surface varies
from a high of 0.1° to 0.2°C (0.18° to 0.36°F) over
the United States down to negligible amounts over western areas of
the former USSR and easter China. Jones et al. (1990) estimated
that the apparent global warming of the land surface record
attributable to urbanization is no more than about 0.05°C
(0.09°F). When one considers that the land covers about
three-tenths of the global surface area, the bias due to
urbanization in the global temperature record is most likely to be
at least an order of magnitude smaller than observed warming. A
more definitive statement awaits more comprehensive studies.
Another important consideration in the compilation of
hemispheric and global temperatures is the spatial coverage of
observations over both land and sea. The spatial coverage of the
observations since the nineteenth century has not been uniform in
time or space. For example, ships of opportunity, which provide the
greatest portion of the sea surface measurements, have followed
preferred navigational routes and consequently leave vast portions
of the ocean inadequately sampled. The effect of spatial sampling
inadequacies has been addressed for the land areas by Jones et al.
(1986a,b) and for the ocean areas by Bottomley et al. (1990) and
Folland and Colman (1988). These analyses suggest that changes in
spatial coverage have not had a serious impact on our ability to
discern changes in the global thermometric record. Because of the
large-scale coherence of multi-decadal climate variations,
especially over the oceans, the sampling problem probably adds less
than 0.1°C (0.18°F) uncertainty to the observed warming, as
depicted in Figure 14.1.
Other biases and inhomogeneities in the temperature record have
been directly assessed only on a regional basis, but indirectly
assessed on a global basis. These include changes in observing
schedules, types of instrument shelters used, and station
relocations in the land-based record. Studies
OCR for page 121
Page 121
by Jones et al. (1986a), Karl and Jones (1990), and Parker
(1990) indicate that, although these types of biases may be quite
significant on a regional scale, for hemispheric and global
averages many of the biases and inhomogeneities tend to cancel.
Considering all the uncertainties in the thermometric climate
record, it would be most appropriate to provide a range of most
likely rates of warming from the latter half of the nineteenth
century to the present. This range, as given by the IPCC
(Intergovernmental Panel on Climate Change, 1990), is of the order
0.3° to 0.6°C (0.5° to 1.1°F). That is, the warming
rate, calculated either as a trend from the 1860 to 1890 era to the
present, or as the difference in temperature for the 1980s minus
the value for the period from the 1860s to the 1890s, is between
0.3° and 0.6°C (0.5° and 1.1°F). At this time,
there are no compelling reasons to dispute the range given. Whether
this warming is related to the greenhouse effect is discussed in
the next section.
Spatial and Temporal
Characteristics
The increase in temperature has occurred somewhat differently in
the northern hemisphere than in the southern hemisphere (Figure
14.1). A rapid increase in temperature occurred in the northern
hemisphere during the 1920s into the 1930s, whereas the increase in
the southern hemisphere during this time was much more gradual. A
substantial portion of the global warming observed since the latter
half of the nineteenth century occurred prior to World War II. The
past half-century is characterized by relatively constant global
mean temperatures except for the 0.1° to 0.2°C (0.18°
to 0.36°F) steplike temperature increase that occurred around
1980. This relatively constant global mean temperature is
characteristic of both hemispheres, but with some evidence of
cooling in the northern hemisphere during the 1960s and 1970s. Some
analyses suggest that the northern hemisphere cooling may be
related to sulfate aerosol emissions (e.g., Wigley, 1991). The
warmth of the 1980s has continued into the 1990s.
The global mean ocean temperature and the surface air
temperature of the southern hemisphere (which is predominantly
water) have risen at a rate comparable to that over land (Figure
14.3a). This is not altogether consistent with time-dependent GCM
simulations with enhanced greenhouse gases. These simulations
generally have a slower rate of temperature increase in the
southern hemisphere and over the oceans, especially the circumpolar
oceans, than in the northern hemisphere (Stouffer et al., 1989;
Washington and Meehl, 1989; Manabe et al., 1990). At this time,
however, the large variability in transient climate simulations and
the difficulty in linking these simulations to the appropriate part
of the climate record prevent unequivocal statements about the
consistency or lack thereof between simulations and the climate
record.
OCR for page 122
Page 122
FIGURE 14.3 (a) IPCC differences between land
and sea surface temperature anomalies
(relative to 1951 to 1980) for the northern hemisphere, 1861 to
1989. (b) Annual
anomalies of zonal average temperature over the ocean. Shaded
areas represent conditions
cooler than the 1945 to 1986 zonal average. (c) Same as (b) except
for land only. (d) Same
as (b) except for land and ocean combined.
SOURCES: Land air
temperatures are updated from Jones (1988). Sea surface
temperatures are averages of the U.K. Meteorological Office and
Farmer et al. (1989).
OCR for page 123
Page 123
FIGURE 14.3 Continued
OCR for page 124
OCR for page 125
OCR for page 126
OCR for page 127
OCR for page 128
OCR for page 129
OCR for page 130
OCR for page 131
OCR for page 132
OCR for page 133
OCR for page 134
Representative terms from entire chapter:
surface temperature
Page 124
Climate models that have been allowed to reach equilibrium with
2 (sometimes 4) times preindustrial concentrations of CO2 project temperature increases in polar
and high latitudes that would be larger than those at low
latitudes. These are related to the extent of land and sea ice and
other factors. Currently, the largest variations in temperature are
found at high latitudes (Figure 14.3). Changes of temperature as
depicted in Figure 14.3d are over too short a period to reflect
systematic changes in the warmth of the equatorial region relative
to polar regions.
Because of the high natural variability of climate, it is
pertinent to ask when we might expect to unequivocally link the
greenhouse effect to the observed climate variations. Two recent
studies address this question on a regional basis assuming validity
of the IPCC projections. Briffa et al. (1990) used the variability
in a 1400-year reconstructed tree-ring density record to address
this question for Fennoscandia. Briffa et al. (1990) indicated that
because of low-frequency climate variability, it will be decades
before we will be able to confirm or contradict the IPCC
projections in the Fennoscandia region. Karl et al. (1990) used the
central North American observed climate record to determine when
the IPCC projections could either be confirmed or contradicted for
that region. Karl et al. (1990) indicated that if the models with a
4°C (7.2°F) (i.e., high) climate sensitivity to enhanced
greenhouse gases are used, we probably should have already detected
significant warming in this region, but for the low-sensitivity
model (2°C (3.6°F) warming in central North America from
preindustrial times to 2030) we probably will not be able to detect
statistically significant warming rates for at least another two
decades. Thus, at this time, no credible assertion that the recent
temperature rise is the result of changes in greenhouse gas forcing
is justified.
Changes in Extremes
Long-term changes and variations of extreme maximum and minimum
temperatures have recently been assessed over three large land
areas. These include the United States, the former USSR, and the
People's Republic of China (PRC). Until now, the dearth of analyses
about extremes has been due to the difficulty in transferring these
observations to computer-compatible media. Recent work by Karl et
al. (1991) indicates that the warming in the United States and the
former USSR over the past several decades is solely due to an
increase of nighttime temperatures (Figure 14.4). Furthermore, the
range of extreme temperatures, especially during summer in the
United States and the former USSR, has also decreased (Karl et al.,
1991). Climate models with enhanced greenhouse gases cannot yet
reliably predict the expected change in extremes. It has been
demonstrated that in the
Page 125
United States the rise in the minimum temperature is at least
partially related to increases in cloud cover (Plantico et al.,
1990).
The differential change of the maximum and minimum temperatures
points out the limited amount of information that can be derived
from changes in the mean and how cloud changes may already be
influencing the observed climate record. Thus long-term consistent
ancillary climatic data (such as vertical and horizontal cloud
distribution) are needed in addition to basic temperature data.
Temperatures Aloft
Temperatures aloft have been measured by instruments carried by
balloons and, most recently, by satellite instruments. Global
records have been constructed for various atmospheric layers by
Angell (1988) back to 1957 using balloon or radiosonde information.
Spencer and Christy (1990) have used the space-based Microwave
Sounding Unit (MSU) data to reconstruct global temperature
variations back to 1979 for tropospheric layer temperatures. The
global mean annual temperatures of MSU data are in excellent
agreement (r2 = 0.95) with
the mid-tropospheric temperatures as calculated by Angell (1988).
This comparison is consistent with the less complete spatial
coverage of the data used by Angell (1988), at least for the past
decade.
Climate models with enhanced greenhouse gases project not only
increased temperatures in the troposphere but also decreased
temperatures in the stratosphere (in addition to the decrease
accompanying depletion of stratospheric ozone). Mid-tropospheric
temperatures since 1957 have shown an increase, and stratospheric
temperatures a decrease. In addition, however, temperatures in the
higher troposphere have also decreased, a circumstance that is not
projected by climate models that include CO2 changes only. Furthermore, the decrease
in stratospheric temperatures is primarily found in the southern
hemisphere in and around Antarctica, probably related to the
decrease in stratospheric ozone (Trenberth and Olson, 1989).
Finally, a recent study has pointed out the danger of
overinterpreting mid-tropospheric temperature trends based on short
time series. Whereas previous studies showed current temperature
increases compared to 1957, Elms et al. (1990) extended their
examination back to 1950 and found little or no temperature change
from that date.
Precipitation
Unlike model projections of changes in temperature with an
enhanced greenhouse effect, or greenhouse warming, regional and
geographic patterns
Page 126
FIGURE 14.4 Changes in the annual mean daily
maximum and minimum temperature
in the United States (left panels) and the former USSR (right
panels). A nine-point
bimodal filter was used to smooth the data.
SOURCE: Reprinted
courtesy of T. R. Karl.
Page 127
FIGURE 14.4 Continued
Page 128
of precipitation change are not nearly as consistent from one
model to the next. Nonetheless, some general characteristics are
evident, such as (1) a global increase in precipitation; (2)
significantly more precipitation at high latitudes and in the
tropics throughout the year and during winter at mid-latitudes, but
little change over the subtropics; and, of particular interest for
the United States, (3) a suggestion in several but not all of the
models of reduced summer and enhanced winter precipitation in the
interior of North America.
The instrumental record related to global changes of
precipitation is much more difficult to assess than the
thermometric record. Nonetheless, there have been several
large-scale analyses of precipitation variations over the northern
and southern hemisphere land masses (Bradley et al., 1987;
Diaz et al., 1989; Vinnikov et al., 1990), which have demonstrated
that during the past several decades precipitation has tended to
increase in northern hemisphere mid-latitudes and in the southern
hemisphere. The increase in the northern hemisphere is
predominantly due to an increase over the former USSR, and to a
smaller degree over the United States (Figure 14.5). A decrease in
precipitation over the past few decades has been noted over the
subropics of the northern hemisphere. This is primarily due to the
decrease observed over the Sahel, and partially due to lower
monsoonal rainfall over India. Changes of precipitation over
oceanic regions are largely unknown.
Overall, the land data do suggest a general increase in
land-based precipitation over the past few decades. This may be
consistent with model projections, but quantitative inferences are
difficult to defend. Precipitation varies in space and time much
more than does temperature. A much higher density of stations is
needed to calculate precipitation variations than is required for
temperature. Such high-density data do exist, but they are not
exchanged on an international basis. Furthermore, the efficiency of
the collection of precipitation (both frozen and liquid) by
different rain gauges varies with wind speed and raindrop size. In
many countries, collection efficiency has tended to increase as
operational practices have improved, often in poorly documented
ways, possibly lending to an artificial upward trend in some
regions (Groisman et al., 1991). Sevruk (1982) and Folland (1988)
discuss the causes of the collection error. Despite these
potentially serious biases, many of the important variations
apparent in the precipitation records are evident in hydrological
data, such as changes in lake levels and stream flow and the severe
desiccation of the Sahel.
In the recent IPCC scientific assessment (Intergovernmental
Panel on Climate Change, 1990) and summary report (Jäger and
Ferguson, 1991), several scenarios of changes in North American
precipitation were given based on various models (a decrease in
summer precipitation up to 10 percent and an increase in winter
precipitation up to 15 percent). Karl et al. (1990) show that even
if these projections were correct, it would take decades
Page 129
before we could detect such changes. On the other hand, at the
present time there is neither any evidence for increased aridity in
the United States nor any systematic increase in winter to summer
precipitation ratios (Karl et al., 1990). Furthermore, if the rate
of change for the increase of winter to summer precipitation ratios
suggested by the modeling reported by the IPCC were correct, we
probably should have already detected such changes. All in all, the
record cannot support persuasively a quantitative relationship
between the greenhouse gas accumulation and the precipitation
variations of the last century.
Improving our Climate
Observations
At the present time the only reliable methods of measuring daily
temperature and precipitation at the surface are the in situ
measurements made at the thousands of weather stations around the
world. Unfortunately, few (if any) of the stations make
measurements for the purposes of detecting and monitoring climate
change. The primary functions are to serve the needs of weather
prediction and the weather assessment community. Such activities
are quite distinct from monitoring climate change. The World
Meteorological Organization is beginning to take some steps to
rectify this situation (e.g., the Global Climate Baseline Data Base
and the Climate Change Detection Project), but without strong
support from national weather services, which currently do not
operate their stations for the purpose of monitoring climate
change, these programs will not succeed. That support will become
important as new observing techniques and programs are brought
on-line.
In the United States the National Oceanic and Atmospheric
Administration (NOAA) is responsible for observing the nation's
daily weather. NOAA operated 8,640 stations that monitored daily
precipitation in 1967, but by 1988 the total had dropped to about
7,000. The totals for temperature monitoring dropped from 5,920
stations in 1967 to about 5,200 in 1988. The importance of these
temperature and precipitation observation stations is critical,
because many of them are located in rural environments, free from
the urban heat island effect. This decrease in number has occurred
during times of increased interest in global climate change. A
dense network of stations is required to monitor the regional
details of climate change, especially for precipitation, and to
implement corrections for biases in the climate record. Other U.S.
agencies also monitor the daily weather for a variety of purposes.
At present, there is no central collection agency that can make
available the full suite of weather observations made by the
various U.S. agencies. This unfortunate situation should be
rectified.
Furthermore, potentially new sources of bias have been and
continue to be introduced into the NOAA network without an adequate
means of assessing
Page 130
FIGURE 14.5 Changes in the annual total
precipitation averaged over the contiguous United States
from (a) Climate Division data, which make use of all stations
with temperature and precipitation
measurements (about 6,000 in recent decades), (b) the U.S.
Historical Climate Network, which
has a fixed set of higher-quality stations throughout the
twentieth century, and (c) adjusted precipitation
measurements over the former USSR based on optimal averaging
methods (Groisman et al., 1991).
Page 131
FIGURE 14.5
these biases. For example, a new thermometric instrument was
installed at about half of the stations in the U.S. cooperative
network between 1984 and 1988. At the present time, the bias
introduced by this new instrument is significant with respect to
interpreting U.S. climate change (Quayle et al., 1991).
Side-by-side measurements of new and old measurement systems were
not required. Such tests for a period of at least one year (the
annual cycle) should be considered essential for climate
monitoring. In addition, this instrument did not have the ability
to retain maximum and minimum temperatures on a
midnight-to-midnight basis. As a result, the opportunity was lost
to eliminate many of the thermometric biases that had existed in
the network because observers were understandably unwilling to
remain with a fixed observation schedule over the decades.
The United States operates one of the most comprehensive
networks in the world, but it needs to be improved in several
ways:
1. Steps should be taken to ensure the continued operation
of long-term stations in rural areas.
2. The surface observations of climate-related elements by
various departments (e.g., Commerce, Interior, Agriculture, and
Defense) should be integrated and made available for more
comprehensive analyses.
3. Data should be assessed for biases as well as random
errors on a routine basis, and corrections should accompany the
disseminated data.
4. Electronic transfer of weather station observations
should become routine operating procedure.
5. NOAA will soon be implementing an Automated Surface
Observing System (ASOS). The methods of making observations and the
locations of many observing stations are scheduled to undergo
significant change. NOAA should provide for side-by-side operation
of the new and old instruments long enough to ensure that
interpretation uncertainty is not introduced.
Page 132
References
Angell, J. K. 1988. Variations and trends in tropospheric and
stratospheric global temperatures, 1958–87. Journal of
Climate 1:1296–1313.
Balling, R. C., Jr., and S. B. Idso. 1989. Historical
temperature trends in the United States and the effect of urban
population growth. Journal of Geophysical Research
94:3359–3363.
Bottomley, M., C. K. Folland, J. Hsiung, R. E. Newell, and D. E.
Parker. 1990. Global Ocean Surface Temperature Atlas (GOSTA). Joint
Meteorological Office/Massachusetts Institute of Technology
Project. London: U.K. Department of Energy and Environment.
Bradley, R. S., H. F. Diaz, J. K. Eischeid, P. D. Jones, P. M.
Kelly, and C. M. Goodess. 1987. Precipitation fluctuations over
northern hemisphere land areas since the mid-19th century. Science
237:171–175.
Briffa, K. R., T. S. Bartholin, D. Eckstein, P. D. Jones, W.
Karlen, F. H. Schweingruber, and P. Zetterberg. 1990. A 1400-year
tree-ring record of summer temperatures in Fennoscandia. Nature
346:434–439.
Diaz, H. F., R. S. Bradley, and J. K. Eischeid. 1989.
Precipitation fluctuations over global land areas since the late
1800s. Journal of Geophysical Research 94;1195–1210.
Elms, J. D., T. R. Karl, A. McNab, and J. Christy. 1990. A
preliminary analysis of the covariation of surface and
midtropospheric temperatures. Proposed for the 41st International
Astronautical Congress, Dresden, Germany. American Institute of
Aeronautics and Astronautics, Washington, D.C.
Farmer, G., T. M. L. Wigley, P. D. Jones, and M. Salmon. 1989.
Documenting and explaining recent global-mean temperature changes.
Norwich, U.K.: Climatic Research Unit.
Folland, C. K. 1988. Numerical models of the raingauge exposure
problem, field experiments and an improved collector design.
Quarterly Journal of the Royal Meteorological Society
114:1485–1516.
Folland, C. K., and A. W. Colman. 1988. An interim analysis of
the leading covariance eigenvectors of worldwide sea surface
temperature anomalies for 1951–80. LRFC 20. U.K.: U.K.
Meteorological Office.
Folland, C. K., and D. E. Parker. 1990. Observed variations of
sea surface temperature. In Proceedings of the NATO Advanced
Research Workshop on Climate-Ocean Interaction. Norwell, Mass.:
Kluwer Academic Press.
Groisman, P. Ya., V. V. Koknaeva, T. A. Belokrylova, and T. R.
Karl. 1991. Overcoming biases of precipitation measurement: A
history of the USSR experience. Bulletin of the American
Meteorological Society 72(11):1725–1733.
Hansen, J., and S. Lebedeff. 1987. Global trends of measured
surface air temperature. Journal of Geophysical Research
92:13345–13372.
Hansen, J., and S. Lebedeff. 1988. Global surface temperatures:
Update through 1987. Geophysical Research Letters
15:323–326.
Page 133
Intergovernmental Panel on Climate Change. 1990. Climate Change:
The IPCC Scientific Assessment, J. T. Houghton, G. J. Jenkins, and
J. J. Ephraums, eds. New York: Cambridge University Press.
Jäger, J., and H. L. Ferguson, eds. 1991. Climate Change:
Science, Impacts and Policy: Proceedings of the Second World
Climate Conference. New York: Cambridge University Press.
Jones, P. D. 1988. Hemispheric surface air temperature
variations: Recent trends and an update to 1987. Journal of Climate
1:654–660.
Jones, P. D., S. C. B. Raper, R. S. Bradley, H. F. Diaz, P. M.
Kelly, and T. M. L. Wigley. 1986a. Northern hemisphere surface air
temperature variations, 1851–1984. Journal of Climate and
Applied Meteorology 25:161–179.
Jones, P. D., S. C. B. Raper, R. S. Bradley, H. F. Diaz, P. M.
Kelly, and T. M. L. Wigley. 1986b. Southern hemisphere surface air
temperature variations, 1851–1984. Journal of Climate and
Applied Meteorology 25:1213–1230.
Jones, P. D., P. M. Kelly, G. B. Goodess, and T. R. Karl. 1989.
The effect of urban warming on the northern hemisphere temperature
average. Journal of Climate 2:285–290.
Jones, P. D., P. Ya. Groisman, M. Coughlan, N. Plummer, W-C.
Wang, and T. R. Karl. 1990. Assessment of urbanization effects in
time-series of surface air-temperature over land. Nature
347:169–172.
Karl, T. R., and P. D. Jones. 1989. Urban bias in area-averaged
surface temperature trends. Bulletin of the American Meteorological
Society 70:265–270.
Karl, T. R., and P. D. Jones. 1990. Reply to comments on ''Urban
bias in area-averaged surface temperature trends." Bulletin of the
American Meteorological Society 71:572–574.
Karl, T. R., H. F. Diaz, and G. Kukla. 1988. Urbanization: Its
detection in the United States' climate record. Journal of Climate
1:1099–1123.
Karl, T. R., D. Tarpley, R. G. Quayle, H. F. Diaz, D. A.
Robinson, and R. S. Bradley. 1989. The recent climate record: What
it can and cannot tell us. Reviews of Geophysics
27:405–430.
Karl, T. R., R. R. Heim, Jr., and R. G. Quayle. 1990. The
greenhouse effect in central North America: If not now, when?
Science 251:1058–1061.
Karl, T. R., G. Kukla, V. N. Raguvayev, M. Changeny, R. G.
Quayle, R. R. Heim, Jr., and D. Fasterling. 1991. Global warming:
Evidence for asymmetric diurnal trends. Geophysical Research
Letters 18(12):2253–2256.
Manabe, S., K. Bryan, and M. J. Spelman. 1990. Transient
response of a global ocean-atmosphere model to a doubling of
atmospheric carbon dioxide. Journal of Physical Oceanography
20:722–749.
Parker, D. E. 1990. Effects of changing exposure of thermometers
at land stations. In Climate Change: The IPCC Scientific
Assessment, J. T. Houghton, G. J. Jenkins, and J. J. Ephraums, eds.
New York: Cambridge University Press.
Plantico, M., T. R. Karl, G. Kukla, and J. Gavin. 1990. Are
recent changes of temperature, cloudiness, sunshine, and
precipitation across the United States related to rising levels of
anthropogenic greenhouse gases? Journal of Geophysical Research
95:16617–16637.
Quayle, R. G., D. R. Easterly, T. R. Karl, and P. J. Young.
1991. Effects of recent thermometer changes in the cooperative
station network. Bulletin of the American Meteorological Society
72(11):1718–1723.
Page 134
Sevruk, B. 1982. Methods of Correcting for Systematic Error in
Point Precipitation measurement for Operation Use. Operational
Hydrology Report No. 21. Geneva: World Meteorological
Organization.
Spencer, R. W., and J. R. Christy. 1990. Precise monitoring of
global temperature trends from satellites. Science
247:1558–1562.
Stouffer, R. J., S. manabe, and K. Bryan. 1989. Interhemispheric
asymmetry in climate responses to a gradual increase of atmospheric
CO2. Nature 342:660–662.
Trenberth, K. E., and J. G. Olson. 1989. Temperature trends at
the South Pole and McMurdo Sound. Journal of Climate
2:1196–1206.
Vinnikov, K. Va., P. Ya. Groisman, and K. M. Lugina. 1990. The
empirical data on modern global climate changes (temperature and
precipitation). Journal of Climate 3:662–677.
Washington, W. M., and G. A. Meehl. 1989. Climate sensitivity
due to increased CO2: Experiments
with a coupled atmosphere and ocean general circulation model.
Climate Dynamics 4:1–38.
Wigley, T. M. L. 1991. Could reducing fossil-fuel emissions
cause global warming? Nature 349:503–506.
