United States
The following figure from the IPCC AR4 provides the results of models for North America (pink= models with CO2, blue= models without CO2, black= observed)
More temperature measurement stations exist in the US than any other country or area of the world (about 30 percent of the world’s stations historically, about 50 percent at present).
The following temperature plots are left: for North America (excluding the Arctic), and right: comparing North America [blue] with the United States [red]. This shows no significant difference between the United States and all of North America.
Combining the IPCC model plot and the observed temperature time series yields the following plot.
The models without CO2 (blue band) only deviate from the averaged temperature after the mid-1970’s. Every other year in the 1990’s is also within the blue band. The data used here is prior to the re-adjustment of the official data on August 7, 2007, due to an error in the adjustment algorithm used by NASA, and identified by Steve MacIntyre [www.climateaudit.org]. For further explanation of the see [http://www.norcalblogs.com/watts/2007/08/1998_no_longer_the_hottest_yea.html ] As a result of the readjustment, 1934 is now the warmest year on record. The following table lists the 10 warmest years in the United States following the re-adjustment (the New column refers to the re-adjusted data after 2007/08/07).
The following figure shows the temperature trend for the United States. The left-hand figure shows the annual average temperatures (black) along with the 5-year average (red) and the 5-year average of the global average temperature (blue). The right-hand figure compares the same US data with the IPCC global average. As can be seen, the United States exhibits significantly more variation than the global average; the temperature increase in the US is similar to the 1930’s.
The following figure shows the temperature trend for several regions within the United States. Most regions are just approaching the 1930’s temperatures. The central 1930’s dust-bowl region (Kansas, Nebraska. Oklahoma, etc.) does not show much recent warming. The southeast is also well below the 1930’s. The only significant recent warming has occurred in the desert southwest.
A March 31, 2007 Science Daily article “Climate Data Shows California Has Been Heating Up” reporting on a NASA study [http://www.sciencedaily.com/releases/2007/03/070330221144.htm] provides some moderation to the GHG scenario: “Their objective was to shed new insights into the relative roles humans and natural climate events play in affecting California regional temperatures… (using air temperature patterns from 1950 to 2000 )… Climate change models and assessments often assume global warming's influence here would be uniform. That is not the case. If we assume global warming affects all regions of the state, then the small increases our study found in rural stations can be an estimate of this general warming over land. Larger increases would therefore be due to local or regional changes in land surface use due to human activities… The largest temperature increases were seen in the state's urban areas … Rural, non-agricultural regions warmed the least." Note on the individual station graphs that for rural areas, that the selection of starting year (in the study case 1950) can affect the trend. Using 1950 ignores the heat of the 1930’s.
Another example comparing urban and rural stations is shown below for Seattle and Winthrop, Washington.
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See the other regional summaries covering North America for further examples of urban versus rural differences:
· Western US: www.appinsys.com/GlobalWarming/RS_WesternNorthAmerica.htm (including a comparison of southwest cities with nearby rural stations).
· Central US: www.appinsys.com/GlobalWarming/RS_CentralNorthAmerica.htm
· Eastern US: www.appinsys.com/GlobalWarming/RS_EasternNorthAmerica.htm
NOAA’s National Climatic Data Center provides historical monthly data on extreme wet and dry conditions in the US: http://www.ncdc.noaa.gov/oa/climate/research/2008/jul/uspctarea-wetdry-svr.txt. Plotting this data shows the following results (1900 to July 2008):
Severe to Extreme Dry (Percent Area)
Severe to Extreme Wet (Percent Area)
A study of extreme drought and precipitation in the US (United States Geological Survey (2004, March 10). Research Links Long Droughts In U.S. To Ocean Temperature Variations) [http://www.sciencedaily.com/releases/2004/03/040310080316.htm] states: “researchers believe that such large and sustained shifts in U.S. precipitation are linked with the natural variability of sea surface temperatures, the mechanisms are not well understood and cannot yet be used to help predict the likelihood of droughts. These sea surface temperature variations are characterized by climatic indices dubbed the Pacific Decadal Oscillation, or PDO, and the Atlantic Multidecadal Oscillation, or AMO. McCabe and his coauthors suggest that large-scale droughts in the United States are likely to be associated with positive AMO -- the kind of warming of sea surface temperatures that occurred over the North Atlantic in the 1930s, 50s, and since 1995.”
See www.appinsys.com/GlobalWarming/PDO_AMO.htm for more details on these oceanic cycles.
A study of past 1930s-type dustbowl droughts (National Oceanic And Atmospheric Administration (1998, December 21). Droughts More Severe Than Dust Bowl Likely) [http://www.sciencedaily.com/releases/1998/12/981221083346.htm] states: “The authors found a greater range of drought variability in the past than found in the instrumental record. Droughts of the 20th century have been only moderately severe and relatively short, compared with droughts of much longer ago. Woodhouse said that paleoclimatic records of the past 400 years strongly indicate that the severe droughts of the 20th century, the 1930s Dust Bowl and the l950s drought, were not unusual events and suggest that we can expect to have droughts of this magnitude once or twice a century.”