1. Instrumental Surface Temperature Record
Snow/Ice Report
Finish Climates of the Past
Data Sources
Land vs. Ocean Patterns
Instrument Siting Concerns
For Next Class: Read Climate Studies Ch

2. Figure SPM.1a Observed globally averaged combined land and ocean surface temperature anomaly
All Figures © IPCC 2013
Figure SPM.1, Panel a
Complete caption of Figure SPM.1:
Figure SPM.1 | (a) Observed global mean combined land and ocean surface temperature anomalies, from 1850 to 2012 from three data sets. Top panel: annual mean values. Bottom panel: decadal mean values including the estimate of uncertainty for one dataset (black). Anomalies are relative to the mean of 1961−1990. (b) Map of the observed surface temperature change from 1901 to 2012 derived from temperature trends determined by linear regression from one dataset (orange line in panel a). Trends have been calculated where data availability permits a robust estimate (i.e., only for grid boxes with greater than 70% complete records and more than 20% data availability in the first and last 10% of the time period). Other areas are white. Grid boxes where the trend is significant at the 10% level are indicated by a + sign. For a listing of the datasets and further technical details see the Technical Summary Supplementary Material. {Figures 2.19–2.21; Figure TS.2}

3. Figure SPM.1b Observed change in surface temperature 1901-2012
All Figures © IPCC 2013
Figure SPM.1, Panel b
Complete caption of Figure SPM.1:
Figure SPM.1 | (a) Observed global mean combined land and ocean surface temperature anomalies, from 1850 to 2012 from three data sets. Top panel: annual mean values. Bottom panel: decadal mean values including the estimate of uncertainty for one dataset (black). Anomalies are relative to the mean of 1961−1990. (b) Map of the observed surface temperature change from 1901 to 2012 derived from temperature trends determined by linear regression from one dataset (orange line in panel a). Trends have been calculated where data availability permits a robust estimate (i.e., only for grid boxes with greater than 70% complete records and more than 20% data availability in the first and last 10% of the time period). Other areas are white. Grid boxes where the trend is significant at the 10% level are indicated by a + sign. For a listing of the datasets and further technical details see the Technical Summary Supplementary Material. {Figures 2.19–2.21; Figure TS.2}

4. Trends in Mean Annual Temperature
Enormous amounts of observational data from over the land and sea go into computing the global mean surface temperature
The trend in global mean temperature was generally upward from 1880 until about 1940, downward or steady from 1940 to about 1970, and upward again through the 1990s and early 2000s
© AMS

5. Trends in Mean Annual Temperature
© AMS

6. Weather Coder

7. Surface Temperature Summary
Surface temperature records indicate significant warming has occurred nearly everywhere on Earth since 1900.
Warming has been most pronounced since the late 1970s and at high latitudes in the Northern Hemisphere.

8. Surface Temperature Concerns?
Do you have any concerns about the surface temperature record? If so, what are they?

9. Trends in Mean Annual Temperature
Integrity of Instrument Data
Potential sources of error in hemispheric or global mean temperature records:
At sea, huge gaps in monitoring networks
Improved reliability of weather instruments through the period of record
Changes in location & exposure of instruments
Warming effect of urbanization
© AMS

10. Urban Bias on Temperature?
Have urban-affected temperature records significantly biased large-scale temporal trends?
“Some individual stations may be affected but all global-scale studies indicate the urban heat island affect is a very small component of large-scale averages” (Trenberth et al. 2007, p. 244).

11. The Urban Environment
Figure 4.21 11

12. Urban Heat Island
Figure 4.22 12

15. Recent Research
Suggests that station siting quality (e.g., 1 vs. 5) is more important influence on temperature bias than geographical location.