The following data shows the average global temperature difference since the mid-1800s. This is a modified version of the data available at the Climatic Research Unit (CRU) in the United Kingdom .

The first value in the table is 0.56 for the year 1960. This indicates that the global temperature in 1960 was about half a degree (Celsius) warmer than it was in the mid 1800s.

1960	0.56
1961	0.7
1962	0.69
1963	0.71
1964	0.4
1965	0.46
1966	0.54
1967	0.57
1968	0.52
1969	0.64
1970	0.63
1971	0.5
1972	0.6
1973	0.72
1974	0.48
1975	0.49
1976	0.36
1977	0.69
1978	0.62
1979	0.68
1980	0.77
1981	0.85
1982	0.67
1983	0.88
1984	0.7
1985	0.67
1986	0.75
1987	0.88
1988	0.92
1989	0.83
1990	0.97
1991	0.92

The figure to the left is a histogram of the relative frequency for the data. Does it appear to be normally distributed? Perhaps more important for this project, do you find the range of values disturbing? Recall that these data record the difference in temperature relative to the mid-1800s.

While it seems obvious that recent temperatures are higher than those of the last century, try to remain skeptical when reviewing statistical analyses--think about what we may be missing. What questions might we be ignoring in this analysis?

Some argue that the global temperature is not increasing in any dangerous way, but instead that global temperatures are cyclic. If we are merely on the top of a natural 'temperature wave', would this analysis mean that we have cause for concern in global warming?

Mean	0.668
Std Dev	0.157
Std Error	0.028
Upper 95% CI	0.724	The 95% confidence interval for the mean is (0.611, 0.724). Is this evidence that the past 30 years are significantly warmer than it was 100 years ago?
Lower 95% CI	0.611
N>	32

See the following graphics for a deeper understanding of the situation. This plot shows global temperature changes from the mid 1800s to the present. For more details, refer to the explanation of the data, or review the following explanation (which includes a good graphical explanation) of the historical timeline behind the global warming phenomenon.

Note, however, that not all scientists agree about the facts underlying the data. There are some who question the estimates. This article, presenting an opposing view, helps to explain some of the statistical questions about the data.

The following charts, graphs, and tables present a picture of the issues surrounding global warming.

• Facts about Global Warming

• Graph of Temperatures Over the Past 100 Years

• Collection of Links for Global Warming Information