DEAT

At any one location, year to year variations in weather can be large, but analyses of meteorological and other data over large areas and over periods of decades have provided evidence for the following systematic changes

Global mean surface air temperature has increased by between 0.3 and 0.6 oC since the late 19th century;
Recent years have been among the warmest since 1860 (i.e. since instrumental record keeping began – and despite the cooling effect of the Mount Pinatubo volcanic eruption).
Night temperatures over land have generally increased more than day-time temperatures
Regional changes are also evident. For example, recent warming has been greatest over the mid-latitude continents in winter and spring; a few areas of cooling have occurred (over the North Atlantic Ocean for example). Precipitation has increased over land in the high latitudes of the Northern Hemisphere, especially during the cold season.
Global sea level has risen by between 10 and 25 cm over the past 100 years and much of the rise may be related to increase in global mean temperature.
There is inadequate data to determine whether consistent global changes in climate variability or weather extremes have occurred over the 20th century. On regional scales there is clear evidence of changes in some extremes and climate variability indicators. Some of these changes have been towards greater variability; some have been towards lower variability.
The 1990 to mid 1995 persistent warm phase of the El Nino Southern Oscillation (which causes droughts and floods in many areas) was unusual in the context of the past 120 years.

The UNFCCC Climate Change Information Kit contains more information on changes in past climates: Evidence from past climates