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Global Climate
Global average temperatures are increasing, but this increase is not uniform across the globe. Different parts of the world are warming at different rates, and the effects of climate change that are currently being observed vary from region to region.
Mean temperatures have increased more over land than over the Oceans. The Arctic is warming at a much quicker rate than the global average. The Eastern region of North America is experiencing increased precipitation, while other regions, like the Sahel, are experiencing increased drought (1). One common observation can be made: all regions are experiencing change.
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Global Averages
Although the overall magnitude of climate warming varies from region to region in the world, the overall trend is that the planet as a whole is warming. Instrumentally recorded temperature data indicates overall temperature increases, with a faster rate of warming occurring in recent years.
Changes to precipitation patterns are also a signal of climate change, although these changes are harder to detect and are harder to attribute to specific triggers. Given that precipitation is an important source of fresh water for many regions on Earth, current changes to precipitation patterns and possible future changes are of great interest to the global community.
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Temperature
Global average temperatures have increased by approximately 0.74°C during the course of the twentieth century (from 1901-2000)2. The rate at which warming is occurring has been accelerating in recent years (Figure 1). In the twelve years ranging from 1995 to 2006, eleven of these years have been among the warmest twelve years since 18502. These temperature increases have been recorded instrumentally, and are the result of data compilation from around the world. Although different areas of the globe are warming at different rates, the trend is clear: the world as a whole is warming, and is warming faster now than at any time since we have begun recording temperature instrumentally.
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Figure 1: Global mean temperature (°C) and global average temperature departure from the 1961 to 1990 normal (°C). Data shown is for period from 1850 to 2005. The rate of warming in recent decades has accelerated, as can be seen by the trend lines above.
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Precipitation
Changes to precipitation patterns can (and most likely do already) occur in response to global warming. Changes to the amount of precipitation that certain regions receive, the kind of precipitation that falls (rain, snow), the distribution of precipitation, as well as the occurrence of more extreme precipitation events are all likely to occur as the planet warms.
Changes in precipitation patterns can mean increased flooding in some areas, while others experience a greater frequency of drought. Potential changes to the amount and distribution of precipitation is of great interest to all regions of the world. Precipitation is of vital importance to the maintenance of our water resources. The uncertainty of how precipitation patterns could change in the future makes adaptation efforts difficult.
