Available observational evidence indicates that regional changes in climate, particularly increases in temperature, have already affected a diverse set of physical and biological systems in many parts of the world. Examples of observed changes include shrinkage of glaciers, thawing of permafrost, later freezing and earlier break-up of ice on rivers and lakes, lengthening of mid- to high-latitude growing seasons, poleward and latitudinal shifts of plant and animal ranges, declines of some plant and animal populations, and earlier flowering of trees, emergence of insects, and egg-laying in birds. Associations between changes in regional temperatures and observed changes in physical and biological systems have been documented in many aquatic, terrestrial, and marine environments.
In most cases where changes in biological and physical systems were detected, the direction of change was that expected on the basis of known mechanisms. The probability that the observed changes in the expected direction (with no reference to magnitude) could occur by chance alone is negligible. In many parts of the world, precipitation-related impacts may be important. At present, there is a lack of systematic concurrent climatic and biophysical data of sufficient length (2 or more decades) that are considered necessary for assessment of precipitation impacts. Factors such as land-use change and pollution also act on these physical and biological systems, making it difficult to attribute changes to particular causes in some specific cases. However, taken together, the observed changes in these systems are consistent in direction and coherent across diverse localities and/or regions with the expected effects of regional changes in temperature. Thus, from the collective evidence, there is high confidence6 that recent regional changes in temperature have had discernible impacts on many physical and biological systems.
As the world warms, some extreme climate events, like the frequency of heat waves and very heavy precipitation, are expected to increase, but it remains uncertain whether or not to expect changes in the frequency of some other extremes. Moreover, it is important to note that it is not possible to link any particular weather or climate event definitively to global warming .
The causal linkage, if any, between the frequency of extreme events and global warming only can be determined through statistical analyses of long- term data, because the natural climate system can produce weather and climate events that often appear to be uncharacteristic of the recent climate.
Data on climate extremes in many regions of the world are inadequate to draw definitive conclusions about possible changes that may have occurred on a global scale. However, in some regions where good data are available, there have been some significant increases and decreases in extreme events over time. For example, there has been a clear trend to fewer extremely low minimum temperatures in several widely separated areas in recent decades (e.g., Australia, the United States, Russia, and China). The impact of such changes can manifest itself in fewer freezing days and late season frosts, such as have been documented in Australia and the United States. Indeed, we expect that the number of days with extremely low temperatures should continue to decrease as global temperatures rise.
Widespread, extended periods of extremely high temperatures are also expected to become more frequent with continued global warming , such as the unprecedented high nighttime temperatures during the 1995 heat wave in Chicago, Illinois, and the midwestern United States that caused an estimated 830 deaths. However, the global frequency of such heat waves has not been analyzed at this time.
Higher temperatures lead to higher rates of evaporation and precipitation. As the Earth warms, we expect more precipitation and it is likely to fall over shorter intervals of time, thereby increasing the frequency of very heavy and extreme precipitation events. Analyses of observed changes in precipitation intensity have been conducted only for a few countries. Perhaps the best evidence of increases in extreme and very heavy precipitation events comes from data in North America as depicted for the United States in Figure 8.1. In Australia, which is historically prone to heavy precipitation, an increase in rainfall amount from major storms has also been observed. Analyses for South Africa also show increases in extreme precipitation rates. In another area, China, where data have been analyzed for the last several decades, no obvious trends are apparent, but high concentrations of air pollution (such as sulfate particles that can cool the climate) may be counteracting such changes in this region.
There is as yet no evidence for a worldwide rise in the frequency of droughts. In the future, however, it is expected that many regions will experience more frequent, prolonged, or more severe droughts, primarily due to the more rapid evaporation of moisture from plants, soils, lakes, and reservoirs. This is expected to occur even as precipitation increases and heavy precipitation events become more common.
Humans actively and productively use and manipulate large portions of the land surface of the Earth, whether it be for agriculture, housing, energy, or forestry. These practices have created a mosaic of different land uses and ecosystem types, resulting in fewer remaining large and contiguous areas of a single type of habitat than existed in the past. Therefore it will often be difficult for plants and animals to move to a location with a more suitable climate even if a species was able to migrate quickly enough. This was not the case thousands of years ago, when ecosystems last experienced rapid climate change. Now, many of the world's ecosystems are essentially trapped on small islands, cut off from one another, only capable of travel over a limited and shrinking number of bridges. As this increasingly occurs, more species are likely to be stranded in an environment in which they cannot survive and/or reproduce.
Further complicating the response of many of the Earth's terrestrial and aquatic ecosystems to climate change is the prevalence of stress from other disturbances associated with resource use. In the case of trees, for example, many species are already weakened by air pollution. Increased concentrations of carbon dioxide in the atmosphere will raise the photosynthetic capacity of many plants, but the net effect on ecosystem productivity is unclear, particularly when combined with higher air temperatures or where soil nutrients are limiting.
As i've posted before about the warning from whales spotted at swallow water of Philippines, Australia, and Africa.... and recently another schools of whales stranded at the coast of Australia.... this is very puzzling why a schools of deep sea creatures are stranded at shallow water... a bizarre event that need not be ignored or a big one will happen soon.... Philippines, Australia and Africa are located at the ring of fire... where major fault line of earth and active and dreaded volcanoes are located....
Act now or we all suffer the wrath of mother nature.....
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