Melting Ice and Snow (3)
Impact on Wildlife-Some Examples
Coral Golden, Toad Mountain, Pine Beetle, Tropical Cyclones, Hurricanes, and Typhoons
Coral reefs are the skeletons of tiny marine animals that serve as habitats for about one-fourth of the world’s marine species. The individual coral polyps typically form colonies that establish a symbiotic relationship with algae.
The algae contribute some of the color characteristic of a living reef. In takes years for the corals to secrete enough calcium carbonate to form a reef.
Changes in ocean temperature or salinity are believed to lead to a condition affecting coral reefs called coral bleaching. Coral bleaching has become more common since the 1970s as a result of increasing ocean temperatures associated with global warming. IPCC scientists estimate that as much as 80 percent of the coral reefs in the Caribbean may have been lost. The 1998 El Nino event killed robust coral colonies that may have persisted for centuries. It is unlikely that coral will be able to adapt to increased temperature by migrating. However, scientists are watching to determine whether species of algae that are tolerant of a slightly higher temperature may delay the complete loss of coral reefs.
Golden Toad
Most people probably have never seen or even heard of the golden toad. This creature once occupied a very narrow ecologic niche that included a habitat in a 5-km2 region of Costa Rica. The golden toad is now believed to be extinct.
These toads used to lay their eggs during the spring months in pools of rainwater. Warmer temperatures resulted in decreased local rainfall. In 1987, 1500 toads were observed. Since 1989, no toads have been found despite extensive searching. This species represents a potential loss of biodiversity worldwide. Some of the early effects of this loss of biodiversity are becoming noticeable around the world, but loss of the golden toad serves as a warning of possible things to come.
Mountain Pine Beetle
The mountain pine beetle inhabits the forests of the western part of North America. Mountain pine beetles infest trees such as spruce and ponderosa pine. These beetles bore through the bark of the trees, resulting in their destruction. The spread of the beetles is limited by frost. With the number of frost-free days increasing, the pine beetles have that much more time to damage trees. As a result, many additional acres of evergreen forest in the Pacifi c Northwest have been destroyed.
Tropical Cyclones, Hurricanes, and Typhoons
Sea surface temperatures greater than 26°C (79°F) are needed to produce hurricane-force winds. Since hurricanes derive their energy from the ocean’s heat, greater sea surface temperatures can be expected to contribute to the frequency and severity of hurricanes. Records of the destructiveness of hurricanes show a significant increase since the 1970s. The number of named storms since 1994 has risen. Overall, storms last longer and are more intense. This correlates with the observed increase in the number of hurricanes that reach category 4 or 5 status since 1970.
This was the case in the summer of 2005. Because of a prevailing El Nino, the sea was warmer than usual that year. The sea, especially in tropical areas where there is little reflection from the water and where the sun’s ray are most direct, absorbs solar heat very efficiently. Hurricane Katrina was unusually powerful, and its effects were especially severe because of its impact on an especially vulnerable coastal area.
Katrina dropped about 30 cm (12 in) of rain on the Gulf Coast states of the United States in 2005. One estimate (by Kevin Trenbeth. Warmer Oceans, Stronger Hurricanes, Scientific American, July 2007) claims that 8 percent of this storm’s total rainfall, or 2.5 cm (1 in), was the direct result of global warming. However, global warming most likely did not cause Katrina. It is probably more accurate to say that the storm was intensified by perhaps one category level by the excess heat in the ocean at the time.
The next summer, many people expected that a new precedent had been set and braced for what they thought might be a repeat of the previous intense hurricane season. However, 2006, to the surprise of many forecasters, was a very calm year. This was not because global warming had suddenly stopped but rather because El Niña conditions were occurring that resulted in cooler sea surface temperatures that year.
In the summer of 2002, there were widespread floods in Europe. The next year, 2003, brought record-breaking heat waves and drought. Weather has it own drivers, including recurring natural climate cycles (such as the ENSO). It appears that global warming is making El Niño conditions more severe. Figure 3-23 shows a pattern of tropical storms based on data from the National Hurricane Center (compiled by Neumann and coworkers).
Notice that there is a recent increase for all storms, hurricanes, and major hurricanes. There are also long-term fluctuations in all three records suggestive of natural cycles such as the ENSO. For instance, there is a lull in the 1920s and an increase in intensity toward the end of the 1930s. In all fairness, some of the recent upswing in major hurricanes is partly a result of more thorough recent monitoring. In particular, the use of surveillance flights into the eyes of hurricanes has become more routine in recent years and has made it possible to classify storms more accurately-particularly the most severe ones-on the Safi r-Simpson scale which measures the intensity of hurricane strength.
There have been storms, droughts, and floods in the past. Tropical storms are strongly influenced by El Niño/ENSO, with an increase in one part of the world coinciding with a decrease in another part. This also has caused a movement of the jet streams closer to the poles (since the 1960s), resulting in conditions that favor the formation of tropical storms. It is premature to definitively attribute current storm patterns to climate change without first separating natural climate cycle (e.g., ENSO, etc.) effects.
