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Why do small changes in Earth's temperature have a big impact?

Most crops have a fairly narrow range of temperatures at which they will grow. See more green science pictures.
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Global warming and climate change are controversial topics. A scientific consensus reached by more than 2,500 experts concludes that the Earth is undergoing climate change on a global scale and that it's likely much of this is due to human activities. There are other scientists with dissenting opinions who say the evidence doesn't support this conclusion, though most of them also agree that the data shows a gradual increase in the Earth's temperature. Whether you agree with the consensus or not, there's no denying that even a small change in temperature can have enormous consequences.

Temperature plays an important part in shaping weather patterns, guiding the life cycle of various organisms and maintaining ocean levels. Shifting the temperature a couple of degrees can throw an entire ecosystem into chaos.

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Most plants have a range of temperatures in which they will flourish. That's part of the reason why you don't see the same crops growing in every region, though other factors like the quality of the soil and the amount of rainfall the region receives also play a vital role. Outside of this range of temperatures, crops have trouble producing large yields. Crank the temperature up just a couple of degrees and you'll see productivity drop [source: Climate Change and U.S. Agriculture].

As it gets warmer, plants go through a process called transpiration, during which moisture escapes primarily through the plants' leaves. The increased rate of transpiration could cause plants to wilt and eventually die.

Meanwhile, the heat can speed up the breakdown process of organic matter in the soil. As the organic matter breaks down, the soil retains less moisture, which isn't good news for plants.

Higher temperatures can provide a foothold for invasive species such as weeds that grow in tropical or subtropical regions to move into new areas. These nuisance plants can also have a negative impact on crops.

A rise in temperature doesn't just affect the plants in a region. Next, we'll look at how insects react to hotter temperatures.

Heat, Insect Life Cycles and Animals

Warmer temperatures could mean longer, more frequent waves of mosquito infestations.
Warmer temperatures could mean longer, more frequent waves of mosquito infestations.
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Temperature plays an important part in the life cycle of insects. Many insects die during the colder winter months. But if temperatures should increase by just a couple of degrees, a number -- perhaps a significant number -- of these insects won't die. This could lead to a jump in insect population. Insects may also breed earlier in the year, which is bad news for crops. The growing season is when plants tend to be the most vulnerable -- if insects breed earlier they may wreak havoc during the crop growing season.

Higher temperatures tend to increase the speed of an insect's life cycle. That means insects will mature, mate and reproduce in a shorter span of time than normal. It also means there will be less time between one generation of insects and the next. Before long, you have a potential plague of pests infesting the area.

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Another charming characteristic of insects -- they can carry diseases. Mosquitoes, for example, are known for being carriers of various illnesses, such as malaria. As temperatures increase, these mosquitoes will be active through more of the year and will be able to reproduce in greater numbers. As a result, we can expect to see disease rates rise, particularly in developing countries. The cost of managing illnesses and combating the mosquito populations could be enormous.

Many animals are able to cope with a slight increase in temperatures, but some live in regions that are more vulnerable to temperature changes. A good example is the polar bear. As temperatures increase, polar bears lose large portions of their habitat. Ice melts, and polar bears have fewer places where they can go hunting. Other species may experience similar problems, facing starvation as native plants struggle to survive in a warmer environment.

Ultimately, warmer temperatures can lead to a decrease in biodiversity in certain areas. Why is this important? Biodiversity helps protect the life of a region. As diversity decreases, the remaining populations become more vulnerable to catastrophic events like famine and disease. It's possible that a particularly rough year could wipe out a significant percentage of the organisms in a region.

Let's take a look at how an increase of just a couple of degrees could affect weather patterns and life in the sea.

Temperature, the Oceans and Weather Patterns

As temperatures rise, will we see hurricanes in greater numbers and intensity?
As temperatures rise, will we see hurricanes in greater numbers and intensity?
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Weather is a complex phenomenon. While we've created sophisticated computer models to analyze and predict weather patterns, we're still learning the intricacies of weather patterns and cycles. For example, the phenomenon of El Niño is particularly complicated.

El Niño is a weather cycle that appears every few years. During a year without El Niño, trade winds typically blow westward across the Pacific Ocean. As the winds travel, they push warm water at the surface of the ocean to the west. Back east, toward South America, cool water from the deeper levels of the ocean rises to the surface. The cooler water is richer in nutrients than warm water. The nutrients help support marine life and play a vital role in the fisheries off the coast of South America.

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During an El Niño event, these trade winds weaken. The warm water at the surface of the eastern side of the Pacific stays where it is, preventing the cooler water from rising to the surface. That means the marine life that depends upon the nutrients that normally rise up suffers.

It also means that weather patterns change. Rain develops as water evaporates from the warmer parts of the ocean. The trade winds in a normal year push the rain toward the west, so that part of the Pacific gets rain while the eastern region remains relatively dry. But during El Niño, the temperature of the surface water doesn't vary as much. Rain can form in the eastern Pacific, causing flooding in South America.

While El Niño is a cyclical event, as temperatures increase, the effects we see during El Niño could become more common. The change in weather patterns could in turn drastically alter everything from marine life to crop cycles on land.

Another potential effect is that global warming could lead to more frequent and stronger hurricanes. We still don't fully understand the relationship between water temperature and hurricane frequency and intensity. Climatologists debate whether warmer oceans will lead to a more intense hurricane season. So while it's possible global warming could lead to stronger hurricanes, we don't have enough data to be sure of that outcome.

It's also important to remember that when we talk about global warming, we focus on a rise in the mean temperature of an area. The mean is the average temperature. So while a couple of degrees seems like no big deal, it also means that the region can experience more extreme weather events like heat waves. An area that might typically experience heat waves 75 days out of the year may see 90 or more after warming just a couple of degrees. That makes a big impact.

Learn more about global warming, its impact on us and the world around us and what we can do about it by following the links on the next page.

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More Great Links

Sources

  • Environmental Protection Agency. "Climate Change - Health and Environmental Effects." April 27, 2010. (July 28, 2010) http://www.epa.gov/climatechange/effects/health.html
  • Jones, Hilary. "How the El Nino cycle works." Cosmos Online. Jan. 16, 2008. (July 27, 2010) http://www.cosmosmagazine.com/features/online/1787/how-el-nino-cycle-works
  • NASA. "The current and future consequences of global change." (July 27, 2010) http://climate.nasa.gov/effects/
  • NOAA. "What is an El Nino?" (July 29, 2010) http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html
  • Rosenzweig, Cynthia et al. "Climate Change and U.S. Agriculture: The Impacts of Warming and Extreme Weather Events on Productivity, Plant Diseases and Pests." Harvard. May 2000. (July 27, 2010) http://chge.med.harvard.edu/publications/documents/agricultureclimate.pdf
  • Shah, Anup. "Climate Change and Global Warming." Global Issues. June 6, 2010. (July 27, 2010) http://www.globalissues.org/article/233/climate-change-and-global-warming-introduction
  • Union of Concerned Scientists. "Global Warming FAQ." July 14, 2010. (July 27, 2010) http://www.ucsusa.org/global_warming/science_and_impacts/science/global-warming-faq.html
  • Vecchi, Gabriel A. and Soden, Brian J. "Effect of remote sea surface temperature change on tropical cyclone potential intensity." Nature. Vol. 450, pp. 1066-1170. Dec. 13, 2007. (July 27, 2010) http://www.nature.com/nature/journal/v450/n7172/full/nature06423.html