Effects of Global Warming: Weather

Storm Surge Barrier, The Netherlands

Some experts predict that an increase in global warming will result in unpredictable weather patterns, including storm surges in which wind piles up water in low-lying areas. The curved arms of the New Waterway Storm Surge Barrier in The Netherlands protect Rotterdam and other inland cities from flooding during large storms on the North Sea. Normally, the large, curved arms are retracted to allow ships from the North Sea to travel to ports along the New Waterway. When a dangerous storm is anticipated, the arms are swung out to block off the waterway and prevent large waves from pushing floodwaters inland.

    Scientists project that the polar regions of the Northern Hemisphere will heat up more than other areas of the planet, and glaciers and sea ice will shrink as a result. Regions that now experience light winter snows may receive no snow at all. In temperate mountains, snowlines will be higher and snowpacks will melt earlier. Growing seasons will be longer in some areas. Winter and nighttime temperatures will tend to rise more than summer and daytime temperatures. Many of these trends are already beginning to be observed. Arctic temperatures, for example, have increased almost twice as much as the global average over the past 100 years.

   A warmer world will be generally more humid as a result of more water evaporating from the oceans. A more humid atmosphere can both contribute to and offset further warming. On the one hand, water vapor is a greenhouse gas, and its increased presence would further increase warming. On the other hand, more water vapor in the atmosphere will produce more clouds, which reflect sunlight back into space, thereby slowing the warming process (see Water Cycle). It is uncertain which of these effects will be greater in the future, and scientists factor in both possibilities when projecting temperature increases. This is one of the main reasons that projections include ranges of high and low temperatures for different emissions scenarios.

   Storms are expected to be more frequent and more intense in a warmer world. Water will also evaporate more rapidly from soil, causing it to dry out faster between rains. Some regions might actually become drier than before. Overall, higher latitudes are projected to receive more rainfall, and subtropical areas are projected to receive less. Shifting patterns of precipitation (both snow and rain) have been observed in many regions since 1900. Significantly wetter conditions have been recorded in the eastern parts of North and South America, northern Europe, and northern and central Asia. Drier conditions have prevailed in the Sahel region of western Africa, southern Africa, the Mediterranean, and parts of southern Asia. Droughts are projected to become longer and more intense; in fact, this has already been observed since the 1970s, particularly in the tropics and subtropics.

  Weather patterns are expected to be less predictable and more extreme. Storm tracks are projected to move toward the poles, shifting wind, rainfall, and temperature patterns. Heat waves will continue to become more frequent and intense, a trend already observed. Hurricanes, violent storms that draw their force from warm ocean water, are likely to become more severe. The intensity of hurricanes has already increased since the 1970s.