In the 1870s, scientist and explorer John Wesley Powell observed a dramatic change between the arid Western plains of North America and the wetter eastern region. He noted a remarkable transformation: lush grasslands giving way to bare ground with occasional cacti. This transition line, stretching from Mexico to Manitoba, cuts through the continent's breadbasket, where farmers grow rain-loving corn to the east and drought-resistant wheat to the west.
Known as the 100th Meridian, this climatic boundary is named after the longitudinal line it approximately follows. However, recent studies by climate scientist Richard Seager of Columbia University's Lamont–Doherty Earth Observatory and his colleagues reveal that this transition is shifting.
Various factors contribute to the existence of this line. The Rocky Mountains force Pacific moisture to rain out before reaching the plains, while Atlantic storms and Gulf of Mexico winds bring moisture to the east. Changes are occurring: although rainfall has not significantly altered in the northern plains, rising temperatures are increasing soil evaporation and drying the region. Additionally, shifts in wind patterns are reducing rainfall further south. Seager's research indicates that the line has moved approximately 225 kilometers (140 miles) eastward since 1980. While current shifts may be due to natural variability, they align with expected trends driven by climate change, suggesting that the line will continue to shift eastward as the planet warms.
Af - Tropical rainforest climate, Am - Tropical monsoon climate,Aw - Tropical savanna climate, BSh - Hot semi-arid climates, BSk - Cold semi-arid climates, BWh - Hot desert climates, BWk - Cold desert climates, Cfa - Humid subtropical climate, Cfb - Oceanic climate, Cfc - Subpolar oceanic climate, Csa - Hot-summer Mediterranean climate, Csb - Warm-summer Mediterranean climate, Cwa - Humid subtropical climate, Cwb - Subtropical highland oceanic climate, Dfa - Hot humid continental climate, Dfb - Warm humid continental climate, Dfc - Subarctic climate, Dfd - Subarctic climate, Dsa - Hot humid continental climate, Dsb - Warm humid continental climate, Dsc - Subarctic climate, Dwa - Humid continental climate, Dwb - Warm humid continental climate, Dwc - Subarctic climate, ET - Tundra climate.
In general terms, the climate in the United States is expected to change in several ways in the future. This includes an overall increase in temperatures, and changes in precipitation patterns leading to more intense and frequent extreme weather events such as storms, droughts, and heatwaves. Sea levels are also projected to rise, impacting coastal areas.
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