This trend indicates less “cooling off” at night. Unusually hot summer nights (lows) have become more common at an even faster rate. Since the 1970s, unusually hot summer days (highs) have become more common over the last few decades in the United States. Many extreme temperature conditions are becoming more common. Spring temperatures have increased by about 2☏, while summer and fall temperatures have increased by 1.4☏. Since 1896, average winter temperatures across the contiguous 48 states have increased by nearly 3☏. As the Earth warms overall, average temperatures increase throughout the year, but the increases may be larger in certain seasons than in others. Within the United States, temperatures in parts of the North, the West, and Alaska have increased the most. Average global temperatures show a similar trend, and all of the top 10 warmest years on record worldwide have occurred since 2005. Eight of the top 10 warmest years on record have occurred since 1998. Average temperatures have risen across the contiguous 48 states since 1901, with an increased rate of warming over the past 30 years.
While increased precipitation can replenish water supplies and support agriculture, intense storms can damage property, cause loss of life and population displacement, and temporarily disrupt essential services such as transportation, telecommunications, energy, and water supplies. More frequent and intense extreme heat events can increase illnesses and deaths, especially among vulnerable populations, and damage some crops. More extreme variations in weather are also a threat to society. For example, warmer average temperatures could increase air conditioning costs and affect the spread of diseases like Lyme disease, but could also improve conditions for growing some crops. Long-term changes in climate can directly or indirectly affect many aspects of society in potentially disruptive ways.
This chapter focuses on observed changes in temperature, precipitation, storms, floods, and droughts. Scientific studies indicate that extreme weather events such as heat waves and large storms are likely to become more frequent or more intense with human-induced climate change. Rising global average temperature is associated with widespread changes in weather patterns.
0 kommentar(er)
