Extreme temperatures represent significant deviations from historical climate averages, including both intense heatwaves and severe cold snaps. They are not merely temporary discomforts but substantial meteorological phenomena with wide-ranging consequences. Understanding these extremes involves recognizing their departure from normal weather patterns as part of a broader shift in global weather behavior.
The Science Behind Temperature Extremes
Extreme heat events are often the result of high-pressure systems that settle over a region, creating a “heat dome.” This phenomenon occurs when the atmosphere traps hot ocean air like a lid. The high-pressure system pushes warm air downward and prevents it from rising, causing it to compress and heat up further. This process leads to prolonged periods of high temperatures as the sun’s radiation heats the ground and the trapped air.
Extreme cold is frequently linked to the behavior of the polar vortex, a large area of low pressure and cold air that circulates around the Earth’s poles. A strong jet stream—a fast-flowing river of air high in the atmosphere—normally keeps this frigid air contained in the Arctic. When the jet stream weakens or becomes wavy, it can allow this cold air to dip southward into mid-latitude regions, causing sudden drops in temperature.
A phenomenon called sudden stratospheric warming can disrupt the polar vortex, weakening it and allowing the cold air to escape its usual confines. This warming in the upper atmosphere can trigger the southward plunge of arctic air, leading to severe cold spells. Studies suggest that changes in climate, particularly the warming of the Arctic, may be contributing to a weaker and more erratic jet stream, making these polar vortex disruptions more common.
Physiological Impact on the Human Body
The human body maintains a core temperature of approximately 37°C, primarily through the evaporation of sweat. During extreme heat, the body’s ability to release heat can be overwhelmed, leading to heat stress. This forces the cardiovascular system to work harder to pump blood to the skin’s surface to dissipate heat, putting strain on the heart and other organs.
Initial symptoms of heat-related illness often manifest as heat exhaustion, which includes dizziness, heavy sweating, nausea, and a rapid heartbeat. If the body is not cooled down, this can progress to heatstroke, a life-threatening condition where the core temperature rises above 40°C. At this stage, the sweating mechanism often fails, the skin becomes hot and dry, and confusion or loss of consciousness can occur.
In extreme cold, the body employs defense mechanisms like vasoconstriction, the narrowing of blood vessels in the extremities, to redirect blood flow and heat to vital organs. Shivering is another response, where involuntary muscle contractions generate heat. If these measures are insufficient, the body’s core temperature begins to drop, leading to hypothermia. Symptoms progress from shivering and confusion to slurred speech and drowsiness as body temperature falls.
Frostbite is a localized injury that occurs when body tissues freeze, typically affecting extremities like fingers, toes, the nose, and ears. Ice crystals form within the cells, causing physical damage and cutting off circulation. The skin may appear waxy and feel numb, but severe cases can lead to permanent tissue death and the need for amputation.
Environmental and Infrastructural Consequences
Extreme temperatures have significant effects on the natural environment. Prolonged heat and lack of precipitation lead to drought conditions, stressing water resources and increasing the risk of wildfires. These conditions also place pressure on ecosystems, altering habitats and affecting the life cycles of plants and animals. In agriculture, high temperatures can reduce crop yields and stress livestock, impacting the food supply.
Human-built systems are also susceptible to the stresses of extreme temperatures. Power grids face strain as demand for air conditioning during heatwaves or heating during cold snaps increases, which can lead to blackouts. Transportation infrastructure is vulnerable, with high heat causing railway tracks to buckle and pavement to soften. Extreme cold can lead to frozen pipes and icy roads, disrupting supply chains and daily commutes.
Factors Influencing Vulnerability
An individual’s susceptibility to extreme temperatures is influenced by a combination of physiological, socioeconomic, and geographic factors. Physiologically, the very young and the elderly are more at risk because their bodies are less efficient at thermoregulation. People with pre-existing health conditions, such as cardiovascular or respiratory diseases, also face a heightened risk as extreme temperatures put additional strain on their bodies.
Socioeconomic conditions also determine vulnerability. Lower-income communities may lack access to adequate housing or air conditioning, making it difficult to find relief during a heatwave. Outdoor workers, such as those in construction or agriculture, have higher exposure and are more susceptible to heat-related illnesses.
Geography contributes to risk, particularly through the urban heat island effect, where cities are warmer than surrounding rural areas due to heat absorbed by buildings and pavement. This phenomenon intensifies heatwaves, especially at night, preventing urban residents from getting a reprieve from the heat.